Re: Scrolling Drawing Area

[John Cupitt ng-london org uk]

Subhankar Chakraborty wrote:
> I have a drawing area within a ScrolledWindow. I want to scroll the 
> drawing area appropriately whenever my mouse pointer moves out of the 
> boundary of the enclosing window. That is, I want to scroll the drawing 
> area such that the user may get to see a coordinate of the darea (if it 
> is not already visible within the window) when the mouse moves out of 
> the main window in the appropriate direction.
>  
> I just don't know how to go about it. I mean, how do I know whether a 
> point of the drawing area is visible to the user, within the window ?? 
> And, how do I scroll the darea to have the point in the middle of the 
> window ???

Hi, I do this in my app:

- listen to "changed" on the horizontal and vertical GtkAdjustments
   for the scrolled window to get the current position and size of
   the part of the drawing area which is visible

- during a drag with a mouse button pressed, check the mouse position
   against the viewport and set flags for "mouse is to right of
   viewport", or whatever

- have a background thing running (on a gtk_timeout) which looks at the
   flags and scrolls the drawingarea (by setting values for the
   adjustments) if necessary

works OK for me,

John




========================================================== 
Fabric of Vision 
Dress and Drapery in Painting 

19 June - 8 September 2002 

For information and tickets: 
http://www.nationalgallery.org.uk/exhibitions/fabric/