From bfa89b3d5f262d240ddfa0a788b41452b6a678c4 Mon Sep 17 00:00:00 2001
From: Frank Praznik <[EMAIL REDACTED]>
Date: Thu, 16 Oct 2025 21:31:28 -0400
Subject: [PATCH] wayland: Refactor event processing
Clean up and implement some best practices for event polling and handling:
- Ensure that events are still pumped, even if existing events are in the queue, to ensure that the most recent data is always processed.
- Handle wl_display_flush returning EAGAIN by trying to poll the socket until it can be written to.
- Ensure that events are always pumped on interrupts and broken pipe errors to handle quit events.
- Minimize double-pumping of events, since returning a success code from a wait will implicitly pump events again.
- Wake to poll when using a DBus IME, but the text input protocol is not enabled, to ensure that text events are delivered.
---
src/video/wayland/SDL_waylandevents.c | 208 ++++++++++++++------------
1 file changed, 112 insertions(+), 96 deletions(-)
diff --git a/src/video/wayland/SDL_waylandevents.c b/src/video/wayland/SDL_waylandevents.c
index 695af204a8258..5d4bf4b04bb9d 100644
--- a/src/video/wayland/SDL_waylandevents.c
+++ b/src/video/wayland/SDL_waylandevents.c
@@ -495,117 +495,102 @@ void Wayland_SendWakeupEvent(SDL_VideoDevice *_this, SDL_Window *window)
WAYLAND_wl_display_flush(d->display);
}
-static int dispatch_queued_events(SDL_VideoData *viddata)
-{
- int rc;
-
- /*
- * NOTE: When reconnection is implemented, check if libdecor needs to be
- * involved in the reconnection process.
- */
-#ifdef HAVE_LIBDECOR_H
- if (viddata->shell.libdecor) {
- libdecor_dispatch(viddata->shell.libdecor, 0);
- }
-#endif
-
- rc = WAYLAND_wl_display_dispatch_pending(viddata->display);
- return rc >= 0 ? 1 : rc;
-}
-
int Wayland_WaitEventTimeout(SDL_VideoDevice *_this, Sint64 timeoutNS)
{
SDL_VideoData *d = _this->internal;
SDL_WaylandSeat *seat;
- bool key_repeat_active = false;
-
- WAYLAND_wl_display_flush(d->display);
+ Uint64 start = SDL_GetTicksNS();
+ const int display_fd = WAYLAND_wl_display_get_fd(d->display);
+ int ret;
+ bool poll_alarm_set = false;
#ifdef SDL_USE_IME
SDL_Window *keyboard_focus = SDL_GetKeyboardFocus();
if (!d->text_input_manager && keyboard_focus && SDL_TextInputActive(keyboard_focus)) {
- SDL_IME_PumpEvents();
+ // If a DBus IME is active with no text input protocol, periodically wake to poll it.
+ if (timeoutNS < 0 || SDL_MS_TO_NS(200) <= timeoutNS) {
+ timeoutNS = SDL_MS_TO_NS(200);
+ poll_alarm_set = true;
+ }
}
#endif
-#ifdef SDL_USE_LIBDBUS
- SDL_DBus_PumpEvents();
-#endif
-
// If key repeat is active, we'll need to cap our maximum wait time to handle repeats
wl_list_for_each (seat, &d->seat_list, link) {
if (keyboard_repeat_is_set(&seat->keyboard.repeat)) {
- Wayland_SeatSetKeymap(seat);
-
- const Uint64 elapsed = SDL_GetTicksNS() - seat->keyboard.repeat.sdl_press_time_ns;
- if (keyboard_repeat_handle(&seat->keyboard.repeat, elapsed)) {
- // A repeat key event was already due
- return 1;
- } else {
- const Uint64 next_repeat_wait_time = (seat->keyboard.repeat.next_repeat_ns - elapsed) + 1;
- if (timeoutNS >= 0) {
- timeoutNS = SDL_min(timeoutNS, next_repeat_wait_time);
- } else {
- timeoutNS = next_repeat_wait_time;
- }
- key_repeat_active = true;
+ const Uint64 elapsed = start - seat->keyboard.repeat.sdl_press_time_ns;
+ const Uint64 next_repeat_wait_time = (seat->keyboard.repeat.next_repeat_ns - elapsed) + 1;
+ if (timeoutNS < 0 || next_repeat_wait_time <= timeoutNS) {
+ timeoutNS = next_repeat_wait_time;
+ poll_alarm_set = true;
}
}
}
- /* wl_display_prepare_read() will return -1 if the default queue is not empty.
