Revert "Fix display of a math hull inset in a tight inset"

[lyx.git] / src / TextMetrics.cpp

/**
 * \file src/TextMetrics.cpp
 * This file is part of LyX, the document processor.
 * Licence details can be found in the file COPYING.
 *
 * \author Asger Alstrup
 * \author Lars Gullik Bjønnes
 * \author Jean-Marc Lasgouttes
 * \author John Levon
 * \author André Pönitz
 * \author Dekel Tsur
 * \author Jürgen Vigna
 * \author Abdelrazak Younes
 *
 * Full author contact details are available in file CREDITS.
 */

#include <config.h>

#include "TextMetrics.h"

#include "Buffer.h"
#include "BufferParams.h"
#include "BufferView.h"
#include "CoordCache.h"
#include "Cursor.h"
#include "CutAndPaste.h"
#include "Layout.h"
#include "LyXRC.h"
#include "MetricsInfo.h"
#include "ParagraphParameters.h"
#include "RowPainter.h"
#include "Session.h"
#include "Text.h"
#include "TextClass.h"
#include "VSpace.h"

#include "insets/InsetSeparator.h"
#include "insets/InsetText.h"

#include "mathed/MacroTable.h"

#include "frontends/FontMetrics.h"
#include "frontends/NullPainter.h"

#include "support/debug.h"
#include "support/lassert.h"
#include "support/Changer.h"

#include <stdlib.h>
#include <cmath>

using namespace std;


namespace lyx {

using frontend::FontMetrics;

namespace {


int numberOfLabelHfills(Paragraph const & par, Row const & row)
{
        pos_type last = row.endpos() - 1;
        pos_type first = row.pos();

        // hfill *DO* count at the beginning of paragraphs!
        if (first) {
                while (first < last && par.isHfill(first))
                        ++first;
        }

        last = min(last, par.beginOfBody());
        int n = 0;
        for (pos_type p = first; p < last; ++p) {
                if (par.isHfill(p))
                        ++n;
        }
        return n;
}

// FIXME: this needs to be rewritten, probably by merging it into some
// code that, besides counting, sets the active status of the space
// inset in the row element.
int numberOfHfills(Row const & row, ParagraphMetrics const & pm,
                   pos_type const body_pos)
{
        int n = 0;
        Row::const_iterator cit = row.begin();
        Row::const_iterator const end = row.end();
        for ( ; cit != end ; ++cit)
                if (cit->pos >= body_pos
                    && cit->inset && pm.hfillExpansion(row, cit->pos))
                        ++n;
        return n;
}


} // namespace

/////////////////////////////////////////////////////////////////////
//
// TextMetrics
//
/////////////////////////////////////////////////////////////////////


TextMetrics::TextMetrics(BufferView * bv, Text * text)
        : bv_(bv), text_(text), dim_(bv_->workWidth(), 10, 10),
          max_width_(dim_.wid), tight_(false)
{}


bool TextMetrics::contains(pit_type pit) const
{
        return par_metrics_.find(pit) != par_metrics_.end();
}


pair<pit_type, ParagraphMetrics const *> TextMetrics::first() const
{
        ParMetricsCache::const_iterator it = par_metrics_.begin();
        return make_pair(it->first, &it->second);
}


pair<pit_type, ParagraphMetrics const *> TextMetrics::last() const
{
        LBUFERR(!par_metrics_.empty());
        ParMetricsCache::const_reverse_iterator it = par_metrics_.rbegin();
        return make_pair(it->first, &it->second);
}


bool TextMetrics::isLastRow(Row const & row) const
{
        ParagraphList const & pars = text_->paragraphs();
        return row.endpos() >= pars[row.pit()].size()
                && row.pit() + 1 == pit_type(pars.size());
}


bool TextMetrics::isFirstRow(Row const & row) const
{
        return row.pos() == 0 && row.pit() == 0;
}


void TextMetrics::setRowChanged(pit_type pit, pos_type pos)
{
        for (auto & pm_pair : par_metrics_)
                if (pm_pair.first == pit)
                        for (Row & row : pm_pair.second.rows())
                                if (row.pos() == pos)
                                        row.changed(true);
}


ParagraphMetrics & TextMetrics::parMetrics(pit_type pit, bool redo)
{
        ParMetricsCache::iterator pmc_it = par_metrics_.find(pit);
        if (pmc_it == par_metrics_.end()) {
                pmc_it = par_metrics_.insert(
                        make_pair(pit, ParagraphMetrics(text_->getPar(pit)))).first;
        }
        if (pmc_it->second.rows().empty() && redo)
                redoParagraph(pit);
        return pmc_it->second;
}


ParagraphMetrics const & TextMetrics::parMetrics(pit_type pit) const
{
        return const_cast<TextMetrics *>(this)->parMetrics(pit, true);
}


ParagraphMetrics & TextMetrics::parMetrics(pit_type pit)
{
        return parMetrics(pit, true);
}


void TextMetrics::newParMetricsDown()
{
        pair<pit_type, ParagraphMetrics> const & last = *par_metrics_.rbegin();
        pit_type const pit = last.first + 1;
        if (pit == int(text_->paragraphs().size()))
                return;

        // do it and update its position.
        redoParagraph(pit);
        par_metrics_[pit].setPosition(last.second.position()
                + last.second.descent() + par_metrics_[pit].ascent());
        updatePosCache(pit);
}


void TextMetrics::newParMetricsUp()
{
        pair<pit_type, ParagraphMetrics> const & first = *par_metrics_.begin();
        if (first.first == 0)
                return;

        pit_type const pit = first.first - 1;
        // do it and update its position.
        redoParagraph(pit);
        par_metrics_[pit].setPosition(first.second.position()
                - first.second.ascent() - par_metrics_[pit].descent());
        updatePosCache(pit);
}


bool TextMetrics::metrics(MetricsInfo const & mi, Dimension & dim, int min_width)
{
        LBUFERR(mi.base.textwidth > 0);
        max_width_ = mi.base.textwidth;
        tight_ = mi.tight_insets;
        // backup old dimension.
        Dimension const old_dim = dim_;
        // reset dimension.
        dim_ = Dimension();
        dim_.wid = min_width;
        pit_type const npar = text_->paragraphs().size();
        if (npar > 1 && !tight_)
                // If there is more than one row, expand the text to
                // the full allowable width.
                dim_.wid = max_width_;

        //lyxerr << "TextMetrics::metrics: width: " << mi.base.textwidth
        //      << " maxWidth: " << max_width_ << "\nfont: " << mi.base.font << endl;

        bool changed = false;
        int h = 0;
        for (pit_type pit = 0; pit != npar; ++pit) {
                // create rows, but do not set alignment yet
                changed |= redoParagraph(pit, false);
                ParagraphMetrics const & pm = par_metrics_[pit];
                h += pm.height();
                if (dim_.wid < pm.width())
                        dim_.wid = pm.width();
        }

        // Now set alignment for all rows (the width might not have been known before).
        for (pit_type pit = 0; pit != npar; ++pit) {
                ParagraphMetrics & pm = par_metrics_[pit];
                for (Row & row : pm.rows())
                        setRowAlignment(row, dim_.wid);
        }

        dim_.asc = par_metrics_[0].ascent();
        dim_.des = h - dim_.asc;
        //lyxerr << "dim_.wid " << dim_.wid << endl;
        //lyxerr << "dim_.asc " << dim_.asc << endl;
        //lyxerr << "dim_.des " << dim_.des << endl;

        changed |= dim_ != old_dim;
        dim = dim_;
        return changed;
}


void TextMetrics::updatePosCache(pit_type pit) const
{
        frontend::NullPainter np;
        PainterInfo pi(bv_, np);
        drawParagraph(pi, pit, origin_.x_, par_metrics_[pit].position());
}


int TextMetrics::rightMargin(ParagraphMetrics const & pm) const
{
        return text_->isMainText() ? pm.rightMargin(*bv_) : 0;
}


int TextMetrics::rightMargin(pit_type const pit) const
{
        return text_->isMainText() ? par_metrics_[pit].rightMargin(*bv_) : 0;
}


void TextMetrics::applyOuterFont(Font & font) const
{
        FontInfo lf(font_.fontInfo());
        lf.reduce(bv_->buffer().params().getFont().fontInfo());
        font.fontInfo().realize(lf);
}


// This is an arbitrary magic value
static const pos_type force_label = -12345;

// if pos == force_label, this function will return the label font instead.
// This undocumented and only for use by labelDisplayFont()
Font TextMetrics::displayFont(pit_type pit, pos_type pos) const
{
        LASSERT(pos >= 0 || pos == force_label, { static Font f; return f; });

        ParagraphList const & pars = text_->paragraphs();
        Paragraph const & par = pars[pit];
        Layout const & layout = par.layout();
        Buffer const & buffer = bv_->buffer();
        // FIXME: broken?
        BufferParams const & bparams = buffer.params();
        bool const label = pos < par.beginOfBody() || pos == force_label;

        Font f = (pos == force_label) ? Font(inherit_font, bparams.language)
                                      : par.getFontSettings(bparams, pos);
        FontInfo const & lf = label ? layout.labelfont : layout.font;

        // We specialize the 95% common case:
        if (!par.getDepth()) {
                if (!text_->isMainText())
                        applyOuterFont(f);

