2d272b705c
The DRM event queue in the kernel is quite small and can be easily exhausted by DRI clients. When the event queue is full, that means nothing can be queued onto it anymore, which can lead to incorrect presentation times for DRI clients and failure when attempting to queue a page flip. To make matters worse, once an event is placed onto the kernel's event queue, there's no straightforward way to prematurely remove it from the kernel's event queue in userspace, which means that aborting a sequence number doesn't free up space in the event queue. Since vblank events from DRI clients are the largest consumers of the event queue, and since it's often easy to know the desired target MSC of their vblank events without querying the kernel for a CRTC's current MSC, we can coalesce vblank events occurring at the same MSC such that only one of them is placed onto the kernel's event queue, instead of allowing duplicate vblank events to pollute the event queue. This is achieved by tracking the next kernel-queued event's MSC on a per-CRTC basis and then running all of that CRTC's vblank event handlers which have reached their target MSC when the queued MSC is signaled. Signed-off-by: Sultan Alsawaf <sultan@kerneltoast.com>
X Server
The X server accepts requests from client applications to create windows, which are (normally rectangular) "virtual screens" that the client program can draw into.
Windows are then composed on the actual screen by the X server (or by a separate composite manager) as directed by the window manager, which usually communicates with the user via graphical controls such as buttons and draggable titlebars and borders.
For a comprehensive overview of X Server and X Window System, consult the following article: https://en.wikipedia.org/wiki/X_server
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https://gitlab.freedesktop.org/xorg/xserver
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