[Chromoting] Implement GlRenderer

remoting/client/gl_math.cc

 // 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.
 
 #include "remoting/client/gl_math.h"
 
 #include <sstream>
 
 namespace {
 
-// | m0, m1, m2, |   | Scale_x  0        Offset_x |
-// | m3, m4, m5, | = | 0        Scale_y  Offset_y |
+// | m0, m1, m2, |   | Scale_x  Skew_x   Offset_x |
+// | m3, m4, m5, | = | Skew_y   Scale_y  Offset_y |
 // | m6, m7, m8  |   | 0        0        1        |
 
 const int kXScaleKey = 0;
+const int kXSkewKey = 1;
+const int kXOffsetKey = 2;
+
+const int kYSkewKey = 3;
 const int kYScaleKey = 4;
-const int kXOffsetKey = 2;
 const int kYOffsetKey = 5;
 
+const int kXOffsetTransposedKey = 6;
+const int kYOffsetTransposedKey = 7;
+
 }  // namespace
 
 namespace remoting {
 
 void NormalizeTransformationMatrix(int view_width,
                                    int view_height,
                                    int canvas_width,
                                    int canvas_height,
                                    std::array<float, 9>* matrix) {
   (*matrix)[kXScaleKey] = canvas_width * (*matrix)[kXScaleKey] / view_width;
   (*matrix)[kYScaleKey] = canvas_height * (*matrix)[kYScaleKey] / view_height;
   (*matrix)[kXOffsetKey] /= view_width;
   (*matrix)[kYOffsetKey] /= view_height;
 }
 
+void TransposeTransformationMatrix(std::array<float, 9>* matrix) {
+  std::swap((*matrix)[kXOffsetKey], (*matrix)[kXOffsetTransposedKey]);
+  std::swap((*matrix)[kYOffsetKey], (*matrix)[kYOffsetTransposedKey]);
+  std::swap((*matrix)[kXSkewKey], (*matrix)[kYSkewKey]);
+}
+
 void FillRectangleVertexPositions(float left,
                                   float top,
                                   float width,
                                   float height,
                                   std::array<float, 8>* positions) {
   (*positions)[0] = left;
   (*positions)[1] = top;
 
   (*positions)[2] = left;
   (*positions)[3] = top + height;
@@ skipping 12 matching lines @@
     for (int j = 0; j < num_cols; j++) {
       outstream << mat[i * num_cols + j] << ", ";
     }
     outstream << "\n";
   }
   outstream << "]";
   return outstream.str();
 }
 
 }  // namespace remoting