Re: mouse pan and zoom

[Ethan M. <merritt@u.washington.edu>]

On Friday 17 July 2009, James R. Van Zandt wrote:
> 
> I've just checked in code to do "pan and zoom" with the mouse wheel.

First thoughts:

It works nicely here in x11, but doesn't do anything at all in wxt or
in the new canvas or qt terminals.  I understand that extra javascript
would be needed for the canvas,  but what is needed in order to support
this for other interactive terminal types?

Wouldn't it be logical to apply this in 3D also?

It does not immediately strike me as useful to save the settings on the
zoom stack.  Unlike a click-and-drag zoom operation, the inverse is easy
to achieve by reversing the direction of the mouse wheel.


> These commands work like Acroread or Gimp:
> 
>  - control-wheel-up zooms in toward the center of the plot
>  - control-wheel-down  reverses the above
> 
>  - wheel-up move the viewpoint up (increases both ymin and ymax by ten
>    percent of the plot range)
> 
>  - wheel-down moves the viewpoint down
> 
>  - shift-wheel-up moves the viewpoint left (decreases both xmin and xmax
>    by ten percent of the plot range)
> 
>  - shift-wheel-down moves the viewpoint right
> 
> 
> I implemented these just for completeness:
> 
>  - shift-control-wheel-up zooms in only the X axis
>  - shift-control-wheel-down zooms out only the X axis
> 
> 
> These work for linear or log axes.
> 
> A simple plot for testing, with or without log axes:
> 
> set parametric; plot sin(t)+1.02,cos(t)+1.02
> 
> (If zero is not currently on an axis, you can use "L" to toggle
> logscale along that axis.)
> 
> 
> I'll be glad to add documentation, but first I'll see what changes
> people want.  E.g.:
> 
>  - Are the pan and zoom steps reasonable?  Should they be user-tunable?
>  - Do you have a better idea for shift-control-wheel?
>  - Each of these commands is added to the zoom stack, so they can be
> undone individually.  That was easy to implement, but do we want that?
> Does "u" recover all that memory?  Should we suggest that the user
> type "u" occasionally?
> 
>         - Jim Van Zandt
> 
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