[PATCH RFC xserver] xwayland-input: Fake crossing to rootwin

[Olivier Fourdan]

Hi all,

So this patch might deserve some more explanation...

This is for https://bugs.freedesktop.org/show_bug.cgi?id=96437

The problem occurs when the pointer moves from an X11 window to a Wayland native window which overlaps it:


              +----------------------------------+
              |                                  |
              | > weston-terminal                |
              |                                  |
              |                                  |
  +-----------|                                  |
  |           |                                  |
  |     xev   |                                  |
  |           |                                  |
  |           +----------------------------------+
  +--------------+


When the pointer leaves the Xwayland client window to enter a Wayland native surface, pointer_handle_leave() in xwayland-input.c calls CheckMotion() with an NULL event, so that the Enter/Leave notify events get emitted as expected.

CheckMotion() from dix/events.c will save the previous WindowPtr as prevSpriteWin and calls XYToWindow() to find the new window where the pointer resides.

But since that new window is a Wayland native window unknown to Xwayland, XYToWindow() via miXYToWindow() and miSpriteTrace() will return the Xwayland window under the current pointer positioon, and that happens to be still the same window (due to the overlap betwee nthe Wayland native window and the Xwayland window).

Therefore, newSpriteWin (as returned by XYToWindow) remains the same as prevSpriteWin and therfore DoEnterLeaveEvents() is not invoked (as Xwayland reckons the pointer is still within the X11 window...).

What this patch does is to re-add the previously removed XYToWindow() vfunc in Xwayland to return the root window if there is no xwl_seat->focus_window set. As xwl_seat->focus_window is cleared in pointer_handle_leave(), in effects it means that when the pointer leaves an X11 window to enter a Wayland native window, XYToWindow() returns the root window and CheckMotion will emit the expected LeaveNotify event.

Cheers,
Olivier



----- Original Message -----
> This partially reverts commit c1565f3.
> 
> When the pointer moves from an X11 window to a Wayland native window,
> no LeaveNotify event is emitted which can lead to various unexpected
> behaviors like tooltips remaining visible after the pointer has left the
> window.
> 
> Yet the pointer_handle_leave() is called and so is the DIX CheckMotion()
> but since the pointer enters a Wayland native window with no other
> Xwayland window matching, DoEnterLeaveEvents() does not get invoked and
> therefore no LeaveNotify event is sent to the X11 client at the time the
> pointer leaves the window for a Wayland native surface.
> 
> Restore the XYToWindow() handler in xwayland-input that was previously
> removed with commit c1565f3 and use that handler to pretend that the
> pointer entered the root window in this case so that the LeaveNotify
> event is emitted.
> 
> Signed-off-by: Olivier Fourdan <ofourdan at redhat.com>
> Bugzilla: https://bugs.freedesktop.org/show_bug.cgi?id=96437
> ---
>  Sending this as an RFC for now.
>  See also: https://bugzilla.gnome.org/show_bug.cgi?id=766377
> 
>  hw/xwayland/xwayland-input.c | 23 +++++++++++++++++++++++
>  hw/xwayland/xwayland.h       |  1 +
>  2 files changed, 24 insertions(+)
> 
> diff --git a/hw/xwayland/xwayland-input.c b/hw/xwayland/xwayland-input.c
> index 0735d43..246defa 100644
> --- a/hw/xwayland/xwayland-input.c
> +++ b/hw/xwayland/xwayland-input.c
> @@ -944,6 +944,26 @@ DDXRingBell(int volume, int pitch, int duration)
>  {
>  }
>  
> +static WindowPtr
> +xwl_xy_to_window(ScreenPtr screen, SpritePtr sprite, int x, int y)
> +{
> +    struct xwl_seat *xwl_seat = NULL;
> +    DeviceIntPtr device;
> +
> +    for (device = inputInfo.devices; device; device = device->next) {
> +        if (device->deviceProc == xwl_pointer_proc &&
> +            device->spriteInfo->sprite == sprite) {
> +            xwl_seat = device->public.devicePrivate;
> +            break;
> +        }
> +    }
> +
> +    if (xwl_seat == NULL || !xwl_seat->focus_window)
> +        return sprite->spriteTrace[0];
> +
> +    return (*xwl_seat->xwl_screen->XYToWindow)(screen, sprite, x, y);
> +}
> +
>  void
>  xwl_seat_clear_touch(struct xwl_seat *xwl_seat, WindowPtr window)
>  {
> @@ -970,6 +990,9 @@ InitInput(int argc, char *argv[])
>      wl_registry_add_listener(xwl_screen->input_registry, &input_listener,
>                               xwl_screen);
>  
> +    xwl_screen->XYToWindow = pScreen->XYToWindow;
> +    pScreen->XYToWindow = xwl_xy_to_window;
> +
>      wl_display_roundtrip(xwl_screen->display);
>      while (xwl_screen->expecting_event)
>          wl_display_roundtrip(xwl_screen->display);
> diff --git a/hw/xwayland/xwayland.h b/hw/xwayland/xwayland.h
> index 70a0492..ef8811f 100644
> --- a/hw/xwayland/xwayland.h
> +++ b/hw/xwayland/xwayland.h
> @@ -63,6 +63,7 @@ struct xwl_screen {
>      DestroyWindowProcPtr DestroyWindow;
>      RealizeWindowProcPtr RealizeWindow;
>      UnrealizeWindowProcPtr UnrealizeWindow;
> +    XYToWindowProcPtr XYToWindow;
>  
>      struct xorg_list output_list;
>      struct xorg_list seat_list;
> --
> 2.7.4
> 
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