AnimatedImageDrawable: Eliminate unnecessary calls to redraw

Bug: 78866720
Test: Manual + systrace; existing CTS

Previously, we set hasAnimations to true when the AnimatedImageDrawable,
so that we would get a call to redraw. But if the image does not need to
show its next frame yet, the redraw was unnecessary.

Instead, add a new field to TreeInfo::Out, representing the delay time
until the image will need to be redrawn - i.e. when the duration of the
current frame has passed. Each call to prepareTree will post at most one
message to redraw, in time for the earliest animated image to be
redrawn. Post the message for one rendered frame ahead of time, so that
when it is time to show the next frame, the image has already gotten the
message to update.

On a screen with a single animated image, this drops the number of calls
to dispatchFrameCallbacks to as infrequent as possible. It is called
only when we need to draw a new frame of the image. On a screen with
multiple animated images, the calls may be redundant, but they will not
be more frequent than they would be without this change.

Switch to nsecs_t and systemTime internally, matching the rest of HWUI.

Remove mDidDraw and related. Its purpose was to prevent advancing the
animation while the image is not being drawn. But it isn't really
necessary. If it's not drawn, onDraw is not called, which is where we
trigger decoding. And onDraw already has a defense against getting too
far ahead - if its timer indicates that it should skip a frame or show
it very briefly, it will back up its timer. More importantly, mDidDraw
caused a bug, when combined with less frequent redraws. If the display
list containing the drawable doesn't need to be redrawn for other
reasons, the drawable's timer never advanced, so its animation stopped.

Fix software drawing. Compute the milliseconds in the future to draw the
next frame, and add that to SystemClock.uptimeMillis() to compute the
time to pass to scheduleSelf.

Change-Id: I13aab49922fa300f73b327be25561d7120c09ec4

1 files changed, 3 insertions, 0 deletions

diff --git a/libs/hwui/renderthread/CanvasContext.h b/libs/hwui/renderthread/CanvasContext.h
index c2cc72a6917f..e52b6447a611 100644
--- a/libs/hwui/renderthread/CanvasContext.h
+++ b/libs/hwui/renderthread/CanvasContext.h
@@ -213,6 +213,9 @@ private:
     // stopped indicates the CanvasContext will reject actual redraw operations,
     // and defer repaint until it is un-stopped
     bool mStopped = false;
+    // Incremented each time the CanvasContext is stopped. Used to ignore
+    // delayed messages that are triggered after stopping.
+    int mGenerationID;
     // CanvasContext is dirty if it has received an update that it has not
     // painted onto its surface.
     bool mIsDirty = false;