Drawable in pygtk ! cant get it work

[e=mc^3]

Hello,

After a night searching and trying, finally i think i need your help. Here is the code first:



import gtk

win=gtk.Window()

drawing_area = gtk.DrawingArea()
drawing_area.set_size_request(600, 400)

win.set_default_size(600,400)

win.add(drawing_area)

#retrieve the wrapped gtk.gdk.window... as the tutorial ...
drawable=drawing_area.window

#and draw... just a point
drawable.draw_point(xgc,100,100)

draw_area.show()
win.show()
gtk.main()

Look ugly right ? I just to make it as simple as possible. What i want to know is how the drawable and drawing thing in Pygtk work. So i do all the step as the tutorial. First to make a drawing area, then retrieve the wrapped gtk.gdk.window and then draw onto it.

But it doesnt work. It said:

drawable.draw_point(xgc,100,100)
AttributeError: 'NoneType' object has no attribute 'draw_point'

So, basically what is the simplest way to make it works ? I can do as the sample code in the tutorial and it works perfectly but i dont understand (drawing happen in the expose_event....as the tutorial).

The tutorial dont say anything about the expose event. But i read somewhere it say that "When things need drawing in GTK+ an “expose-event” will be emitted" and "When an expose event occurs, GTK+ will also give us other information, including the area of the widget that we need to redraw. All of this information is contained within the GdkEventExpose object."

I dont get it :( If i just move all the drawing code into the expose_event handler then connect the expose_event handler to the drawing_area then it works ! So all drawing stuff MUST be INSIDE the call back function for expose event ?


If we draw with cairo, is it the same way ?

Thanks

Chuong

[nvteighen]

The tutorial tells you you have to use the realize() method before grabbing the gtk.gdk.Window...



The DrawingArea must be realized (i.e. the Widget methods realize() or show() have been called) to have an associated gtk.gdk.Window that can be used for drawing.

[e=mc^3]

Thank you.

After i realize it, i can retrieve the gtk.gdk.window. It runs, but it dont display what i paint :D. Hmm, i guess i have to stick to the expose event.