Make QGLWidgets have the same background colour as QWidgets

QWidgets are filled with Qt::transparent when WA_TranslucentBackground
is set, reguardless of what their background colour has been set to.
This patch makes QGLWidgets behave the same way.

Reviewed-By: Samuel Rødal

4 files changed, 22 insertions, 17 deletions

diff --git a/src/opengl/gl2paintengineex/qpaintengineex_opengl2.cpp b/src/opengl/gl2paintengineex/qpaintengineex_opengl2.cpp
index 5c8b364..f7dbed3 100644
--- a/src/opengl/gl2paintengineex/qpaintengineex_opengl2.cpp
+++ b/src/opengl/gl2paintengineex/qpaintengineex_opengl2.cpp
@@ -1083,16 +1083,6 @@ bool QGL2PaintEngineEx::begin(QPaintDevice *pdev)
 //     qDebug("You should see green now");
 //     sleep(5);
 
-    const QColor &c = d->drawable.backgroundColor();
-    glClearColor(c.redF(), c.greenF(), c.blueF(), d->drawable.format().alpha() ? c.alphaF() : 1.0);
-    if (d->drawable.context()->d_func()->clear_on_painter_begin && d->drawable.autoFillBackground()) {
-        GLbitfield clearBits = GL_COLOR_BUFFER_BIT | GL_DEPTH_BUFFER_BIT;
-#ifndef QT_OPENGL_ES
-        clearBits |= GL_ACCUM_BUFFER_BIT;
-#endif
-        glClear(clearBits);
-    }
-
     d->brushTextureDirty = true;
     d->brushUniformsDirty = true;
     d->matrixDirty = true;
@@ -1105,11 +1095,14 @@ bool QGL2PaintEngineEx::begin(QPaintDevice *pdev)
     glDisable(GL_SCISSOR_TEST);
 
     QGLPixmapData *source = d->drawable.copyOnBegin();
-    if (d->drawable.autoFillBackground()) {
-        QColor color = d->drawable.backgroundColor();
-
-        float alpha = color.alphaF();
-        glClearColor(color.redF() * alpha, color.greenF() * alpha, color.blueF() * alpha, alpha);
+    if (d->drawable.context()->d_func()->clear_on_painter_begin && d->drawable.autoFillBackground()) {
+        if (d->drawable.hasTransparentBackground())
+            glClearColor(0.0, 0.0, 0.0, 0.0);
+        else {
+            const QColor &c = d->drawable.backgroundColor();
+            float alpha = c.alphaF();
+            glClearColor(c.redF() * alpha, c.greenF() * alpha, c.blueF() * alpha, alpha);
+        }
         glClear(GL_COLOR_BUFFER_BIT);
     } else if (source) {
         d->transferMode(ImageDrawingMode);
diff --git a/src/opengl/qgl.cpp b/src/opengl/qgl.cpp
index 9626a3d..ced3452 100644
--- a/src/opengl/qgl.cpp
+++ b/src/opengl/qgl.cpp
@@ -4530,6 +4530,11 @@ QColor QGLDrawable::backgroundColor() const
     return QApplication::palette().brush(QPalette::Background).color();
 }
 
+bool QGLDrawable::hasTransparentBackground() const
+{
+    return widget && widget->testAttribute(Qt::WA_TranslucentBackground);
+}
+
 QGLContext *QGLDrawable::context() const
 {
     if (widget)
diff --git a/src/opengl/qgl_p.h b/src/opengl/qgl_p.h
index 9657416..b1a63b5 100644
--- a/src/opengl/qgl_p.h
+++ b/src/opengl/qgl_p.h
@@ -314,6 +314,7 @@ public:
     QColor backgroundColor() const;
     QGLContext *context() const;
     bool autoFillBackground() const;
+    bool hasTransparentBackground() const;
 
 #if !defined(QT_OPENGL_ES_1) && !defined(QT_OPENGL_ES_1_CL)
     QGLPixmapData *copyOnBegin() const;
diff --git a/src/opengl/qpaintengine_opengl.cpp b/src/opengl/qpaintengine_opengl.cpp
index d5bf1dc..e3d8a1d 100644
--- a/src/opengl/qpaintengine_opengl.cpp
+++ b/src/opengl/qpaintengine_opengl.cpp
@@ -1330,9 +1330,15 @@ bool QOpenGLPaintEngine::begin(QPaintDevice *pdev)
 
     d->offscreen.begin();
 
-    const QColor &c = d->drawable.backgroundColor();
-    glClearColor(c.redF(), c.greenF(), c.blueF(), d->drawable.format().alpha() ? c.alphaF() : 1.0);
     if (d->drawable.context()->d_func()->clear_on_painter_begin && d->drawable.autoFillBackground()) {
+
+        if (d->drawable.hasTransparentBackground())
+            glClearColor(0.0, 0.0, 0.0, 0.0);
+        else {
+            const QColor &c = d->drawable.backgroundColor();
+            glClearColor(c.redF(), c.greenF(), c.blueF(), 1.0);
+        }
+
         GLbitfield clearBits = GL_COLOR_BUFFER_BIT | GL_DEPTH_BUFFER_BIT;
 #ifndef QT_OPENGL_ES
         clearBits |= GL_ACCUM_BUFFER_BIT;