[Bf-committers] "correct" edge selection state?

[Geoffrey Bantle]

>Seemingly simple question:

>When a mesh edge is selected/deselected with Edge
Select 
>mode, and the vertices of neighboring edges are
already 
>selected, should the neighboring edges become 
>selected/deselected also?  Should vertex selection
state 
>have any impact on the edge selection state?

The answer to this is that 'it depends'. In edge
exclusive mode, its possible that an edge may have
only one of its vertices selected (this is a bug). In
vert+edge or vert+edge+face mode (but not edge+face!),
if two selected edges share a vertex and one edge is
deselected then the neighbor edge is also deselected.

Got a headache yet? :)

>Another way to ask: is edge/face selection dependent 
>or independent of vertex selection state?

The short answer is 'yes'. The longer answer is that
the current state of blenders vert/edge/face selection
methods is a bit complicated. 

Right now in blender when a face is
deselected/selected with 'EM_select_face' all of its
vertices and edges are deselected/selected as well.
Similarly when an edge is deselected/selected with
'EM_edge_select'  its vertices are deslected/selected.

Furthermore when the vertices of an edge are selected
in vertex or multiselect mode the edge becomes
selected. Also when the vertices or edges of a face
become selected in either vertex, edge or multi-select
mode the face and its edges become selected. This is
handled through the 'EM_select_flush' and
'EM_selectmode_flush' functions in editmesh_lib.c.

Unfortunatley the behavior of EM_select_flush and
EM_selectmode_flush makes multiselect mode 'broken' in
about a couple dozen ways. One user I spoke to
summarized the problem very succintly when he said
'You can't actually select what you want with
multi-select mode'. As far as I can tell this problem
is entirely due to blenders 'flushing' Multi-select
and flushing behavior should probably be
reviewed/revised soon.

Ton, can you comment on this?

Cheers,
Geoff Bantle

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