cc: Adding support for RGBA_4444 tile textures

cc/resources/resource_provider.cc

Index: cc/resources/resource_provider.cc
diff --git a/cc/resources/resource_provider.cc b/cc/resources/resource_provider.cc
index 9779a546958441a5af186e05e316b4dcc795e1bd..66b31183ffdaedb9c17c174b2cf2c1ee2ae05bbc 100644
--- a/cc/resources/resource_provider.cc
+++ b/cc/resources/resource_provider.cc
@@ -7,6 +7,10 @@
 #include <algorithm>
 #include <limits>
 
+#if defined(OS_ANDROID)
+#include "base/android/sys_utils.h"
+#endif
+
 #include "base/containers/hash_tables.h"
 #include "base/debug/alias.h"
 #include "base/stl_util.h"
@@ -681,8 +685,13 @@ ResourceProvider::ResourceProvider(OutputSurface* output_surface,
       use_texture_usage_hint_(false),
       use_shallow_flush_(false),
       max_texture_size_(0),
-      best_texture_format_(0) {
+      best_texture_format_(0),

[epennerAtGoogle, 2013/09/05 01:54:15]

Could we have best_texture_type in addition to best_texture_format, and avoid
any #ifdefs/booleans?

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

Done.

+      use_16_bit_textures_(false) {
   DCHECK(output_surface_->HasClient());
+#if defined(OS_ANDROID)
+  if (base::android::SysUtils::IsLowEndDevice())
+    use_16_bit_textures_ = true;

[enne (OOO), 2013/09/05 02:01:19]

Please make this a LayerTreeSetting and keep the #ifdef out of cc so that this
setting can be tested in a device-independent manner.

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

Done.

+#endif
 }
 
 void ResourceProvider::InitializeSoftware() {
@@ -719,7 +728,10 @@ bool ResourceProvider::InitializeGL() {
   use_texture_usage_hint_ = caps.texture_usage;
 
   texture_uploader_ =
-      TextureUploader::Create(context3d, use_map_sub, use_shallow_flush_);
+      TextureUploader::Create(context3d,
+                              use_map_sub,
+                              use_shallow_flush_,
+                              use_16_bit_textures_);
   GLC(context3d, context3d->getIntegerv(GL_MAX_TEXTURE_SIZE,
                                         &max_texture_size_));
   best_texture_format_ = PlatformColor::BestTextureFormat(use_bgra);
@@ -975,9 +987,10 @@ void ResourceProvider::AcquirePixelBuffer(ResourceId id) {
     context3d->bindBuffer(
         GL_PIXEL_UNPACK_TRANSFER_BUFFER_CHROMIUM,
         resource->gl_pixel_buffer_id);
+    size_t bytes_per_pixel = use_16_bit_textures_ ? 2 : 4;
     context3d->bufferData(
         GL_PIXEL_UNPACK_TRANSFER_BUFFER_CHROMIUM,
-        4 * resource->size.GetArea(),
+        bytes_per_pixel * resource->size.GetArea(),
         NULL,
         GL_DYNAMIC_DRAW);
     context3d->bindBuffer(GL_PIXEL_UNPACK_TRANSFER_BUFFER_CHROMIUM, 0);
@@ -1159,6 +1172,8 @@ void ResourceProvider::BeginSetPixels(ResourceId id) {
     context3d->beginQueryEXT(
         GL_ASYNC_PIXEL_UNPACK_COMPLETED_CHROMIUM,
         resource->gl_upload_query_id);
+    GLenum texture_data_type = use_16_bit_textures_

[enne (OOO), 2013/09/05 02:01:19]

Rather than having to pass around booleans and settings that force every texture
into one mode or the other, can resources just have a texture_data_type value? 
Maybe there could just be a LayerTreeSetting for preferred texture_data_type and
ResourceProvider could try to respect that when generating resources.

That way you could (potentially) have two different formats at once and cc gets
a feature rather than a mode.

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

Great point, I didn't have time for it today. I'll look into it tomorrow.

+        ? GL_UNSIGNED_SHORT_4_4_4_4 : GL_UNSIGNED_BYTE;
     if (allocate) {
       context3d->asyncTexImage2DCHROMIUM(GL_TEXTURE_2D,
                                          0, /* level */
@@ -1167,7 +1182,7 @@ void ResourceProvider::BeginSetPixels(ResourceId id) {
                                          resource->size.height(),
                                          0, /* border */
                                          resource->format,
-                                         GL_UNSIGNED_BYTE,
+                                         texture_data_type,
                                          NULL);
     } else {
       context3d->asyncTexSubImage2DCHROMIUM(GL_TEXTURE_2D,
@@ -1177,7 +1192,7 @@ void ResourceProvider::BeginSetPixels(ResourceId id) {
                                             resource->size.width(),
                                             resource->size.height(),
                                             resource->format,
-                                            GL_UNSIGNED_BYTE,
+                                            texture_data_type,
                                             NULL);
     }
     context3d->endQueryEXT(GL_ASYNC_PIXEL_UNPACK_COMPLETED_CHROMIUM);
@@ -1288,6 +1303,8 @@ void ResourceProvider::LazyAllocate(Resource* resource) {
                                               size.width(),
                                               size.height()));
   } else {
+    GLenum texture_data_type = use_16_bit_textures_
+        ? GL_UNSIGNED_SHORT_4_4_4_4 : GL_UNSIGNED_BYTE;
     GLC(context3d, context3d->texImage2D(GL_TEXTURE_2D,
                                          0,
                                          format,
@@ -1295,7 +1312,7 @@ void ResourceProvider::LazyAllocate(Resource* resource) {
                                          size.height(),
                                          0,
                                          format,
-                                         GL_UNSIGNED_BYTE,
+                                         texture_data_type,
                                          NULL));
   }
 }