Adding a mirror modifier in edit-mode crashed.
Freeing meshes that hold a shallow copy happens in multiple places
while calculating modifiers, making it impractical to clear the
edit-mode pointer before freeing the mesh (as done in
BKE_editmesh_free_derived_caches).
Add a struct member to the edit-mesh struct so evaluated copies
don't free the edit-mesh contents.
- BKE_mesh_copy_parameters_for_eval to be used for evaluated meshes only
as it doesn't handle ID user-counts.
- BKE_mesh_copy_parameters is a general function for copying parameters
between meshes.
This uses mesh's runtime mutex for both `BKE_mesh_runtime_looptri_ensure`
(was using its own global RW mutex before), and `BKE_mesh_wrapper_ensure_mdata`
(was not protected at all before).
This is more like a band-aid than a proper fix, as mentioned in the report
proper fix would be for the modifier to request those data (the relevant
BVHTree, which would implicitely also call the tow others) through flags,
just like it does for regular CDData layers. But this is a much bigger
refactor to be done outside of bugfix scope.
Reviewed By: sergey
Maniphest Tasks: T78285
Differential Revision: https://developer.blender.org/D8415
This resolves a performance regression in 2.8x where every edit-mode
update performed an edit-mesh to mesh conversion.
Now the conversion will be lazily initialized if/when it's required.
New BKE_mesh_wrapper_* functions abstract over mesh data access.
Currently only edit-mesh and regular meshes are supported.
In the future sub-surface meshes may be supported too.
