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

ui/base/x/x11_util.cc

 // Copyright (c) 2012 The Chromium Authors. All rights reserved.
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
 // This file defines utility functions for X11 (Linux only). This code has been
 // ported from XCB since we can't use XCB on Ubuntu while its 32-bit support
 // remains woefully incomplete.
 
 #include "ui/base/x/x11_util.h"
 
 #include <ctype.h>
 #include <sys/ipc.h>
 #include <sys/shm.h>
 
 #include <list>
 #include <map>
 #include <utility>
 #include <vector>
 
 #include <X11/extensions/shape.h>
 #include <X11/extensions/XInput2.h>
 #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"
 #include "base/message_loop/message_loop.h"
 #include "base/metrics/histogram.h"
 #include "base/strings/string_number_conversions.h"
 #include "base/strings/string_util.h"
 #include "base/strings/stringprintf.h"
 #include "base/sys_byteorder.h"
 #include "base/threading/thread.h"
@@ skipping 10 matching lines @@
 #include "ui/gfx/canvas.h"
 #include "ui/gfx/geometry/insets.h"
 #include "ui/gfx/geometry/point.h"
 #include "ui/gfx/geometry/point_conversions.h"
 #include "ui/gfx/geometry/rect.h"
 #include "ui/gfx/geometry/size.h"
 #include "ui/gfx/image/image_skia.h"
 #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>
 #include <sys/types.h>
 #endif
 
 namespace ui {
 
 namespace {
 
@@ skipping 1337 matching lines @@
   LOG(WARNING)
       << "X error received: "
       << "serial " << error_event.serial << ", "
       << "error_code " << static_cast<int>(error_event.error_code)
       << " (" << error_str << "), "
       << "request_code " << static_cast<int>(error_event.request_code) << ", "
       << "minor_code " << static_cast<int>(error_event.minor_code)
       << " (" << request_str << ")";
 }
 
+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);
+
+    // 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) {
+          s_visual = info.visual;
+          s_depth = info.depth;

[piman, 2015/11/20 21:56:58]

nit: break;

[Julien Isorce Samsung, 2015/11/20 23:26:39]

Ah right, I completely missed that one, thx.

+        }
+      }
+    } 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;
+}
+
 // ----------------------------------------------------------------------------
 // End of x11_util_internal.h
 
 
 }  // namespace ui