[PATCH weston] compositor: quick fix for sub-surface mapping

[Jason Ekstrand]

I don't like it but, sure, it shouldn't break anything much further.
--Jason


On Mon, Jun 30, 2014 at 2:10 AM, Pekka Paalanen <ppaalanen at gmail.com> wrote:

> From: Pekka Paalanen <pekka.paalanen at collabora.co.uk>
>
> If a client does this:
> 1. create a main window and map it
> 2. create a wl_surface, and make it a sub-surface of the main window
> 3. set the sub-surface to desync
> 4. commit content to the sub-surface to map it
>
> Then step 4 should cause the sub-surface to become mapped. However,
> Weston fails to schedule a repaint in that case, so the sub-surface will
> not appear until something else causes a repaint on that output, e.g.
> the main window.
>
> A quick and dirty fix is to set the output mask for the surface in
> Weston, which allows the repaint to be scheduled. This patch implements
> that, and might only work right on single-output systems.
>
> A proper fix would involve rewriting the whole "is surface mapped"
> mechanism in Weston, to not rely on output assignments but to have a
> separate flag for "mapped", and figuring out how to schedule repaints
> for the right outputs.
>
> Following is the actual protocol sequence used to trigger the problem:
>
> [3224648.125]  -> wl_compositor at 4.create_surface(new id wl_surface at 3)
> [3224648.206]  -> xdg_shell at 7.get_xdg_surface(new id xdg_surface at 8,
> wl_surface at 3)
> [3224648.311]  -> xdg_surface at 8.set_title("simple-shm")
> [3224648.378]  -> wl_surface at 3.damage(0, 0, 250, 250)
> [3224649.888]  -> wl_shm at 6.create_pool(new id wl_shm_pool at 9, fd 6, 250000)
> [3224650.031]  -> wl_shm_pool at 9.create_buffer(new id wl_buffer at 10, 0,
> 250, 250, 1000, 1)
> [3224650.244]  -> wl_shm_pool at 9.destroy()
> [3224651.975]  -> wl_surface at 3.attach(wl_buffer at 10, 0, 0)
> [3224652.100]  -> wl_surface at 3.damage(20, 20, 210, 210)
> [3224652.243]  -> wl_surface at 3.frame(new id wl_callback at 11)
> [3224652.317]  -> wl_surface at 3.commit()
> [3228652.535]  -> wl_compositor at 4.create_surface(new id wl_surface at 12)
> [3228652.610]  -> wl_subcompositor at 5.get_subsurface(new id
> wl_subsurface at 13, wl_surface at 12, wl_surface at 3)
> [3228652.644]  -> wl_subsurface at 13.set_desync()
> [3228652.659]  -> wl_subsurface at 13.set_position(100, 100)
> [3228654.090]  -> wl_shm at 6.create_pool(new id wl_shm_pool at 14, fd 6,
> 250000)
> [3228654.140]  -> wl_shm_pool at 14.create_buffer(new id wl_buffer at 15, 0,
> 250, 250, 1000, 1)
> [3228654.180]  -> wl_shm_pool at 14.destroy()
> [3228654.408]  -> wl_surface at 12.attach(wl_buffer at 15, 0, 0)
> [3228654.436]  -> wl_surface at 12.damage(0, 0, 250, 250)
> [3228654.462]  -> wl_surface at 12.commit()
>
> Signed-off-by: Pekka Paalanen <pekka.paalanen at collabora.co.uk>
> Cc: George Kiagiadakis <george.kiagiadakis at collabora.com>
> Cc: Jason Ekstrand <jason.ekstrand at intel.com>
>
> ---
>
> Do we want this patch in Weston upstream master or even 1.5 stable?
> I am not sure when I would have time for the proper fix.
> ---
>  src/compositor.c | 11 ++++++++---
>  1 file changed, 8 insertions(+), 3 deletions(-)
>
> diff --git a/src/compositor.c b/src/compositor.c
> index fa8730f..d78314a 100644
> --- a/src/compositor.c
> +++ b/src/compositor.c
> @@ -2512,6 +2512,8 @@ subsurface_configure(struct weston_surface *surface,
> int32_t dx, int32_t dy)
>          * will not be drawn either.
>          */
>         if (!weston_surface_is_mapped(surface)) {
> +               struct weston_output *output;
> +
>                 /* Cannot call weston_surface_update_transform(),
>                  * because that would call it also for the parent surface,
>                  * which might not be mapped yet. That would lead to
> @@ -2521,11 +2523,14 @@ subsurface_configure(struct weston_surface
> *surface, int32_t dx, int32_t dy)
>                  * Instead just assing any output, to make
>                  * weston_surface_is_mapped() return true, so that when the
>                  * parent surface does get mapped, this one will get
> -                * included, too. See surface_list_add().
> +                * included, too. See view_list_add().
>                  */
>                 assert(!wl_list_empty(&compositor->output_list));
> -               surface->output =
> container_of(compositor->output_list.next,
> -                                              struct weston_output, link);
> +               output = container_of(compositor->output_list.next,
> +                                     struct weston_output, link);
> +
> +               surface->output = output;
> +               weston_surface_update_output_mask(surface, 1 <<
> output->id);
>         }
>  }
>
> --
> 1.8.5.5
>
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