[Usability] Query Drag - right instead of middle Click

[Andy Owen <andy-gnome-usability ultra-premium com>]

In the HIG there is a section on the Query Drag:
http://library.gnome.org/devel/hig-book/stable/input-mouse.html.en#drag-drop-query


10.1.3.1.2. Query Drag
Allow the user to drag objects with the middle button , or with Alt left
button. Pop up a menu when the mouse button is released, offering the
choice of Copy, Move and Link (or whichever subset of those actions is
available), and Cancel. Dragging in this way is known as query drag
because it prompts the user before changing anything.


I'm proposing that we change it to a right button drag. This is how I
see it:

1) On a mouse with a wheel (especially one of those new horizontal
scrolling tilt wheels), it is actually quite difficult to do this
operation.
2) It might be useful to support the scroll wheel during drag operations
in the future (e.g. dragging a selection in a document, using the
workspace switcher when dragging a file)
3) There is already a strong association with right click and popup
menus. If I were to guess which button to use to drag a file and be
presented with a menu, then based on the fact that right clicking a file
brings up a menu, I would guess that a right click drag would do so.

On the negative side:
4) This raises the question of what to do when the right mouse button is
depressed, should we show the context menu, or wait a bit to see if they
are dragging? (waiting for mouse up isn't ok, because of 5)
5) I can imagine that there are people who will use a right click drag
to select an item in the context menu (e.g. right mouse down on a file,
then while keeping the button down, mouse over the menu item you want
and release)

In spite of these issues, I think it would be quite possible to find a
solution which doesn't surprise you. I haven't played with any mockups
or anything, but I'd imagine that if there was a (fairly generous)
timeout on the button down event (which also brought up the context menu
- possibly after a (fairly short) delay, and if the cursor leaves a
'certain area' before that timeout then it is a drag operation and the
context menu disappears. Otherwise it is a context menu operation. The
'certain area' would be a bit bigger than the context menu, and maybe a
little bit bigger than the thing being dragged.

Does anyone have any further thoughts or comments?

Andy