Hierarchy lines (like we also have in the Outliner) make it easier to
visually parse the hierarchy, and avoid confusion about nesting level.
Especially when some items have icons and/or collapse chevrons and some
not (thus different levels of visual indentation).
They were planned for #93582 and #107881, also see
https://code.blender.org/2023/05/the-next-big-step-grease-pencil-3-0/#layer-groups.
The drawing is implemented as a general tree-view feature, so all
tree-views with collapsable items (which excludes the spreadsheet
data-set tree view) will get them without further setup.
A lot of files were missing copyright field in the header and
the Blender Foundation contributed to them in a sense of bug
fixing and general maintenance.
This change makes it explicit that those files are at least
partially copyrighted by the Blender Foundation.
Note that this does not make it so the Blender Foundation is
the only holder of the copyright in those files, and developers
who do not have a signed contract with the foundation still
hold the copyright as well.
Another aspect of this change is using SPDX format for the
header. We already used it for the license specification,
and now we state it for the copyright as well, following the
FAQ:
https://reuse.software/faq/
These often want to store a non-const reference to its owner, i.e. the
object that created them. I don't really like removing const here, but
it makes sense to enable this use case.
Previously UI view items would support custom drop controllers (so they
could react to data being dragged over them and dropped). This is now
more generalized so the views themselves can do this as well.
Main changes:
- Support calculating a bounding box for the view, so this can be used
for recognizing mouse hovering.
- Rename "drop controller" to "drop target", this is more clear, less
abstract naming.
- Generalize drop controllers/targets. There is a new
`ui::DropTargetInterface` now.
- Add support for drop targets in the `ui::AbstractView` base class, so
custom views can use this.
Pull Request: https://projects.blender.org/blender/blender/pulls/105963
