Make use of the buffer data null hint a GrContextOption

TBR=bsalomon@google.com
Change-Id: I5a3fd18479ca8c95e1bc8c087c28346264049eb0
Reviewed-on: https://skia-review.googlesource.com/111604
Commit-Queue: Robert Phillips <robertphillips@google.com>
Reviewed-by: Greg Daniel <egdaniel@google.com>

1 files changed, 13 insertions, 0 deletions

diff --git a/include/gpu/GrContextOptions.h b/include/gpu/GrContextOptions.h
index 74ec7feb1f..69ea181bbb 100644
--- a/include/gpu/GrContextOptions.h
+++ b/include/gpu/GrContextOptions.h
@@ -132,6 +132,19 @@ struct GrContextOptions {
     bool fAvoidStencilBuffers = false;
 
     /**
+     * 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 be an unoptimization on some platforms, esp. Chrome.
+     * Chrome's cmd buffer will create a new allocation and memset the whole thing
+     * to zero (for security reasons).
+     * Defaults to the value of GR_GL_USE_BUFFER_DATA_NULL_HINT #define (which is, by default, 1).
+     */
+    Enable fUseGLBufferDataNullHint = Enable::kDefault;
+
+    /**
      * If true, texture fetches from mip-mapped textures will be biased to read larger MIP levels.
      * This has the effect of sharpening those textures, at the cost of some aliasing, and possible
      * performance impact.