This decouple the vertex display from the face+edges.
This is to reduce the number of triangles required to fix the edges
artifacts (aliasing) and increase viewport reactivity when not actively
navigating (ie. mouse scroll).
Also it makes all vertices visible (not cut-off) even when navigating.
However it makes the navigation drawing a bit slower because it has to
render twice.
Also add a depth bias to the wires to avoid depth fighting when previewing
final mesh (modifiers applied).
This makes is easy to create nested drawcalls that will inherit all the
parents properties. This is usefull if only a few uniforms changes for that
drawcall.
Both original handle types are based on location, and Absolute uses it
in a weird way: the Start handle uses the head, while End uses the tail.
This makes controlling the shape of the B-Bone via control bone rotation
really non-intuitive, especially if trying to add a single control for
the tangent in the middle of a B-Bone chain.
To remedy this, add a new custom handle type that uses the orientation
of the control bone, while completely ignoring location. It is even
possible to control both ends of one B-Bone with the same handle bone,
resulting in an S shape.
Reviewers: brecht
Differential Revision: https://developer.blender.org/D3769
Specifically, it should always use the position of the custom handle
bone head, even when affecting the handle at the tail of the main bone,
and shouldn't apply the special handling for joining two B-Bones.
This handle type was unusably broken before a bug fix included in
recent changes, so it should be safe to break backward compatibility.
The rest shape of B-Bones is actually affected by custom handles or
the default connected parent/child mechanism. Ignoring these effects
thus leads to the edit mode shape being different from the actual
rest pose.
This splits the b_bone_spline_setup function that is used to compute
the correct rest and pose shape from pose channels into two parts,
and applies the data structure independent half to edit mode.
In order to access the custom handle settings in Edit Mode, they are
moved to Bone and EditBone, while the bPoseChannel fields are downgraded
in status to a cache for performance. Also, instead of flags, introduce
an enum to specify the handle operation modes, so that new ones could
be added later.
Reviewers: aligorith, brecht
Differential Revision: https://developer.blender.org/D3588
Avoid accessing object mode via the view layer active object
when drawing since it's done everywhere we store the active object mode
in the draw-context.
