Re: [Java-gnome-developer] Assertion failure while drawing on DrawingArea

[Jaime <re...@sa...>]

On Sun, 2004-12-12 at 16:55 +0000, Mark Howard wrote:
> Hi,
> 
> I'm not familiar with the drawing widgets, so this is completely off the top of
> my head:
> 
> You've created a window and filled it with a DrawingArea. 
> You try to draw on the window, but this fails. I'm guessing that this fails
> since there is already something else on the window -- the DrawingArea. 
> 
> Try changing your code to DrawPoint on the drawingarea instead. Please write
> back saying if it works or not.
> 
Hi Mark.

Unfortunately, neither the "top level window" (of type
org.gnu.gtk.Window) nor the DrawingArea embedded inside it (of type
org.gnu.gtk.DrawingArea) possess a drawPoint() method - the only class
which does (according to the javadocs) is an
"org.gnu.gdk.Window" (notice the change from gtk.Window to gdk.Window!) 

This itself, is fine, as it seems to agree with the following
documentation:

a) The javadocs for org.gnu.gtk.Widget.getWindow() ("Return the widget's
gdk window. This is the window to draw upon when writing custom widgets.
It's available after the widget has been mapped. Thus if you listen to
LifeCycleEvents, you can fetch the Window instance using this method
after an LifeCycleEvent of type MAP has occured. Returns: the widget's
gdk window, or null if a) it hasn't been mapped yet or b) it is of a
type that doesn't have a gdk window.

b) http://www.pygtk.org/pygtk2tutorial/sec-DrawingMethods.html
The example code "drawingarea.py" is what I'm actually trying to port to
java - line 41, for example, refers to:
self.area.window.draw_point(self.gc, x+30, y+30)
("area" is the drawing area, the "window" attribute is its embedded
gdkWindow, which gets drawn upon using the "draw_point" method)

c) http://developer.gnome.org/doc/API/2.0/gtk/GtkDrawingArea.html
and http://www.gtk.org/tutorial/sec-thedrawingareawidget.html

Incidently, I've tried using both the gdk.Window returned by both
area.getWindow() _and_ window.getWindow(), but they both return the same
error.

Hope some of this makes sense,

Jaime :-)