Re: size-request

[Jamie Guinan <guinan bluebutton com>]

On 9 Jan 2002, Havoc Pennington wrote:
> 
> Jamie Guinan <guinan bluebutton com> writes:
> > I have an application in which I want to use a GtkDrawingArea, 
> > and I want to control how it responds to size-request events.
> > 
> > Should I,
> > 
> > A. Connect to the "size-request" signal?   Does modifying
> >    requisition->width/height in a handler have any effect?
> >
> 
> It ought to, if you connect_after, but I've had it not work in the
> past I think. Maybe I was doing something weird. You must
> connect_after though or the default handler will overwrite what you
> put in.

What I was looking to do was have a layout like,

  GtkWindow
  `-GtkVBox
     |-GtkDrawingArea
     `-GtkStatusBar

created with a default "preferred" size for the GtkDrawingArea, but be
able to resize it and catch the size changes so that I could scale or crop
the contents accordingly.

I was a bit confused about the semantics of size-request.  I expected
it to mean "this is how much space I'm giving you, change it if you want
to", and that the requisition would be different every time I resized 
the window. I was surprised to find that the requisition does *not* 
change, its always what I last set it to.  And with,

 gtk_window_set_policy(GTK_WINDOW(main_window), FALSE, TRUE, FALSE);

I can't resize the window below the requisition limits.  I guess this
makes sense for most widgets, where one doesn't want them to be hidden 
when the window size is reduced, but it makes it a little awkward for
what I'm trying to do.  I ended up dancing around with two signals:

1. I connect to "size-request", and pass my preferred initial size the 
   first time (the GtkDrawingArea is created that size), then 
   {0,0} every successive time, which allows the window to be 
   sized down.

2. I connect to "size-allocate", and scale/crop the GtkDrawingArea 
   contents in that handler.

Maybe there's a better way, but this works well enough.

-Jamie