What we do and don't expose to client toolkits

[Alan Griffiths]

On 02/09/16 15:44, Alan Griffiths wrote:
> On 02/09/16 15:42, Thomas Voß wrote:
>> This only works in the fullscreen case and I
>> cannot think of a scenario where this impacts overall
>> user experience. The app already is the one "owning" the display in fullscreen.
> Why would you think it only work in the fullscreen case?

there was an IRC conversation to sort this out between myself William
and Thomas.

I think the resulting consensus was:

1. Mir will constrain the placement anchor of the aux_rect to the parent
surface. I don't think we agreed exactly how (e.g. do we "clip" the
rect? What happens if there is *no* intersection?)

2. Mir will constrain the the offset placement anchor to the parent
surface. Again I don't think we agreed how. (Slide it horizontally
and/or vertically the minimum amount?)

3. Mir will provide a new notification of the placement rectangle.

4. Clients can then probe the display boundaries:

    E.g.

      MirRectangle aux { 0, 0, 0, 0 };

     auto const surface_spec = mir_connection_create_spec_for_tip(connection, a_big_width, ...);
     mir_surface_spec_set_placement(
        surface_spec, &aux, 
        mir_placement_gravity_northwest, // rect anchor
        mir_placement_gravity_northeast, // surface anchor
        mir_placement_hints_resize_x, 
        0,
        0);

    Will result in a "tip" surface whose width is the distance to the
    left hand side of the screen.

5. Clients using the result of such probing may get stupid results. We
don't care.
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