Re: [patch] middle button panning

[Krzysztof Foltman <kfoltman onet pl>]

Lars Clausen wrote:

>variables for this -- the Tool already has userdata that could hold the
>former tool data.
>
Does it ? I think it doesn't:

struct _Tool {
  ToolType type;
 
  /*  Action functions  */
  ButtonPressFunc    button_press_func;
  ButtonReleaseFunc  button_release_func;
  MotionFunc         motion_func;
  DoubleClickFunc    double_click_func;
};

... and using tool_select to select the new tool is not exactly right 
because it will free the Tool structure.

There are of course many solutions available:

- add userdata field to Tool
- introduce a new variable transient_tool (separate from active_tool), 
which would be mostly NULL unless middle button panning (and similar 
functions, triggered by Shift- Ctrl- Alt- dragging, like Ctrl-dragging 
clone) is in progress (best OOD-wise I think)
- add former state field to ScrollTool, and cast the pointer+check 
userdata instead of checking is_middle_panning (breaks encapsulation => 
not very futureproof)

What do you think ?

>Instant zoom would probably be highly useful.  That sounds like a good
>combo.
>
I'll try to include it in the fixed patch. Of course, there are 
situations where it isn't a good idea (two wheel mice, one wheel for X 
one for Y?).

Krzysztof