1 files changed, 108 insertions, 0 deletions
diff --git a/ui/gl/gl_fence.cc b/ui/gl/gl_fence.cc
new file mode 100644
index 0000000..82cdf30
--- /dev/null
+++ b/ui/gl/gl_fence.cc
@@ -0,0 +1,108 @@
+// 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.
+
+#include "ui/gl/gl_fence.h"
+
+#include "base/compiler_specific.h"
+#include "ui/gl/gl_bindings.h"
+#include "ui/gl/gl_context.h"
+
+namespace {
+
+class GLFenceNVFence: public gfx::GLFence {
+ public:
+  GLFenceNVFence() {
+    // What if either of these GL calls fails? TestFenceNV will return true.
+    // See spec:
+    // http://www.opengl.org/registry/specs/NV/fence.txt
+    //
+    // What should happen if TestFenceNV is called for a name before SetFenceNV
+    // is called?
+    //     We generate an INVALID_OPERATION error, and return TRUE.
+    //     This follows the semantics for texture object names before
+    //     they are bound, in that they acquire their state upon binding.
+    //     We will arbitrarily return TRUE for consistency.
+    glGenFencesNV(1, &fence_);
+    glSetFenceNV(fence_, GL_ALL_COMPLETED_NV);
+    glFlush();
+  }
+
+  virtual bool HasCompleted() OVERRIDE {
+    return IsContextLost() || glTestFenceNV(fence_);
+  }
+
+ private:
+  ~GLFenceNVFence() {
+    glDeleteFencesNV(1, &fence_);
+  }
+
+  GLuint fence_;
+};
+
+class GLFenceARBSync: public gfx::GLFence {
+ public:
+  GLFenceARBSync() {
+    sync_ = glFenceSync(GL_SYNC_GPU_COMMANDS_COMPLETE, 0);
+    glFlush();
+  }
+
+  virtual bool HasCompleted() OVERRIDE {
+    // Handle the case where FenceSync failed.
+    if (!sync_ || IsContextLost())
+      return true;
+
+    GLsizei length = 0;
+    GLsizei value = 0;
+    glGetSynciv(sync_,
+                GL_SYNC_STATUS,
+                1,  // bufSize
+                &length,
+                &value);
+    return length == 1 && value == GL_SIGNALED;
+  }
+
+ private:
+  ~GLFenceARBSync() {
+    glDeleteSync(sync_);
+  }
+
+  GLsync sync_;
+};
+
+}  // namespace
+
+namespace gfx {
+
+GLFence::GLFence() {
+}
+
+GLFence::~GLFence() {
+}
+
+// static
+GLFence* GLFence::Create() {
+  if (gfx::g_GL_NV_fence) {
+    return new GLFenceNVFence();
+  } else if (gfx::g_GL_ARB_sync) {
+    return new GLFenceARBSync();
+  } else {
+    return NULL;
+  }
+}
+
+// static
+bool GLFence::IsContextLost() {
+  if (!gfx::g_GL_ARB_robustness)
+    return false;
+
+  if (!gfx::GLContext::GetCurrent() ||
+      !gfx::GLContext::GetCurrent()->
+          WasAllocatedUsingARBRobustness())
+    return false;
+
+  GLenum status = glGetGraphicsResetStatusARB();
+  return status != GL_NO_ERROR;
+}
+
+}  // namespace gfx