command_buffer_gles2: Implement EGL default Display as a global object

gpu/gles2_conform_support/egl/thread_state.h

+// Copyright (c) 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 GPU_GLES2_CONFORM_SUPPORT_EGL_STATE_H_
+#define GPU_GLES2_CONFORM_SUPPORT_EGL_STATE_H_
+
+#include "base/macros.h"
+#include "base/memory/ref_counted.h"
+#include <EGL/egl.h>
+
+namespace egl {
+
+class Context;
+class Display;
+class Surface;
+
+// Thread-local API state of EGL.
+class ThreadState {
+ public:
+  // Factory getter for the class. Should only be called by the API layer, and
+  // then passed through Display in order to avoid lock issues.
+  static ThreadState* Get();
+  static void ReleaseThread();
+
+  ThreadState();
+  ~ThreadState();

[Sami Väisänen, 2016/02/19 14:10:15]

If lifetime management happens through Get and Release functions, ctor and dtor
could be moved to private scope?

[Kimmo Kinnunen, 2016/02/22 06:43:08]

Done.

+
+  Surface* current_surface() const { return current_surface_.get(); }
+  Context* current_context() const { return current_context_.get(); }

[Sami Väisänen, 2016/02/19 14:10:15]

return value is not const Context*, so I'm not sure if this member should be
const either.

[Kimmo Kinnunen, 2016/02/22 06:43:08]

So the returned objects are not part of the logical state of the class, they
belong to global state. So this is fine.

Function saying "I'm not modifying ThreadState pointed by a" by saying "const
ThreadState* a" does not modify ThreadState even if it modifies
a->current_surface()

+
+  template <typename T>
+  T ReturnError(EGLint error, T return_value) {
+    error_code_ = error;
+    return return_value;
+  }
+  template <typename T>
+  T ReturnSuccess(T return_value) {
+    error_code_ = EGL_SUCCESS;
+    return return_value;
+  }
+  EGLint ConsumeErrorCode();
+
+  Display* GetDefaultDisplay();
+  Display* GetDisplay(EGLDisplay);
+  void SetCurrent(Surface*, Context*);
+  void ApplyCurrentContext();
+
+  class AutoApplyCurrentContext {
+   public:
+    AutoApplyCurrentContext(ThreadState*);
+    ~AutoApplyCurrentContext();
+
+   private:
+    ThreadState* thread_state_;
+  };

[Sami Väisänen, 2016/02/19 14:10:15]

if this is a RAII type, maybe disallow copyctor and assignment.

[Kimmo Kinnunen, 2016/02/22 06:43:08]

Done.

+
+ private:
+  EGLint error_code_;
+  scoped_refptr<Surface> current_surface_;
+  scoped_refptr<Context> current_context_;
+  DISALLOW_COPY_AND_ASSIGN(ThreadState);
+};
+
+}  // namespace egl
+
+#endif