[LyX/master] Fix spacing problems in previews with math macros (#13120)

[Juergen Spitzmueller]

commit 9ffacb341dd7f63e31782e8c8f81be2c2074dd08
Author: Juergen Spitzmueller <spitz at lyx.org>
Date:   Wed Nov 6 18:26:14 2024 +0100

    Fix spacing problems in previews with math macros (#13120)
    
    This occurs on the legacy path when no cropping tools are available.
---
 src/mathed/InsetMathHull.cpp | 7 +++++--
 1 file changed, 5 insertions(+), 2 deletions(-)

diff --git a/src/mathed/InsetMathHull.cpp b/src/mathed/InsetMathHull.cpp
index bf04577e4f..de20771e38 100644
--- a/src/mathed/InsetMathHull.cpp
+++ b/src/mathed/InsetMathHull.cpp
@@ -817,8 +817,11 @@ void InsetMathHull::usedMacros(MathData const & md, DocIterator const & pos,
 			if (data) {
 				odocstringstream macro_def;
 				data->write(macro_def, true);
-				macro_def << endl;
-				defs.insert(macro_def.str());
+				// Empty lines will generate full rows
+				// with legacy preview and tightpage (#13120).
+				// So remove all preceding and trailing line breaks
+				// and re-add one at the end of the snippet
+				defs.insert(trim(macro_def.str(), "\n") + "\n");
 				asArray(data->definition(), ar);
 			}
 			usedMacros(ar, pos, macros, defs);