Implement display of roots more faithfully

This is a follow-up to 758de957.

- unify the metrics and drawing of \sqrt and \root using helper
  functions mathed_root_metrics and mathed_draw_root.

- compute the vertical spacing above the nucleus of the root following
  rule 11 of the TeXbook. In particular, it is different in inline and
  display style.

- draw the root glyph without hard-coded pixel values. Make the line
  width depend on the zoom.

more work is needed to implement properly rule 11:

- Ideally, we should use sqrt glyphs from the math fonts. Note that
  then we would get rule thickness from there.

- The positioning of the root MathData is arbitrary. It should
  follow the definition of \root...\of... in The Texbook in
  Apprendix B page 360.

Fixes bug #10814.

diff --git a/src/mathed/InsetMathRoot.cpp b/src/mathed/InsetMathRoot.cpp
index 8b86c5965ba3ab6ce02fe5737a4209671dce2f32..8650cb712d1c7a08a0685fc130f3b71b8048bbf8 100644 (file)
--- a/src/mathed/InsetMathRoot.cpp
+++ b/src/mathed/InsetMathRoot.cpp
@@ -13,7 +13,6 @@
 
 #include "InsetMathRoot.h"
 
-#include "MathData.h"
 #include "MathStream.h"
 #include "MathSupport.h"
 
@@ -28,6 +27,7 @@ using namespace std;
 
 namespace lyx {
 
+using namespace frontend;
 
 InsetMathRoot::InsetMathRoot(Buffer * buf)
        : InsetMathNest(buf, 2)
@@ -40,56 +40,101 @@ Inset * InsetMathRoot::clone() const
 }
 
 
-void InsetMathRoot::metrics(MetricsInfo & mi, Dimension & dim) const
+void mathed_root_metrics(MetricsInfo & mi, MathData const & nucleus,
+                         MathData const * root, Dimension & dim)
 {
        Changer dummy = mi.base.changeEnsureMath();
-       Dimension dim0;
-       {
+       Dimension dimr;
+       if (root) {
                Changer script = mi.base.font.changeStyle(LM_ST_SCRIPTSCRIPT);
-               cell(0).metrics(mi, dim0);
+               root->metrics(mi, dimr);
                // make sure that the dim is high enough for any character
                Dimension fontDim;
                math_font_max_dim(mi.base.font, fontDim.asc, fontDim.des);
-               dim0 += fontDim;
+               dimr += fontDim;
        }
 
-       Dimension dim1;
-       cell(1).metrics(mi, dim1);
+       Dimension dimn;
+       nucleus.metrics(mi, dimn);
        // make sure that the dim is high enough for any character
-       Dimension fontDim;
-       math_font_max_dim(mi.base.font, fontDim.asc, fontDim.des);
-       dim1 += fontDim;
+       // Dimension fontDim;
+       // math_font_max_dim(mi.base.font, fontDim.asc, fontDim.des);
+       // dimn += fontDim;
+
+       // Some room for the decoration
+       // The width of left decoration was 9 pixels with a 10em font
+       int const w = 9 * mathed_font_em(mi.base.font) / 10;
+       /* See rule 11 in Appendix G of Rhe TeXbook for the computation of the spacing
+        * above nucleus.
+        * FIXME more work is needed to implement properly rule 11.
+        * * Ideally, we should use sqrt glyphs from the math fonts. Note
+         that then we would get rule thickness from there.
+        * * The positioning of the root MathData is arbitrary. It should
+     *   follow the definition of \root...\of... in The Texbook in
+     *   Apprendix B page 360.
+        *
+        */
+       int const t = mi.base.solidLineThickness();
+       int const x_height = mathed_font_x_height(mi.base.font);
+       int const phi = (mi.base.font.style() == LM_ST_DISPLAY) ? x_height : t;
+       // first part is the spacing, second part is the line width
+       // itself, and last one is the spacing above.
+       int const space_above = (t + phi / 4) + t + t;
+       int const a = dimn.ascent();
+       int const d = dimn.descent();
+       // Not sure what the 1 stands for, it is needed to have some spacing at small sizes.
+       dim.asc = max(dimr.ascent() + (d - a) / 2, a + space_above) + 1;
+       dim.des = max(dimr.descent() - (d - a) / 2, d);
+       dim.wid = max(dimr.width() + 3 * w / 8, w) + dimn.width();
+}
+
 
