Blender Git Loki

Support multiple panels of the same type

The name for the uiBlock associated with a panel was just the panel type's
idname, so the old block found at the start of drawing was the same for
every panel of a certain type.

Panel blocks for list panels are now named with the list index appended
to the end of the name. The panel list is also rebuilt when reordering
panels of the same type.

Include Potrace lib as new extern

Thanks to @lazydodo for his help.

Merge branch 'master' into greasepencil-object

Merge branch 'master' into modifier-panels-ui

Merge branch 'master' into greasepencil-object

Free panelsort panels from recreate list reordering

Merge branch 'temp-checkbox-layout-tweaks' into modifier-panels-ui

GPencil: Fix return value error

GPencil: Fix problem with some linked not selected

In some files, the active object is not visible in the selected objects of the view.

Initial changes to checkbox layout: Use split layout & better section headings

See T65965.
Checkboxes now use the split layout as proposed in the design task and
columns can define headings now (`uiLayout.column(heading="Foo")`).
These headings are placed in the left column of the first item if that
doesn't add its own label there. Otherwise an own row is inserted for
the heading.

GPencil: Check object type in poll for Bake Animation

Merge branch 'master' into uuid-undo-experiments

Conflicts:
source/blender/blenloader/intern/readfile.c

Not really a merge, accepting changes from master and loosing most of
recently added debug prints here... Not a big deal, those are easy to
add back once needed.

GPencil: Cleanup unused variable

Merge branch 'master' into greasepencil-object

EEVEE: Motion Blur: Make motion blur closer to cycles by evaluating 3 step

For now we always center the delta around the frame time. We store 2 motion
steps, one before and one after the current frame. However, this also means
storing 2 motion vectors for each pixels, doubling the vram usage of the
motion vector buffer.

This patch also cleanup some uneeded complexity. We use the motion vectors
as is and don't use a multiplier.

EEVEE: Motion Blur: Use orig_object->data instead of orig_data as key

This fix issue with some modifier setup

Always add recreate list panels in the correct place.

This requires adding a start type in case we're adding the first
recreate panel.

Explode, Particle Instance modifier layouts

EEVEE: Implement deformation motion blur

This adds deformation motion blur by saving the vertex buffers of the
previous frame.

We modify the surface batch to pass the vert position as new attributes.

DRW: Batch Cache: Expose position vertex buffer to engine

This is in order to compute position deltas for motion blur. The engine
is responsible to handle the data. However it is not the owner of the data.
So a copy must be performed if the data needs to be kept accross frame.