X11: Use better visuals for OpenGL

ui/gl/gl_visual_picker_glx.h

+// Copyright 2016 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.
+
+#ifndef UI_GL_GL_VISUAL_PICKER_GLX_H_
+#define UI_GL_GL_VISUAL_PICKER_GLX_H_
+
+#include <X11/Xutil.h>
+
+#include <vector>
+
+#include "base/macros.h"
+#include "ui/gfx/x/x11_types.h"
+#include "ui/gl/gl_export.h"
+
+namespace base {
+template <typename T>
+struct DefaultSingletonTraits;
+}
+
+namespace gl {
+
+// Picks the best X11 visuals to use for GL.  This class is adapted from GTK's
+// pick_better_visual_for_gl.  Tries to find visuals that
+// 1. Support GL
+// 2. Support double buffer
+// 3. Have an alpha channel only if we want one
+class GL_EXPORT GLVisualPickerGLX {
+ public:
+  static GLVisualPickerGLX* GetInstance();
+
+  ~GLVisualPickerGLX();
+
+  const XVisualInfo& system_visual() { return system_visual_; };
+
+  const XVisualInfo& rgba_visual() { return rgba_visual_; };
+
+ private:
+  friend struct base::DefaultSingletonTraits<GLVisualPickerGLX>;
+
+  XVisualInfo PickBestGlVisual(const std::vector<XVisualInfo>& visuals,
+                               bool want_alpha) const;
+
+  XVisualInfo PickBestSystemVisual(
+      const std::vector<XVisualInfo>& visuals) const;
+
+  XVisualInfo PickBestRgbaVisual(const std::vector<XVisualInfo>& visuals) const;
+
+  XDisplay* display_;
+
+  bool has_glx_visual_rating_;
+  bool has_glx_multisample_;
+
+  XVisualInfo system_visual_;
+  XVisualInfo rgba_visual_;
+
+  GLVisualPickerGLX();
+
+  DISALLOW_COPY_AND_ASSIGN(GLVisualPickerGLX);
+};
+
+}  // namespace gl
+
+#endif  // UI_GL_GL_VISUAL_PICKER_GLX_H_