Fix immutable tex srgb emulation issue of generateMipmap

gpu/command_buffer/service/gles2_cmd_srgb_converter.cc

 // Copyright (c) 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 "gpu/command_buffer/service/gles2_cmd_srgb_converter.h"
 
 #include "gpu/command_buffer/service/texture_manager.h"
 #include "ui/gl/gl_version_info.h"
 
 namespace {
@@ skipping 397 matching lines @@
   GLsizei width;
   GLsizei height;
   GLsizei depth;
   GLenum type = 0;
   GLenum internal_format = 0;
   GLenum format = 0;
   GLsizei base_level = tex->base_level();
   tex->GetLevelSize(target, base_level, &width, &height, &depth);
   tex->GetLevelType(target, base_level, &type, &internal_format);
   format = TextureManager::ExtractFormatFromStorageFormat(internal_format);
-  const GLint mipmap_levels =
-      TextureManager::ComputeMipMapCount(target, width, height, depth);
+  GLint mipmap_levels;
+  if (tex->IsImmutable()) {
+    mipmap_levels = tex->GetImmutableLevels();
+  } else {
+    mipmap_levels =
+        TextureManager::ComputeMipMapCount(target, width, height, depth);
+  }
 
   glBindTexture(GL_TEXTURE_2D, srgb_converter_textures_[1]);
   if (feature_info_->ext_color_buffer_float_available() &&
       feature_info_->oes_texture_float_linear_available()) {
     glTexImage2D(GL_TEXTURE_2D, 0, GL_RGBA32F, width, height, 0, GL_RGBA,
                  GL_FLOAT, nullptr);
   } else {
     glTexImage2D(GL_TEXTURE_2D, 0, GL_RGBA8, width, height, 0, GL_RGBA,
                  GL_UNSIGNED_BYTE, nullptr);
   }
@@ skipping 21 matching lines @@
   glDrawArrays(GL_TRIANGLES, 0, 6);
 
   glBindTexture(GL_TEXTURE_2D, srgb_converter_textures_[1]);
   glGenerateMipmapEXT(GL_TEXTURE_2D);
 
   // bind tex with rgba format and render with srgb_converter_program_
   glBindFramebufferEXT(GL_DRAW_FRAMEBUFFER, srgb_encoder_fbo_);
   glBindTexture(GL_TEXTURE_2D, srgb_converter_textures_[1]);
   glTexParameteri(GL_TEXTURE_2D, GL_TEXTURE_MIN_FILTER,
                   GL_NEAREST_MIPMAP_NEAREST);
-  width >>= 1;
-  height >>= 1;
+
+  width = (width == 1) ? 1 : width >> 1;
+  height = (height == 1) ? 1 : height >> 1;
 
   // TODO(yizhou): An optimization. Attach 1 level at a time, once for every
   // iteration of the loop.
   for (GLint level = base_level + 1; level < base_level + mipmap_levels;

[qiankun, 2017/04/24 11:37:58]

When base_level + mipmap_levels is larger than tex->max_level(), this isn't
correct.

[yizhou.jiang, 2017/04/25 04:47:56]

Done.

        ++level) {
     // copy mipmaps level by level from srgb_converter_textures_[1] to tex
     // generate mipmap for tex manually
     glBindTexture(GL_TEXTURE_2D, tex->service_id());
-    glTexImage2D(GL_TEXTURE_2D, level, internal_format, width, height, 0,
-                 format, type, nullptr);
+    if (!tex->IsImmutable()) {
+      glTexImage2D(GL_TEXTURE_2D, level, internal_format, width, height, 0,
+                   format, type, nullptr);
+    }
     glFramebufferTexture2DEXT(GL_DRAW_FRAMEBUFFER, GL_COLOR_ATTACHMENT0,
                               GL_TEXTURE_2D, tex->service_id(), level);
 
     glBindTexture(GL_TEXTURE_2D, srgb_converter_textures_[1]);
     glViewport(0, 0, width, height);
     glDrawArrays(GL_TRIANGLES, 0, 6);
-    width >>= 1;
-    height >>= 1;
+    width = (width == 1) ? 1 : width >> 1;
+    height = (height == 1) ? 1 : height >> 1;
   }
 
   // Restore state
   decoder->RestoreAllAttributes();
   decoder->RestoreTextureUnitBindings(0);
   decoder->RestoreActiveTexture();
   decoder->RestoreProgramBindings();
   decoder->RestoreBufferBindings();
   decoder->RestoreFramebufferBindings();
   decoder->RestoreGlobalState();
   decoder->RestoreTextureState(tex->service_id());
 }
 
 }  // namespace gles2.
 }  // namespace gpu