Re: I'm looking for a drag-and-zoom box. Where to start?
- From: James Johnson <johnsjam comcast net>
- To: "Paul van Haren" <paul vanharen zonnet nl>
- Cc: gtk-app-devel-list gnome org
- Subject: Re: I'm looking for a drag-and-zoom box. Where to start?
- Date: Wed, 20 Oct 2004 23:47:39 -0700
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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