Don't send NULL buffer data hint in chrome

Review URL: http://codereview.appspot.com/4657067/



git-svn-id: http://skia.googlecode.com/svn/trunk@1778 2bbb7eff-a529-9590-31e7-b0007b416f81

4 files changed, 22 insertions, 0 deletions

diff --git a/gpu/include/GrGLConfig.h b/gpu/include/GrGLConfig.h
index b4ca78cee5..e59fe553cf 100644
--- a/gpu/include/GrGLConfig.h
+++ b/gpu/include/GrGLConfig.h
@@ -65,6 +65,16 @@
  * Setting this build flag enables this behavior. GR_GL_NO_CONSTANT_ATTRIBUTES
  * must not be set since this uses constant attributes for the matrices. 
  * Defaults to 0.
+ *
+ * GR_GL_USE_BUFFER_DATA_NULL_HINT: When specifing new data for a vertex/index
+ * buffer that replaces old data Ganesh can give a hint to the driver that the
+ * previous data will not be used in future draws like this:
+ *  glBufferData(GL_..._BUFFER, size, NULL, usage);       //<--hint, NULL means
+ *  glBufferSubData(GL_..._BUFFER, 0, lessThanSize, data) //   old data can't be
+ *                                                        //   used again.
+ * However, this can cause a performance decrease on Chrome cmd buffer because
+ * it will create a new allocation and memset the whole thing to zero (for
+ * security reasons). Defaults to 1 (enabled).
  */
 
 #if !defined(GR_GL_LOG_CALLS)
@@ -91,6 +101,10 @@
     #define GR_GL_ATTRIBUTE_MATRICES        0
 #endif
 
+#if !defined(GR_GL_USE_BUFFER_DATA_NULL_HINT)
+    #define GR_GL_USE_BUFFER_DATA_NULL_HINT 1
+#endif
+
 #if(GR_GL_NO_CONSTANT_ATTRIBUTES) && (GR_GL_ATTRIBUTE_MATRICES)
     #error "Cannot combine GR_GL_NO_CONSTANT_ATTRIBUTES and GR_GL_ATTRIBUTE_MATRICES"
 #endif
diff --git a/gpu/include/GrGLConfig_chrome.h b/gpu/include/GrGLConfig_chrome.h
index 738e80186b..9c25cb254a 100644
--- a/gpu/include/GrGLConfig_chrome.h
+++ b/gpu/include/GrGLConfig_chrome.h
@@ -10,4 +10,8 @@
 // ANGLE creates a temp VB for vertex attributes not specified per-vertex.
 #define GR_GL_NO_CONSTANT_ATTRIBUTES    GR_WIN32_BUILD
 
+// cmd buffer allocates memory and memsets it to zero when it sees glBufferData
+// with NULL.
+#define GR_GL_USE_BUFFER_DATA_NULL_HINT 0
+
 #endif
diff --git a/gpu/src/GrGLIndexBuffer.cpp b/gpu/src/GrGLIndexBuffer.cpp
index 4fb1e99ce4..1d3f89319d 100644
--- a/gpu/src/GrGLIndexBuffer.cpp
+++ b/gpu/src/GrGLIndexBuffer.cpp
@@ -106,7 +106,9 @@ bool GrGLIndexBuffer::updateData(const void* src, size_t srcSizeInBytes) {
     if (size() == srcSizeInBytes) {
         GR_GL(BufferData(GR_GL_ELEMENT_ARRAY_BUFFER, srcSizeInBytes, src, usage));
     } else {
+#if GR_GL_USE_BUFFER_DATA_NULL_HINT
         GR_GL(BufferData(GR_GL_ELEMENT_ARRAY_BUFFER, size(), NULL, usage));
+#endif
         GR_GL(BufferSubData(GR_GL_ELEMENT_ARRAY_BUFFER, 0, srcSizeInBytes, src));
     }
     return true;
diff --git a/gpu/src/GrGLVertexBuffer.cpp b/gpu/src/GrGLVertexBuffer.cpp
index 3fa1425d02..5d274aa260 100644
--- a/gpu/src/GrGLVertexBuffer.cpp
+++ b/gpu/src/GrGLVertexBuffer.cpp
@@ -105,7 +105,9 @@ bool GrGLVertexBuffer::updateData(const void* src, size_t srcSizeInBytes) {
     if (size() == srcSizeInBytes) {
         GR_GL(BufferData(GR_GL_ARRAY_BUFFER, srcSizeInBytes, src, usage));
     } else {
+#if GR_GL_USE_BUFFER_DATA_NULL_HINT
         GR_GL(BufferData(GR_GL_ARRAY_BUFFER, size(), NULL, usage));
+#endif
         GR_GL(BufferSubData(GR_GL_ARRAY_BUFFER, 0, srcSizeInBytes, src));
     }
     return true;