From 4e981b034eba8b04534931e570a8f64b7396ad7d Mon Sep 17 00:00:00 2001
From: Jean-Marc Lasgouttes <lasgouttes@lyx.org>
Date: Fri, 27 Apr 2018 00:03:48 +0200
Subject: [PATCH] Adapt caret height to context in mathed.

Compute a height from current font and current cell vertical
dimensions in MathData::metrics(), because this is where current font
is known.

Introduce BufferView::setCaretAscentDescent to remember this value.

This mechanism is not used for text because Cursor::current_font is
restored by undo, and the caret height would not be changed then. But
in principle it is doable.

(cherry picked from commit 90cfe4ec3b4ff22ef798a63e98ca70d0d33a1656)
---
 src/BufferView.cpp      | 33 +++++++++++++++++++++++++++------
 src/BufferView.h        |  2 ++
 src/mathed/MathData.cpp | 14 +++++++++++---
 status.23x              |  4 ++++
 4 files changed, 44 insertions(+), 9 deletions(-)

diff --git a/src/BufferView.cpp b/src/BufferView.cpp
index 2101ede702..da09fcd273 100644
--- a/src/BufferView.cpp
+++ b/src/BufferView.cpp
@@ -229,7 +229,8 @@ enum ScreenUpdateStrategy {
 
 struct BufferView::Private
 {
-	Private(BufferView & bv) : update_strategy_(FullScreenUpdate),
+	Private(BufferView & bv) :
+		update_strategy_(FullScreenUpdate),
 		update_flags_(Update::Force),
 		wh_(0), cursor_(bv),
 		anchor_pit_(0), anchor_ypos_(0),
@@ -237,7 +238,8 @@ struct BufferView::Private
 		last_inset_(0), clickable_inset_(false),
 		mouse_position_cache_(),
 		bookmark_edit_position_(-1), gui_(0),
-		horiz_scroll_offset_(0)
+		horiz_scroll_offset_(0),
+		caret_ascent_(0), caret_descent_(0)
 	{
 		xsel_cache_.set = false;
 	}
@@ -316,6 +318,12 @@ struct BufferView::Private
 	/// a slice pointing to the start of the row where cursor was
 	/// at previous draw event
 	CursorSlice last_row_slice_;
+
+	// The vertical size of the blinking caret. Only used for math
+	// Using it for text could be bad when undo restores the cursor
+	// current font, since the caret size could become wrong.
+	int caret_ascent_;
+	int caret_descent_;
 };
 
 
@@ -2984,13 +2992,26 @@ bool BufferView::paragraphVisible(DocIterator const & dit) const
 }
 
 
+void BufferView::setCaretAscentDescent(int asc, int des)
+{
+	d->caret_ascent_ = asc;
+	d->caret_descent_ = des;
+}
+
+
 void BufferView::caretPosAndHeight(Point & p, int & h) const
 {
+	int asc, des;
 	Cursor const & cur = cursor();
-	Font const font = cur.real_current_font;
-	frontend::FontMetrics const & fm = theFontMetrics(font);
-	int const asc = fm.maxAscent();
-	int const des = fm.maxDescent();
+	if (cur.inMathed()) {
+		asc = d->caret_ascent_;
+		des = d->caret_descent_;
+	} else {
+		Font const font = cur.real_current_font;
+		frontend::FontMetrics const & fm = theFontMetrics(font);
+		asc = fm.maxAscent();
+		des = fm.maxDescent();
+	}
 	h = asc + des;
 	p = getPos(cur);
 	p.y_ -= asc;
diff --git a/src/BufferView.h b/src/BufferView.h
index 733e66f926..1089781ffd 100644
--- a/src/BufferView.h
+++ b/src/BufferView.h
@@ -305,6 +305,8 @@ public:
 	bool paragraphVisible(DocIterator const & dit) const;
 	/// is the cursor currently visible in the view
 	bool cursorInView(Point const & p, int h) const;
+	/// set the ascent and descent of the caret
+	void setCaretAscentDescent(int asc, int des);
 	/// get the position and height of the caret
 	void caretPosAndHeight(Point & p, int & h) const;
 
diff --git a/src/mathed/MathData.cpp b/src/mathed/MathData.cpp
index a4a960a7d2..059b8b56b7 100644
--- a/src/mathed/MathData.cpp
+++ b/src/mathed/MathData.cpp
@@ -267,6 +267,7 @@ bool isInside(DocIterator const & it, MathData const & ar,
 void MathData::metrics(MetricsInfo & mi, Dimension & dim, bool tight) const
 {
 	frontend::FontMetrics const & fm = theFontMetrics(mi.base.font);
+	BufferView * bv = mi.base.bv;
 	int const Iascent = fm.dimension('I').ascent();
 	int xascent = fm.dimension('x').ascent();
 	if (xascent >= Iascent)
@@ -278,8 +279,8 @@ void MathData::metrics(MetricsInfo & mi, Dimension & dim, bool tight) const
 
 	MathRow mrow(mi, this);
 	mrow.metrics(mi, dim);
-	mrow_cache_[mi.base.bv] = mrow;
-	kerning_ = mrow.kerning(mi.base.bv);
+	mrow_cache_[bv] = mrow;
+	kerning_ = mrow.kerning(bv);
 
 	// Set a minimal ascent/descent for the cell
 	if (tight)
@@ -291,8 +292,15 @@ void MathData::metrics(MetricsInfo & mi, Dimension & dim, bool tight) const
 		dim.des = max(dim.des, fm.maxDescent());
 	}
 
+	// This is one of the the few points where the drawing font is known,
+	// so that we can set the caret vertical dimensions.
+	Cursor & cur = bv->cursor();
+	if (cur.inMathed() && &cur.cell() == this)
+		bv->setCaretAscentDescent(min(dim.asc, fm.maxAscent()),
+		                          min(dim.des, fm.maxDescent()));
+
 	// Cache the dimension.
-	mi.base.bv->coordCache().arrays().add(this, dim);
+	bv->coordCache().arrays().add(this, dim);
 }
 
 
diff --git a/status.23x b/status.23x
index 49f5458b03..881f7cd8cb 100644
--- a/status.23x
+++ b/status.23x
@@ -73,6 +73,8 @@ What's new
   to relevant directories) by setting the preference
   \use_native_filedialog true
 
+- Let caret height depend on character size in math editor.
+
 - Handle properly top/bottom of inset with mac-like cursor movement
   (bug 10701).
 
@@ -197,6 +199,8 @@ What's new
 
 - Improve rendering of square roots in math editor (bug 10814).
 
+- Set minimum height for math cells (bug 11050).
+
 - Fix display of citation labels when pasting from a document
   with other citation type (bug 10829).
 
-- 
2.39.5