                FontInfo rlf = label ? layout.reslabelfont : layout.resfont;

                // In case the default family has been customized
                if (lf.family() == INHERIT_FAMILY)
                        rlf.setFamily(bparams.getFont().fontInfo().family());
                f.fontInfo().realize(rlf);
                return f;
        }

        // The uncommon case need not be optimized as much.
        // FIXME : the two code paths seem different in function.
        f.fontInfo().realize(lf);

        if (!text_->isMainText())
                applyOuterFont(f);

        // Realize against environment font information
        // NOTE: the cast to pit_type should be removed when pit_type
        // changes to a unsigned integer.
        if (pit < pit_type(pars.size()))
                f.fontInfo().realize(text_->outerFont(pit).fontInfo());

        // Realize with the fonts of lesser depth.
        f.fontInfo().realize(bparams.getFont().fontInfo());

        return f;
}


Font TextMetrics::labelDisplayFont(pit_type pit) const
{
        return displayFont(pit, force_label);
}


bool TextMetrics::isRTL(CursorSlice const & sl, bool boundary) const
{
        if (!sl.text())
                return false;

        int correction = 0;
        if (boundary && sl.pos() > 0)
                correction = -1;

        return displayFont(sl.pit(), sl.pos() + correction).isVisibleRightToLeft();
}


bool TextMetrics::isRTLBoundary(pit_type pit, pos_type pos) const
{
        // no RTL boundary at paragraph start
        if (pos == 0)
                return false;

        Font const & left_font = displayFont(pit, pos - 1);

        return isRTLBoundary(pit, pos, left_font);
}


// isRTLBoundary returns false on a real end-of-line boundary,
// because otherwise the two boundary types get mixed up.
// This is the whole purpose of this being in TextMetrics.
bool TextMetrics::isRTLBoundary(pit_type pit, pos_type pos,
                Font const & font) const
{
        if (// no RTL boundary at paragraph start
            pos == 0
            // if the metrics have not been calculated, then we are not
            // on screen and can safely ignore issues about boundaries.
            || !contains(pit))
                return false;

        ParagraphMetrics const & pm = par_metrics_[pit];
        // no RTL boundary in empty paragraph
        if (pm.rows().empty())
                return false;

        pos_type const endpos = pm.getRow(pos - 1, false).endpos();
        pos_type const startpos = pm.getRow(pos, false).pos();
        // no RTL boundary at line start:
        // abc\n   -> toggle to RTL ->    abc\n     (and not:    abc\n|
        // |                              |                               )
        if (pos == startpos && pos == endpos) // start of cur row, end of prev row
                return false;

        Paragraph const & par = text_->getPar(pit);
        // no RTL boundary at line break:
        // abc|\n    -> move right ->   abc\n       (and not:    abc\n|
        // FED                          FED|                     FED     )
        if (startpos == pos && endpos == pos && endpos != par.size()
                && (par.isNewline(pos - 1)
                        || par.isEnvSeparator(pos - 1)
                        || par.isLineSeparator(pos - 1)
                        || par.isSeparator(pos - 1)))
                return false;

        bool const left = font.isVisibleRightToLeft();
        bool right;
        if (pos == par.size())
                right = par.isRTL(bv_->buffer().params());
        else
                right = displayFont(pit, pos).isVisibleRightToLeft();

        return left != right;
}


bool TextMetrics::redoParagraph(pit_type const pit, bool const align_rows)
{
        Paragraph & par = text_->getPar(pit);
        // IMPORTANT NOTE: We pass 'false' explicitly in order to not call
        // redoParagraph() recursively inside parMetrics.
        Dimension old_dim = parMetrics(pit, false).dim();
        ParagraphMetrics & pm = par_metrics_[pit];
        pm.reset(par);

        Buffer & buffer = bv_->buffer();
        bool changed = false;

        // Check whether there are InsetBibItems that need fixing
        // FIXME: This check ought to be done somewhere else. It is the reason
        // why text_ is not const. But then, where else to do it?
        // Well, how can you end up with either (a) a biblio environment that
        // has no InsetBibitem, (b) a biblio environment with more than one
        // InsetBibitem or (c) a paragraph that has a bib item but is no biblio
        // environment? I think the answer is: when paragraphs are merged;
        // when layout is set; when material is pasted.
        if (par.brokenBiblio()) {
                Cursor & cur = bv_->cursor();
                // In some cases, we do not know how to record undo
                if (&cur.inset() == &text_->inset())
                        cur.recordUndo(pit, pit);

                int const moveCursor = par.fixBiblio(buffer);

                // Is it necessary to update the cursor?
                if (&cur.inset() == &text_->inset() && cur.pit() == pit) {
                        if (moveCursor > 0)
                                cur.posForward();
                        else if (moveCursor < 0 && cur.pos() >= -moveCursor)
                                cur.posBackward();
                }
        }

        // Optimisation: this is used in the next two loops
        // so better to calculate that once here.
        int const right_margin = rightMargin(pm);

        // iterator pointing to paragraph to resolve macros
        DocIterator parPos = text_->macrocontextPosition();
        if (!parPos.empty())
                parPos.pit() = pit;
        else {
                LYXERR(Debug::INFO, "MacroContext not initialised!"
                        << " Going through the buffer again and hope"
                        << " the context is better then.");
                // FIXME audit updateBuffer calls
                // This should not be here, but it is not clear yet where else it
                // should be.
                bv_->buffer().updateBuffer();
                parPos = text_->macrocontextPosition();
                LBUFERR(!parPos.empty());
                parPos.pit() = pit;
        }

        // redo insets
        par.setBeginOfBody();
        Font const bufferfont = buffer.params().getFont();
        CoordCache::Insets & insetCache = bv_->coordCache().insets();
        for (auto const & e : par.insetList()) {
                // FIXME Doesn't this HAVE to be non-empty?
                // position already initialized?
                if (!parPos.empty()) {
                        parPos.pos() = e.pos;

                        // A macro template would normally not be visible
                        // by itself. But the tex macro semantics allow
                        // recursion, so we artifically take the context
                        // after the macro template to simulate this.
                        if (e.inset->lyxCode() == MATHMACRO_CODE)
                                parPos.pos()++;
                }

                // If there is an end of paragraph marker, its size should be
                // substracted to the available width. The logic here is
                // almost the same as in tokenizeParagraph, remember keep them in sync.
                int eop = 0;
                if (e.pos + 1 == par.size()
                      && (lyxrc.paragraph_markers || par.lookupChange(par.size()).changed())
                      && size_type(pit + 1) < text_->paragraphs().size()) {
                        Font f(text_->layoutFont(pit));
                        // ¶ U+00B6 PILCROW SIGN
                        eop = theFontMetrics(f).width(char_type(0x00B6));
                }

                // do the metric calculation
                Dimension dim;
                int const w = max_width_ - leftMargin(pit, e.pos)
                        - right_margin - eop;
                Font const & font = e.inset->inheritFont() ?
                        displayFont(pit, e.pos) : bufferfont;
                MacroContext mc(&buffer, parPos);
                MetricsInfo mi(bv_, font.fontInfo(), w, mc, e.pos == 0, tight_);
                mi.base.outer_font = displayFont(pit, e.pos).fontInfo();
                e.inset->metrics(mi, dim);
                if (!insetCache.has(e.inset) || insetCache.dim(e.inset) != dim) {
                        insetCache.add(e.inset, dim);
                        changed = true;
                }
        }

        // Transform the paragraph into a single row containing all the elements.
        Row const bigrow = tokenizeParagraph(pit);
        // Split the row in several rows fitting in available width
        pm.rows() = breakParagraph(bigrow);

        /* If there is more than one row, expand the text to the full
         * allowable width. This setting here is needed for the
         * setRowAlignment() below. We do nothing when tight insets are
         * requested.
         */
        if (pm.rows().size() > 1 && !tight_ && dim_.wid < max_width_)
                        dim_.wid = max_width_;

        // Compute height and alignment of the rows.
        for (Row & row : pm.rows()) {
                setRowHeight(row);
                if (align_rows)
                        setRowAlignment(row, max(dim_.wid, row.width()));

                pm.dim().wid = max(pm.dim().wid, row.width() + row.right_margin);
                pm.dim().des += row.height();
        }

        // This type of margin can only be handled at the global paragraph level
        if (par.layout().margintype == MARGIN_RIGHT_ADDRESS_BOX) {
                int offset = 0;
                if (par.isRTL(buffer.params())) {
                        // globally align the paragraph to the left.
                        int minleft = max_width_;
                        for (Row const & row : pm.rows())
                                minleft = min(minleft, row.left_margin);
                        offset = right_margin - minleft;
                } else {
                        // globally align the paragraph to the right.
                        int maxwid = 0;
                        for (Row const & row : pm.rows())
                                maxwid = max(maxwid, row.width());
                        offset = max_width_ - right_margin - maxwid;
                }

                for (Row & row : pm.rows()) {
                        row.left_margin += offset;
                        row.dim().wid += offset;
                }
        }

        // The space above and below the paragraph.
        int top = parTopSpacing(pit);
        int bottom = parBottomSpacing(pit);

