From 375691c6c21162ddcf49f072e648ee5ebc701c0e Mon Sep 17 00:00:00 2001
From: Aleix Pol <aleixpol@kde.org>
Date: Wed, 23 Sep 2020 22:32:33 +0200
Subject: [PATCH] Improve opacity detection

If the opaque area covers all the window's shape, it means that it's an
opaque window.
This is how GTK presents opacity right now, so we'll get to skip
rendering under GTK clients and other compatible ones.
Qt is still not emitting opacity.
---
 scene.cpp | 4 ++++
 1 file changed, 4 insertions(+)

diff --git a/scene.cpp b/scene.cpp
index cb121ef10..edb447f87 100644
--- a/scene.cpp
+++ b/scene.cpp
@@ -294,6 +294,10 @@ void Scene::paintSimpleScreen(int orig_mask, const QRegion &region)
                 const QRegion shape = windowPixmap->mapToGlobal(windowPixmap->shape());
                 const QRegion opaque = windowPixmap->mapToGlobal(windowPixmap->opaque());
                 data.clip = shape & opaque;
+
+                if (opaque == shape) {
+                    data.mask = orig_mask | PAINT_WINDOW_OPAQUE;
+                }
             }
         } else {
             data.clip = QRegion();