gpu: Avoid scissor test for glCopyTextureCHROMIUM if possible.

gpu/command_buffer/service/gles2_cmd_copy_texture_chromium.cc

 // Copyright (c) 2012 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 "gpu/command_buffer/service/gles2_cmd_copy_texture_chromium.h"
 
 #include <algorithm>
 
 #include "base/basictypes.h"
 #include "gpu/command_buffer/service/gl_utils.h"
@@ skipping 411 matching lines @@
       (source_internal_format == GL_RGBA && dest_internal_format == GL_RGB);
   // GL_TEXTURE_RECTANGLE_ARB on FBO is supported by OpenGL, not GLES2,
   // so restrict this to GL_TEXTURE_2D.
   if (source_target == GL_TEXTURE_2D && !flip_y && !premultiply_alpha_change &&
       source_format_contain_superset_of_dest_format) {
     DoCopyTexSubImage2D(decoder, source_target, source_id, dest_id, xoffset,
                         yoffset, x, y, width, height, framebuffer_);
     return;
   }
 
-  DoCopyTextureInternal(decoder, source_target, source_id, dest_id, xoffset - x,
-                        yoffset - y, dest_width, dest_height, source_width,
-                        source_height, flip_y, premultiply_alpha,
-                        unpremultiply_alpha, kIdentityMatrix, xoffset, yoffset,
-                        width, height);
+  DoCopyTextureInternal(decoder, source_target, source_id, dest_id, xoffset,
+                        yoffset, x, y, width, height, dest_width, dest_height,
+                        source_width, source_height, flip_y, premultiply_alpha,
+                        unpremultiply_alpha, kIdentityMatrix);
 }
 
 void CopyTextureCHROMIUMResourceManager::DoCopyTextureWithTransform(
     const gles2::GLES2Decoder* decoder,
     GLenum source_target,
     GLuint source_id,
     GLuint dest_id,
     GLsizei width,
     GLsizei height,
     bool flip_y,
     bool premultiply_alpha,
     bool unpremultiply_alpha,
     const GLfloat transform_matrix[16]) {
   GLsizei dest_width = width;
   GLsizei dest_height = height;
-  DoCopyTextureInternal(decoder, source_target, source_id, dest_id, 0, 0,
-                        dest_width, dest_height, width, height, flip_y,
-                        premultiply_alpha, unpremultiply_alpha,
-                        transform_matrix, 0, 0, dest_width, dest_height);
+  DoCopyTextureInternal(decoder, source_target, source_id, dest_id, 0, 0, 0, 0,
+                        width, height, dest_width, dest_height, width, height,
+                        flip_y, premultiply_alpha, unpremultiply_alpha,
+                        transform_matrix);
 }
 
 void CopyTextureCHROMIUMResourceManager::DoCopyTextureInternal(
     const gles2::GLES2Decoder* decoder,
     GLenum source_target,
     GLuint source_id,
     GLuint dest_id,
     GLint xoffset,
     GLint yoffset,
+    GLint x,
+    GLint y,
+    GLsizei width,
+    GLsizei height,
     GLsizei dest_width,
     GLsizei dest_height,
     GLsizei source_width,
     GLsizei source_height,
     bool flip_y,
     bool premultiply_alpha,
     bool unpremultiply_alpha,
-    const GLfloat transform_matrix[16],
-    GLint scissor_x,
-    GLint scissor_y,
-    GLsizei scissor_width,
-    GLsizei scissor_height) {
+    const GLfloat transform_matrix[16]) {
   DCHECK(source_target == GL_TEXTURE_2D ||
          source_target == GL_TEXTURE_RECTANGLE_ARB ||
          source_target == GL_TEXTURE_EXTERNAL_OES);
   DCHECK(xoffset >= 0 && xoffset + source_width <= dest_width);
   DCHECK(yoffset >= 0 && yoffset + source_height <= dest_height);
   if (!initialized_) {
     DLOG(ERROR) << "CopyTextureCHROMIUM: Uninitialized manager.";
     return;
   }
 