        // Top and bottom margin of the document (only at top-level)
        // FIXME: It might be better to move this in another method
        // specially tailored for the main text.
        if (text_->isMainText()) {
                if (pit == 0)
                        top += bv_->topMargin();
                if (pit + 1 == pit_type(text_->paragraphs().size())) {
                        bottom += bv_->bottomMargin();
                }
        }

        // Add the top/bottom space to rows and paragraph metrics
        pm.rows().front().dim().asc += top;
        pm.rows().back().dim().des += bottom;
        pm.dim().des += top + bottom;

        // Move the pm ascent to be the same as the first row ascent
        pm.dim().asc += pm.rows().front().ascent();
        pm.dim().des -= pm.rows().front().ascent();

        changed |= old_dim.height() != pm.dim().height();

        return changed;
}


LyXAlignment TextMetrics::getAlign(Paragraph const & par, Row const & row) const
{
        LyXAlignment align = par.getAlign(bv_->buffer().params());

        // handle alignment inside tabular cells
        Inset const & owner = text_->inset();
        bool forced_block = false;
        switch (owner.contentAlignment()) {
        case LYX_ALIGN_BLOCK:
                // In general block align is the default state, but here it is
                // an explicit choice. Therefore it should not be overridden
                // later.
                forced_block = true;
                // fall through
        case LYX_ALIGN_CENTER:
        case LYX_ALIGN_LEFT:
        case LYX_ALIGN_RIGHT:
                if (align == LYX_ALIGN_NONE || align == LYX_ALIGN_BLOCK)
                        align = owner.contentAlignment();
                break;
        default:
                // unchanged (use align)
                break;
        }

        // Display-style insets should always be on a centered row
        if (Inset const * inset = par.getInset(row.pos())) {
                if (inset->rowFlags() & Display) {
                        if (inset->rowFlags() & AlignLeft)
                                align = LYX_ALIGN_LEFT;
                        else if (inset->rowFlags() & AlignRight)
                                align = LYX_ALIGN_RIGHT;
                        else
                                align = LYX_ALIGN_CENTER;
                }
        }

        if (align == LYX_ALIGN_BLOCK) {
                // If this row has been broken abruptly by a display inset, or
                // it is the end of the paragraph, or the user requested we
                // not justify stuff, then don't stretch.
                // A forced block alignment can only be overridden the 'no
                // justification on screen' setting.
                if ((row.flushed() && !forced_block)
                    || !bv_->buffer().params().justification)
                        align = row.isRTL() ? LYX_ALIGN_RIGHT : LYX_ALIGN_LEFT;
        }

        return align;
}


void TextMetrics::setRowAlignment(Row & row, int width) const
{
        row.label_hfill = 0;
        row.separator = 0;

        Paragraph const & par = text_->getPar(row.pit());

        int const w = width - row.right_margin - row.width();
        // FIXME: put back this assertion when the crash on new doc is solved.
        //LASSERT(w >= 0, /**/);

        // is there a manual margin with a manual label
        Layout const & layout = par.layout();

        int nlh = 0;
        if (layout.margintype == MARGIN_MANUAL
            && layout.labeltype == LABEL_MANUAL) {
                /// We might have real hfills in the label part
                nlh = numberOfLabelHfills(par, row);

                // A manual label par (e.g. List) has an auto-hfill
                // between the label text and the body of the
                // paragraph too.
                // But we don't want to do this auto hfill if the par
                // is empty.
                if (!par.empty())
                        ++nlh;

                if (nlh && !par.getLabelWidthString().empty())
                        row.label_hfill = labelFill(row) / double(nlh);
        }

        // are there any hfills in the row?
        ParagraphMetrics const & pm = par_metrics_[row.pit()];
        int nh = numberOfHfills(row, pm, par.beginOfBody());
        int hfill = 0;
        int hfill_rem = 0;

        // We don't have to look at the alignment if the row is already
        // larger then the permitted width as then we force the
        // LEFT_ALIGN'edness!
        if (row.width() >= max_width_)
                return;

        if (nh == 0) {
                // Common case : there is no hfill, and the alignment will be
                // meaningful
                switch (getAlign(par, row)) {
                case LYX_ALIGN_BLOCK:
                        // Expand expanding characters by a total of w
                        if (!row.setExtraWidth(w) && row.isRTL()) {
                                // Justification failed and the text is RTL: align to the right
                                row.left_margin += w;
                                row.dim().wid += w;
                        }
                        break;
                case LYX_ALIGN_LEFT:
                        // a displayed inset that is flushed
                        if (Inset const * inset = par.getInset(row.pos())) {
                                row.left_margin += inset->indent(*bv_);
                                row.dim().wid += inset->indent(*bv_);
                        }
                        break;
                case LYX_ALIGN_RIGHT:
                        if (Inset const * inset = par.getInset(row.pos())) {
                                int const new_w = max(w - inset->indent(*bv_), 0);
                                row.left_margin += new_w;
                                row.dim().wid += new_w;
                        } else {
                                row.left_margin += w;
                                row.dim().wid += w;
                        }
                        break;
                case LYX_ALIGN_CENTER:
                        row.dim().wid += w / 2;
                        row.left_margin += w / 2;
                        break;
                case LYX_ALIGN_NONE:
                case LYX_ALIGN_LAYOUT:
                case LYX_ALIGN_SPECIAL:
                case LYX_ALIGN_DECIMAL:
                        break;
                }
                return;
        }

        // Case nh > 0. There are hfill separators.
        hfill = w / nh;
        hfill_rem = w % nh;
        row.dim().wid += w;
        // Set size of hfill insets
        pos_type const endpos = row.endpos();
        pos_type body_pos = par.beginOfBody();
        if (body_pos > 0
            && (body_pos > endpos || !par.isLineSeparator(body_pos - 1)))
                body_pos = 0;

        CoordCache::Insets & insetCache = bv_->coordCache().insets();
        for (Row::Element & e : row) {
                if (row.label_hfill && e.endpos == body_pos
                    && e.type == Row::SPACE)
                        e.dim.wid -= int(row.label_hfill * (nlh - 1));
                if (e.inset && pm.hfillExpansion(row, e.pos)) {
                        if (e.pos >= body_pos) {
                                e.dim.wid += hfill;
                                --nh;
                                if (nh == 0)
                                        e.dim.wid += hfill_rem;
                        } else
                                e.dim.wid += int(row.label_hfill);
                        // Cache the inset dimension.
                        insetCache.add(e.inset, e.dim);
                }
        }
}


int TextMetrics::labelFill(Row const & row) const
{
        Paragraph const & par = text_->getPar(row.pit());
        LBUFERR(par.beginOfBody() > 0 || par.isEnvSeparator(0));

        int w = 0;
        // iterate over elements before main body (except the last one,
        // which is extra space).
        for (Row::Element const & e : row) {
                if (e.endpos >= par.beginOfBody())
                        break;
                w += e.dim.wid;
        }

        docstring const & label = par.params().labelWidthString();
        if (label.empty())
                return 0;

        FontMetrics const & fm
                = theFontMetrics(text_->labelFont(par));

        return max(0, fm.width(label) - w);
}


namespace {

/**
 * Calling Text::getFont is slow. While rebreaking we scan a
 * paragraph from left to right calling getFont for every char.  This
 * simple class address this problem by hidding an optimization trick
 * (not mine btw -AB): the font is reused in the whole font span.  The
 * class handles transparently the "hidden" (not part of the fontlist)
 * label font (as getFont does).
 **/
class FontIterator
{
public:
        ///
        FontIterator(TextMetrics const & tm,
                Paragraph const & par, pit_type pit, pos_type pos)
                : tm_(tm), par_(par), pit_(pit), pos_(pos),
                font_(tm.displayFont(pit, pos)),
                endspan_(par.fontSpan(pos).last),
                bodypos_(par.beginOfBody())
        {}

        ///
        Font const & operator*() const { return font_; }

        ///
        FontIterator & operator++()
        {
                ++pos_;
                if (pos_ < par_.size() && (pos_ > endspan_ || pos_ == bodypos_)) {
                        font_ = tm_.displayFont(pit_, pos_);
                        endspan_ = par_.fontSpan(pos_).last;
                }
                return *this;
        }

        ///
        Font * operator->() { return &font_; }

private:
        ///
        TextMetrics const & tm_;
        ///
        Paragraph const & par_;
        ///
        pit_type pit_;
        ///
        pos_type pos_;
        ///
        Font font_;
        ///
        pos_type endspan_;
        ///
        pos_type bodypos_;
};

} // namespace


Row TextMetrics::tokenizeParagraph(pit_type const pit) const
{
        Row row;
        row.pit(pit);
        Paragraph const & par = text_->getPar(pit);
        Buffer const & buf = text_->inset().buffer();
        BookmarksSection::BookmarkPosList bpl =
                theSession().bookmarks().bookmarksInPar(buf.fileName(), par.id());

        pos_type const end = par.size();
        pos_type const body_pos = par.beginOfBody();

        // check for possible inline completion
        DocIterator const & ic_it = bv_->inlineCompletionPos();
        pos_type ic_pos = -1;
        if (ic_it.inTexted() && ic_it.text() == text_ && ic_it.pit() == pit)
                ic_pos = ic_it.pos();

