Clamp YUV videos to their visible size in the shader

cc/output/shader.cc

 // Copyright 2011 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 "cc/output/shader.h"
 
 #include <algorithm>
 
 #include "base/basictypes.h"
 #include "base/logging.h"
@@ skipping 173 matching lines @@
       void main() {
         gl_Position = matrix * a_position;
         v_texCoord = a_texCoord;
       }
       // clang-format off
   );  // NOLINT(whitespace/parens)
   // clang-format on
 }
 
 VertexShaderPosTexYUVStretchOffset::VertexShaderPosTexYUVStretchOffset()
-    : matrix_location_(-1), tex_scale_location_(-1), tex_offset_location_(-1) {
+    : matrix_location_(-1),
+      tex_scale_location_(-1),
+      tex_offset_location_(-1),
+      clamp_size_location_(-1) {
 }
 
 void VertexShaderPosTexYUVStretchOffset::Init(GLES2Interface* context,
                                               unsigned program,
                                               int* base_uniform_index) {
   static const char* uniforms[] = {
-      "matrix", "texScale", "texOffset",
+      "matrix", "texScale", "texOffset", "clampSize",
   };
   int locations[arraysize(uniforms)];
 
   GetProgramUniformLocations(context,
                              program,
                              arraysize(uniforms),
                              uniforms,
                              locations,
                              base_uniform_index);
   matrix_location_ = locations[0];
   tex_scale_location_ = locations[1];
   tex_offset_location_ = locations[2];
+  clamp_size_location_ = locations[3];
 }
 
 std::string VertexShaderPosTexYUVStretchOffset::GetShaderString() const {
   // clang-format off
   return VERTEX_SHADER(
       // clang-format on
-      precision mediump float;
-      attribute vec4 a_position;
-      attribute TexCoordPrecision vec2 a_texCoord;
-      uniform mat4 matrix;
+      precision mediump float; attribute vec4 a_position;
+      attribute TexCoordPrecision vec2 a_texCoord; uniform mat4 matrix;
       varying TexCoordPrecision vec2 v_texCoord;
       uniform TexCoordPrecision vec2 texScale;
       uniform TexCoordPrecision vec2 texOffset;
-      void main() {
+      uniform TexCoordPrecision vec2 clampSize; void main() {

[danakj, 2015/01/28 01:02:00]

formatting..

[enne (OOO), 2015/01/31 01:32:13]

git cl format T_T

         gl_Position = matrix * a_position;
-        v_texCoord = a_texCoord * texScale + texOffset;
+        v_texCoord = min(clampSize, a_texCoord * texScale + texOffset);

[danakj, 2015/01/28 01:02:00]

do we not have to clamp on the left/top too?

[enne (OOO), 2015/01/31 01:32:13]

Turns out we do.  Thanks.  I changed clampSize to clampRect in the shader, but
left it as "texture size" in the quad, since that's easier to specify.

       }
       // clang-format off
   );  // NOLINT(whitespace/parens)
   // clang-format on
 }
 
 VertexShaderPos::VertexShaderPos() : matrix_location_(-1) {
 }
 
 void VertexShaderPos::Init(GLES2Interface* context,
@@ skipping 1744 matching lines @@
         vec2 coord = mod(floor(texCoord * frequency * 2.0), 2.0);
         float picker = abs(coord.x - coord.y);  // NOLINT
         gl_FragColor = mix(color1, color2, picker) * alpha;
       }
       // clang-format off
   );  // NOLINT(whitespace/parens)
   // clang-format on
 }
 
 }  // namespace cc