Allow keyboard and pointer grabs to hook clear_focus()

This is necessary for some grabs, which currently have no way of knowing
when the pointer/keyboard focus has left a surface. For example, without
this, a drag-and-drop grab can erroneously drop into a window that the
cursor is no longer over.

This is the plumbing needed to properly fix swaywm/sway#5220. The
existing fix, swaywm/sway#5222, relies on every grab's `enter()` hook
allowing a `NULL` surface. This is not guaranteed by the API and, in
fact, is not the case for the xdg-shell popup grab and results in a
crash when the cursor leaves a surface and does not immediately enter
another one while a popup is open (#2161).

This fix also adds an assertion to wlr_seat_pointer_notify_enter() that
ensures it's never called with a `NULL` surface. This will make Sway
crash much more until it fixes its usage of the API, so we should land
this at the same time as a fix in Sway (which I haven't posted yet).

1 files changed, 18 insertions, 0 deletions

diff --git a/include/wlr/types/wlr_seat.h b/include/wlr/types/wlr_seat.h
index f6221939..7b47da08 100644
--- a/include/wlr/types/wlr_seat.h
+++ b/include/wlr/types/wlr_seat.h
@@ -78,6 +78,7 @@ struct wlr_seat_pointer_grab;
 struct wlr_pointer_grab_interface {
 	void (*enter)(struct wlr_seat_pointer_grab *grab,
 			struct wlr_surface *surface, double sx, double sy);
+	void (*clear_focus)(struct wlr_seat_pointer_grab *grab);
 	void (*motion)(struct wlr_seat_pointer_grab *grab, uint32_t time_msec,
 			double sx, double sy);
 	uint32_t (*button)(struct wlr_seat_pointer_grab *grab, uint32_t time_msec,
@@ -95,6 +96,7 @@ struct wlr_keyboard_grab_interface {
 	void (*enter)(struct wlr_seat_keyboard_grab *grab,
 			struct wlr_surface *surface, uint32_t keycodes[],
 			size_t num_keycodes, struct wlr_keyboard_modifiers *modifiers);
+	void (*clear_focus)(struct wlr_seat_keyboard_grab *grab);
 	void (*key)(struct wlr_seat_keyboard_grab *grab, uint32_t time_msec,
 			uint32_t key, uint32_t state);
 	void (*modifiers)(struct wlr_seat_keyboard_grab *grab,
@@ -354,6 +356,8 @@ void wlr_seat_pointer_enter(struct wlr_seat *wlr_seat,
 
 /**
  * Clear the focused surface for the pointer and leave all entered surfaces.
+ * This function does not respect pointer grabs: you probably want
+ * `wlr_seat_pointer_notify_clear_focus()` instead.
  */
 void wlr_seat_pointer_clear_focus(struct wlr_seat *wlr_seat);
 
@@ -400,6 +404,12 @@ void wlr_seat_pointer_notify_enter(struct wlr_seat *wlr_seat,
 		struct wlr_surface *surface, double sx, double sy);
 
 /**
+ * Notify the seat of a pointer leave event to the currently-focused surface.
+ * Defers to any grab of the pointer.
+ */
+void wlr_seat_pointer_notify_clear_focus(struct wlr_seat *wlr_seat);
+
+/**
  * Notify the seat of motion over the given surface. Pass surface-local
  * coordinates where the pointer motion occurred. Defers to any grab of the
  * pointer.
@@ -485,6 +495,8 @@ void wlr_seat_keyboard_enter(struct wlr_seat *seat,
 
 /**
  * Clear the focused surface for the keyboard and leave all entered surfaces.
+ * This function does not respect keyboard grabs: you probably want
+ * `wlr_seat_keyboard_notify_clear_focus()` instead.
  */
 void wlr_seat_keyboard_clear_focus(struct wlr_seat *wlr_seat);
 
@@ -512,6 +524,12 @@ void wlr_seat_keyboard_notify_enter(struct wlr_seat *seat,
 		struct wlr_keyboard_modifiers *modifiers);
 
 /**
+ * Notify the seat of a keyboard leave event to the currently-focused surface.
+ * Defers to any keyboard grabs.
+ */
+void wlr_seat_keyboard_notify_clear_focus(struct wlr_seat *wlr_seat);
+
+/**
  * Start a grab of the keyboard of this seat. The grabber is responsible for
  * handling all keyboard events until the grab ends.
  */