        // Now we iterate through until we reach the right margin
        // or the end of the par, then build a representation of the row.
        pos_type i = 0;
        FontIterator fi = FontIterator(*this, par, pit, 0);
        // The real stopping condition is a few lines below.
        while (true) {
                // Firstly, check whether there is a bookmark here.
                if (lyxrc.bookmarks_visibility == LyXRC::BMK_INLINE)
                        for (auto const & bp_p : bpl)
                                if (bp_p.second == i) {
                                        Font f = *fi;
                                        f.fontInfo().setColor(Color_bookmark);
                                        // ❶ U+2776 DINGBAT NEGATIVE CIRCLED DIGIT ONE
                                        char_type const ch = 0x2775 + bp_p.first;
                                        row.addVirtual(i, docstring(1, ch), f, Change());
                                }

                // The stopping condition is here so that the display of a
                // bookmark can take place at paragraph start too.
                if (i >= end)
                        break;

                char_type c = par.getChar(i);
                // The most special cases are handled first.
                if (par.isInset(i)) {
                        Inset const * ins = par.getInset(i);
                        Dimension dim = bv_->coordCache().insets().dim(ins);
                        row.add(i, ins, dim, *fi, par.lookupChange(i));
                } else if (c == ' ' && i + 1 == body_pos) {
                        // This space is an \item separator. Represent it with a
                        // special space element, which dimension will be computed
                        // in breakRow.
                        FontMetrics const & fm = theFontMetrics(text_->labelFont(par));
                        int const wid = fm.width(par.layout().labelsep);
                        row.addMarginSpace(i, wid, *fi, par.lookupChange(i));
                } else if (c == '\t')
                        row.addSpace(i, theFontMetrics(*fi).width(from_ascii("    ")),
                                     *fi, par.lookupChange(i));
                else if (c == 0x2028 || c == 0x2029) {
                        /**
                         * U+2028 LINE SEPARATOR
                         * U+2029 PARAGRAPH SEPARATOR

                         * These are special unicode characters that break
                         * lines/pragraphs. Not handling them leads to trouble wrt
                         * Qt QTextLayout formatting. We add a visible character
                         * on screen so that the user can see that something is
                         * happening.
                        */
                        row.finalizeLast();
                        // ⤶ U+2936 ARROW POINTING DOWNWARDS THEN CURVING LEFTWARDS
                        // ¶ U+00B6 PILCROW SIGN
                        char_type const screen_char = (c == 0x2028) ? 0x2936 : 0x00B6;
                        row.add(i, screen_char, *fi, par.lookupChange(i));
                } else
                        // row elements before body are unbreakable
                        row.add(i, c, *fi, par.lookupChange(i));

                // add inline completion width
                // draw logically behind the previous character
                if (ic_pos == i + 1 && !bv_->inlineCompletion().empty()) {
                        docstring const comp = bv_->inlineCompletion();
                        size_t const uniqueTo =bv_->inlineCompletionUniqueChars();
                        Font f = *fi;

                        if (uniqueTo > 0) {
                                f.fontInfo().setColor(Color_inlinecompletion);
                                row.addVirtual(i + 1, comp.substr(0, uniqueTo), f, Change());
                        }
                        f.fontInfo().setColor(Color_nonunique_inlinecompletion);
                        row.addVirtual(i + 1, comp.substr(uniqueTo), f, Change());
                }

                ++i;
                ++fi;
        }
        row.finalizeLast();
        row.endpos(end);

        // End of paragraph marker, either if LyXRc requires it, or there
        // is an end of paragraph change. The logic here is almost the
        // same as in redoParagraph, remember keep them in sync.
        ParagraphList const & pars = text_->paragraphs();
        Change const & endchange = par.lookupChange(end);
        if (endchange.changed())
                row.needsChangeBar(true);
        if ((lyxrc.paragraph_markers || endchange.changed())
            && size_type(pit + 1) < pars.size()) {
                // add a virtual element for the end-of-paragraph
                // marker; it is shown on screen, but does not exist
                // in the paragraph.
                Font f(text_->layoutFont(pit));
                f.fontInfo().setColor(Color_paragraphmarker);
                f.setLanguage(par.getParLanguage(buf.params()));
                // ¶ U+00B6 PILCROW SIGN
                row.addVirtual(end, docstring(1, char_type(0x00B6)), f, endchange);
        }

        return row;
}


namespace {

/** Helper template flexible_const_iterator<T>
 * A way to iterate over a const container, but insert fake elements in it.
 * In the case of a row, we will have to break some elements, which
 * create new ones. This class allows to abstract this.
 * Only the required parts are implemented for now.
 */
template<class T>
class flexible_const_iterator {
        typedef typename T::value_type value_type;
public:

        //
        flexible_const_iterator & operator++() {
                if (pile_.empty())
                        ++cit_;
                else
                        pile_.pop_back();
                return *this;
        }

        value_type operator*() const { return pile_.empty() ? *cit_ : pile_.back(); }

        value_type const * operator->() const { return pile_.empty() ? &*cit_ : &pile_.back(); }

        void put(value_type const & e) { pile_.push_back(e); }

        // Put a sequence of elements on the pile (in reverse order!)
        void put(vector<value_type> const & elts) {
                pile_.insert(pile_.end(), elts.rbegin(), elts.rend());
        }

// This should be private, but declaring the friend functions is too much work
//private:
        typename T::const_iterator cit_;
        // A vector that is used as like a pile to store the elements to
        // consider before incrementing the underlying iterator.
        vector<value_type> pile_;
};


template<class T>
flexible_const_iterator<T> flexible_begin(T const & t)
{
        return { t.begin(), vector<typename T::value_type>() };
}


template<class T>
flexible_const_iterator<T> flexible_end(T const & t)
{
        return { t.end(), vector<typename T::value_type>() };
}


// Equality is only possible if respective piles are empty
template<class T>
bool operator==(flexible_const_iterator<T> const & t1,
                flexible_const_iterator<T> const & t2)
{
        return t1.cit_ == t2.cit_ && t1.pile_.empty() && t2.pile_.empty();
}


Row newRow(TextMetrics const & tm, pit_type pit, pos_type pos, bool is_rtl)
{
        Row nrow;
        nrow.pit(pit);
        nrow.pos(pos);
        nrow.left_margin = tm.leftMargin(pit, pos);
        nrow.right_margin = tm.rightMargin(pit);
        nrow.setRTL(is_rtl);
        if (is_rtl)
                swap(nrow.left_margin, nrow.right_margin);
        // Remember that the row width takes into account the left_margin
        // but not the right_margin.
        nrow.dim().wid = nrow.left_margin;
        return nrow;
}


void cleanupRow(Row & row, bool at_end)
{
        if (row.empty()) {
                row.endpos(row.pos());
                return;
        }

        row.endpos(row.back().endpos);
        // remove trailing spaces on row break
        if (!at_end && !row.flushed())
                row.back().rtrim();
        // boundary exists when there was no space at the end of row
        row.end_boundary(!at_end && row.back().endpos == row.endpos());
        // make sure that the RTL elements are in reverse ordering
        row.reverseRTL();
}


// Implement the priorities described in RowFlags.h.
bool needsRowBreak(int f1, int f2)
{
        if (f1 & AlwaysBreakAfter /*|| f2 & AlwaysBreakBefore*/)
                return true;
        if (f1 & NoBreakAfter || f2 & NoBreakBefore)
                return false;
        if (f1 & BreakAfter || f2 & BreakBefore)
                return true;
        return false;
}


}


RowList TextMetrics::breakParagraph(Row const & bigrow) const
{
        RowList rows;
        bool const is_rtl = text_->isRTL(bigrow.pit());
        bool const end_label = text_->getEndLabel(bigrow.pit()) != END_LABEL_NO_LABEL;
        int const next_width = max_width_ - leftMargin(bigrow.pit(), bigrow.endpos())
                - rightMargin(bigrow.pit());

        int width = 0;
        flexible_const_iterator<Row> fcit = flexible_begin(bigrow);
        flexible_const_iterator<Row> const end = flexible_end(bigrow);
        while (true) {
                bool const row_empty = rows.empty() || rows.back().empty();
                // The row flags of previous element, if there is one.
                // Otherwise we use NoBreakAfter to avoid an empty row before
                // e.g. a displayed equation.
                int const f1 = row_empty ? NoBreakAfter : rows.back().back().row_flags;
                // The row flags of next element, if there is one.
                // Otherwise we use NoBreakBefore (see above), unless the
                // paragraph has an end label (for which an empty row is OK).
                int const f2 = (fcit == end) ? (end_label ? Inline : NoBreakBefore)
                                             : fcit->row_flags;
                if (rows.empty() || needsRowBreak(f1, f2)) {
                        if (!rows.empty()) {
                                // Flush row as requested by row flags
                                rows.back().flushed((f1 & Flush) || (f2 & FlushBefore));
                                cleanupRow(rows.back(), false);
                        }
                        pos_type pos = rows.empty() ? 0 : rows.back().endpos();
                        rows.push_back(newRow(*this, bigrow.pit(), pos, is_rtl));
                        // the width available for the row.
                        width = max_width_ - rows.back().right_margin;
                }

                // The stopping condition is here because we may need a new
                // empty row at the end.
                if (fcit == end)
                        break;

