cc: Adding support for RGBA_4444 tile textures

cc/scheduler/texture_uploader.cc

Index: cc/scheduler/texture_uploader.cc
diff --git a/cc/scheduler/texture_uploader.cc b/cc/scheduler/texture_uploader.cc
index 920c38e669275d0992d6b5166a1683464aecaad4..c24b2c47f760efc9383eca6e11c1cc9fd340ae5a 100644
--- a/cc/scheduler/texture_uploader.cc
+++ b/cc/scheduler/texture_uploader.cc
@@ -77,13 +77,15 @@ unsigned TextureUploader::Query::Value() {
 
 TextureUploader::TextureUploader(WebKit::WebGraphicsContext3D* context,
                                  bool use_map_tex_sub_image,
-                                 bool use_shallow_flush)
+                                 bool use_shallow_flush,
+                                 bool use_16_bit_textures)
     : context_(context),
       num_blocking_texture_uploads_(0),
       use_map_tex_sub_image_(use_map_tex_sub_image),
       sub_image_size_(0),
       use_shallow_flush_(use_shallow_flush),
-      num_texture_uploads_since_last_flush_(0) {
+      num_texture_uploads_since_last_flush_(0),
+      use_16_bit_textures_(use_16_bit_textures) {
   for (size_t i = kUploadHistorySizeInitial; i > 0; i--)
     textures_per_second_history_.insert(kDefaultEstimatedTexturesPerSecond);
 }
@@ -207,11 +209,13 @@ void TextureUploader::UploadWithTexSubImage(const uint8* image,
   gfx::Vector2d offset(source_rect.origin() - image_rect.origin());
 
   const uint8* pixel_source;
-  unsigned int bytes_per_pixel = Resource::BytesPerPixel(format);
+  unsigned int bytes_per_pixel = Resource::BytesPerPixel(format,
+                                                         use_16_bit_textures_);
+  // TODO(kaanb): anything to do to GL_UNPACK_ALIGNMENT for 16_bit?

[Sami, 2013/09/05 14:13:26]

Yes, it needs to be set to 2 bytes. Otherwise odd-width bitmaps will look, well,
odd :) The alternative is to allocate our 16 bit source bitmaps with 4-byte
aligned strides. I'm not sure if Skia supports that.

[kaanb, 2013/09/06 02:05:54]

Silly question, how and where should it be set?

   // Use 4-byte row alignment (OpenGL default) for upload performance.
   // Assuming that GL_UNPACK_ALIGNMENT has not changed from default.
   unsigned int upload_image_stride =
-      RoundUp(bytes_per_pixel * source_rect.width(), 4u);
+      RoundUp(bytes_per_pixel * source_rect.width(), bytes_per_pixel);
 
   if (upload_image_stride == image_rect.width() * bytes_per_pixel &&
       !offset.x()) {
@@ -233,6 +237,8 @@ void TextureUploader::UploadWithTexSubImage(const uint8* image,
     pixel_source = &sub_image_[0];
   }
 
+  GLenum texture_data_type = use_16_bit_textures_
+      ? GL_UNSIGNED_SHORT_4_4_4_4 : GL_UNSIGNED_BYTE;
   context_->texSubImage2D(GL_TEXTURE_2D,
                           0,
                           dest_offset.x(),
@@ -240,7 +246,7 @@ void TextureUploader::UploadWithTexSubImage(const uint8* image,
                           source_rect.width(),
                           source_rect.height(),
                           format,
-                          GL_UNSIGNED_BYTE,
+                          texture_data_type,
                           pixel_source);
 }
 
@@ -277,12 +283,16 @@ void TextureUploader::UploadWithMapTexSubImage(const uint8* image,
   // Offset from image-rect to source-rect.
   gfx::Vector2d offset(source_rect.origin() - image_rect.origin());
 
-  unsigned int bytes_per_pixel = Resource::BytesPerPixel(format);
+  unsigned int bytes_per_pixel = Resource::BytesPerPixel(format,
+                                                         use_16_bit_textures_);
+  // TODO(kaanb): anything to do to GL_UNPACK_ALIGNMENT for 16 bit?
   // Use 4-byte row alignment (OpenGL default) for upload performance.
   // Assuming that GL_UNPACK_ALIGNMENT has not changed from default.
   unsigned int upload_image_stride =
-      RoundUp(bytes_per_pixel * source_rect.width(), 4u);
+      RoundUp(bytes_per_pixel * source_rect.width(), bytes_per_pixel);
 
+  GLenum texture_data_type = use_16_bit_textures_
+      ? GL_UNSIGNED_SHORT_4_4_4_4 : GL_UNSIGNED_BYTE;
   // Upload tile data via a mapped transfer buffer
   uint8* pixel_dest = static_cast<uint8*>(
       context_->mapTexSubImage2DCHROMIUM(GL_TEXTURE_2D,
@@ -292,7 +302,7 @@ void TextureUploader::UploadWithMapTexSubImage(const uint8* image,
                                          source_rect.width(),
                                          source_rect.height(),
                                          format,
-                                         GL_UNSIGNED_BYTE,
+                                         texture_data_type,
                                          GL_WRITE_ONLY));
 
   if (!pixel_dest) {