If EGL fails to provide a valid Visual ID, try XRender for ARGBs

This patch is inspired by the "Fix ARGB visuals" patch in the Maemo
branch. Thanks go to the author of that patch (who isn't signed up to
Gitorious and thus can't be named - you know who you are! Thanks!!).

This patch should also fix ARGB visuals (even if they are supplied by
EGL) as such visuals require a colormap.

1 files changed, 55 insertions, 9 deletions

diff --git a/src/opengl/qgl_x11egl.cpp b/src/opengl/qgl_x11egl.cpp
index 74b9038..514e763 100644
--- a/src/opengl/qgl_x11egl.cpp
+++ b/src/opengl/qgl_x11egl.cpp
@@ -295,7 +295,8 @@ void QGLWidget::setContext(QGLContext *context, const QGLContext* shareContext,
         int matchingCount = 0;
         chosenVisualInfo = XGetVisualInfo(x11Info().display(), VisualIDMask, &vi, &matchingCount);
         if (chosenVisualInfo) {
-            memcpy(&vi, chosenVisualInfo, sizeof(XVisualInfo));
+            qDebug("Using X Visual ID (%d) provided by EGL", (int)vi.visualid);
+            vi = *chosenVisualInfo;
             XFree(chosenVisualInfo);
         }
         else {
@@ -305,11 +306,38 @@ void QGLWidget::setContext(QGLContext *context, const QGLContext* shareContext,
         }
     }
 
+    // If EGL does not know the visual ID, so try to select an appropriate one ourselves, first
+    // using XRender if we're supposed to have an alpha, then falling back to XGetVisualInfo
+
+    bool useArgb = context->format().alpha() && !context->deviceIsPixmap();
+#if !defined(QT_NO_XRENDER)
+    if (vi.visualid == 0 && useArgb) {
+        // Try to use XRender to find an ARGB visual we can use
+        vi.screen  = x11Info().screen();
+        vi.depth   = 32;
+        vi.c_class = TrueColor;
+        XVisualInfo *matchingVisuals;
+        int matchingCount = 0;
+        matchingVisuals = XGetVisualInfo(x11Info().display(),
+                                         VisualScreenMask|VisualDepthMask|VisualClassMask,
+                                         &vi, &matchingCount);
+
+        for (int i = 0; i < matchingCount; ++i) {
+            XRenderPictFormat *format;
+            format = XRenderFindVisualFormat(x11Info().display(), matchingVisuals[i].visual);
+            if (format->type == PictTypeDirect && format->direct.alphaMask) {
+                vi = matchingVisuals[i];
+                qDebug("Using X Visual ID (%d) for ARGB visual as provided by XRender", (int)vi.visualid);
+                break;
+            }
+        }
+        XFree(matchingVisuals);
+    }
+#endif
+
     if (vi.visualid == 0) {
-        // EGL does not know the visual ID, so try to select an appropriate one ourselves:
         EGLint depth;
         qeglCtx->configAttrib(EGL_BUFFER_SIZE, &depth);
-
         int err;
         err = XMatchVisualInfo(x11Info().display(), x11Info().screen(), depth, TrueColor, &vi);
         if (err == 0) {
@@ -320,13 +348,27 @@ void QGLWidget::setContext(QGLContext *context, const QGLContext* shareContext,
             if (err == 0) {
                 qWarning("Error: Couldn't get any matching X visual!");
                 return;
-            }
-            else
+            } else
                 qWarning("         - Falling back to X11 suggested depth (%d)", depth);
-        }
+        } else
+            qDebug("Using X Visual ID (%d) for EGL provided depth (%d)", (int)vi.visualid, depth);
 
+        // Don't try to use ARGB now unless the visual is 32-bit - even then it might stil fail :-(
+        if (useArgb)
+            useArgb = vi.depth == 32;
     }
 
+//    qDebug("Visual Info:");
+//    qDebug("   bits_per_rgb=%d", vi.bits_per_rgb);
+//    qDebug("   red_mask=0x%x", vi.red_mask);
+//    qDebug("   green_mask=0x%x", vi.green_mask);
+//    qDebug("   blue_mask=0x%x", vi.blue_mask);
+//    qDebug("   colormap_size=%d", vi.colormap_size);
+//    qDebug("   c_class=%d", vi.c_class);
+//    qDebug("   depth=%d", vi.depth);
+//    qDebug("   screen=%d", vi.screen);
+//    qDebug("   visualid=%d", vi.visualid);
+
     XSetWindowAttributes a;
 
     Window p = RootWindow(x11Info().display(), x11Info().screen());
@@ -337,9 +379,13 @@ void QGLWidget::setContext(QGLContext *context, const QGLContext* shareContext,
     a.background_pixel = colmap.pixel(palette().color(backgroundRole()));
     a.border_pixel = colmap.pixel(Qt::black);
 
-    Window w = XCreateWindow(X11->display, p, x(), y(), width(), height(),
-                              0, vi.depth, InputOutput, vi.visual,
-                              CWBackPixel|CWBorderPixel, &a);
+    unsigned int valueMask = CWBackPixel|CWBorderPixel;
+    if(useArgb) {
+        a.colormap = XCreateColormap(x11Info().display(), p, vi.visual, AllocNone);
+        valueMask |= CWColormap;
+    }
+    Window w = XCreateWindow(x11Info().display(), p, x(), y(), width(), height(),
+                             0, vi.depth, InputOutput, vi.visual, valueMask, &a);
 
     if (deleteOldContext)
         delete oldcx;