[Remoting] OpenGL Rendering Layer

remoting/client/gl_canvas.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 REMOTING_CLIENT_OPENGL_GL_CANVAS_H_
+#define REMOTING_CLIENT_OPENGL_GL_CANVAS_H_
+
+#include "base/macros.h"
+#include "base/threading/thread_checker.h"
+#include "remoting/client/sys_opengl.h"
+
+namespace remoting {
+
+// This class holds zoom and pan configurations of the canvas and is used to
+// draw textures on the canvas.
+// Must be constructed after the OpenGL surface is created and destroyed before
+// the surface is destroyed.
+//
+// Coordinates to be used for GlCanvas should be normalized texture coordinates.
+// In the view of a point on the canvas, the canvas has width 1 and height 1,
+// with the origin at the upper-left corner of the canvas.
+class GlCanvas {
+ public:
+  // gl_version: version number of the OpenGL ES context. Either 2 or 3.
+  GlCanvas(int gl_version);
+
+  ~GlCanvas();
+
+  // Sets the normalized transformation matrix. This matrix defines how the
+  // canvas should be shown on the view.
+  // 3 by 3 transformation matrix, [ m0, m1, m2, m3, m4, m5, m6, m7, m8 ].
+  // The matrix will be multiplied with the positions (with projective space,
+  // (x, y, 1)) to draw the textures with the right zoom and pan configuration.
+  //
+  // | m0, m1, m2, |   | x |
+  // | m3, m4, m5, | * | y |
+  // | m6, m7, m8  |   | 1 |
+  //
+  // For a typical transformation matrix such that m1=m3=m6=m7=0 and m8=1, m0
+  // and m4 defines the ratio of canvas width or height over view width or
+  // height. m2 and m5 defines the offset of the upper-left corner in percentage
+  // of the view's width or height. An identity matrix will stretch the canvas
+  // to fit the whole view.
+  void SetNormalizedTransformation(const float* matrix);

[Sergey Ulanov, 2016/07/09 01:01:20]

nit: would be more typesafe to use std::array<float, 9> here.

[Yuwei, 2016/07/09 01:21:24]

Just curious will there be performance drawback compared to C array?

[Yuwei, 2016/07/11 22:38:23]

Done. Also use std::array everywhere else.

[Sergey Ulanov, 2016/07/13 04:42:11]

no, as long as it's passed by reference or pointer.

[Yuwei, 2016/07/13 18:14:16]

Acknowledged.

+
+  // Draws the texture on the canvas. Nothing will happen if
+  // SetNormalizedTransformation() has not been called.
+  // vertex_buffer: reference to the 2x4x2 float vertex buffer.
+  //                [ four (x, y) normalized vertex positions on the canvas,
+  //                  four (x, y) vertex positions to define the visible area ]
+  void DrawTexture(int texture_id, GLuint texture_handle, GLuint vertex_buffer);
+
+  // Returns the version number of current OpenGL ES context. Either 2 or 3.
+  int GetGlVersion() const;
+
+ private:
+  int gl_version_;
+
+  // True IFF the transformation has been set.
+  bool transformation_set_ = false;
+
+  // Handles.
+  GLuint vertex_shader_;
+  GLuint fragment_shader_;
+  GLuint program_;
+
+  // Locations of the corresponding shader attributes.
+  GLuint transform_location_;
+  GLuint texture_location_;
+  GLuint position_location_;
+  GLuint tex_cord_location_;
+
+  base::ThreadChecker thread_checker_;
+
+  DISALLOW_COPY_AND_ASSIGN(GlCanvas);
+};
+
+}  // namespace remoting
+
+#endif  // REMOTING_CLIENT_OPENGL_GL_CANVAS_H_