gl_surface_egl: ensure off and on screen surfaces use the same EGLConfig

ui/base/x/x11_util.cc

Index: ui/base/x/x11_util.cc
diff --git a/ui/base/x/x11_util.cc b/ui/base/x/x11_util.cc
index f36aa0101cebfc17d925b5d7a2c1fd764f98e6c1..b253a778b79bba0667d4f8f161559244cd90d92b 100644
--- a/ui/base/x/x11_util.cc
+++ b/ui/base/x/x11_util.cc
@@ -53,6 +53,11 @@
 #include "ui/gfx/skia_util.h"
 #include "ui/gfx/x/x11_error_tracker.h"
 
+#if !defined(OS_CHROMEOS)
+#include "base/command_line.h"
+#include "ui/gfx/x/x11_switches.h"
+#endif
+
 #if defined(OS_FREEBSD)
 #include <sys/sysctl.h>
 #include <sys/types.h>
@@ -1409,6 +1414,64 @@ void LogErrorEventDescription(XDisplay* dpy,
       << " (" << request_str << ")";
 }
 
+#if !defined(OS_CHROMEOS)
+void ChooseVisualForWindow(Visual** visual, int* depth) {
+  static Visual* s_visual = NULL;
+  static int s_depth = 0;
+
+  if (!s_visual) {
+    XDisplay* display = gfx::GetXDisplay();
+    XAtom NET_WM_CM_S0 = XInternAtom(display, "_NET_WM_CM_S0", False);
+
+    if (base::CommandLine::ForCurrentProcess()->HasSwitch(
+            switches::kEnableTransparentVisuals) &&
+        XGetSelectionOwner(display, NET_WM_CM_S0) != None) {
+      // Choose the first ARGB8888 visual
+      XVisualInfo visual_template;
+      visual_template.screen = 0;
+
+      int visuals_len;
+      gfx::XScopedPtr<XVisualInfo[]> visual_list(XGetVisualInfo(
+          display, VisualScreenMask, &visual_template, &visuals_len));
+      for (int i = 0; i < visuals_len; ++i) {
+        // Why support only 8888 ARGB? Because it's all that GTK+ supports. In
+        // gdkvisual-x11.cc, they look for this specific visual and use it for
+        // all their alpha channel using needs.
+        //
+        // TODO(erg): While the following does find a valid visual, some GL
+        // drivers
+        // don't believe that this has an alpha channel. According to marcheu@,
+        // this should work on open source driver though. (It doesn't work with
+        // NVidia's binaries currently.) http://crbug.com/369209
+        const XVisualInfo& info = visual_list[i];
+        if (info.depth == 32 && info.visual->red_mask == 0xff0000 &&
+            info.visual->green_mask == 0x00ff00 &&
+            info.visual->blue_mask == 0x0000ff) {
+          s_visual = info.visual;
+          s_depth = info.depth;
+          break;
+        }
+      }
+    } else {
+      XWindowAttributes windowAttribs;
+      Window root = XDefaultRootWindow(display);
+      Status status = XGetWindowAttributes(display, root, &windowAttribs);
+      DCHECK(status != 0);
+      s_visual = windowAttribs.visual;
+      s_depth = windowAttribs.depth;
+    }
+  }  // !s_visual
+
+  DCHECK(s_visual);
+  DCHECK(s_depth > 0);
+
+  if (visual)
+    *visual = s_visual;
+  if (depth)
+    *depth = s_depth;
+}
+#endif
+
 // ----------------------------------------------------------------------------
 // End of x11_util_internal.h