Add 16-bit support for browser compositor surface

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 b6a7184c129f7e3e18588c69864f775420ab7ae3..ab03b131d42f609c308d3cfd0b20c906e07c1286 100644
--- a/ui/gl/gl_surface_egl.cc
+++ b/ui/gl/gl_surface_egl.cc
@@ -10,6 +10,7 @@
 
 #if defined(OS_ANDROID)
 #include <android/native_window_jni.h>
+#include "base/android/sys_utils.h"
 #endif
 
 #include "base/command_line.h"
@@ -137,7 +138,7 @@ bool GLSurfaceEGL::InitializeOneOff() {
 
   // Choose an EGL configuration.
   // On X this is only used for PBuffer surfaces.
-  static const EGLint kConfigAttribs[] = {
+  static EGLint config_attribs_8888[] = {
     EGL_BUFFER_SIZE, 32,
     EGL_ALPHA_SIZE, 8,
     EGL_BLUE_SIZE, 8,
@@ -148,11 +149,31 @@ bool GLSurfaceEGL::InitializeOneOff() {
     EGL_NONE
   };
 
+#if defined(OS_ANDROID)
+  static EGLint config_attribs_565[] = {
+    EGL_BUFFER_SIZE, 16,
+    EGL_BLUE_SIZE, 5,
+    EGL_GREEN_SIZE, 6,
+    EGL_RED_SIZE, 5,
+    EGL_RENDERABLE_TYPE, EGL_OPENGL_ES2_BIT,
+    EGL_SURFACE_TYPE, EGL_WINDOW_BIT | EGL_PBUFFER_BIT,
+    EGL_NONE
+  };
+#endif
+
+  EGLint* choose_attributes = config_attribs_8888;
+
+#if defined(OS_ANDROID)
+  if (base::android::SysUtils::IsLowEndDevice()) {
+    choose_attributes = config_attribs_565;
+  }
+#endif
+
 #if defined(USE_OZONE)
   const EGLint* config_attribs =
-      surface_factory->GetEGLSurfaceProperties(kConfigAttribs);
+      surface_factory->GetEGLSurfaceProperties(choose_attributes);
 #else
-  const EGLint* config_attribs = kConfigAttribs;
+  const EGLint* config_attribs = choose_attributes;
 #endif
 
   EGLint num_configs;
@@ -171,16 +192,64 @@ bool GLSurfaceEGL::InitializeOneOff() {
     return false;
   }
 
+  int config_size = 1;
+  EGLConfig* config_data = &g_config;
+
+#if defined(OS_ANDROID)
+  scoped_ptr<EGLConfig[]> matching_configs(new EGLConfig[num_configs]);
+  if (base::android::SysUtils::IsLowEndDevice()) {
+    config_size = num_configs;
+    config_data = matching_configs.get();
+  }
+#endif
+
   if (!eglChooseConfig(g_display,
                        config_attribs,
-                       &g_config,
-                       1,
+                       config_data,
+                       config_size,
                        &num_configs)) {
     LOG(ERROR) << "eglChooseConfig failed with error "
                << GetLastEGLErrorString();
     return false;
   }
 
+#if defined(OS_ANDROID)
+  if (base::android::SysUtils::IsLowEndDevice()) {
+    // Because of the EGL config sort order, we have to iterate
+    // through all of them (it'll put higher sum(R,G,B) bits
+    // first with the above attribs).
+    bool match_found = false;
+    int default_format = 0;
+    for (int i = 0; i < num_configs; i++) {
+      EGLBoolean success;
+      EGLint red, green, blue, alpha;
+      // Read the relevent attributes of the EGLConfig.
+      success = eglGetConfigAttrib(g_display, matching_configs[i],
+                                   EGL_RED_SIZE, &red);
+      success &= eglGetConfigAttrib(g_display, matching_configs[i],
+                                    EGL_BLUE_SIZE, &blue);
+      success &= eglGetConfigAttrib(g_display, matching_configs[i],
+                                    EGL_GREEN_SIZE, &green);
+      success &= eglGetConfigAttrib(g_display, matching_configs[i],
+                                    EGL_ALPHA_SIZE, &alpha);
+      if ((success == EGL_TRUE) && (red == 8) &&
+        (green == 8) && (blue == 8) && (alpha == 8)) {

[no sievers, 2014/01/21 19:47:46]

Do you think it might be better to take the first config that matches this
rather than the last?
I'm just wondering if we could somehow end up picking a weird config (such as
multisampled, I dunno). The way all the sorting rules work it might be more
promising to pick the first one that matches this criteria. wdyt?

[sivag, 2014/01/22 15:48:20]

I think we should go with the first match as per the sorting rules.
And as per the current code , as we have already choosed the 565 config in
lowend device mode  and if we are not able to find any match for that , we may
never get the fallback choice of  ARGB (because the choosed attributes are for
16bit buffers).So we may have to choose it again with the right ARGB atrributes,
buffer size etc ...to enter the fallback mode.

I am changing the code accordingly, will update the patch by tomorrow.

[sivag, 2014/01/23 11:50:02]

Done.

[sivag, 2014/01/23 11:50:02]

Done.

+         // Fallback to default format when the device fails to support 565.
+         default_format = i;

[no sievers, 2014/01/21 19:47:46]

nit: indent

[sivag, 2014/01/23 11:50:02]

Done.

+      } else if ((success == EGL_TRUE) && (red == 5) &&
+                 (green == 6) && (blue == 5)) {
+        g_config = matching_configs[i];
+        match_found = true;
+        break;
+      }
+    }
+    if (!match_found) {
+      LOG (ERROR) << "Falling back to default 32 bit format";

[no sievers, 2014/01/21 19:47:46]

nit: no space after LOG. Also maybe make it WARNING or INFO.

[sivag, 2014/01/23 11:50:02]

Done.

+      g_config = matching_configs[default_format];
+    }
+  }
+#endif
+
   g_egl_extensions = eglQueryString(g_display, EGL_EXTENSIONS);
   g_egl_create_context_robustness_supported =
       HasEGLExtension("EGL_EXT_create_context_robustness");