[PATCH weston v3 3/3] compositor-x11: remove manual mouse button grab/ungrab

[Benoit Gschwind]

In current compositor-x11, the mouse buttons are grabbed and ungrabbed
manually that cause bugs, in particular when release event is received.
For example starting a move of a window with the left mouse button then
while holding it clicking the right mouse button release the grab. That
allow the mouse to go out the compositor window, while the compositor
still thinking that the mouse is inside. After that, if you release the
mouse outside the compositor window, the compositor never release the
mouse. There is several example of issues starting from this example.

The patch avoid the issue by using the simpler passive button grab, that
automatically grab buttons as soon as they occur. The passive grab
include an automatic ungrab when all mouse button are released. Another
way to fix the issue is to implement this later behavior manually,
which require a lot more code.

Signed-off-by: Benoit Gschwind <gschwind at gnu-log.net>
---
 libweston/compositor-x11.c | 27 +++++++++++++--------------
 1 file changed, 13 insertions(+), 14 deletions(-)

diff --git a/libweston/compositor-x11.c b/libweston/compositor-x11.c
index b6acccd..5d063b5 100644
--- a/libweston/compositor-x11.c
+++ b/libweston/compositor-x11.c
@@ -892,6 +892,19 @@ x11_backend_create_output(struct x11_backend *b, int x, int y,
 
 	x11_output_set_wm_protocols(b, output);
 
+	/* Automatically grab and ungrab mouse buttons */
+	xcb_grab_button(b->conn, 0, output->window,
+			XCB_EVENT_MASK_BUTTON_PRESS |
+			XCB_EVENT_MASK_BUTTON_RELEASE |
+			XCB_EVENT_MASK_POINTER_MOTION |
+			XCB_EVENT_MASK_ENTER_WINDOW |
+			XCB_EVENT_MASK_LEAVE_WINDOW,
+			XCB_GRAB_MODE_ASYNC,
+			XCB_GRAB_MODE_ASYNC,
+			output->window, XCB_CURSOR_NONE,
+			XCB_BUTTON_INDEX_ANY,
+			XCB_MOD_MASK_ANY);
+
 	xcb_map_window(b->conn, output->window);
 
 	if (fullscreen)
@@ -1063,20 +1076,6 @@ x11_backend_deliver_button_event(struct x11_backend *b,
 	if (!output)
 		return;
 
-	if (is_button_pressed)
-		xcb_grab_pointer(b->conn, 0, output->window,
-				 XCB_EVENT_MASK_BUTTON_PRESS |
-				 XCB_EVENT_MASK_BUTTON_RELEASE |
-				 XCB_EVENT_MASK_POINTER_MOTION |
-				 XCB_EVENT_MASK_ENTER_WINDOW |
-				 XCB_EVENT_MASK_LEAVE_WINDOW,
-				 XCB_GRAB_MODE_ASYNC,
-				 XCB_GRAB_MODE_ASYNC,
-				 output->window, XCB_CURSOR_NONE,
-				 button_event->time);
-	else
-		xcb_ungrab_pointer(b->conn, button_event->time);
-
 	if (!b->has_xkb)
 		update_xkb_state_from_core(b, button_event->state);
 
-- 
2.7.3