- * If the default queue is empty, it will prepare us for our SDL_IOReady() call. */
if (WAYLAND_wl_display_prepare_read(d->display) == 0) {
- // Use SDL_IOR_NO_RETRY to ensure SIGINT will break us out of our wait
- int err = SDL_IOReady(WAYLAND_wl_display_get_fd(d->display), SDL_IOR_READ | SDL_IOR_NO_RETRY, timeoutNS);
- if (err > 0) {
- // There are new events available to read
- WAYLAND_wl_display_read_events(d->display);
- return dispatch_queued_events(d);
- } else if (err == 0) {
- int ret = 0;
-
- // No events available within the timeout
- WAYLAND_wl_display_cancel_read(d->display);
+ if (timeoutNS > 0) {
+ const Uint64 now = SDL_GetTicksNS();
+ const Uint64 elapsed = now - start;
+ start = now;
+ timeoutNS = elapsed <= timeoutNS ? timeoutNS - elapsed : 0;
+ }
- // If key repeat is active, we might have woken up to generate a key event
- if (key_repeat_active) {
- wl_list_for_each (seat, &d->seat_list, link) {
- if (keyboard_repeat_is_set(&seat->keyboard.repeat)) {
- Wayland_SeatSetKeymap(seat);
+ ret = WAYLAND_wl_display_flush(d->display);
- const Uint64 elapsed = SDL_GetTicksNS() - seat->keyboard.repeat.sdl_press_time_ns;
- if (keyboard_repeat_handle(&seat->keyboard.repeat, elapsed)) {
- ++ret;
- }
- }
- }
+ if (ret == -1 && errno == EAGAIN) {
+ // Unable to write to the socket; poll until the socket can be written to, it times out, or is interrupted.
+ ret = SDL_IOReady(display_fd, SDL_IOR_WRITE | SDL_IOR_NO_RETRY, timeoutNS);
+
+ if (ret <= 0) {
+ // The poll operation timed out or experienced an error, so see if there are any events to read without waiting.
+ timeoutNS = 0;
}
+ }
- return ret;
- } else {
- // Error returned from poll()/select()
+ if (ret < 0) {
+ // Pump events on an interrupt or broken pipe to handle the error.
+ WAYLAND_wl_display_cancel_read(d->display);
+ return errno == EINTR || errno == EPIPE ? 1 : ret;
+ }
+
+ if (timeoutNS > 0) {
+ const Uint64 now = SDL_GetTicksNS();
+ const Uint64 elapsed = now - start;
+ start = now;
+ timeoutNS = elapsed <= timeoutNS ? timeoutNS - elapsed : 0;
+ }
+
+ // Use SDL_IOR_NO_RETRY to catch EINTR.
+ ret = SDL_IOReady(display_fd, SDL_IOR_READ | SDL_IOR_NO_RETRY, timeoutNS);
+ if (ret <= 0) {
+ // Timeout or error, cancel the read.
WAYLAND_wl_display_cancel_read(d->display);
- if (errno == EINTR) {
- /* If the wait was interrupted by a signal, we may have generated a
- * SDL_EVENT_QUIT event. Let the caller know to call SDL_PumpEvents(). */
- return 1;
+ // The poll timed out with no data to read, but signal the caller to pump events if polling is required.
+ if (ret == 0) {
+ return poll_alarm_set ? 1 : 0;
} else {
- return err;
+ // Pump events on an interrupt or broken pipe to handle the error.
+ return errno == EINTR || errno == EPIPE ? 1 : ret;
}
}
- } else {
- // We already had pending events
- return dispatch_queued_events(d);
+
+ ret = WAYLAND_wl_display_read_events(d->display);
+ if (ret == -1) {
+ return ret;
+ }
}
+
+ // Signal to the caller that there might be an event available.
+ return 1;
}
void Wayland_PumpEvents(SDL_VideoDevice *_this)
{
SDL_VideoData *d = _this->internal;
SDL_WaylandSeat *seat;
- int err;
+ const int display_fd = WAYLAND_wl_display_get_fd(d->display);
+ int ret = 0;
#ifdef SDL_USE_IME
SDL_Window *keyboard_focus = SDL_GetKeyboardFocus();
@@ -618,37 +603,70 @@ void Wayland_PumpEvents(SDL_VideoDevice *_this)
SDL_DBus_PumpEvents();
#endif
+ // Synthesize key repeat events.
