Blender Git Loki

initial changes

Sculpt dyntopo: fix missing bit from last commit

* BM_mesh_bm_to_me now saves id layers by default.

Sculpt dyntopo:

Seperate enabling PBVH_BMESH from enabling DynTopo:

* Created a new option to globally disabled
DynTopo.
* The DynTopo panel header now reads "Dynamic Mode",
to hopefully signal that turning on PBVH_BMESH is
a seperate step from enabling or disabling DynTopo
itself.
* The first checkbox in the panel is "DynTopo" so it
should be clear enough (it's on by default, with multiple
layers of file versioning checks).

PBVH_BMesh's undo system:

* CD_MESH_ID layers are now permanently saved once
they are created (by default they are not). This
fixed a *lot* of bugs:

Before this the undo system had to save maps between
mesh indices and mesh IDs on transitioning
between sculpt and global undo steps. This was
extremely error prone, and it simply wasn't possible
to cover all of the corner cases

* Note that there is still an odd bug where the first
global undo push after a sculpt step gets ignored,
I dunno what's up with this.

* Dyntopo undo should be nearly (hopefully completely)
bug-free after this commit.

C++20

* Made a few small changes to get blender to compile
with c++20. std::result_of was removed, had to
replace a couple of usages of it with std::invoke_result.

* I'm planning to do some design studies on rewriting
sculpt into C++.

* I strongly suspect we are going to need C++20'a new
concepts feature if we move sculpt into C++.
I'm planning to do some design studies on how
that might work.

Merge remote-tracking branch 'origin/master' into temp-lineart-contained

Merge branch 'temp-lineart-contained' into lineart-shadow

Merge remote-tracking branch 'origin/master' into temp-lineart-contained

USD Import: minor format fix

Cleanup: Remove unused variable

UI: Use right-arrow icon for sub menus

UI: Match subpanels look with regular panels

By having coloured headers and offset the background.

TODO: Add margin to the bottom on the last subpanel.

wip - reuse thumbnails when scaling

Set handle type of outer handles of arc to Vector

Removed redundancy in spline position calculations

Cycles X: Cover string startswith/endswith with tests

Cycles X: Switch startswith/endswith to string_view

Currently no functional changes. Making this internal API flexible to
be used for any string-like objects.

The implementation is a bit lower-level than one would expect from the
C++'s string_view. This is because the string_view implementation is
coming from OIIO./

Differential Revision: https://developer.blender.org/D12483

Merge branch 'master' into asset-browser-snap-dragging

Use box select as default tool in preview

Add clear transform operators to preview, since it is only keymap change

Fix incorrect origin range

Fix incorrect initial origin value