From 3733abab2c5c3d7d769c23756e9472f3e7ac26c8 Mon Sep 17 00:00:00 2001
From: Kai Uwe Broulik <kai_uwe.broulik@mbition.io>
Date: Thu, 24 Mar 2022 14:55:14 +0100
Subject: [PATCH] scenes/opengl: Paint background with alpha 0

In conjunction with a buffer format with alpha channel this allows
to have KWin's backdrop transparent to see through to a display
layer below.

Signed-off-by: Eike Hein <eike.hein@mbition.io>
---
 src/scenes/opengl/scene_opengl.cpp | 4 ++--
 1 file changed, 2 insertions(+), 2 deletions(-)

diff --git a/src/scenes/opengl/scene_opengl.cpp b/src/scenes/opengl/scene_opengl.cpp
index 5ef7623b03..1c3a1a5ab9 100644
--- a/src/scenes/opengl/scene_opengl.cpp
+++ b/src/scenes/opengl/scene_opengl.cpp
@@ -131,7 +131,7 @@ QMatrix4x4 SceneOpenGL::transformation(int mask, const ScreenPaintData &data) co
 void SceneOpenGL::paintBackground(const QRegion &region)
 {
     if (region == infiniteRegion()) {
-        glClearColor(0, 0, 0, 1);
+        glClearColor(0, 0, 0, 0);
         glClear(GL_COLOR_BUFFER_BIT);
     } else if (!region.isEmpty()) {
         QVector<float> verts;
@@ -294,7 +294,7 @@ void SceneOpenGL::doPaintBackground(const QVector< float >& vertices)
 {
     GLVertexBuffer *vbo = GLVertexBuffer::streamingBuffer();
     vbo->reset();
-    vbo->setUseColor(true);
+    vbo->setColor(QColor(0, 0, 0, 0));
     vbo->setData(vertices.count() / 2, 2, vertices.data(), nullptr);
 
     ShaderBinder binder(ShaderTrait::UniformColor);