[PATCH weston v1 3/3] compositor-x11: remove manual mouse button grab/ungrab

[Benoit Gschwind]

Hello Bill,

You are right, thus I dug into the git history and I found that the grab
is mostly to confine the cursor into the X11 window. For reference, the
git commit id [1] and the related bug [2].

Since I do not want introduce a regression, I think the minor
improvement is valid.

Best regards.

[1] 7330862f9e25d513cfcc49358b7187524a9e1940
[2] https://bugs.freedesktop.org/show_bug.cgi?id=53558

On 13/05/2016 18:35, Bill Spitzak wrote:
> Does the x11 compositor have to do this at all? It owns that window so
> it gets automatic grabs. This is for one client to eat the events being
> passed to another client.
> 
> 
> On Fri, May 13, 2016 at 4:34 AM, Benoit Gschwind <gschwind at gnu-log.net
> <mailto:gschwind at gnu-log.net>> wrote:
> 
>     In current compositor-x11, the mouse buttons are grabbed and ungrabbed
>     manually that may produce weird cases like starting a grab while the
>     buttons are already released, due to asynchronous X11 events
>     dispatching.
> 
>     The patch avoid the issue by using the better 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.
> 
>     This probably fix some mysterious bugs.
> 
>     Signed-off-by: Benoit Gschwind <gschwind at gnu-log.net
>     <mailto:gschwind at gnu-log.net>>
>     ---
>      src/compositor-x11.c | 27 +++++++++++++--------------
>      1 file changed, 13 insertions(+), 14 deletions(-)
> 
>     diff --git a/src/compositor-x11.c b/src/compositor-x11.c
>     index 5b76dba..ae155d1 100644
>     --- a/src/compositor-x11.c
>     +++ b/src/compositor-x11.c
>     @@ -882,6 +882,19 @@ 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)
>     @@ -1052,20 +1065,6 @@ 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
> 
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