@@ skipping 28 matching lines @@
     glGetProgramiv(info->program, GL_LINK_STATUS, &linked);
     if (!linked)
       DLOG(ERROR) << "CopyTextureCHROMIUM: program link failure.";
 #endif
     info->matrix_handle = glGetUniformLocation(info->program, "u_matrix");
     info->half_size_handle = glGetUniformLocation(info->program, "u_half_size");
     info->sampler_handle = glGetUniformLocation(info->program, "u_sampler");
   }
   glUseProgram(info->program);
 
-  if (!xoffset && !yoffset) {
+  GLint x_translate = xoffset - x;
+  GLint y_translate = yoffset - y;
+  if (!x_translate && !y_translate) {
     glUniformMatrix4fv(info->matrix_handle, 1, GL_FALSE, transform_matrix);
   } else {
     // transform offsets from ([0, dest_width], [0, dest_height]) coord.
     // to ([-1, 1], [-1, 1]) coord.
-    GLfloat xoffset_on_vertex = ((2.f * xoffset) / dest_width);
-    GLfloat yoffset_on_vertex = ((2.f * yoffset) / dest_height);
+    GLfloat x_translate_on_vertex = ((2.f * x_translate) / dest_width);
+    GLfloat y_translate_on_vertex = ((2.f * y_translate) / dest_height);
 
     // Pass view_matrix * offset_matrix to the program.
     GLfloat view_transform[16];
     memcpy(view_transform, transform_matrix, 16 * sizeof(GLfloat));
-    PreTranslate(view_transform, xoffset_on_vertex, yoffset_on_vertex, 0);
+    PreTranslate(view_transform, x_translate_on_vertex, y_translate_on_vertex,
+                 0);
     glUniformMatrix4fv(info->matrix_handle, 1, GL_FALSE, view_transform);
   }
   if (source_target == GL_TEXTURE_RECTANGLE_ARB)
     glUniform2f(info->half_size_handle, source_width / 2.0f,
                 source_height / 2.0f);
   else
     glUniform2f(info->half_size_handle, 0.5f, 0.5f);
 
   if (BindFramebufferTexture2D(GL_TEXTURE_2D, dest_id, framebuffer_)) {
 #ifndef NDEBUG
@@ skipping 21 matching lines @@
     glTexParameteri(source_target, GL_TEXTURE_MAG_FILTER, GL_NEAREST);
     glTexParameteri(source_target, GL_TEXTURE_MIN_FILTER, GL_NEAREST);
 
     glDisable(GL_DEPTH_TEST);
     glDisable(GL_STENCIL_TEST);
     glDisable(GL_CULL_FACE);
     glColorMask(GL_TRUE, GL_TRUE, GL_TRUE, GL_TRUE);
     glDepthMask(GL_FALSE);
     glDisable(GL_BLEND);
 
-    glEnable(GL_SCISSOR_TEST);
-    glScissor(scissor_x, scissor_y, scissor_width, scissor_height);
+    bool need_scissor =
+        xoffset || yoffset || width != dest_width || height != dest_height;
+    if (need_scissor) {
+      glEnable(GL_SCISSOR_TEST);
+      glScissor(xoffset, yoffset, width, height);
+    }
     glViewport(0, 0, dest_width, dest_height);
     glDrawArrays(GL_TRIANGLE_FAN, 0, 4);
   }
 
   decoder->RestoreAllAttributes();
   decoder->RestoreTextureState(source_id);
   decoder->RestoreTextureState(dest_id);
   decoder->RestoreTextureUnitBindings(0);
   decoder->RestoreActiveTexture();
   decoder->RestoreProgramBindings();
   decoder->RestoreBufferBindings();
   decoder->RestoreFramebufferBindings();
   decoder->RestoreGlobalState();
 }
 
 }  // namespace gpu