modifiers for the second selection

[Tim Janik <timj gtk org>]

hi all,

in the course of reimplementing drag-selection for a widget,
i did a small survey of modifier behaviour in other (gnome/
gtk) programs and had to figure that there's no current
standard behaviour to adhere to:

for all applications, the first selection works as
expected, i.e. press-drag-release selects the region
(box) the mouse was draged over. also, starting a new
selection without pressing any modifiers simply replaces
the first one. differences occour when holding a modifier
(shift or ctrl) when starting the second selection.

Gimp:
Shift upon button press:	the new seleciton is added to the existing one
Ctrl upon button press:		the new selection is subtracted from the
				existing one
Shift during drag:		the selection area (box or circle) has fixed
				aspect ratio
Ctrl during drag:		the position of the initial button press
				serves as center of the selected box/circle,
				rather than the upper left corner

Gnumeric:
Shift upon button press:	the first selection is resized
Ctrl upon button press:		the new seleciton is added to the existing one

Abiword (selecting text regions):
Shift upon button press:	the first selection is resized
Ctrl upon button press:		triggers a compound (word) selection that
				replaces the first selection

Mozilla (selecting text regions):
Shift upon button press:	the first selection is resized

Nautilus:
Shift or Ctrl upon buttn press:	the new selection is added to or subtracted
				from the first selection, depending on whether
				the newly selected region was selected before.
				i.e. implementing XOR integration of the newly
				selected area into the first.

i'm not pointing this out to start a flame war over what selection style
is good or bad and i do realize that different applications have
different needs (i.e. abiword does need compound selection, and
the aspect-ratio/centering style for gimp wouldn't make too much
sense for text), but i think for the benfit of the (new) users,
there should me more consistency regarding modifier association
with adding/subtracting/resizing/xoring to/from existing selections.

---
ciaoTJ