How to do_size_allocate properly in a gtk.Viewport subclass

[Joel Hedlund]

Hi!

I've raised this issue on #pygtk and #gtk+ but with no luck. I haven't
been able to solve this even with aid of google, the pygtk reference and
the gtk C source, so pretty please help?

I'm making an application that you can think of as an image viewer. I
want to display a widget in a gtk.Viewport. The widget can have any size
from tiny to humungous. I don't want the viewport to ever give the
widget a larger size allocation than requested, and I don't want the
viewport to ever resize to accomodate a large widget. It should rather
leave grey areas around the widget/show only a portion of the widget.

To do this I have subclassed gtk.Viewport (MyViewport) and overrided the
do_size_allocate method:

def do_size_allocate(self, allocation):
self.allocation = allocation
child_req = self.child.get_child_requisition()
child_alloc = gtk.gdk.Rectangle(0, 0, *child_req)
self.child.size_allocate(child_alloc)
self.props.hadjustment.update(allocation.width, child_alloc.width)
self.props.vadjustment.update(allocation.height, child_alloc.height)
if self.flags() & gtk.REALIZED:
self.window.move_resize(*self.allocation)
self.child.window()

When I add a very large widget (a gtk.DrawingArea) to MyViewport only
the originally visible portion of the widget is redrawn when I resize
the window using the mouse, and the grey area around widget gets
littered with grey lines that are not redrawn if you minimize and
restore the window. I assume this comes from that the proper gdk windows
haven't been updated, and that the grey lines are remnants of old
Viewport borders.

In gtk_viewport_size_allocate in gtkviewport.c, gdk_window_move_resize
is called on three gdk windows: viewport->window, viewport->view_window
and viewport->bin_window, but in pygtk I only have gtk.Viewport.window.
I assume that this is the problem? If so, how can I fix this? Or is
there something else that I have overlooked?

And another relevant question: am I overcomplicating this? Is there some
kind of flag that I could set on a vanilla viewport to accomplish this?

Thanks in advance,
Joel

[Hrvoje Niksic]

Joel Hedlund <jo**********@gmail.comwrites:

I've raised this issue on #pygtk and #gtk+ but with no luck.

Note that there's a mailing list dedicated to PyGTK,
<py***@daa.com.au>, so you might also want to ask your question there.

[Joel Hedlund]

Hrvoje Niksic wrote:

Note that there's a mailing list dedicated to PyGTK,
<py***@daa.com.au>, so you might also want to ask your question there.

Thanks. I'll try that and hope people won't take offense from
cross-posting. I'll be wathching this thread for answers too though. In
my experience, c.l.p usually delivers.

Cheers!
/Joel

[Joel Hedlund]

Joel Hedlund wrote:

And another relevant question: am I overcomplicating this?

Yes. :-)

The proper way of doing this is to pack the widget in a container, and
then add the container (with viewport) to a scrolledwindow.

For example, for a centered widget choose a 1x1 gtk.Table and attach the
widget using xoptions = yoptions = gtk.EXPAND (and not gtk.FILL). For a
widget glued to the upper left corner choose a gtk.Alignment().

Thanks John Finlay at py***@daa.com.au!

/Joel