The higher the level of magnification being used, the more significant each movement of the mouse is.  This makes it difficult for some users to locate a desired item that's not currently visible.  It also makes it difficult to read a document with long lines.  Therefore, Orca should provide support for smooth/linear panning of the zoomer.

Possibilities:

1. Unbound keybindings:
   a. Pan left
   b. Pan right
   c. Pan up
   d. Pan down

2. Option to constrict the direction of the mouse movement:
   Hold down some key (maybe Shift or Control) while moving the mouse
   and the mouse pointer will move either vertically or horizontally, 
   but not both. (i.e. we'd detect the primary direction).