[LyX/master] Reduce the value of (above|below)displayskip

[Jean-Marc Lasgouttes]

commit 41d29ce3877016e813cf8ef285d63fc8c7d0c478
Author: Jean-Marc Lasgouttes <lasgouttes at lyx.org>
Date:   Sun Feb 21 20:33:57 2021 +0100

    Reduce the value of (above|below)displayskip
    
    The value of 10pt is too large, use a 'mean' value of 8.5pt.
    
    Tentative fix to bug #12153.
---
 src/mathed/InsetMathHull.cpp |    3 ++-
 1 files changed, 2 insertions(+), 1 deletions(-)

diff --git a/src/mathed/InsetMathHull.cpp b/src/mathed/InsetMathHull.cpp
index 24e4397..bcde5d3 100644
--- a/src/mathed/InsetMathHull.cpp
+++ b/src/mathed/InsetMathHull.cpp
@@ -480,12 +480,13 @@ void InsetMathHull::metrics(MetricsInfo & mi, Dimension & dim) const
 {
 	/* Compute \(above|below)displayskip
 	   true value in LaTeX is 10pt plus 2pt minus 5pt (in normal size at 10pt)
+	   We use the 'mean' value (12 + 5) / 2 = 8.5pt.
 	   FIXME: make this dependent of current size? (minor improvement)
 	   FIXME: if would be nice if this was not part of the inset, but
 	          just increased the row ascent/descent.
 	   FIXME: even better would be to handle the short skip case.
 	*/
-	int const bottom_display_margin = mi.base.inPixels(Length(10, Length::PT));
+	int const bottom_display_margin = mi.base.inPixels(Length(8.5, Length::PT));
 	int top_display_margin = bottom_display_margin;
 	// at start of paragraph, add an empty line
 	if (mi.vmode)