                // Next element to consider is either the top of the temporary
                // pile, or the place when we were in main row
                Row::Element elt = *fcit;
                Row::Elements tail;
                elt.splitAt(width - rows.back().width(), next_width, Row::FIT, tail);
                Row & rb = rows.back();
                if (elt.type == Row::MARGINSPACE)
                        elt.dim.wid = max(elt.dim.wid, leftMargin(bigrow.pit()) - rb.width());
                rb.push_back(elt);
                rb.finalizeLast();
                if (rb.width() > width) {
                        // Keep the tail for later; this ought to be rare, but play safe.
                        if (!tail.empty())
                                fcit.put(tail);
                        // if the row is too large, try to cut at last separator.
                        tail = rb.shortenIfNeeded(width, next_width);
                }

                // Go to next element
                ++fcit;

                // Handle later the elements returned by splitAt or shortenIfNeeded.
                fcit.put(tail);
        }

        if (!rows.empty()) {
                // Last row in paragraph is flushed
                rows.back().flushed(true);
                cleanupRow(rows.back(), true);
                // Is there an end-of-paragraph change?
                if (bigrow.needsChangeBar())
                        rows.back().needsChangeBar(true);
        }

        return rows;
}


int TextMetrics::parTopSpacing(pit_type const pit) const
{
        Paragraph const & par = text_->getPar(pit);
        Layout const & layout = par.layout();

        int asc = 0;
        ParagraphList const & pars = text_->paragraphs();
        double const dh = defaultRowHeight();

        BufferParams const & bparams = bv_->buffer().params();
        Inset const & inset = text_->inset();
        // some parskips VERY EASY IMPLEMENTATION
        if (bparams.paragraph_separation == BufferParams::ParagraphSkipSeparation
                && !inset.getLayout().parbreakIsNewline()
                && !par.layout().parbreak_is_newline
                && pit > 0
                && ((layout.isParagraph() && par.getDepth() == 0)
                    || (pars[pit - 1].layout().isParagraph()
                        && pars[pit - 1].getDepth() == 0))) {
                asc += bparams.getDefSkip().inPixels(*bv_);
        }

        if (par.params().startOfAppendix())
                asc += int(3 * dh);

        // special code for the top label
        if (layout.labelIsAbove()
            && (!layout.isParagraphGroup() || text_->isFirstInSequence(pit))
            && !par.labelString().empty()) {
                FontInfo labelfont = text_->labelFont(par);
                FontMetrics const & lfm = theFontMetrics(labelfont);
                asc += int(lfm.maxHeight() * layout.spacing.getValue()
                                           * text_->spacing(par)
                           + (layout.topsep + layout.labelbottomsep) * dh);
        }

        // Add the layout spaces, for example before and after
        // a section, or between the items of a itemize or enumerate
        // environment.

        pit_type prev = text_->depthHook(pit, par.getDepth());
        Paragraph const & prevpar = pars[prev];
        double layoutasc = 0;
        if (prev != pit
            && prevpar.layout() == layout
            && prevpar.getDepth() == par.getDepth()
            && prevpar.getLabelWidthString() == par.getLabelWidthString()) {
                layoutasc = layout.itemsep * dh;
        } else if (pit != 0 && layout.topsep > 0)
                // combine the separation between different layouts (with same depth)
                layoutasc = max(0.0,
                        prevpar.getDepth() != par.getDepth() ? layout.topsep
                        : layout.topsep - prevpar.layout().bottomsep) * dh;

        asc += int(layoutasc * 2 / (2 + pars[pit].getDepth()));

        prev = text_->outerHook(pit);
        if (prev != pit_type(pars.size())) {
                asc += int(pars[prev].layout().parsep * dh);
        } else if (pit != 0) {
                Paragraph const & prevpar2 = pars[pit - 1];
                if (prevpar2.getDepth() != 0 || prevpar2.layout() == layout)
                        asc += int(layout.parsep * dh);
        }

        return asc;
}


int TextMetrics::parBottomSpacing(pit_type const pit) const
{
        double layoutdesc = 0;
        ParagraphList const & pars = text_->paragraphs();
        double const dh = defaultRowHeight();

        // add the layout spaces, for example before and after
        // a section, or between the items of a itemize or enumerate
        // environment
        pit_type nextpit = pit + 1;
        if (nextpit != pit_type(pars.size())) {
                pit_type cpit = pit;

                if (pars[cpit].getDepth() > pars[nextpit].getDepth()) {
                        double usual = pars[cpit].layout().bottomsep * dh;
                        double unusual = 0;
                        cpit = text_->depthHook(cpit, pars[nextpit].getDepth());
                        if (pars[cpit].layout() != pars[nextpit].layout()
                                || pars[nextpit].getLabelWidthString() != pars[cpit].getLabelWidthString())
                                unusual = pars[cpit].layout().bottomsep * dh;
                        layoutdesc = max(unusual, usual);
                } else if (pars[cpit].getDepth() == pars[nextpit].getDepth()) {
                        if (pars[cpit].layout() != pars[nextpit].layout()
                                || pars[nextpit].getLabelWidthString() != pars[cpit].getLabelWidthString())
                                layoutdesc = int(pars[cpit].layout().bottomsep * dh);
                }
        }

        return int(layoutdesc * 2 / (2 + pars[pit].getDepth()));
}


void TextMetrics::setRowHeight(Row & row) const
{
        Paragraph const & par = text_->getPar(row.pit());
        Layout const & layout = par.layout();
        // leading space (line spacing) factor based on current paragraph
        double spacing_val = layout.spacing.getValue() * text_->spacing(par);

        // if this is the first row but not the first paragraph, take into
        // account the spacing of the previous paragraph.
        if (row.pos() == 0 && row.pit() > 0) {
                // for the first row in the paragraph,
                // use previous paragraphs line spacing if it is larger
                Paragraph const & previousPar = text_->getPar(row.pit() - 1);
                Layout const & previousLayout = previousPar.layout();
                // leading space factor based on previous paragraph
                double const previous_spacing_val
                        = previousLayout.spacing.getValue() * text_->spacing(previousPar);
                if (previous_spacing_val > spacing_val)
                        spacing_val = previous_spacing_val;
        }

        // Initial value for ascent (useful if row is empty).
        Font const font = displayFont(row.pit(), row.pos());
        FontMetrics const & fm = theFontMetrics(font);
        int maxasc = int(fm.maxAscent()
                // add leading space
                + fm.maxHeight() * (spacing_val - 1));
        int maxdes = int(fm.maxDescent());

        // Take label string into account (useful if labelfont is large)
        if (row.pos() == 0 && layout.labelIsInline()) {
                FontInfo const labelfont = text_->labelFont(par);
                FontMetrics const & lfm = theFontMetrics(labelfont);
                maxasc = max(maxasc, int(lfm.maxAscent()
                        // add leading space
                        + lfm.maxHeight() * (spacing_val - 1)));
                maxdes = max(maxdes, int(lfm.maxDescent()));
        }

        // Find the ascent/descent of the row contents
        for (Row::Element const & e : row) {
                if (e.inset) {
                        maxasc = max(maxasc, e.dim.ascent());
                        maxdes = max(maxdes, e.dim.descent());
                } else {
                        FontMetrics const & fm2 = theFontMetrics(e.font);
                        maxasc = max(maxasc, int(fm2.maxAscent()
                                // add leading space
                                + fm2.maxHeight() * (spacing_val - 1)));
                        maxdes = max(maxdes, int(fm2.maxDescent()));
                }
        }

        // This is nicer with box insets
        ++maxasc;
        ++maxdes;

        row.dim().asc = maxasc;
        row.dim().des = maxdes;

        // This is useful for selections
        row.contents_dim() = row.dim();
}


// x is an absolute screen coord
// returns the column near the specified x-coordinate of the row
// x is set to the real beginning of this column
pos_type TextMetrics::getPosNearX(Row const & row, int & x,
                                  bool & boundary) const
{
        //LYXERR0("getPosNearX(" << x << ") row=" << row);
        /// For the main Text, it is possible that this pit is not
        /// yet in the CoordCache when moving cursor up.
        /// x Paragraph coordinate is always 0 for main text anyway.
        int const xo = origin_.x_;
        x -= xo;

        // Adapt to cursor row scroll offset if applicable.
        int const offset = bv_->horizScrollOffset(text_, row.pit(), row.pos());
        x += offset;

        pos_type pos = row.pos();
        boundary = false;
        if (row.empty())
                x = row.left_margin;
        else if (x <= row.left_margin) {
                pos = row.front().left_pos();
                x = row.left_margin;
        } else if (x >= row.width()) {
                pos = row.back().right_pos();
                x = row.width();
        } else {
                double w = row.left_margin;
                Row::const_iterator cit = row.begin();
                Row::const_iterator cend = row.end();
                for ( ; cit != cend; ++cit) {
                        if (w <= x &&  w + cit->full_width() > x) {
                                int x_offset = int(x - w);
                                pos = cit->x2pos(x_offset);
                                x = int(x_offset + w);
                                break;
                        }
                        w += cit->full_width();
                }
                if (cit == row.end()) {
                        pos = row.back().right_pos();
                        x = row.width();
                }
                /** This tests for the case where the cursor is placed
                 * just before a font direction change. See comment on
                 * the boundary_ member in DocIterator.h to understand
                 * how boundary helps here.
                 */
                else if (pos == cit->endpos
                         && ((!cit->isRTL() && cit + 1 != row.end()
                              && (cit + 1)->isRTL())
                             || (cit->isRTL() && cit != row.begin()
                                 && !(cit - 1)->isRTL())))
                        boundary = true;
        }

