Full translucent background support in xcb and xlib backend.

Make sure to pick an alpha visual also for non-GL surface types, and to
ask for alpha in the window format if the WA_TranslucentBackground
attribute is set.

Reviewed-by: Janusz Lewandowski

2 files changed, 13 insertions, 1 deletions

diff --git a/src/plugins/platforms/xcb/qxcbwindow.cpp b/src/plugins/platforms/xcb/qxcbwindow.cpp
index 3365c22..0dd29eb 100644
--- a/src/plugins/platforms/xcb/qxcbwindow.cpp
+++ b/src/plugins/platforms/xcb/qxcbwindow.cpp
@@ -113,7 +113,8 @@ QXcbWindow::QXcbWindow(QWidget *tlw)
 
 #if defined(XCB_USE_GLX) || defined(XCB_USE_EGL)
     if (tlw->platformWindowFormat().windowApi() == QPlatformWindowFormat::OpenGL
-        && QApplicationPrivate::platformIntegration()->hasCapability(QPlatformIntegration::OpenGL))
+        && QApplicationPrivate::platformIntegration()->hasCapability(QPlatformIntegration::OpenGL)
+        || tlw->platformWindowFormat().alpha())
     {
 #if defined(XCB_USE_GLX)
         XVisualInfo *visualInfo = qglx_findVisualInfo(DISPLAY_FROM_XCB(m_screen),m_screen->screenNumber(), tlw->platformWindowFormat());
diff --git a/src/plugins/platforms/xcb/qxcbwindowsurface.cpp b/src/plugins/platforms/xcb/qxcbwindowsurface.cpp
index 38c01f9..88a54dc 100644
--- a/src/plugins/platforms/xcb/qxcbwindowsurface.cpp
+++ b/src/plugins/platforms/xcb/qxcbwindowsurface.cpp
@@ -54,6 +54,7 @@
 #include <stdio.h>
 
 #include <qdebug.h>
+#include <qpainter.h>
 
 class QXcbShmImage : public QXcbObject
 {
@@ -189,6 +190,16 @@ QPaintDevice *QXcbWindowSurface::paintDevice()
 void QXcbWindowSurface::beginPaint(const QRegion &region)
 {
     m_image->preparePaint(region);
+
+    if (m_image->image()->hasAlphaChannel()) {
+        QPainter p(m_image->image());
+        p.setCompositionMode(QPainter::CompositionMode_Source);
+        const QVector<QRect> rects = region.rects();
+        const QColor blank = Qt::transparent;
+        for (QVector<QRect>::const_iterator it = rects.begin(); it != rects.end(); ++it) {
+            p.fillRect(*it, blank);
+        }
+    }
 }
 
 void QXcbWindowSurface::endPaint(const QRegion &)