cc: Adding support for RGBA_4444 tile textures

ui/gl/gl_surface_egl.cc

Index: ui/gl/gl_surface_egl.cc
diff --git a/ui/gl/gl_surface_egl.cc b/ui/gl/gl_surface_egl.cc
index 8c29342ab408e2f0e10fb0ff370807d449c5646c..67e2a15629559e03aa50250bdedb237e592bad94 100644
--- a/ui/gl/gl_surface_egl.cc
+++ b/ui/gl/gl_surface_egl.cc
@@ -9,6 +9,7 @@
 #include "ui/gl/gl_surface_egl.h"
 
 #if defined(OS_ANDROID)
+#include "base/android/sys_utils.h"
 #include <android/native_window_jni.h>
 #endif
 
@@ -125,6 +126,11 @@ bool GLSurfaceEGL::InitializeOneOff() {
     return false;
   }
 
+  bool use_16bit_surface = false;
+#if defined(OS_ANDROID)
+  use_16bit_surface = base::android::SysUtils::IsLowEndDevice();

[no sievers, 2013/08/13 01:13:58]

can you make this static so it's clear that we are not supposed to start using
different configs?

[kaanb, 2013/08/13 04:20:40]

Done.

+#endif
+
   // Choose an EGL configuration.
   // On X this is only used for PBuffer surfaces.
   static const EGLint kConfigAttribs[] = {
@@ -138,9 +144,16 @@ bool GLSurfaceEGL::InitializeOneOff() {
     EGL_NONE
   };
 
+  static const EGLint kConfigAttribs16bit[] = {
+    EGL_BUFFER_SIZE, 16,
+    EGL_RENDERABLE_TYPE, EGL_OPENGL_ES2_BIT,
+    EGL_SURFACE_TYPE, EGL_WINDOW_BIT | EGL_PBUFFER_BIT,

[no sievers, 2013/08/13 01:13:58]

We need to make sure that this config works across devices with pbuffers and
windows for virtual contexts (offscreen contexts might be made current with both
onscreen and offscreen surfaces).

+    EGL_NONE
+  };
+
   EGLint num_configs;
   if (!eglChooseConfig(g_display,
-                       kConfigAttribs,
+                       use_16bit_surface ? kConfigAttribs16bit : kConfigAttribs,
                        NULL,
                        0,
                        &num_configs)) {
@@ -155,7 +168,7 @@ bool GLSurfaceEGL::InitializeOneOff() {
   }
 
   if (!eglChooseConfig(g_display,
-                       kConfigAttribs,
+                       use_16bit_surface ? kConfigAttribs16bit : kConfigAttribs,

[no sievers, 2013/08/13 01:13:58]

It seems like num_configs could be >0 (since it's more vague above). If you are
DCHECKing() for the precise config you want below, why don't you just add it to
kConfigAttribs16bit in the first place then?

[kaanb, 2013/08/13 04:20:40]

The trouble is if you explicitly ask for 5-6-5 you get a 8-8-8 or 8-8-8-8 as
higher resolutions have higher priority. Just asking for 16bits is the only
reliable way of getting 16bits. It is explained here:

http://malideveloper.arm.com/develop-for-mali/sample-code/selecting-the-corre...

                        &g_config,
                        1,
                        &num_configs)) {
@@ -164,6 +177,17 @@ bool GLSurfaceEGL::InitializeOneOff() {
     return false;

[no sievers, 2013/08/13 01:13:58]

Also, if we don't get a 16bit config, should we fall back to 32bit?

[kaanb, 2013/08/13 04:20:40]

I think the eglChooseConfig will automatically select the 32bit configuration if
it's the only available one. So we don't need a fallback logic.

   }
 
+  if (use_16bit_surface) {
+    EGLint red_size, green_size, blue_size;
+    eglGetConfigAttrib(g_display, g_config, EGL_RED_SIZE, &red_size);
+    eglGetConfigAttrib(g_display, g_config, EGL_GREEN_SIZE, &green_size);
+    eglGetConfigAttrib(g_display, g_config, EGL_BLUE_SIZE, &blue_size);
+
+    DCHECK_EQ(5, red_size);
+    DCHECK_EQ(6, green_size);
+    DCHECK_EQ(5, blue_size);
+  }
+
   g_egl_extensions = eglQueryString(g_display, EGL_EXTENSIONS);
   g_egl_create_context_robustness_supported =
       HasEGLExtension("EGL_EXT_create_context_robustness");