[LyX/master] Improve fix for #12153

[Enrico Forestieri]

commit 2629bd6dfb06a831d2e45b4e9d53a3b64cebb10b
Author: Enrico Forestieri <forenr at lyx.org>
Date:   Tue Feb 23 17:34:19 2021 +0100

    Improve fix for #12153
    
    Use a WYSIWYM approach instead of a WYSIWYG one.
---
 src/mathed/InsetMathHull.cpp |    4 ++--
 1 files changed, 2 insertions(+), 2 deletions(-)

diff --git a/src/mathed/InsetMathHull.cpp b/src/mathed/InsetMathHull.cpp
index b885f63..1c3d70e 100644
--- a/src/mathed/InsetMathHull.cpp
+++ b/src/mathed/InsetMathHull.cpp
@@ -480,9 +480,9 @@ 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)
-	   But 12 pixels is what we are used to.
+	   But we use a fixed number of pixels and scale them with zoom.
 	*/
-	int const bottom_display_margin = 12;
+	int const bottom_display_margin = mi.base.bv->zoomedPixels(6);
 	int top_display_margin = bottom_display_margin;
 	// at start of paragraph, add an empty line
 	if (mi.vmode)