Mouse clicks are sometimes slowed (preventing double-clicks)

[joshuahhh]

This diagram isn't very complex. But for some reason, successive mouse clicks are processed over 400ms apart, so double-clicks cannot be registered. I'll poke around.

EDIT: Profiling suggests there's a big lag from serialization! Possible solutions:

• Make double-click a single event, rather than a pair of events (selection, double-click selection).
• Fix something serialization-scheduling-related.
• Check if there's some reason serialization of this particular diagram is problematic... I guess the file is unusually large...