RFR: 8312198: [macos] metal pipeline - window rendering stops after display sleep

[Alexey Ushakov]

On Wed, 21 May 2025 06:11:18 GMT, Jayathirth D V <jdv at openjdk.org> wrote:

> In stress based scenarios it is observed that nothing is drawn in UI content when display wakes up from sleep in Metal pipeline of macOS. Unfortunately i am not able to reproduce it, but based on details in the bug it looks like we are hitting a race condition. Call to CVDisplayLinkCreateWithActiveCGDisplays is becoming a no-op as there are no active displays right after NSWorkspaceScreensDidWakeNotification. Looks like if we continue to call CVDisplayLinkCreateWithActiveCGDisplays after screen wakeup we are able to get the list of ActiveDisplays and then able to create displayLink.
> 
> So now the code is modified to check whether CVDisplayLinkCreateWithActiveCGDisplays is successful or not. If not we will try to call CVDisplayLinkCreateWithActiveCGDisplays for 5 instances each with 1 second delay. There is no regression test for this change because it needs a stress based test with display wakeup/sleep(As captured in JBS, i am not able to reproduce this issue).
> 
> I have tested this change for sanity by running animation examples from SwingSet2 and continuously connecting/disconnecting external display. Also by multiple display sleep and wakeup scenarios, i don't see any regressions. Also whole clientlibs CI run is done with this patch and it is also green.
> 
> While working on this bug also noticed that many functions of CVDisplayLink is deprecated from macOS 14 and going forward we need to use CADisplayLink/CAMetalDisplayLink. I have raised [JDK-8357418](https://bugs.openjdk.org/browse/JDK-8357418) for the same.

Changes requested by avu (Committer).

src/java.desktop/macosx/native/libawt_lwawt/java2d/metal/MTLLayer.m line 52:

> 50: - (void) createDisplayLink {
> 51:     CVReturn r = CVDisplayLinkCreateWithActiveCGDisplays(&displayLink);
> 52:     if (r != kCVReturnSuccess) {

We may still miss an update of the window for a noticeable time (depending on the application code) because DisplayLink will not work during the retry period.

src/java.desktop/macosx/native/libawt_lwawt/java2d/metal/MTLLayer.m line 54:

> 52:     if (r != kCVReturnSuccess) {
> 53:         if (self.displayLinkFailCount == 5) {
> 54:             // We have tried for 5 seconds to create CVDisplayLink

It would be better to move this magic number to the beginning of the file as a verbose constant. Also, for reliability reasons, I would prefer the `>=` check here.

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PR Review: https://git.openjdk.org/jdk/pull/25342#pullrequestreview-2860218856
PR Review Comment: https://git.openjdk.org/jdk/pull/25342#discussion_r2101917612
PR Review Comment: https://git.openjdk.org/jdk/pull/25342#discussion_r2101924670