Originally posted by dee.
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LightDM Caught Off-Guard By Mir, Plans For Wayland
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Originally posted by dee. View PostOk so from what I gather it looks something like this (please correct me if I'm wrong about any of this):
Code:+ Wayland system compositor +--- Splash screen +--- Display manager +--+ Wayland compositor +--- XWayland
The system compositor is at the bottom of the stack, and basically doesn't do any actual compositing per se, it just switches inputs between splash screen, display manager and the actual compositor.
But what about the *output*? Each of these component display things.. So either they takeover the videocard in which case there may be some synchronisation issue or the system compositor must "compose" their output but this reduce performance because now the composition is done twice (once in the session compositor, once in the system compositor).
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Originally posted by renox View PostThis isn't the first time that I read about "switching input" and I think that this should be more detailed because I'm not sure that I fully get it: is-it just sending input events (like mouse clicks, keyboard) to either the splash screen, the display manager or the actual compositor?
But what about the *output*? Each of these component display things.. So either they takeover the videocard in which case there may be some synchronisation issue or the system compositor must "compose" their output but this reduce performance because now the composition is done twice (once in the session compositor, once in the system compositor).
Also, it seems that the system compositor is an optional part of the stack, it's not necessary to have it at all.
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Originally posted by dee. View PostBut since the system compositor doesn't do any actual compositing, it can pass a direct reference to video memory instead, so in practice the window manager writes directly on the screen, except in the transition periods where the system compositor changes its input from window manager to display manager or vice versa. So there shouldn't be any performance loss, and this also allows effects like crossfades between the dm and wm.
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Originally posted by renox View PostInteresting, thanks for your reply, IMHO your reply is similar to "each component take over the videocard", but there is still a fuzzy point: if there is a need to change the state of the videocard (to change the resolution for example), who is doing it? (1) the session compositor or (2)the system compositor.
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