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..a0d10805b897a078ad6e739ee1dee402832638fd 100644
--- a/ui/base/x/x11_util.cc
+++ b/ui/base/x/x11_util.cc
@@ -14,6 +14,7 @@
 
 #include <list>
 #include <map>
+#include <mutex>
 #include <utility>
 #include <vector>
 
@@ -22,6 +23,7 @@
 #include <X11/Xcursor/Xcursor.h>
 
 #include "base/bind.h"
+#include "base/command_line.h"
 #include "base/logging.h"
 #include "base/memory/scoped_ptr.h"
 #include "base/memory/singleton.h"
@@ -52,6 +54,7 @@
 #include "ui/gfx/image/image_skia_rep.h"
 #include "ui/gfx/skia_util.h"
 #include "ui/gfx/x/x11_error_tracker.h"
+#include "ui/gfx/x/x11_switches.h"
 
 #if defined(OS_FREEBSD)
 #include <sys/sysctl.h>
@@ -1409,6 +1412,65 @@ void LogErrorEventDescription(XDisplay* dpy,
       << " (" << request_str << ")";
 }
 
+static void ChooseARGBVisualForWindowOnce(Visual** visual, int* depth) {
+  XDisplay* display = gfx::GetXDisplay();
+  XAtom NET_WM_CM_S0 = XInternAtom(display, "_NET_WM_CM_S0", False);
+
+  // TODO(cwallez) make the switch be a constant again
+  if (base::CommandLine::ForCurrentProcess()->HasSwitch(
+          "enable-transparent-visuals") &&
+      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) {
+        *visual = info.visual;
+        *depth = info.depth;
+      }
+    }
+  } else {
+    XWindowAttributes windowAttribs;
+    Window root = XDefaultRootWindow(display);
+    Status status = XGetWindowAttributes(display, root, &windowAttribs);
+    DCHECK(status != 0);
+    *visual = windowAttribs.visual;
+    *depth = windowAttribs.depth;
+  }
+}
+
+void ChooseARGBVisualForWindow(Visual** visual, int* depth) {
+  static std::once_flag init_flag;
+  static Visual* s_visual = NULL;
+  static int s_depth = 0;
+
+  std::call_once(init_flag, ChooseARGBVisualForWindowOnce, &s_visual, &s_depth);

[piman, 2015/11/20 01:44:41]

std::call_once is a c++11 library feature that is not yet allowed by the style
guide - see https://chromium-cpp.appspot.com/#library-whitelist

[Julien Isorce Samsung, 2015/11/20 09:13:55]

Acknowledged.

+
+  DCHECK(s_visual);
+  DCHECK(s_depth > 0);
+
+  if (visual)
+    *visual = s_visual;
+  if (depth)
+    *depth = s_depth;
+}
+
 // ----------------------------------------------------------------------------
 // End of x11_util_internal.h