-       dim.asc = max(dim0.ascent()  + 5, dim1.ascent()) + 1;
-       dim.des = max(dim0.descent() - 5, dim1.descent());
-       dim.wid = dim0.width() + dim1.width() + 4;
+void InsetMathRoot::metrics(MetricsInfo & mi, Dimension & dim) const
+{
+       mathed_root_metrics(mi, cell(1), &cell(0), dim);
 }
 
 
-void InsetMathRoot::draw(PainterInfo & pi, int x, int y) const
+void mathed_draw_root(PainterInfo & pi, int x, int y, MathData const & nucleus,
+                      MathData const * root, Dimension const & dim)
 {
        Changer dummy = pi.base.changeEnsureMath();
-       Dimension const dim = dimension(*pi.base.bv);
+       // The width of left decoration was 9 pixels with a 10em font
+       int const w = 9 * mathed_font_em(pi.base.font) / 10;
+       // the height of the hook was 5 with a 10em font
+       int const h = 5 * mathed_font_em(pi.base.font) / 10;
        int const a = dim.ascent();
        int const d = dim.descent();
-       Dimension const & dim0 = cell(0).dimension(*pi.base.bv);
-       int const w = dim0.width();
+       int const t = pi.base.solidLineThickness();
+       Dimension const dimn = nucleus.dimension(*pi.base.bv);
+       // the width of the left part of the root
+       int const wl = dim.width() - dimn.width();
        // the "exponent"
-       {
+       if (root) {
                Changer script = pi.base.font.changeStyle(LM_ST_SCRIPTSCRIPT);
-               cell(0).draw(pi, x, y + (d - a)/2 - dim0.descent());
+               Dimension const dimr = root->dimension(*pi.base.bv);
+               int const root_offset = wl - 3 * w / 8 - dimr.width();
+               root->draw(pi, x + root_offset, y + (d - a)/2);
        }
        // the "base"
-       cell(1).draw(pi, x + w + 4, y);
+       nucleus.draw(pi, x + wl, y);
        int xp[4];
        int yp[4];
-       pi.pain.line(x + dim.width(), y - a + 1,
-                               x + w + 4, y - a + 1, pi.base.font.color());
-       xp[0] = x + w + 4;         yp[0] = y - a + 1;
-       xp[1] = x + w;             yp[1] = y + d;
-       xp[2] = x + w - 2;         yp[2] = y + (d - a)/2 + 2;
-       xp[3] = x + w - 5;         yp[3] = y + (d - a)/2 + 4;
-       pi.pain.lines(xp, yp, 4, pi.base.font.color());
+       pi.pain.line(x + dim.width(), y - a + 2 * t,
+                    x + wl, y - a + 2 * t, pi.base.font.color(),
+                    Painter::line_solid, t);
+       xp[0] = x + wl;              yp[0] = y - a + 2 * t;
+       xp[1] = x + wl - w / 2;      yp[1] = y + d;
+       xp[2] = x + wl - w + h / 4;  yp[2] = y + d - h;
+       xp[3] = x + wl - w;          yp[3] = y + d - h + h / 4;
+       pi.pain.lines(xp, yp, 4, pi.base.font.color(),
+                     Painter::fill_none, Painter::line_solid, t);
+}
+
+
+void InsetMathRoot::draw(PainterInfo & pi, int x, int y) const
+{
+       mathed_draw_root(pi, x, y, cell(1), &cell(0), dimension(*pi.base.bv));
 }
 
 

diff --git a/src/mathed/InsetMathRoot.h b/src/mathed/InsetMathRoot.h
index 18bacbbf18888bc825da8c080217ea50c9d50733..923e9a5f61f9b4b3d709e8e26fa6b789ab8c41a4 100644 (file)
--- a/src/mathed/InsetMathRoot.h
+++ b/src/mathed/InsetMathRoot.h
@@ -54,6 +54,11 @@ private:
        virtual Inset * clone() const;
 };
 