        /** This tests for the case where the cursor is set at the end
         * of a row which has been broken due something else than a
         * separator (a display inset or a forced breaking of the
         * row). We know that there is a separator when the end of the
         * row is larger than the end of its last element.
         */
        if (!row.empty() && pos == row.back().endpos
            && row.back().endpos == row.endpos()) {
                Inset const * inset = row.back().inset;
                if (inset && (inset->lyxCode() == NEWLINE_CODE
                              || inset->lyxCode() == SEPARATOR_CODE))
                        pos = row.back().pos;
                else
                        boundary = row.end_boundary();
        }

        x += xo - offset;
        //LYXERR0("getPosNearX ==> pos=" << pos << ", boundary=" << boundary);

        return pos;
}


pos_type TextMetrics::x2pos(pit_type pit, int row, int x) const
{
        // We play safe and use parMetrics(pit) to make sure the
        // ParagraphMetrics will be redone and OK to use if needed.
        // Otherwise we would use an empty ParagraphMetrics in
        // upDownInText() while in selection mode.
        ParagraphMetrics const & pm = parMetrics(pit);

        LBUFERR(row < int(pm.rows().size()));
        bool bound = false;
        Row const & r = pm.rows()[row];
        return getPosNearX(r, x, bound);
}


// y is screen coordinate
pit_type TextMetrics::getPitNearY(int y)
{
        LASSERT(!text_->paragraphs().empty(), return -1);
        LASSERT(!par_metrics_.empty(), return -1);
        LYXERR(Debug::PAINTING, "y: " << y << " cache size: " << par_metrics_.size());

        // look for highest numbered paragraph with y coordinate less than given y
        pit_type pit = -1;
        int yy = -1;
        ParMetricsCache::const_iterator it = par_metrics_.begin();
        ParMetricsCache::const_iterator et = par_metrics_.end();
        ParMetricsCache::const_iterator last = et;
        --last;

        ParagraphMetrics const & pm = it->second;

        if (y < it->second.position() - pm.ascent()) {
                // We are looking for a position that is before the first paragraph in
                // the cache (which is in priciple off-screen, that is before the
                // visible part.
                if (it->first == 0)
                        // We are already at the first paragraph in the inset.
                        return 0;
                // OK, this is the paragraph we are looking for.
                pit = it->first - 1;
                newParMetricsUp();
                return pit;
        }

        ParagraphMetrics const & pm_last = par_metrics_[last->first];

        if (y >= last->second.position() + pm_last.descent()) {
                // We are looking for a position that is after the last paragraph in
                // the cache (which is in priciple off-screen), that is before the
                // visible part.
                pit = last->first + 1;
                if (pit == int(text_->paragraphs().size()))
                        //  We are already at the last paragraph in the inset.
                        return last->first;
                // OK, this is the paragraph we are looking for.
                newParMetricsDown();
                return pit;
        }

        for (; it != et; ++it) {
                LYXERR(Debug::PAINTING, "examining: pit: " << it->first
                        << " y: " << it->second.position());

                ParagraphMetrics const & pm2 = par_metrics_[it->first];

                if (it->first >= pit && it->second.position() - pm2.ascent() <= y) {
                        pit = it->first;
                        yy = it->second.position();
                }
        }

        LYXERR(Debug::PAINTING, "found best y: " << yy << " for pit: " << pit);

        return pit;
}


Row const & TextMetrics::getPitAndRowNearY(int & y, pit_type & pit,
        bool assert_in_view, bool up)
{
        ParagraphMetrics const & pm = par_metrics_[pit];

        int yy = pm.position() - pm.ascent();
        LBUFERR(!pm.rows().empty());
        RowList::const_iterator rit = pm.rows().begin();
        RowList::const_iterator rlast = pm.rows().end();
        --rlast;
        for (; rit != rlast; yy += rit->height(), ++rit)
                if (yy + rit->height() > y)
                        break;

        if (assert_in_view) {
                if (!up && yy + rit->height() > y) {
                        if (rit != pm.rows().begin()) {
                                y = yy;
                                --rit;
                        } else if (pit != 0) {
                                --pit;
                                newParMetricsUp();
                                ParagraphMetrics const & pm2 = par_metrics_[pit];
                                rit = pm2.rows().end();
                                --rit;
                                y = yy;
                        }
                } else if (up && yy != y) {
                        if (rit != rlast) {
                                y = yy + rit->height();
                                ++rit;
                        } else if (pit < int(text_->paragraphs().size()) - 1) {
                                ++pit;
                                newParMetricsDown();
                                ParagraphMetrics const & pm2 = par_metrics_[pit];
                                rit = pm2.rows().begin();
                                y = pm2.position();
                        }
                }
        }
        return *rit;
}


// x,y are absolute screen coordinates
// sets cursor recursively descending into nested editable insets
Inset * TextMetrics::editXY(Cursor & cur, int x, int y,
        bool assert_in_view, bool up)
{
        if (lyxerr.debugging(Debug::WORKAREA)) {
                LYXERR0("TextMetrics::editXY(cur, " << x << ", " << y << ")");
                cur.bv().coordCache().dump();
        }
        pit_type pit = getPitNearY(y);
        LASSERT(pit != -1, return 0);
        Row const & row = getPitAndRowNearY(y, pit, assert_in_view, up);
        cur.pit() = pit;

        // Do we cover an inset?
        InsetList::Element * e = checkInsetHit(pit, x, y);

        if (!e) {
                // No inset, set position in the text
                bool bound = false; // is modified by getPosNearX
                cur.pos() = getPosNearX(row, x, bound);
                cur.boundary(bound);
                cur.setCurrentFont();
                cur.setTargetX(x);
                return 0;
        }

        Inset * inset = e->inset;
        //lyxerr << "inset " << inset << " hit at x: " << x << " y: " << y << endl;

        // Set position in front of inset
        cur.pos() = e->pos;
        cur.boundary(false);
        cur.setTargetX(x);

        // Try to descend recursively inside the inset.
        Inset * edited = inset->editXY(cur, x, y);
        // FIXME: it is not clear that the test on position is needed
        // Remove it if/when semantics of editXY is clarified
        if (cur.text() == text_ && cur.pos() == e->pos) {
                // non-editable inset, set cursor after the inset if x is
                // nearer to that position (bug 9628)
                bool bound = false; // is modified by getPosNearX
                cur.pos() = getPosNearX(row, x, bound);
                cur.boundary(bound);
                cur.setCurrentFont();
                cur.setTargetX(x);
        }

        if (cur.top().text() == text_)
                cur.setCurrentFont();
        return edited;
}


void TextMetrics::setCursorFromCoordinates(Cursor & cur, int const x, int const y)
{
        LASSERT(text_ == cur.text(), return);
        pit_type const pit = getPitNearY(y);
        LASSERT(pit != -1, return);

        ParagraphMetrics const & pm = par_metrics_[pit];

        int yy = pm.position() - pm.rows().front().ascent();
        LYXERR(Debug::PAINTING, "x: " << x << " y: " << y <<
                " pit: " << pit << " yy: " << yy);

        int r = 0;
        LBUFERR(pm.rows().size());
        for (; r < int(pm.rows().size()) - 1; ++r) {
                Row const & row = pm.rows()[r];
                if (yy + row.height() > y)
                        break;
                yy += row.height();
        }

        Row const & row = pm.rows()[r];

        LYXERR(Debug::PAINTING, "row " << r << " from pos: " << row.pos());

        bool bound = false;
        int xx = x;
        pos_type const pos = getPosNearX(row, xx, bound);

        LYXERR(Debug::PAINTING, "setting cursor pit: " << pit << " pos: " << pos);

        text_->setCursor(cur, pit, pos, true, bound);
        // remember new position.
        cur.setTargetX();
}


//takes screen x,y coordinates
InsetList::Element * TextMetrics::checkInsetHit(pit_type pit, int x, int y)
{
        Paragraph const & par = text_->paragraphs()[pit];
        CoordCache::Insets const & insetCache = bv_->coordCache().getInsets();

        LYXERR(Debug::PAINTING, "x: " << x << " y: " << y << "  pit: " << pit);

        for (InsetList::Element const & e : par.insetList()) {
                LYXERR(Debug::PAINTING, "examining inset " << e.inset);

                if (insetCache.covers(e.inset, x, y)) {
                        LYXERR(Debug::PAINTING, "Hit inset: " << e.inset);
                        return const_cast<InsetList::Element *>(&e);
                }
        }

        LYXERR(Debug::PAINTING, "No inset hit. ");
        return nullptr;
}


//takes screen x,y coordinates
Inset * TextMetrics::checkInsetHit(int x, int y)
{
        pit_type const pit = getPitNearY(y);
        LASSERT(pit != -1, return 0);
        InsetList::Element * e = checkInsetHit(pit, x, y);

        if (!e)
                return 0;

        return e->inset;
}


int TextMetrics::cursorX(CursorSlice const & sl,
                bool boundary) const
{
        LASSERT(sl.text() == text_, return 0);

