Re: How to get the widget's current width and height?

[Tristan Van Berkom <vantr touchtunes com>]

Tom Liu wrote:

> To get the current widget size need a reason? Sorry to say that but
> there are a lot of reasons. Sizes and positions are basic stuff!
>
> For example: I have a widget dynamicly draw a clock, I want the clock 
> Just fit into the widget, I need the size information every minutes.
>
> Sure, I can connect the size alloc and remember the size by myself.
> But...
>
> Thanks iain just told me:
>         GTK_WIDGET (widget)->allocation.width;
>         GTK_WIDGET (widget)->allocation.height;
> This code works! And thanks GTK+ use C so that we can access all the
> private data they have.
>  
When gtk_widget_size_allocate() gets called; or when
a widget gets "realized" for that matter; It is the responsability
of the widget in question to allocate the underlying gdk resources
based on that widgets GtkAllocation. Once the widget has
"allocated underlying gdk resources"; At least the data structures
will be present in memory but its not garaunteed that the actual
X resource is present on the X server's RAC list  (i.e. 
gdk_window_foriegn_new( XID )
might fail with a "bad pixmap" error) unless you make a call to 
XSync(Display *).

So you see that:
> having a function to query the current size would
> just facilitate writing fundamentally broken code.

Because you can't really know what size you're window is;
You can only know what size your window is "planned to be".

Regards,
                               -Tristan

> -----Original Message-----
> From: John K Luebs [mailto:jkluebs luebsphoto com] 
> Sent: Tuesday, November 18, 2003 11:52 PM
> To: Tom Liu
> Cc: gtk-app-devel-list gnome org
> Subject: Re: How to get the widget's current width and height?
>
> On Tue, Nov 18, 2003 at 09:29:50AM -0500, Tom Liu wrote:
>  
>
> > gdk_drawable_get_size(w->window,&wid,&hi); may work for the widget
> >    
> which
>  
>
> > has a xwindow such as eventbox. For vbox, label, button etc. It will
> >    
> not
>  
>
> > work.
> > Can't believe there is no function to retrive size of widget?!
> >
> >    
>
> There is a good reason for this. The size of a widget (it's allocation) 
> is dynamic (can be changed by the user, WM, etc.), so having a function
> to query the current size would just facilitate writing fundamentally
> broken code. There's no point in getting a value that could become
> invalid the moment you return to the mainloop.
>
> As another poster has told you, you should connect to size-allocate.
> This way you know that you always have the correct size, and can react
> appropriately.
>
> You should also take a moment to think about why you need the size.
> Are you sure this is not something you can do in a more
> straightforward manner using the packing mechanisms?
>
> --jkl
>
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