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core: reading from X server is fine

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Signed-off-by: Yuxuan Shui <yshuiv7@gmail.com>
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Yuxuan Shui 2024-06-24 12:36:48 +01:00
parent 23563c1ac8
commit 5b92f0bc1e
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GPG key ID: D3A4405BE6CC17F4
1 changed files with 18 additions and 40 deletions
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58
src/picom.c
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@ -1535,8 +1535,7 @@ static void unredirect(session_t *ps) {
/// And if we don't get new ones, we won't render, i.e. we would freeze. libxcb
/// keeps an internal queue of events, so we have to be 100% sure no events are
/// left in that queue before we go to sleep.
static void handle_queued_x_events(EV_P attr_unused, ev_prepare *w, int revents attr_unused) {
session_t *ps = session_ptr(w, event_check);
static void handle_x_events(struct session *ps) {
// Flush because if we go into sleep when there is still requests in the
// outgoing buffer, they will not be sent for an indefinite amount of
// time. Use XFlush here too, we might still use some Xlib functions
@ -1557,41 +1556,6 @@ static void handle_queued_x_events(EV_P attr_unused, ev_prepare *w, int revents
vblank_handle_x_events(ps->vblank_scheduler);
}
xcb_generic_event_t *ev;
while ((ev = xcb_poll_for_queued_event(ps->c.c))) {
ev_handle(ps, ev);
free(ev);
};
int err = xcb_connection_has_error(ps->c.c);
if (err) {
log_fatal("X11 server connection broke (error %d)", err);
exit(1);
}
}
/// Handle all events X server has sent us so far, so that our internal state will catch
/// up with the X server's state. It only makes sense to call this function in the X
/// critical section, otherwise we will be chasing a moving goal post.
///
/// (Disappointingly, grabbing the X server doesn't actually prevent the X server state
/// from changing. It should, but in practice we have observed window still being
/// destroyed while we have the server grabbed. This is very disappointing and forces us
/// to use some hacky code to recover when we discover we are out-of-sync.)
///
/// This function is different from `handle_queued_x_events` in that this will keep
/// reading from the X server until there is nothing left. Whereas
/// `handle_queued_x_events` is only concerned with emptying the internal buffer of
/// libxcb, so we don't go to sleep with unprocessed data.
static void handle_all_x_events(struct session *ps) {
assert(ps->server_grabbed);
XFlush(ps->c.dpy);
xcb_flush(ps->c.c);
if (ps->vblank_scheduler) {
vblank_handle_x_events(ps->vblank_scheduler);
}
xcb_generic_event_t *ev;
while ((ev = xcb_poll_for_event(ps->c.c))) {
ev_handle(ps, ev);
@ -1604,9 +1568,14 @@ static void handle_all_x_events(struct session *ps) {
}
}
static void handle_x_events_ev(EV_P attr_unused, ev_prepare *w, int revents attr_unused) {
session_t *ps = session_ptr(w, event_check);
handle_x_events(ps);
}
static void handle_new_windows(session_t *ps) {
while (!wm_complete_import(ps->wm, &ps->c, ps->atoms)) {
handle_all_x_events(ps);
handle_x_events(ps);
}
// Check tree changes first, because later property updates need accurate
@ -1696,7 +1665,16 @@ static void handle_pending_updates(struct session *ps, double delta_t) {
ps->server_grabbed = true;
// Catching up with X server
handle_all_x_events(ps);
/// Handle all events X server has sent us so far, so that our internal state will
/// catch up with the X server's state. It only makes sense to call this function
/// in the X critical section, otherwise we will be chasing a moving goal post.
///
/// (Disappointingly, grabbing the X server doesn't actually prevent the X server
/// state from changing. It should, but in practice we have observed window still
/// being destroyed while we have the server grabbed. This is very disappointing
/// and forces us to use some hacky code to recover when we discover we are
/// out-of-sync.)
handle_x_events(ps);
if (ps->pending_updates || wm_has_incomplete_imports(ps->wm) ||
wm_has_tree_changes(ps->wm)) {
log_debug("Delayed handling of events, entering critical section");
@ -2515,7 +2493,7 @@ static session_t *session_init(int argc, char **argv, Display *dpy,
//
// So we make use of a ev_prepare handle, which is called right before libev
// goes into sleep, to handle all the queued X events.
ev_prepare_init(&ps->event_check, handle_queued_x_events);
ev_prepare_init(&ps->event_check, handle_x_events_ev);
// Make sure nothing can cause xcb to read from the X socket after events are
// handled and before we going to sleep.
ev_set_priority(&ps->event_check, EV_MINPRI);