        ParagraphMetrics const & pm = par_metrics_[sl.pit()];
        if (pm.rows().empty())
                return 0;
        Row const & row = pm.getRow(sl.pos(), boundary);
        pos_type const pos = sl.pos();

        double x = 0;
        row.findElement(pos, boundary, x);
        return int(x);

}


int TextMetrics::cursorY(CursorSlice const & sl, bool boundary) const
{
        //lyxerr << "TextMetrics::cursorY: boundary: " << boundary << endl;
        ParagraphMetrics const & pm = parMetrics(sl.pit());
        if (pm.rows().empty())
                return 0;

        int h = 0;
        h -= parMetrics(0).rows()[0].ascent();
        for (pit_type pit = 0; pit < sl.pit(); ++pit) {
                h += parMetrics(pit).height();
        }
        int pos = sl.pos();
        if (pos && boundary)
                --pos;
        size_t const rend = pm.pos2row(pos);
        for (size_t rit = 0; rit != rend; ++rit)
                h += pm.rows()[rit].height();
        h += pm.rows()[rend].ascent();
        return h;
}


// the cursor set functions have a special mechanism. When they
// realize you left an empty paragraph, they will delete it.

bool TextMetrics::cursorHome(Cursor & cur)
{
        LASSERT(text_ == cur.text(), return false);
        ParagraphMetrics const & pm = par_metrics_[cur.pit()];
        Row const & row = pm.getRow(cur.pos(),cur.boundary());
        return text_->setCursor(cur, cur.pit(), row.pos());
}


bool TextMetrics::cursorEnd(Cursor & cur)
{
        LASSERT(text_ == cur.text(), return false);
        // if not on the last row of the par, put the cursor before
        // the final space exept if I have a spanning inset or one string
        // is so long that we force a break.
        pos_type end = cur.textRow().endpos();
        if (end == 0)
                // empty text, end-1 is no valid position
                return false;
        bool boundary = false;
        if (end != cur.lastpos()) {
                if (!cur.paragraph().isLineSeparator(end-1)
                    && !cur.paragraph().isNewline(end-1)
                    && !cur.paragraph().isEnvSeparator(end-1))
                        boundary = true;
                else
                        --end;
        } else if (cur.paragraph().isEnvSeparator(end-1))
                --end;
        return text_->setCursor(cur, cur.pit(), end, true, boundary);
}


void TextMetrics::deleteLineForward(Cursor & cur)
{
        LASSERT(text_ == cur.text(), return);
        if (cur.lastpos() == 0) {
                // Paragraph is empty, so we just go forward
                text_->cursorForward(cur);
        } else {
                cur.resetAnchor();
                cur.selection(true); // to avoid deletion
                cursorEnd(cur);
                cur.setSelection();
                // What is this test for ??? (JMarc)
                if (!cur.selection())
                        text_->deleteWordForward(cur);
                else
                        cap::cutSelection(cur, false);
                cur.checkBufferStructure();
        }
}


int TextMetrics::leftMargin(pit_type pit) const
{
        // FIXME: what is the semantics? It depends on whether the
        // paragraph is empty!
        return leftMargin(pit, text_->paragraphs()[pit].size());
}


int TextMetrics::leftMargin(pit_type const pit, pos_type const pos) const
{
        ParagraphList const & pars = text_->paragraphs();

        LASSERT(pit >= 0, return 0);
        LASSERT(pit < int(pars.size()), return 0);
        Paragraph const & par = pars[pit];
        LASSERT(pos >= 0, return 0);
        // We do not really care whether pos > par.size(), since we do not
        // access the data. It can be actually useful, when querying the
        // margin without indentation (see leftMargin(pit_type).

        Buffer const & buffer = bv_->buffer();
        //lyxerr << "TextMetrics::leftMargin: pit: " << pit << " pos: " << pos << endl;
        DocumentClass const & tclass = buffer.params().documentClass();
        Layout const & layout = par.layout();
        FontMetrics const & bfm = theFontMetrics(buffer.params().getFont());

        docstring parindent = layout.parindent;

        int l_margin = 0;

        if (text_->isMainText()) {
                l_margin += bv_->leftMargin();
                l_margin += bfm.signedWidth(tclass.leftmargin());
        }

        int depth = par.getDepth();
        if (depth != 0) {
                // find the next level paragraph
                pit_type newpar = text_->outerHook(pit);
                if (newpar != pit_type(pars.size())) {
                        if (pars[newpar].layout().isEnvironment()) {
                                int nestmargin = depth * nestMargin();
                                if (text_->isMainText())
                                        nestmargin += changebarMargin();
                                l_margin = max(leftMargin(newpar), nestmargin);
                                // Remove the parindent that has been added
                                // if the paragraph was empty.
                                if (pars[newpar].empty() &&
                                    buffer.params().paragraph_separation ==
                                    BufferParams::ParagraphIndentSeparation) {
                                        docstring pi = pars[newpar].layout().parindent;
                                        l_margin -= bfm.signedWidth(pi);
                                }
                        }
                        if (tclass.isDefaultLayout(par.layout())
                            || tclass.isPlainLayout(par.layout())) {
                                if (pars[newpar].params().noindent())
                                        parindent.erase();
                                else
                                        parindent = pars[newpar].layout().parindent;
                        }
                }
        }

        // Check for reasons to remove indentation.
        // First, at document level.
        if (buffer.params().paragraph_separation ==
                        BufferParams::ParagraphSkipSeparation)
                parindent.erase();
        // This happens after sections or environments in standard classes.
        // We have to check the previous layout at same depth.
        else if (pit > 0 && pars[pit - 1].getDepth() >= par.getDepth()) {
                pit_type prev = text_->depthHook(pit, par.getDepth());
                if (par.layout() == pars[prev].layout()) {
                        if (prev != pit - 1
                            && pars[pit - 1].layout().nextnoindent)
                                parindent.erase();
                } else if (pars[prev].layout().nextnoindent)
                        parindent.erase();
        }
        // The previous paragraph may have ended with a separator inset.
        if (pit > 0) {
                Paragraph const & ppar = pars[pit - 1];
                if (ppar.size() > 0) {
                        auto * in = dynamic_cast<InsetSeparator const *>(ppar.getInset(ppar.size() - 1));
                        if (in != nullptr && in->nextnoindent())
                                parindent.erase();
                }
        }

        FontInfo const labelfont = text_->labelFont(par);
        FontMetrics const & lfm = theFontMetrics(labelfont);

        switch (layout.margintype) {
        case MARGIN_DYNAMIC:
                if (!layout.leftmargin.empty()) {
                        l_margin += bfm.signedWidth(layout.leftmargin);
                }
                if (!par.labelString().empty()) {
                        l_margin += lfm.signedWidth(layout.labelindent);
                        l_margin += lfm.width(par.labelString());
                        l_margin += lfm.width(layout.labelsep);
                }
                break;

        case MARGIN_MANUAL: {
                l_margin += lfm.signedWidth(layout.labelindent);
                // The width of an empty par, even with manual label, should be 0
                if (!par.empty() && pos >= par.beginOfBody()) {
                        if (!par.getLabelWidthString().empty()) {
                                docstring labstr = par.getLabelWidthString();
                                l_margin += lfm.width(labstr);
                                l_margin += lfm.width(layout.labelsep);
                        }
                }
                break;
        }

        case MARGIN_STATIC: {
                l_margin += bfm.signedWidth(layout.leftmargin) * 4
                             / (par.getDepth() + 4);
                break;
        }

        case MARGIN_FIRST_DYNAMIC:
                if (layout.labeltype == LABEL_MANUAL) {
                        // if we are at position 0, we are never in the body
                        if (pos > 0 && pos >= par.beginOfBody())
                                l_margin += lfm.signedWidth(layout.leftmargin);
                        else
                                l_margin += lfm.signedWidth(layout.labelindent);
                } else if (pos != 0
                           // Special case to fix problems with
                           // theorems (JMarc)
                           || (layout.labeltype == LABEL_STATIC
                               && layout.latextype == LATEX_ENVIRONMENT
                               && !text_->isFirstInSequence(pit))) {
                        l_margin += lfm.signedWidth(layout.leftmargin);
                } else if (!layout.labelIsAbove()) {
                        l_margin += lfm.signedWidth(layout.labelindent);
                        l_margin += lfm.width(layout.labelsep);
                        l_margin += lfm.width(par.labelString());
                }
                break;

        case MARGIN_RIGHT_ADDRESS_BOX:
                // This is handled globally in redoParagraph().
                break;
        }

        if (!par.params().leftIndent().zero())
                l_margin += par.params().leftIndent().inPixels(max_width_, lfm.em());

        LyXAlignment align = par.getAlign(bv_->buffer().params());

