Re: I'm looking for a drag-and-zoom box. Where to start?

[James Johnson <johnsjam comcast net>]

Hello,

	You might start by looking at the GTK demo where it has a window that 
comes up that has a really simple pen up pen down example on it(I cant 
remember the exact name).  It shows how to catch signals of mouse up 
and down on a gtk drawing area without polling the cpu for them. As for 
the rectangle you could take a snap shot of the drawing area that the 
mouse has drawn a box over and manipulate with the gdk pixbuf 
functions:

http://developer.gnome.org/doc/API/2.0/gdk/gdk-Pixbufs.html

i.e gdk_pixbuf_get_from_drawable ()

and then run it through what ever functions you need to make it look 
funky and slap it back on the draw area->window.

i.e. gdk_draw_pixbuf ()

Good luck!

Jimmy





On Oct 20, 2004, at 10:03 AM, Paul van Haren wrote:

> Hi,
>
> In my application I have a map, implemented as a GdkPixbuf, that I can 
> manipulate and display. Now I want to extend this app with a zoom 
> function as follows: the user clicks left and draws a non-filled 
> rectangle while keeping the left button pressed. As soon as the left 
> mouse button is depressed, the action is completed and I can execute 
> the zoom function. The new view will show what is inside the drawn 
> rectangle.
>
> However, I have no idea where to start to look for such a function. 
> Should I be using low level primitives such as gdk_draw_rectangle and 
> implement by own backing store, or is there a more convenient way to 
> get it implemented.
>
> Any help is appreciated. Thank, Paul van Haren
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