PlacementStrategy ignores the surface type and state

[Daniel d'Andrada]

The surface type and state are important bits of information when deciding the placement of a surface.

Without this information a poor initial placement might be done causing a surface to resized and repositioned right after it, once the window manager finally has knowledge of all the properties of the surface.

This is happening right now with unity8 as surfaces get unnecessarily resized right after creation, which causes visual glitches as you can see the window "contorting" right after being launched and resizing a surface is a reasonably costly operation. We have worked around it by holding up on displaying the surface until it has finally settled down (i.e. we keep the splash screen for longer).

[Daniel van Vugt (vanvugt)]

Confirmed. I know it is important for placement/size to be determined by surface type and state (also affected by things like decoration sizes too). We just haven't wired up any of that state information to the placement/sizing logic yet.

When this is done, you will for example be able to set mir_surface_state_fullscreen instead of having to specify explicit surface dimensions.

I am wondering however if any part of what you experience in Unity8 is caused by Unity8. Because Mir has no "late resizing" that it will trigger itself. The late resizing would be coming from Unity8. Mir does no resizing except when explicitly requested by the shell. So you could avoid it by creating the surface with correct dimensions, which means any subsequent resize request from Unity8 to the same dimensions will be a no-op.

[Daniel van Vugt (vanvugt)]

When this is all implemented, I'm not sure "PlacementStrategy" will still exist. So maybe we need to describe the problem without mentioning that class.

[Gerry Boland (gerboland)]

Orientation too please :)

[Gerry Boland (gerboland)]

>I am wondering however if any part of what you experience in Unity8
>is caused by Unity8. Because Mir has no "late resizing" that it will
>trigger itself. The late resizing would be coming from Unity8. Mir
>does no resizing except when explicitly requested by the shell. So you
>could avoid it by creating the surface with correct dimensions, which
>means any subsequent resize request from Unity8 to the same
>dimensions will be a no-op.

That's exactly what we're doing now. Currently unity8 isn't deciding intelligently the surface geometry in the Placement Strategy, just making it fullscreen. Only when it has drawn a frame did we resize (as that's when we add it to our scene, and thus its correct geometry is set). But I've branches under review now that gives our scene the ability to decide geometry at PlacementStrategy time.

This bug came about because we foresaw that we'd be lacking enough information to always decide correctly. So we'd need to know as much info about this new surface before it is created: the state, type, parent surface, fullscreen property, and anything else it supplies. In return, shell will want to set the surface's orientation. Perhaps other things too.

[Daniel van Vugt (vanvugt)]

Alright so you could fix this bug entirely in Unity8 right now. Although there is definitely functionality in Mir still missing. That's the area of WM I'm going to focus on again after the current bug fix and optimization efforts for the phone.

[Gerry Boland (gerboland)]

Yep, this bug relates only to the missing functionality we saw in Mir.

[Daniel van Vugt (vanvugt)]

Is this bug still valid after PlacementStrategy is deleted? We removed it in r2694 (scheduled for release in Mir 0.14.0).

[Alan Griffiths (alan-griffiths)]

This was obsoleted in Mir 0.14 (LP doesn't seem to have a way to set a milestone that passed months ago.)