feat/frame scheduling #490
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ardera
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Only diagnose flutter-pi sources by default. The diagnosis results are uploaded as an HTML workflow artifact for debugging. Also, remove the old (unused) CodeQL workflow, which had a lot of hard to disable false positives.
Mostly double-float casts, functions without arguments without an explicit `void` in the parameter list, but in platformchannel.c there were actually some memory leaks on error paths, which are now fixed. Also enable -pedantic for even more diagnostics.
drmdev: (mostly) non-stateful part. Basically a better wrapper around a drm fd. Fully mt-safe. Also properly separate kms_req from drmdev. kms_req now mostly accesses public drmdev API, instead of having access to hidden drmdev state. drm_resources: the DRM state / resources. Is stateful, but does not update itself. To keep it in sync with kernel state, one needs to listen to kernel events with drm_monitor and call drm_resources_update. drm_resources is not mt-safe and only supposed to be used on a single thread. Also add a bunch of QoL stuff to drm_resources.
To be able to specify more surface usage hints, i.e. `GBM_BO_USE_SCANOUT` and `GBM_BO_USE_RENDERING`.
Always do non-blocking atomic commits. To resolve issues with flutter trying to present frames too soon, while another frame was already sent to the kernel (i.e. comitted via KMS atomic commit), we either have to discard subsequent, too-early frames or queue them. In this case, we basically keep a 1-frame deep queue (or 2-frames, if you count the in-kernel waiting-for-scanout frame), with the 1 queued frame being displaced whenever a newer frame is available. (Similar to vulkans MAILBOX swapchain presentation mode)
Call the release callback for the commit that is no longer visible on screen before calling the scanout callback. The scanout callback might already start a new frame, and the release callback releases some resources that could be useful for building the new frame, so this helps avoid resource exhaustion.
libdrm's drmIsKMS was added in libdrm 2.4.105:
https://gitlab.freedesktop.org/mesa/libdrm/-/commit/523b3658aa8efa746417e916c987de23740ce313
Debian bullseye is still on 2.4.104, so it's unfortunately not present
there.
Fix waiting_for_scanout not being set when a frame is presented directly in the on_scanout callback, sometimes causing another frame to be presented, resulting in an EBUSY from drmModeAtomicCommit.
Make frame_scheduler able to time frames, e.g. tell flutter when to start rendering a frame when it receives a frame request. For now, if no frame is currently waiting to be scanned out, this just responds to the frame request with the current frame and a 60Hz frame interval, i.e. starts the frame immediately. If a frame is waiting to be scanned out, this waits until the scanout to reply to the frame timings request. (With the timestamp of the scanout being used as the frame start time in the reply to the frame timings request) If another frame is already queued after that, the scheduler will wait until that other queued frame is scanned out to reply to the frame timings request.
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