From dc5f9d0c3101f95185d3c562d001e0af18f46a0b Mon Sep 17 00:00:00 2001
From: Andy Shaw <andy.shaw@qt.io>
Date: Tue, 2 Oct 2018 15:05:32 +0200
Subject: Only use a translucent background if there is support for alpha

Change-Id: Ia8d9e543fac4b6e790fa38cf04c5a782d72d72df
Reviewed-by: Eirik Aavitsland <eirik.aavitsland@qt.io>
Reviewed-by: Gatis Paeglis <gatis.paeglis@qt.io>
---
 src/plugins/platforms/xcb/nativepainting/qbackingstore_x11.cpp | 6 ++++--
 1 file changed, 4 insertions(+), 2 deletions(-)

(limited to 'src')

diff --git a/src/plugins/platforms/xcb/nativepainting/qbackingstore_x11.cpp b/src/plugins/platforms/xcb/nativepainting/qbackingstore_x11.cpp
index 8851ea59e5..ed482e5dae 100644
--- a/src/plugins/platforms/xcb/nativepainting/qbackingstore_x11.cpp
+++ b/src/plugins/platforms/xcb/nativepainting/qbackingstore_x11.cpp
@@ -62,8 +62,10 @@ QXcbNativeBackingStore::QXcbNativeBackingStore(QWindow *window)
     : QPlatformBackingStore(window)
     , m_translucentBackground(false)
 {
-    if (QXcbWindow *w = static_cast<QXcbWindow *>(window->handle()))
-        m_translucentBackground = w->connection()->hasXRender() && QImage::toPixelFormat(w->imageFormat()).alphaSize() > 0;
+    if (QXcbWindow *w = static_cast<QXcbWindow *>(window->handle())) {
+        m_translucentBackground = w->connection()->hasXRender() &&
+            QImage::toPixelFormat(w->imageFormat()).alphaUsage() == QPixelFormat::UsesAlpha;
+    }
 }
 
 QXcbNativeBackingStore::~QXcbNativeBackingStore()
-- 
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