[LyX/master] Remove alpha component of system colors

[Jean-Marc Lasgouttes]

commit 095bb18331f8eb4653691a64520d89d4a2d60fc4
Author: Jean-Marc Lasgouttes <lasgouttes at lyx.org>
Date:   Mon Jul 22 20:36:20 2024 +0200

    Remove alpha component of system colors
    
    When using system colors it may happen (on windows 11 in particular)
    that the background color is actually translucid. This is not
    something we are prepared to handle and it creates ghosts on screen.
    
    The fix is easy: the alpha channel of the colors is set to 255.
    
    Fixes bug #13084.
---
 src/frontends/qt/ColorCache.cpp | 4 +++-
 1 file changed, 3 insertions(+), 1 deletion(-)

diff --git a/src/frontends/qt/ColorCache.cpp b/src/frontends/qt/ColorCache.cpp
index 1c3d68e548..2566b75025 100644
--- a/src/frontends/qt/ColorCache.cpp
+++ b/src/frontends/qt/ColorCache.cpp
@@ -86,7 +86,9 @@ QColor ColorCache::get(Color const & color, bool syscolors) const
 		QPalette::ColorRole const cr = role(color.baseColor);
 		if (syscolors && cr != QPalette::NoRole) {
 			static QColor const white = Qt::white;
-			QColor const c = pal_.brush(QPalette::Active, cr).color();
+			QColor c = pal_.brush(QPalette::Active, cr).color();
+			// Change to fully opaque color
+			c.setAlpha(255);
 			if (cr == QPalette::Base && c == white)
 				return lcolors_[color.baseColor];
 			else