Comment 27 for bug 1340510
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| Alexandros Frantzis (afrantzis) wrote Re: [Mako] Session screen seen upon quick power key strike only when roaming | #27 |
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(Get the code!)
> Krillin and Arale seem to behave fine, but I'm not sure if it's by accident - do we actually have code that waits for something
> (a new frame? feedback from shell?) before powering the screen on?
Before turning the screen on/enabling the compositor, after the power button is pressed, USC currently waits for powerd to notify us that we have come out of suspend. On some devices, this notification takes some time to arrive (about ~0.5 second on Krillin). I haven't tried myself recently but Alberto mentioned that N4 wakes up faster.
The different delays (depending on HW) introduced by this mechanism offer a plausible explanation of why we see the frame on some devices and not on others.
Also see my previous explanation in comment 5 [1]. It's important to note that although we can eventually get a "good enough" solution (e.g. unity8 signals USC that it has rendered the greeter), a 100% perfect solution is difficult to achieve since we can't really know when the frame with the greeter has actually been displayed on screen (vs only rendered and swapped).
[1] https:/