[LyX/master] Reduce the number of accesses to coord cache when drawing a math row

[Jean-Marc Lasgouttes]

commit e5bb491e2e10a8097284d11eae5501a3673731cb
Author: Jean-Marc Lasgouttes <lasgouttes at lyx.org>
Date:   Fri Oct 8 17:38:25 2021 +0200

    Reduce the number of accesses to coord cache when drawing a math row
    
    Each of these accesses is somewhat costly when using large branches
    with lots of maths
    
    Related to bug #12297.
---
 src/CoordCache.h       |    6 ++++++
 src/mathed/MathRow.cpp |   16 +++++++---------
 2 files changed, 13 insertions(+), 9 deletions(-)

diff --git a/src/CoordCache.h b/src/CoordCache.h
index 2780fc3..44ac26c 100644
--- a/src/CoordCache.h
+++ b/src/CoordCache.h
@@ -80,6 +80,12 @@ public:
 		data_[thing].dim = dim;
 	}
 
+	Geometry & geometry(T const * thing)
+	{
+		check(thing, "geometry");
+		return data_.find(thing)->second;
+	}
+
 	Geometry const & geometry(T const * thing) const
 	{
 		check(thing, "geometry");
diff --git a/src/mathed/MathRow.cpp b/src/mathed/MathRow.cpp
index b8a9a95..81b6ad9 100644
--- a/src/mathed/MathRow.cpp
+++ b/src/mathed/MathRow.cpp
@@ -322,18 +322,16 @@ void MathRow::draw(PainterInfo & pi, int x, int const y) const
 			// This is hackish: the math inset does not know that space
 			// has been added before and after it; we alter its dimension
 			// while it is drawing, because it relies on this value.
-			Dimension const d = coords.insets().dim(e.inset);
-			Dimension d2 = d;
-			d2.wid -= e.before + e.after;
-			coords.insets().add(e.inset, d2);
+			Geometry & g = coords.insets().geometry(e.inset);
+			g.dim.wid -= e.before + e.after;
 			if (pi.pain.develMode() && !e.inset->isBufferValid())
-				pi.pain.fillRectangle(x + e.before, y - d2.ascent(),
-				                      d2.width(), d2.height(), Color_error);
+				pi.pain.fillRectangle(x + e.before, y - g.dim.ascent(),
+				                      g.dim.width(), g.dim.height(), Color_error);
 			e.inset->draw(pi, x + e.before, y);
-			coords.insets().add(e.inset, x, y);
-			coords.insets().add(e.inset, d);
+			g.pos = {x, y};
+			g.dim.wid += e.before + e.after;
 			drawMarkers(pi, e, x, y);
-			x += d.wid;
+			x += g.dim.wid;
 			break;
 		}
 		case BEGIN: