client: add wl_display_dispatch_pending_single

As well as wl_display_dispatch_queue_pending_single.

The motivation is writing libwayland bindings for a dynamic language
with exceptions/non-local returns. Since it is invalid for a
wl_dispatcher_func_t callback provided to libwayland to not return,
there is no way to prevent dispatching of further events in the case of
an exception in the dynamic language event handler.

Furthermore, since creating/destroying Wayland objects in an event
handler affects the dispatching of subsequent events by libwayland,
it is not possible to collect Wayland events in a queue outside
libwayland and dispatch them one-by-one after
wl_display_dispatch_pending() returns.

Adding libwayland API to dispatch at most one pending event solves this
problem cleanly. The bindings can have libwayland dispatch a single
event, wait for wl_display_dispatch_pending_single() to return, run the
dynamic language event handler (which may longjmp away), and continue
the loop for as long as there are more events to dispatch.

References: https://codeberg.org/ifreund/janet-wayland
Signed-off-by: Isaac Freund <mail@isaacfreund.com>

1 files changed, 7 insertions, 0 deletions

diff --git a/src/wayland-client-core.h b/src/wayland-client-core.h
index 970e625..e0523e4 100644
--- a/src/wayland-client-core.h
+++ b/src/wayland-client-core.h
@@ -269,9 +269,16 @@ wl_display_dispatch_queue_pending(struct wl_display *display,
 				  struct wl_event_queue *queue);
 
 int
+wl_display_dispatch_queue_pending_single(struct wl_display *display,
+					 struct wl_event_queue *queue);
+
+int
 wl_display_dispatch_pending(struct wl_display *display);
 
 int
+wl_display_dispatch_pending_single(struct wl_display *display);
+
+int
 wl_display_get_error(struct wl_display *display);
 
 uint32_t