Switch to wlr scene-graph

[ghost]

It is still far from done, but apart from (not) raising view on focus it should be at least usable.

Depends on #44 (current commits from there are included) and wlroots 0.15 release.

TODOs –

• [ ] whatever’s a TODO in the code
• [x] use the scene as much as possible (e.g. cursor focus, though that may require further progress of wlroots too)
• [ ] WONTDO don’t make assumptions about new scene nodes (z-index, en/disabled…)
• [x] get rid of state duplication between the scene and kiwmi structs (positioning etc)
• [x] test it
• [ ] LATER maybe provide replacements for view pre/post-render – but it might be saner to keep for later

[heavyrain266]

Definitely looks interesting, not sure what convinced them to use stuff from gamedev and vector graphics editors in 2d linux and bsd desktops though, Scene-graph is widely used practice in game engines and programs in style of Adobe Illustrator to easier view data structure, mayby it makes sense for them 🤔.

[ghost]

6bd805cadd2283b4f702eaab6cc56c5713c9ba59 doesn’t fix the problem i thought it would fix (TODO: remove it, no need to move to another PR). Oh wait, for some reason i built kiwmi with 9c3adf0c414bf8f3bd94eaa8bc4abd7d11655953, which of course doesn’t tell me if the later commit fixed it. I can’t seem to reproduce the crash the usual way, now that i build at the right commit.

I’m not very motivated to write any code at all these days, but i hope i’ll get into it again soon enough.

Here’s a basic-tasks checklist i’ve managed to think of; pls let me know / edit if you come up with something more.

• scene
  • [x] created and destroyed
  • [x] bound to output layout
• strata
  • [x] created
  • [x] correctly sorted
  • [x] destroyed (automatically on scene destroy)
• output
  • [x] nodes created and destroyed
  • [x] shouldn’t segfault with outputs destroyed later than the desktop
  • [x] nodes moved when moving
  • [x] test this thing
• view
  • [x] node created and destroyed
  • [x] initially hidden, ideally bottom-most in the stratum
  • [x] surface geom updated in scene (and it must be correct) – may be handled by wlr later
  • [x] node moved when moving
  • [x] unmaps when unmapped / hidden
  • [x] subsurfaces handled correctly (should be done by wlroots)
• layer
  • [x] node created and destroyed
  • [x] node moved when moving
  • [x] node reparented on layer change
  • [x] (un)mapping correctly handled
• popup
  • [x] node created
  • [x] node destroyed (by wlroots)
  • [x] node moved when moving (handled by wlroots)
  • [x] correctly unconstrained
  • [x] NOT re-unconstrained¹ (for xdg-shell v3, ref 039f9903f2c0778d4768b57add8fe95a3921c473)
• bg color
  • [x] node (rect) created and destroyed (automatically on scene destroy)
  • [x] node resized (and moved?) according to output layout
  • [x] changed on user request (kiwmi:bg_color)
  • [x] what about direct scanout (which will be automatically blocked by the scene_rect)? should we bother with it?
  • [x] pure black → rect is hidden (should black be the default?)
• not required for merge (IMO)
  • [ ] an alternative to view:pre/post_render

---

1. From the xdg-shell protocol:

   For version 2 or older, the configure event for an xdg_popup is only ever sent once for the initial configuration. Starting with version 3, it may be sent again if the popup is setup with an xdg_positioner with set_reactive requested, or in response to xdg_popup.reposition requests.

   …and version 3+ is currently not supported by wlroots (there is wlroots!3514 for wlr 0.16)

[ghost]

Cleaned up the commit history so that it should now be easier to understand. However, there are still things to be done (see checklist in PR description).

[ghost]

This force-push is mostly renaming stuff and moving commits around iirc; there should be no real changes.

[ghost]

I’m planning only one change (plus the two minor TODOs somewhere in the code), namely getting rid of view::hidden. Just one TODO-question is left (it’s got a thread open somewhere above), can you pls help me decide on it?

The PR is ready for review, and if everything is okay, also for merge.

[ghost]

This force-push is mostly splitting commits; only minimal changes.

[buffet]

Thank you very much!