Re: Generic positioning

[Damon Chaplin <damon karuna eclipse co uk>]

On Tue, 2008-10-28 at 20:29 +0100, Armin Burgmeier wrote:
> On Mon, 2008-10-27 at 11:33 +0000, Damon Chaplin wrote:

> > My main problem with this is that if we are going to add x, y, width &
> > height properties to the GooCanvasItem interface then they should have
> > well-defined semantics. But they don't - the x and y properties refer to
> > arbitrary points in the item and the width & height may or may not be
> > the exact width & height of the item.
> > 
> > I would think that if people see generic x, y, width & height properties
> > then they will expect them to refer to the top-left coordinate and the
> > exact width & height of the item.
> 
> What do you mean with the _exact_ width & height, by the way? Is this
> because the width of a rectangle, for example, does not cover the entire
> border? If so, then I think changing that would also break
> compatibility. Does this matter?

I meant the complete enclosing rectangle of the item. Generic
positioning and resizing isn't that useful unless you know exactly what
coordinates you are dealing with.

But you're right, it does break compatibility, so I don't want to do
that.


I'll accept a patch that adds x, y, width & height properties to most of
the items that don't have them, with functionality as in your latest
patch. I don't want to add x, y, width & height properties to the
GooCanvasItem interface though.

For GooCanvasGroup I'd prefer it if the x & y properties set the origin
of the existing transformation matrix rather than adding an extra
translation. I'm not sure about adding width & height though - I'd
prefer not to. (Your code for GooCanvasGroup looks wrong as it uses
goo_canvas_item_get_bounds() to get the child extents, but the bounds
are in device space so may have arbitrary transformations on them.)

For GooCanvasText I'd prefer to use pango_layout_set_height() for the
height of the text, but that is a relatively new function and I don't
want to depend on Pango 1.20 yet. Maybe we could use our own code to
only draw lines of text that are completely visible using the given
height.

Damon