Add back render-ahead support

Currently only supported in the EGL path.
Vulkan support Coming Soon

Bug: 127822449
Test: trace of hwuimacro
Change-Id: Iac2b039e11d964aab5b8ca1bdf2a5430b187e2ea

1 files changed, 17 insertions, 0 deletions

diff --git a/libs/hwui/renderthread/RenderProxy.h b/libs/hwui/renderthread/RenderProxy.h
index a1a5551722bc..a0f08cbd26f9 100644
--- a/libs/hwui/renderthread/RenderProxy.h
+++ b/libs/hwui/renderthread/RenderProxy.h
@@ -123,6 +123,23 @@ public:
     ANDROID_API void removeFrameMetricsObserver(FrameMetricsObserver* observer);
     ANDROID_API void setForceDark(bool enable);
 
+    /**
+     * 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);
     ANDROID_API static void prepareToDraw(Bitmap& bitmap);