+ wl_list_for_each (seat, &d->seat_list, link) {
+ if (keyboard_repeat_is_set(&seat->keyboard.repeat)) {
+ Wayland_SeatSetKeymap(seat);
+
+ const Uint64 elapsed = SDL_GetTicksNS() - seat->keyboard.repeat.sdl_press_time_ns;
+ keyboard_repeat_handle(&seat->keyboard.repeat, elapsed);
+ }
+ }
+
#ifdef HAVE_LIBDECOR_H
if (d->shell.libdecor) {
libdecor_dispatch(d->shell.libdecor, 0);
}
#endif
- WAYLAND_wl_display_flush(d->display);
-
- /* wl_display_prepare_read() will return -1 if the default queue is not empty.
- * If the default queue is empty, it will prepare us for our SDL_IOReady() call. */
- if (WAYLAND_wl_display_prepare_read(d->display) == 0) {
- if (SDL_IOReady(WAYLAND_wl_display_get_fd(d->display), SDL_IOR_READ, 0) > 0) {
- WAYLAND_wl_display_read_events(d->display);
- } else {
- WAYLAND_wl_display_cancel_read(d->display);
+ /* If the queue isn't empty, dispatch any old events, and try to prepare for reading again.
+ * If preparing to read returns -1 on the second try, wl_display_read_events() enqueued new
+ * events at some point between dispatching the old events and preparing for the read,
+ * probably from another thread, which means that the events in the queue are current.
+ */
+ ret = WAYLAND_wl_display_prepare_read(d->display);
+ if (ret == -1) {
+ ret = WAYLAND_wl_display_dispatch_pending(d->display);
+ if (ret < 0) {
+ goto connection_error;
}
+
+ ret = WAYLAND_wl_display_prepare_read(d->display);
}
- // Dispatch any pre-existing pending events or new events we may have read
- err = WAYLAND_wl_display_dispatch_pending(d->display);
+ if (ret == 0) {
+ ret = WAYLAND_wl_display_flush(d->display);
- wl_list_for_each (seat, &d->seat_list, link) {
- if (keyboard_repeat_is_set(&seat->keyboard.repeat)) {
- Wayland_SeatSetKeymap(seat);
+ if (ret == -1 && errno == EAGAIN) {
+ // Unable to write to the socket; wait a brief time to see if it becomes writable.
+ ret = SDL_IOReady(display_fd, SDL_IOR_WRITE, SDL_MS_TO_NS(4));
+ if (ret > 0) {
+ ret = WAYLAND_wl_display_flush(d->display);
+ }
+ }
- const Uint64 elapsed = SDL_GetTicksNS() - seat->keyboard.repeat.sdl_press_time_ns;
- keyboard_repeat_handle(&seat->keyboard.repeat, elapsed);
+ // If the compositor closed the socket, just jump to the error handler.
+ if (ret < 0 && errno == EPIPE) {
+ WAYLAND_wl_display_cancel_read(d->display);
+ goto connection_error;
}
+
+ ret = SDL_IOReady(display_fd, SDL_IOR_READ, 0);
+ if (ret > 0) {
+ ret = WAYLAND_wl_display_read_events(d->display);
+ if (ret == 0) {
+ ret = WAYLAND_wl_display_dispatch_pending(d->display);
+ }
+ } else {
+ WAYLAND_wl_display_cancel_read(d->display);
+ }
+
+ } else {
+ ret = WAYLAND_wl_display_dispatch_pending(d->display);
}
- if (err < 0 && !d->display_disconnected) {
+connection_error:
+ if (ret < 0 && !d->display_disconnected) {
/* Something has failed with the Wayland connection -- for example,
* the compositor may have shut down and closed its end of the socket,
* or there is a library-specific error.
@@ -659,9 +677,7 @@ void Wayland_PumpEvents(SDL_VideoDevice *_this)
d->display_disconnected = 1;
SDL_LogError(SDL_LOG_CATEGORY_VIDEO, "Wayland display connection closed by server (fatal)");
- /* Only send a single quit message, as application shutdown might call
- * SDL_PumpEvents
- */
+ // Only send a single quit message, as application shutdown might call SDL_PumpEvents().
SDL_SendQuit();
}
}