On Wed, Aug 8, 2012 at 7:53 AM, Prasanta Sadhukhan <psadhuk...@gmail.com>wrote:
> Hi, > > I am trying to draw something on offscreen surface and then trying to > render it on primary window. I started with simple primitives like > rectangle but it seems to not draw anything except a blank white window. > Here's my code. > Can anyone suggest as to what I need to do to draw a rectangle on an > offscreen surface and then render to primary visible window? > first of all, you need to grasp the absolutely fundamental fact about drawing widget contents in GTK and more or less any other GUI toolkit: there is only one place you can do this, and that is in the callback/handler that notifies you that the window needs redrawing. In GTK2, that is done in a handler for the expose signal, and in GTK3 its done in a handler for the draw signal. You cannot draw into a widget's on-screen window anywhere other than the code in these handlers. secondly, you should be using cairo for this (drawing into a cairo pattern and then using it as the source in the handler) or a GdkPixbuf. GdkPixmaps are now deprecated. finally, you're code never actually draws anything in the main window at all. you've just drawn into a pixmap, and then displayed a window.
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