Selection issues

[edemaine]

• [ ] Clicking without drag should not trigger rectangular select. This is currently true when clicking on an object, but not true when clicking nowhere.
• [ ] Clicking on a deselected object within the selection bounding box does not work. (eventTop should ignore the selection bounding box.)
• [x] Escape (and maybe other hotkeys?) to deselect all. Only leave history if no selection.

[diomidov]

(Note: in my idiolect "unselected" means "not selected" and "deselected" means "has been deselected")

Here is how selection currently behaves as of June 2: (differences between browsers in bold)

Object	Click in Chrome	Click in Firefox	Ctrl-click or Shift-click in Chrome	Ctrl-click or Shift-click in Firefox
Selected object	Nothing	Nothing	Deselect	Deselect
Selected object's bounding box	Nothing	Nothing	Deselect†	Nothing
Unselected object inside selection bounding box	Nothing	Nothing	Add to selection†	Nothing
Unselected object's bounding box inside selection bounding box	Nothing	Nothing	Add to selection†	Nothing	Deselect all
Empty space inside selection bounding box	Nothing	Nothing	Nothing	Nothing
Unselected object outside selection bounding box	Select only	Select only	Add to selection	Add to selection
Unselected object's bounding box outside selection bounding box	Select only†	Deselect all	Add to selection†	Nothing
Empty space outside selection bounding box	Deselect all	Deselect all	Nothing	Nothing

† Can be combined if clicked on multiple objects/bounding boxes

Inconsistencies/issues:

• In Chrome, clicking within one or more objects' bounding bounding boxes affects all of those objects (technically it's 0x0 rectangular selection). In Firefox, it's equivalent to clicking on empty space.
• In Firefox, there is no way to select an object that's inside selection bounding box (since it relies on rectangular selection)
• (Chrome-only) Shift-clicking on a selected object or a unselected object outside the selection bounding box triggers a click on that object. But Shift-clicking on a unselected object inside the selection bounding box triggers 0x0 rectangular selection.
• (Chrome-only) Ctrl/Shift + rectangular selection computes symmetric difference of the two selections. I expected it to be union instead. Maybe it should depend which modifier key(s) is held? (currently there is no distinction between Ctrl and Shift)
• (Chrome-only) Here is a particular case where symmetric difference is confusing (at least until we get better rectangular section)
  • If you select a straight line A and Shift-click unselected object B within the selection bounding box, the new selection is just {B}.
  • If you select a freehand line A and Shift-click unselected object B within the selection bounding box, the new selection is {A,B}.