Clamp YUV videos to their visible size in the shader

cc/output/gl_renderer.cc

 // Copyright 2010 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/gl_renderer.h"
 
 #include <algorithm>
 #include <limits>
 #include <set>
 #include <string>
@@ skipping 1814 matching lines @@
   scoped_ptr<ResourceProvider::ScopedSamplerGL> a_plane_lock;
   if (use_alpha_plane) {
     a_plane_lock.reset(new ResourceProvider::ScopedSamplerGL(
         resource_provider_, quad->a_plane_resource_id, GL_TEXTURE4, GL_LINEAR));
     DCHECK_EQ(static_cast<GLenum>(GL_TEXTURE_2D), a_plane_lock->target());
   }
 
   int matrix_location = -1;
   int tex_scale_location = -1;
   int tex_offset_location = -1;
+  int clamp_rect_location = -1;
   int y_texture_location = -1;
   int u_texture_location = -1;
   int v_texture_location = -1;
   int a_texture_location = -1;
   int yuv_matrix_location = -1;
   int yuv_adj_location = -1;
   int alpha_location = -1;
   if (use_alpha_plane) {
     const VideoYUVAProgram* program = GetVideoYUVAProgram(tex_coord_precision);
     DCHECK(program && (program->initialized() || IsContextLost()));
     SetUseProgram(program->program());
     matrix_location = program->vertex_shader().matrix_location();
     tex_scale_location = program->vertex_shader().tex_scale_location();
     tex_offset_location = program->vertex_shader().tex_offset_location();
     y_texture_location = program->fragment_shader().y_texture_location();
     u_texture_location = program->fragment_shader().u_texture_location();
     v_texture_location = program->fragment_shader().v_texture_location();
     a_texture_location = program->fragment_shader().a_texture_location();
     yuv_matrix_location = program->fragment_shader().yuv_matrix_location();
     yuv_adj_location = program->fragment_shader().yuv_adj_location();
+    clamp_rect_location = program->fragment_shader().clamp_rect_location();
     alpha_location = program->fragment_shader().alpha_location();
   } else {
     const VideoYUVProgram* program = GetVideoYUVProgram(tex_coord_precision);
     DCHECK(program && (program->initialized() || IsContextLost()));
     SetUseProgram(program->program());
     matrix_location = program->vertex_shader().matrix_location();
     tex_scale_location = program->vertex_shader().tex_scale_location();
     tex_offset_location = program->vertex_shader().tex_offset_location();
     y_texture_location = program->fragment_shader().y_texture_location();
     u_texture_location = program->fragment_shader().u_texture_location();
     v_texture_location = program->fragment_shader().v_texture_location();
     yuv_matrix_location = program->fragment_shader().yuv_matrix_location();
     yuv_adj_location = program->fragment_shader().yuv_adj_location();
+    clamp_rect_location = program->fragment_shader().clamp_rect_location();
     alpha_location = program->fragment_shader().alpha_location();
   }
 
   GLC(gl_,
       gl_->Uniform2f(tex_scale_location,
                      quad->tex_coord_rect.width(),
                      quad->tex_coord_rect.height()));
   GLC(gl_,
       gl_->Uniform2f(tex_offset_location,
                      quad->tex_coord_rect.x(),
                      quad->tex_coord_rect.y()));
+  // Clamping to half a texel inside the tex coord rect prevents bilinear
+  // filtering from filtering outside the tex coord rect.
+  gfx::RectF clamp_rect(quad->tex_coord_rect);
+  // Special case: empty texture size implies no clamping.
+  if (!quad->tex_size.IsEmpty()) {
+    clamp_rect.Inset(0.5f / quad->tex_size.width(),
+                     0.5f / quad->tex_size.height());
+  }
+  GLC(gl_, gl_->Uniform4f(clamp_rect_location, clamp_rect.x(), clamp_rect.y(),
+                          clamp_rect.right(), clamp_rect.bottom()));
+
   GLC(gl_, gl_->Uniform1i(y_texture_location, 1));
   GLC(gl_, gl_->Uniform1i(u_texture_location, 2));
   GLC(gl_, gl_->Uniform1i(v_texture_location, 3));
   if (use_alpha_plane)
     GLC(gl_, gl_->Uniform1i(a_texture_location, 4));
 
   // These values are magic numbers that are used in the transformation from YUV
   // to RGB color values.  They are taken from the following webpage:
   // http://www.fourcc.org/fccyvrgb.php
   float yuv_to_rgb_rec601[9] = {
@@ skipping 1403 matching lines @@
     context_support_->ScheduleOverlayPlane(
         overlay.plane_z_order,
         overlay.transform,
         pending_overlay_resources_.back()->texture_id(),
         overlay.display_rect,
         overlay.uv_rect);
   }
 }
 
 }  // namespace cc