fix(android): paint the letterbox bars, so stale pixels stop surviving in them

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Native video left debris in the padding around the video: the "previous frame"
flash on rotation, a ghost copy of the control bar stranded in the top bar, each
new clock digit drawn over the one before it (35:42 with the 1 still showing
through the 2), and the sleep/quality menus leaving their imprint after closing.
One cause under all of it — nothing painted those bars.

The window surface is opaque; the theme is not translucent and dumpsys window
shows no translucency flag. For an opaque surface HWUI deliberately does NOT
clear the damaged region before replaying a frame: it assumes the view hierarchy
covers every pixel it owns. Here that hierarchy is window background → video
TextureView → transparent WebView, and fitSurfaceToScreen sizes the TextureView
to the letterboxed video rect. So the bars were the window background's alone to
paint, and setTransparent(true) cleared it to TRANSPARENT — leaving them painted
by nobody, with whatever was last in the framebuffer surviving there.

The window background now stays opaque black while compositing. It cannot hide
the video: the TextureView is drawn on top of it, and the WebView's own
background is what lets the picture through.

Three previous attempts missed because they aimed at the window's rotation
animation and at TextureView frame-retention — two postOnAnimation hops, an
onSurfaceTextureUpdated reveal, then ROTATION_ANIMATION_JUMPCUT with
FLAG_FULLSCREEN to make it stick. The pixels were never the animation's, which is
also why the artefact reproduces standing still, with no rotation involved. Those
are removed. The alpha-hiding among them actively made things worse: it blanked
the one view that reliably paints its own rect. FLAG_FULLSCREEN goes too — it
fought edge-to-edge insets for no gain.

Verified on device (HONOR ROD2-W09, Android 16): reproduced with native video on
— ghost control bar in the top bar, doubled clock digit — then absent after the
fix across playback, the control bar and a rotation round-trip.

DR-194 is rewritten to record the real mechanism and marked Done.

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This commit is contained in:

dtourolle

2026-08-16 21:51:14 +02:00

parent 8e98e1c37a

commit 1285908733

4 changed files with 4508 additions and 4602 deletions

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