Add helpers for creating UI components.

mojo/ui/gl_renderer.h

Index: mojo/ui/gl_renderer.h
diff --git a/mojo/ui/gl_renderer.h b/mojo/ui/gl_renderer.h
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+// Copyright 2015 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 MOJO_UI_GL_RENDERER_H_
+#define MOJO_UI_GL_RENDERER_H_
+
+#include <deque>
+#include <memory>
+
+#include "base/callback.h"
+#include "base/macros.h"
+#include "base/memory/weak_ptr.h"
+#include "mojo/public/cpp/bindings/strong_binding.h"
+#include "mojo/services/gfx/composition/interfaces/resources.mojom.h"
+
+namespace mojo {
+
+class GLContext;
+class GLTexture;
+class Size;
+
+namespace ui {
+
+// Provides support for rendering GL commands into a pool of textures
+// and producing scene resources for them.
+class GLRenderer {
+ public:
+  // Called with an active GL context to draw into the framebuffer.
+  using DrawGLCallback = base::Closure;
+
+  GLRenderer(base::WeakPtr<mojo::GLContext> gl_context,
+             uint32_t max_recycled_textures = 3u);
+  ~GLRenderer();
+
+  // Gets the GL context, or null if none.
+  const base::WeakPtr<mojo::GLContext>& gl_context() const {
+    return gl_context_;
+  }
+
+  // Obtains a texture of the specified size.
+  // Returns a nullptr if the GLContext was destroyed.
+  std::unique_ptr<mojo::GLTexture> GetTexture(const mojo::Size& requested_size);
+
+  // Takes ownership of the specified texture, issues GL commands to
+  // produce a mailbox texture, and returns its resource pointer.
+  // The caller should add the resource to its scene.
+  // Returns a nullptr if the GLContext was destroyed.
+  mojo::gfx::composition::ResourcePtr BindTextureResource(
+      std::unique_ptr<GLTexture> texture);
+
+  // Allocates a GL texture, binds it to a framebuffer, invokes the
+  // provided function, then returns the resulting resource.
+  // If |with_depth| is true, provides a depth buffer attachment.
+  mojo::gfx::composition::ResourcePtr DrawGL(const mojo::Size& size,
+                                             bool with_depth,
+                                             const DrawGLCallback& callback);
+
+ private:
+  using GLRecycledTextureInfo =
+      std::pair<std::unique_ptr<mojo::GLTexture>, uint32_t>;
+
+  // TODO(jeffbrown): Avoid creating new callbacks each time, perhaps by
+  // migrating to image pipes.
+  class GLTextureReleaser : mojo::gfx::composition::MailboxTextureCallback {
+   public:
+    GLTextureReleaser(const base::WeakPtr<GLRenderer>& provider,
+                      GLRecycledTextureInfo info);
+    ~GLTextureReleaser() override;
+
+    mojo::gfx::composition::MailboxTextureCallbackPtr StrongBind();
+
+   private:
+    void OnMailboxTextureReleased() override;
+    void Release(bool recyclable);
+
+    base::WeakPtr<GLRenderer> provider_;
+    GLRecycledTextureInfo texture_info_;
+    mojo::StrongBinding<mojo::gfx::composition::MailboxTextureCallback>
+        binding_;
+  };
+
+  void ReleaseTexture(GLRecycledTextureInfo texture_info, bool recyclable);
+
+  const base::WeakPtr<mojo::GLContext> gl_context_;
+  const uint32_t max_recycled_textures_;
+
+  std::deque<GLRecycledTextureInfo> recycled_textures_;
+  uint32_t bound_textures_ = 0u;
+
+  base::WeakPtrFactory<mojo::ui::GLRenderer> weak_factory_;
+
+  DISALLOW_COPY_AND_ASSIGN(GLRenderer);
+};
+
+}  // namespace ui
+}  // namespace mojo
+
+#endif  // MOJO_UI_GL_RENDERER_H_