[PATCH 2/2] window: Only release the widget grab when all buttons are released

[Kristian Høgsberg]

On Mon, Jan 23, 2012 at 2:11 PM, Neil Roberts <neil at linux.intel.com> wrote:
> This copies the algorithm for keeping track of an implicit grab widget
> when a button is pressed from Wayland. Instead of just tracking a
> single button, Wayland keeps a count of all the mouse buttons that are
> down and only releases the grab when all buttons are released. Without
> this it could lose button release events if a second button is pressed
> and held while the original grab button is held because the grab would
> be lost when the grab button is released. Then the release for the
> second mouse button would go nowhere.
>
> The code makes sure to only release the grab if it there is a grab
> button so that it won't release grabs initiated from window_show_menu.

Not sure about this one.  We do miss a button release event in case of
wl_shell_surface_move or dnd.  But we know that we'll lose a release
in those cases, so maybe we can just add a button_count-- in those
places along with the input_ungrab()?

Kristian

> ---
>  clients/window.c |   12 +++++++++++-
>  1 files changed, 11 insertions(+), 1 deletions(-)
>
> diff --git a/clients/window.c b/clients/window.c
> index 1356c75..fb6b307 100644
> --- a/clients/window.c
> +++ b/clients/window.c
> @@ -164,6 +164,8 @@ struct input {
>        struct widget *focus_widget;
>        struct widget *grab;
>        uint32_t grab_button;
> +       /* Number of buttons that are held down */
> +       uint32_t button_count;
>
>        struct wl_data_device *data_device;
>        struct data_offer *drag_offer;
> @@ -1524,6 +1526,11 @@ input_handle_button(void *data,
>        struct input *input = data;
>        struct widget *widget;
>
> +       if (state)
> +               input->button_count++;
> +       else
> +               input->button_count--;
> +
>        if (input->focus_widget && input->grab == NULL && state)
>                input_grab(input, input->focus_widget, button);
>
> @@ -1534,7 +1541,10 @@ input_handle_button(void *data,
>                                          button, state,
>                                          input->grab->user_data);
>
> -       if (input->grab && input->grab_button == button && !state)
> +       /* If we were grabbing because of a button press but there are
> +        * no longer any buttons being pressed then release the
> +        * grab */
> +       if (input->grab && input->grab_button != 0 && input->button_count == 0)
>                input_ungrab(input, time);
>  }
>
> --
> 1.7.3.16.g9464b
>
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