Add an ARGB check for EGL-provided X visuals

Don't just assume they're going to be ARGB just because the config has
an alpha channel. This makes QGLWidgets with WA_TranslucentBackground
set work again on the rx71 when running under xcompmgr.

Reviewed-By: Trustme

1 files changed, 20 insertions, 3 deletions

diff --git a/src/opengl/qgl_x11egl.cpp b/src/opengl/qgl_x11egl.cpp
index 99b026d..c6904fe 100644
--- a/src/opengl/qgl_x11egl.cpp
+++ b/src/opengl/qgl_x11egl.cpp
@@ -258,7 +258,8 @@ void QGLWidget::setContext(QGLContext *context, const QGLContext* shareContext,
     // If the application has set WA_TranslucentBackground and not explicitly set
     // the alpha buffer size to zero, modify the format so it have an alpha channel
     QGLFormat& fmt = d->glcx->d_func()->glFormat;
-    if (testAttribute(Qt::WA_TranslucentBackground) && fmt.alphaBufferSize() == -1)
+    const bool useArgbVisual = testAttribute(Qt::WA_TranslucentBackground);
+    if (useArgbVisual && fmt.alphaBufferSize() == -1)
         fmt.setAlphaBufferSize(1);
 
     bool createFailed = false;
@@ -297,8 +298,24 @@ void QGLWidget::setContext(QGLContext *context, const QGLContext* shareContext,
         int matchingCount = 0;
         chosenVisualInfo = XGetVisualInfo(x11Info().display(), VisualIDMask, &vi, &matchingCount);
         if (chosenVisualInfo) {
-            qDebug("Using X Visual ID (%d) provided by EGL", (int)vi.visualid);
-            vi = *chosenVisualInfo;
+            if (useArgbVisual) {
+                // Check to make sure the visual provided by EGL is ARGB
+                XRenderPictFormat *format;
+                format = XRenderFindVisualFormat(x11Info().display(), chosenVisualInfo->visual);
+                if (format->type == PictTypeDirect && format->direct.alphaMask) {
+                    qDebug("Using opaque X Visual ID (%d) provided by EGL", (int)vi.visualid);
+                    vi = *chosenVisualInfo;
+                }
+                else {
+                    qWarning("Warning: EGL suggested using X visual ID %d for config %d, but this is not ARGB",
+                             nativeVisualId, (int)qeglCtx->config());
+                    vi.visualid = 0;
+                }
+            }
+            else {
+                qDebug("Using opaque X Visual ID (%d) provided by EGL", (int)vi.visualid);
+                vi = *chosenVisualInfo;
+            }
             XFree(chosenVisualInfo);
         }
         else {