container_move_to handled moving containers to new parents, as well as
moving workspaces to new outputs.
This commit removes the workspace-moving code from this function and
introduces workspace_move_to_output. Moving workspaces using
container_move_to only happened from the move command, so it's been
implemented as a static function in that file.
Simplifying container_move_to makes it easier for me to fix some issues
in #2420.
I've got the following SIGSEGV when terminating sway:
```
Program terminated with signal SIGSEGV, Segmentation fault.
0x00005607dc603af5 in view_unmap (view=0x5607dcb3d350) at ../sway/tree/view.c:599
599 if (surviving_ancestor->type >= C_WORKSPACE) {
```
surviving_ancestor was NULL at that time
This commit is trying to fix this problem.
- Some platforms don't expose kill() unless _POSIX_C_SOURCE is defined.
- fork(), execl(), and setsid() need unistd.h on some platforms.
Basically, this fixes some platform-specific build errors.
This creates a root.c and moves bits and pieces from elsewhere into it.
* layout_init has been renamed to root_create and moved into root.c
* root_destroy has been created and is called on shutdown
* scratchpad code has been moved into root.c, because hidden scratchpad
containers are stored in the root struct
Calling container_at_view fails an assertion if the container isn't a
view. Calling tiling_container_at works correctly, as that function
checks if the container is a view and calls container_at_view if so.
When a view unmaps, normally the surviving ancestor (ie. after reaping)
needs to be arranged. When a fullscreen view unmaps, it arranges the
workspace rather than the surviving ancestor, but didn't handle cases
where the workspace itself was reaped. This happens if the workspace is
not currently shown and the fullscreen view was the last container on
that workspace.
This commit rewrites this part of view_unmap so it's more readable, and
fixes the crash by not arranging the workspace if it's been reaped. Note
that it no longer arranges the output under any circumstance - this
wasn't required anyway.
