Add support for render-ahead

For periods of time during which latency is less important
allow a client to request a deeper render-ahead pipeline.

The latency tradeoff results in less overall visual jank

Test: none, only used by macrobench

Change-Id: I516203b70bdc75b6415fa08bf9c4fb1b598b0102

1 files changed, 17 insertions, 1 deletions

diff --git a/libs/hwui/renderthread/RenderProxy.h b/libs/hwui/renderthread/RenderProxy.h
index 3425c5c68a72..bd5c9a9fc922 100644
--- a/libs/hwui/renderthread/RenderProxy.h
+++ b/libs/hwui/renderthread/RenderProxy.h
@@ -119,7 +119,23 @@ public:
 
     ANDROID_API void addFrameMetricsObserver(FrameMetricsObserver* observer);
     ANDROID_API void removeFrameMetricsObserver(FrameMetricsObserver* observer);
-    ANDROID_API long getDroppedFrameReportCount();
+
+    /**
+     * Sets a render-ahead depth on the backing renderer. This will increase latency by
+     * <swapInterval> * renderAhead and increase memory usage by (3 + renderAhead) * <resolution>.
+     * In return the renderer will be less susceptible to jitter, resulting in a smoother animation.
+     *
+     * Not recommended to use in response to anything touch driven, but for canned animations
+     * where latency is not a concern careful use may be beneficial.
+     *
+     * Note that when increasing this there will be a frame gap of N frames where N is
+     * renderAhead - <current renderAhead>. When decreasing this if there are any pending
+     * frames they will retain their prior renderAhead value, so it will take a few frames
+     * for the decrease to flush through.
+     *
+     * @param renderAhead How far to render ahead, must be in the range [0..2]
+     */
+    ANDROID_API void setRenderAheadDepth(int renderAhead);
 
     ANDROID_API static int copySurfaceInto(sp<Surface>& surface, int left, int top, int right,
                                            int bottom, SkBitmap* bitmap);