[Usability]Padding API

[Havoc Pennington <hp redhat com>]

On Tue, Dec 10, 2002 at 05:32:00PM -0600, Gregory Merchan wrote: 
> One way to do this that might work for other things is a padding widget.
> I imagine it'd be a GtkBin subclass:
> 
> struct _GtkPad
> {
>   GtkBin bin;
>   guint  pad_left;
>   guint  pad_right;
>   guint  pad_top;
>   guint  pad_bottom;
> }
> 

Yes, I think that's a decent idea. I've often needed this and ended up
sticking an empty GtkAlignment somewhere and setting its size as a
random bit of padding. In general I think many layouts would be
simpler if you could just say "insert padding here" - the problem is
that GTK always has "border width" or "xpad" or "xscale" when you
really want to independently vary all 4 sides. I find that I almost
never want to pad 2 or 4 sides, I always want a single 12-pixel
spacer.

The feature could alternatively be done as:

 gtk_alignment_set_pad (GtkAlignment *align, 
                        GtkSideType   side,
                        int           padding);

this would avoid creating a new widget. The padding would have to hang
off the GtkAlignment as object data for now to avoid breaking ABI, but
we could demand-create the object data only if we have a nonzero pad.

GtkSideType is deprecated but it's simple to undeprecate.

One downside of using GtkAlignment is just that gtk_alignment_new()
has annoying arguments, but we could have gtk_alignment_new_padding()
perhaps.

Another option is to add this feature to all GtkContainer and make
gtk_container_set_border_width() into a convenience wrapper that sets
all 4 padding values, but I think that's pretty much too
backward-incompatible.

Another option is an interface GtkPaddable or something that any
widget can implement.

Havoc