commit 13d1b4ab10fbee5e81a2ba1ac59cfae1e51d3ef0
author Season Li <seasonl@nvidia.com> Wed Jul 29 17:16:19 2015 -0700
committer John Reck <jreck@google.com> Tue Aug 04 13:01:54 2015 -0700
tree 6844646af7e67205908076b0fa641dcf24cc6e9d
parent 4692f42b7869110631b0521188afe56a4641ebf2

renderthread: add EGL_EXT_buffer_age support

EGL_EXT_buffer_age is better than EGL_BUFFER_PRESERVED
because it can save memory bandwidth used to blit
back buffer into front buffer.

Change-Id: I2fea0ee08dc7dd66e348b04dd694d075d509d01b

libs/hwui/renderthread/EglManager.cpp

diff --git a/libs/hwui/renderthread/EglManager.cpp b/libs/hwui/renderthread/EglManager.cpp
index eb332d5..ac36f53 100644
--- a/libs/hwui/renderthread/EglManager.cpp
+++ b/libs/hwui/renderthread/EglManager.cpp
@@ -76,6 +76,7 @@
         , mEglContext(EGL_NO_CONTEXT)
         , mPBufferSurface(EGL_NO_SURFACE)
         , mAllowPreserveBuffer(load_dirty_regions_property())
+        , mHasBufferAgeExt(false)
         , mCurrentSurface(EGL_NO_SURFACE)
         , mAtlasMap(nullptr)
         , mAtlasMapSize(0) {
@@ -98,7 +99,10 @@
 
     ALOGI("Initialized EGL, version %d.%d", (int)major, (int)minor);
 
-    loadConfig();
+    findExtensions(eglQueryString(mEglDisplay, EGL_EXTENSIONS), mEglExtensionList);
+    mHasBufferAgeExt = hasEglExtension("EGL_EXT_buffer_age");
+
+    loadConfig(mHasBufferAgeExt);
     createContext();
     createPBufferSurface();
     makeCurrent(mPBufferSurface);
@@ -110,8 +114,13 @@
     return mEglDisplay != EGL_NO_DISPLAY;
 }
 
-void EglManager::loadConfig() {
-    EGLint swapBehavior = mCanSetPreserveBuffer ? EGL_SWAP_BEHAVIOR_PRESERVED_BIT : 0;
+bool EglManager::hasEglExtension(const char* extension) const {
+   const std::string s(extension);
+   return mEglExtensionList.find(s) != mEglExtensionList.end();
+}
+
+void EglManager::loadConfig(bool useBufferAgeExt) {
+    EGLint swapBehavior = (!useBufferAgeExt && mCanSetPreserveBuffer) ? EGL_SWAP_BEHAVIOR_PRESERVED_BIT : 0;
     EGLint attribs[] = {
             EGL_RENDERABLE_TYPE, EGL_OPENGL_ES2_BIT,
             EGL_RED_SIZE, 8,
@@ -133,7 +142,7 @@
             ALOGW("Failed to choose config with EGL_SWAP_BEHAVIOR_PRESERVED, retrying without...");
             // Try again without dirty regions enabled
             mCanSetPreserveBuffer = false;
-            loadConfig();
+            loadConfig(useBufferAgeExt);
         } else {
             LOG_ALWAYS_FATAL("Failed to choose config, error = %s", egl_error_str());
         }
@@ -238,7 +247,7 @@
     return true;
 }
 
-void EglManager::beginFrame(EGLSurface surface, EGLint* width, EGLint* height) {
+void EglManager::beginFrame(EGLSurface surface, EGLint* width, EGLint* height, EGLint* framebufferAge) {
     LOG_ALWAYS_FATAL_IF(surface == EGL_NO_SURFACE,
             "Tried to beginFrame on EGL_NO_SURFACE!");
     makeCurrent(surface);
@@ -248,6 +257,9 @@
     if (height) {
         eglQuerySurface(mEglDisplay, surface, EGL_HEIGHT, height);
     }
+    if (useBufferAgeExt()) {
+        eglQuerySurface(mEglDisplay, surface, EGL_BUFFER_AGE_EXT, framebufferAge);
+    }
     eglBeginFrame(mEglDisplay, surface);
 }
 
@@ -304,6 +316,10 @@
     return false;
 }
 
+bool EglManager::useBufferAgeExt() {
+    return mAllowPreserveBuffer && mHasBufferAgeExt;
+}
+
 void EglManager::fence() {
     EGLSyncKHR fence = eglCreateSyncKHR(mEglDisplay, EGL_SYNC_FENCE_KHR, NULL);
     eglClientWaitSyncKHR(mEglDisplay, fence,
@@ -314,6 +330,9 @@
 bool EglManager::setPreserveBuffer(EGLSurface surface, bool preserve) {
     if (CC_UNLIKELY(!mAllowPreserveBuffer)) return false;
 
+    // Use EGL_EXT_buffer_age instead if supported
+    if (mHasBufferAgeExt) return true;
+
     bool preserved = false;
     if (mCanSetPreserveBuffer) {
         preserved = eglSurfaceAttrib(mEglDisplay, surface, EGL_SWAP_BEHAVIOR,
@@ -337,6 +356,19 @@
     return preserved;
 }
 
+void EglManager::findExtensions(const char* extensions, std::set<std::string>& list) const {
+    const char* current = extensions;
+    const char* head = current;
+    do {
+        head = strchr(current, ' ');
+        std::string s(current, head ? head - current : strlen(current));
+        if (s.length()) {
+            list.insert(s);
+        }
+        current = head + 1;
+    } while (head);
+}
+
 } /* namespace renderthread */
 } /* namespace uirenderer */
 } /* namespace android */