mod-key brushing doesn't select all contained nodes

[gordonwoodhull]

Brushing & filtering example: regular brushing works, but with mod keys, some nodes are skipped.

It appears it may be toggling them in real time? But

• one of the keys should straight add, and one should toggle (debatable which is cmd and which is shift)
• toggling should take the previous state before brushing, and then toggle all nodes in the brush (rather than doing anything incremental)

Have not looked into the code - may be misinterpreting this.