        // set the correct parindent
        if (pos == 0
            && (layout.labeltype == LABEL_NO_LABEL
                || layout.labeltype == LABEL_ABOVE
                || layout.labeltype == LABEL_CENTERED
                || (layout.labeltype == LABEL_STATIC
                    && layout.latextype == LATEX_ENVIRONMENT
                    && !text_->isFirstInSequence(pit)))
            && (align == LYX_ALIGN_BLOCK || align == LYX_ALIGN_LEFT)
            && !par.params().noindent()
            // in some insets, paragraphs are never indented
            && !text_->inset().neverIndent()
            // display style insets do not need indentation
            && !(!par.empty()
                 && par.isInset(0)
                 && par.getInset(0)->rowFlags() & Display)
            && (!(tclass.isDefaultLayout(par.layout())
                || tclass.isPlainLayout(par.layout()))
                || buffer.params().paragraph_separation
                                == BufferParams::ParagraphIndentSeparation)) {
                /* use the parindent of the layout when the default
                 * indentation is used otherwise use the indentation set in
                 * the document settings
                 */
                if (buffer.params().getParIndent().empty())
                        l_margin += bfm.signedWidth(parindent);
                else
                        l_margin += buffer.params().getParIndent().inPixels(max_width_, bfm.em());
        }

        return l_margin;
}


void TextMetrics::draw(PainterInfo & pi, int x, int y) const
{
        if (par_metrics_.empty())
                return;

        origin_.x_ = x;
        origin_.y_ = y;

        y -= par_metrics_.begin()->second.ascent();
        for (auto & pm_pair : par_metrics_) {
                pit_type const pit = pm_pair.first;
                ParagraphMetrics & pm = pm_pair.second;
                y += pm.ascent();
                // Save the paragraph position in the cache.
                pm.setPosition(y);
                drawParagraph(pi, pit, x, y);
                y += pm.descent();
        }
}


void TextMetrics::drawParagraph(PainterInfo & pi, pit_type const pit, int const x, int y) const
{
        ParagraphMetrics const & pm = par_metrics_[pit];
        if (pm.rows().empty())
                return;
        size_t const nrows = pm.rows().size();
        // Remember left and right margin for drawing math numbers
        Changer changeleft = changeVar(pi.leftx, x + leftMargin(pit));
        Changer changeright = changeVar(pi.rightx, x + width() - rightMargin(pit));

        // Use fast lane in nodraw stage.
        if (pi.pain.isNull()) {
                for (size_t i = 0; i != nrows; ++i) {

                        Row const & row = pm.rows()[i];
                        // Adapt to cursor row scroll offset if applicable.
                        int row_x = x - bv_->horizScrollOffset(text_, pit, row.pos());
                        if (i)
                                y += row.ascent();

                        RowPainter rp(pi, *text_, row, row_x, y);

                        rp.paintOnlyInsets();
                        y += row.descent();
                }
                return;
        }

        int const ww = bv_->workHeight();
        Cursor const & cur = bv_->cursor();
        DocIterator sel_beg = cur.selectionBegin();
        DocIterator sel_end = cur.selectionEnd();
        bool selection = cur.selection()
                // This is our text.
                && cur.text() == text_
                // if the anchor is outside, this is not our selection
                && cur.normalAnchor().text() == text_
                && pit >= sel_beg.pit() && pit <= sel_end.pit();

        // We store the begin and end pos of the selection relative to this par
        DocIterator sel_beg_par = cur.selectionBegin();
        DocIterator sel_end_par = cur.selectionEnd();

        // We care only about visible selection.
        if (selection) {
                if (pit != sel_beg.pit()) {
                        sel_beg_par.pit() = pit;
                        sel_beg_par.pos() = 0;
                }
                if (pit != sel_end.pit()) {
                        sel_end_par.pit() = pit;
                        sel_end_par.pos() = sel_end_par.lastpos();
                }
        }

        if (text_->isRTL(pit))
                swap(pi.leftx, pi.rightx);

        BookmarksSection::BookmarkPosList bpl =
                theSession().bookmarks().bookmarksInPar(bv_->buffer().fileName(), pm.id());

        for (size_t i = 0; i != nrows; ++i) {

                Row const & row = pm.rows()[i];
                // Adapt to cursor row scroll offset if applicable.
                int row_x = x - bv_->horizScrollOffset(text_, pit, row.pos());
                if (i)
                        y += row.ascent();

                // It is not needed to draw on screen if we are not inside.
                bool const inside = (y + row.descent() >= 0
                        && y - row.ascent() < ww);
                if (!inside) {
                        // Inset positions have already been set in nodraw stage.
                        y += row.descent();
                        continue;
                }

                if (selection)
                        row.setSelectionAndMargins(sel_beg_par, sel_end_par);
                else
                        row.clearSelectionAndMargins();

                // The row knows nothing about the paragraph, so we have to check
                // whether this row is the first or last and update the margins.
                if (row.selection()) {
                        if (row.sel_beg == 0)
                                row.change(row.begin_margin_sel, sel_beg.pit() < pit);
                        if (row.sel_end == sel_end_par.lastpos())
                                row.change(row.end_margin_sel, sel_end.pit() > pit);
                }

                // Take this opportunity to spellcheck the row contents.
                if (row.changed() && pi.do_spellcheck && lyxrc.spellcheck_continuously) {
                        text_->getPar(pit).spellCheck();
                }

                RowPainter rp(pi, *text_, row, row_x, y);

                // Don't paint the row if a full repaint has not been requested
                // and if it has not changed.
                if (!pi.full_repaint && !row.changed()) {
                        // Paint only the insets if the text itself is
                        // unchanged.
                        rp.paintOnlyInsets();
                        rp.paintTooLargeMarks(
                                row_x + row.left_x() < bv_->leftMargin(),
                                row_x + row.right_x() > bv_->workWidth() - bv_->rightMargin());
                        row.changed(false);
                        y += row.descent();
                        continue;
                }

                // Clear background of this row if paragraph background was not
                // already cleared because of a full repaint.
                if (!pi.full_repaint && row.changed()) {
                        LYXERR(Debug::PAINTING, "Clear rect@("
                               << x << ", " << y - row.ascent() << ")="
                               << width() << " x " << row.height());
                        pi.pain.fillRectangle(x, y - row.ascent(),
                                              width(), row.height(), pi.background_color);
                }

                // Instrumentation for testing row cache (see also
                // 12 lines lower):
                if (lyxerr.debugging(Debug::PAINTING)
                    && (row.selection() || pi.full_repaint || row.changed())) {
                        string const foreword = text_->isMainText() ? "main text redraw "
                                : "inset text redraw: ";
                        LYXERR0(foreword << "pit=" << pit << " row=" << i
                                << (row.selection() ? " row_selection": "")
                                << (pi.full_repaint ? " full_repaint" : "")
                                << (row.changed() ? " row.changed" : ""));
                }

                // Backup full_repaint status and force full repaint
                // for inner insets as the Row has been cleared out.
                bool tmp = pi.full_repaint;
                pi.full_repaint = true;

                rp.paintSelection();
                rp.paintAppendix();
                rp.paintDepthBar();
                if (row.needsChangeBar())
                        rp.paintChangeBar();
                if (i == 0)
                        rp.paintFirst();
                if (i == nrows - 1)
                        rp.paintLast();
                rp.paintText();
                rp.paintTooLargeMarks(
                        row_x + row.left_x() < bv_->leftMargin(),
                        row_x + row.right_x() > bv_->workWidth() - bv_->rightMargin());
                // indicate bookmarks presence in margin
                if (lyxrc.bookmarks_visibility == LyXRC::BMK_MARGIN)
                        for (auto const & bp_p : bpl)
                                if (bp_p.second >= row.pos() && bp_p.second < row.endpos())
                                        rp.paintBookmark(bp_p.first);

                y += row.descent();

#if 0
                // This debug code shows on screen which rows are repainted.
                // FIXME: since the updates related to caret blinking restrict
                // the painter to a small rectangle, the numbers are not
                // updated when this happens. Change the code in
                // GuiWorkArea::Private::show/hideCaret if this is important.
                static int count = 0;
                ++count;
                FontInfo fi(sane_font);
                fi.setSize(TINY_SIZE);
                fi.setColor(Color_red);
                pi.pain.text(row_x, y, convert<docstring>(count), fi);
#endif

                // Restore full_repaint status.
                pi.full_repaint = tmp;

                row.changed(false);
        }

        //LYXERR(Debug::PAINTING, ".");
}


void TextMetrics::completionPosAndDim(Cursor const & cur, int & x, int & y,
        Dimension & dim) const
{
        DocIterator from = cur.bv().cursor();
        DocIterator to = from;
        text_->getWord(from.top(), to.top(), PREVIOUS_WORD);

        // The vertical dimension of the word
        Font const font = displayFont(cur.pit(), from.pos());
        FontMetrics const & fm = theFontMetrics(font);
        // the +1's below are related to the extra pixels added in setRowHeight
        dim.asc = fm.maxAscent() + 1;
        dim.des = fm.maxDescent() + 1;

        // get position on screen of the word start and end
        //FIXME: Is it necessary to explicitly set this to false?
        from.boundary(false);
        Point lxy = cur.bv().getPos(from);
        Point rxy = cur.bv().getPos(to);
        dim.wid = abs(rxy.x_ - lxy.x_);

        // calculate position of word
        y = lxy.y_;
        x = min(rxy.x_, lxy.x_);

        //lyxerr << "wid=" << dim.width() << " x=" << x << " y=" << y << " lxy.x_=" << lxy.x_ << " rxy.x_=" << rxy.x_ << " word=" << word << std::endl;
        //lyxerr << " wordstart=" << wordStart << " bvcur=" << bvcur << " cur=" << cur << std::endl;
}

int defaultRowHeight()
{
        return int(theFontMetrics(sane_font).maxHeight() *  1.2);
}

} // namespace lyx