+void mathed_root_metrics(MetricsInfo & mi, MathData const & nucleus,
+                         MathData const * root, Dimension & dim);
+
+void mathed_draw_root(PainterInfo & pi, int x, int y, MathData const & nucleus,
+                      MathData const * root, Dimension const & dim);
 
 
 } // namespace lyx

diff --git a/src/mathed/InsetMathSqrt.cpp b/src/mathed/InsetMathSqrt.cpp
index a7385cc708ccd9b30443c7b03e1554935d931e6f..7416c332f17593a6af750a8c903af1588ee03545 100644 (file)
--- a/src/mathed/InsetMathSqrt.cpp
+++ b/src/mathed/InsetMathSqrt.cpp
@@ -12,6 +12,7 @@
 
 #include "InsetMathSqrt.h"
 
+#include "InsetMathRoot.h"
 #include "MathData.h"
 #include "MathStream.h"
 #include "MathSupport.h"
@@ -38,33 +39,13 @@ Inset * InsetMathSqrt::clone() const
 
 void InsetMathSqrt::metrics(MetricsInfo & mi, Dimension & dim) const
 {
-       Changer dummy = mi.base.changeEnsureMath();
-       cell(0).metrics(mi, dim);
-       // make sure that the dim is high enough for any character
-       Dimension fontDim;
-       math_font_max_dim(mi.base.font, fontDim.asc, fontDim.des);
-       dim += fontDim;
-       // Some room for the decoration
-       dim.asc += 1;
-       dim.wid += 7;
+       mathed_root_metrics(mi, cell(0), nullptr, dim);
 }
 
 
 void InsetMathSqrt::draw(PainterInfo & pi, int x, int y) const
 {
-       Changer dummy = pi.base.changeEnsureMath();
-       cell(0).draw(pi, x + 9, y);
-       Dimension const dim = dimension(*pi.base.bv);
-       int const a = dim.ascent();
-       int const d = dim.descent();
-       int xp[3];
-       int yp[3];
-       pi.pain.line(x + dim.width(), y - a + 1,
-               x + 7, y - a + 1, pi.base.font.color());
-       xp[0] = x + 7;            yp[0] = y - a + 1;
-       xp[1] = x + 4;            yp[1] = y + d - 1;
-       xp[2] = x;                yp[2] = y + (d - a)/2;
-       pi.pain.lines(xp, yp, 3, pi.base.font.color());
+       mathed_draw_root(pi, x, y, cell(0), nullptr, dimension(*pi.base.bv));
 }
 
 

diff --git a/src/mathed/MathSupport.cpp b/src/mathed/MathSupport.cpp
index bb6a21c74d74ce9e302b18c5982a51f1cadfc63b..57eca6ee31ff8bea6a466b7b5a48f262c20e1545 100644 (file)
--- a/src/mathed/MathSupport.cpp
+++ b/src/mathed/MathSupport.cpp
@@ -513,6 +513,12 @@ int mathed_font_em(FontInfo const & font)
        return theFontMetrics(font).em();
 }
 
+
+int mathed_font_x_height(FontInfo const & font)
+{
+       return theFontMetrics(font).ascent('x');
+}
+
 /* The math units. Quoting TeX by Topic, p.205:
  *
  * Spacing around mathematical objects is measured in mu units. A mu

diff --git a/src/mathed/MathSupport.h b/src/mathed/MathSupport.h
index 3e5f67d5cff38942fe5163db1951a5eeb0b2ba60..d9301453dde5bb9c2cb5330c6430f9089e96c213 100644 (file)
--- a/src/mathed/MathSupport.h
+++ b/src/mathed/MathSupport.h
@@ -32,6 +32,8 @@ class LaTeXFeatures;
 
 int mathed_font_em(FontInfo const &);
 
+int mathed_font_x_height(FontInfo const & font);
+
 int mathed_mu(FontInfo const & font, double mu);
 
 int mathed_thinmuskip(FontInfo const & font);