[LyX/master] Fix ColorCache::getAll()

[Koji Yokota]

commit 033c52bcff2e2e04f3f3a3889bb6c301b316d4f5
Author: Koji Yokota <yokota at lyx.org>
Date:   Wed Jun 10 13:21:17 2026 +0900

    Fix ColorCache::getAll()
---
 src/frontends/qt/ColorCache.cpp | 22 ++++++++++++++++------
 1 file changed, 16 insertions(+), 6 deletions(-)

diff --git a/src/frontends/qt/ColorCache.cpp b/src/frontends/qt/ColorCache.cpp
index 357548f27f..a666c529bd 100644
--- a/src/frontends/qt/ColorCache.cpp
+++ b/src/frontends/qt/ColorCache.cpp
@@ -126,12 +126,22 @@ ColorPair ColorCache::getAll(Color const & color, bool syscolors) const
 		ColorPair base_colors = getAll(color.baseColor, syscolors);
 		ColorPair merge_colors = getAll(color.mergeColor, syscolors);
 		return {
-			QColor((base_colors.first.toRgb().red() + merge_colors.first.toRgb().red()) / 2,
-			       (base_colors.first.toRgb().green() + merge_colors.first.toRgb().green()) / 2,
-			       (base_colors.first.toRgb().blue() + merge_colors.first.toRgb().blue()) / 2),
-			QColor((base_colors.second.toRgb().red() + merge_colors.second.toRgb().red()) / 2,
-				(base_colors.second.toRgb().green() + merge_colors.second.toRgb().green()) / 2,
-				(base_colors.second.toRgb().blue() + merge_colors.second.toRgb().blue()) / 2),
+			QColor((base_colors.first.toRgb().red() +
+			        merge_colors.first.toRgb().red()) / 2,
+			       (base_colors.first.toRgb().green() +
+			        merge_colors.first.toRgb().green()) / 2,
+			       (base_colors.first.toRgb().blue() +
+			        merge_colors.first.toRgb().blue()) / 2,
+			       (base_colors.first.toRgb().alpha() +
+			        merge_colors.first.toRgb().alpha()) / 2),
+			QColor((base_colors.second.toRgb().red() +
+			        merge_colors.second.toRgb().red()) / 2,
+			       (base_colors.second.toRgb().green() +
+			        merge_colors.second.toRgb().green()) / 2,
+			       (base_colors.second.toRgb().blue() +
+			        merge_colors.second.toRgb().blue()) / 2,
+			       (base_colors.second.toRgb().alpha() +
+			        merge_colors.second.toRgb().alpha()) / 2),
 		};
 	}
 	// used by branches