libwayland surface coordinate question

[Ken C]

That is going to be it. The client happens to be a minimal gtk3 app.
Thank-you so much for the pointer towards
weston_desktop_surface_get_geometry().


On Thu, Nov 21, 2019 at 5:52 PM Scott Anderson
<scott.anderson at collabora.com> wrote:
>
> On 22/11/19 2:40 pm, Ken C wrote:
> > I am just starting out with libweston and have a beginner question
> > regarding surface/view coordinates. I am looking to implement
> > something along the lines of issue #277 on gitlab[1], "New shell
> > plugin for single-app usecases". I have swapped out
> > weston-desktop-shell with a toy client just to get grounded, and am
> > using the X11 and RDP backends for testing. I can see where the
> > initial client position gets set up in
> > weston_view_set_initial_position() in shell.c. However I am finding
> > that even if weston_view_set_position() is called with {0,0}, the
> > resulting window on output is offset by ~32ish pixels. I've also
> > started from westiny[2], which is about as simple as it gets, but find
> > the same mysterious (to me) offset. I can set the initial position to
> > a negative x,y value in weston_view_set_initial_position(), forcing
> > the window into the corner. Maximizing the toy client interestingly
> > enough fills the screen (a single head).
> >
> > I've looked high and low for where that ~32 pixel offset comes from,
> > but have not had luck. While I look some more maybe someone has a
> > quick pointer. If I can set a breakpoint I'm sure it will become
> > obvious.
> >
> > [1] https://gitlab.freedesktop.org/wayland/weston/issues/277
> > [2] https://gitlab.freedesktop.org/daniels/westiny/blob/master/westiny.c
>
> Hi,
>
> It may be because of the client's "window geometry"[1]. There may be
> some drop shadows or otherwise transparent border around the client's
> contents, and the window geometry will tell you which part of the
> surface you should consider to be the client's contents.
>
> If you'll excuse the terrible ASCII drawing:
>
> (0,0)
> +---------------+ <--- Surface
> | (32,32)       |
> |  +---------+<------- Geometry
> |  |         |# |
> |  |         |# |
> |  |         |# |
> |  +---------+# |
> |  ############ |
> +---------------+
>
> When a client is maximized or fullscreened, they're asked to not draw
> these kinds of things, and should fill the entire surface with their
> window's contents.
>
> weston_desktop_surface_get_geometry is the function you call to get this
> information.
>
> Scott
>
>
> [1]:
> https://gitlab.freedesktop.org/wayland/wayland-protocols/blob/master/stable/xdg-shell/xdg-shell.xml#L445-476
>