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.

src/BufferView.cpp

@@ -230,7 +230,8 @@ 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),
@@ -238,7 +239,8 @@ 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;
 	}
@@ -317,6 +319,12 @@ 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_;
 };
 
 
@@ -2982,13 +2990,26 @@ 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();
+	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);
-	int const asc = fm.maxAscent();
+		asc = fm.maxAscent();
-	int const des = fm.maxDescent();
+		des = fm.maxDescent();
+	}
 	h = asc + des;
 	p = getPos(cur);
 	p.y_ -= asc;

src/BufferView.h

@@ -307,6 +307,8 @@ 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;
 

src/mathed/MathData.cpp

@@ -262,6 +262,7 @@ 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)
@@ -273,8 +274,8 @@ void MathData::metrics(MetricsInfo & mi, Dimension & dim, bool tight) const
 
 	MathRow mrow(mi, this);
 	mrow.metrics(mi, dim);
-	mrow_cache_[mi.base.bv] = mrow;
+	mrow_cache_[bv] = mrow;
-	kerning_ = mrow.kerning(mi.base.bv);
+	kerning_ = mrow.kerning(bv);
 
 	// Set a minimal ascent/descent for the cell
 	if (tight)
@@ -286,8 +287,15 @@ 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);
 }