On Thu, May 01, 2003 at 03:11:28AM +0100, Glynn Clements wrote:
Axel Simon wrote:
IMHO the classes should just reflect the object hierarchy. If we have e.g.
class Button b where... class ToggleButton b where... instance Button ToggleButton where...
Different toolkits have different hierarchies; e.g.:
[..] Yes, I expected that. But perhaps we can create a (rather flat) object hierarchy which maps onto all backends.
Anyhow, to get back to the original issue, the key problem isn't the relative positions of push-buttons etc, but the fact that top-level windows are effectively subclasses of "widget" on some toolkits but not on others. If you're assuming that "widget" is the topmost level of the object hierarchy, this is likely to be a problem.
I would be happy with just a hierarchy for widgets. To answer Wolfgang's question:
Could somebody who has an opinion on these issues knock up a concrete example; I'm not thinking of code, just some class declarations and signatures...
This was my proposal: http://haskell.org/pipermail/gui/2003-April/000459.html As far as I can tell this is equivalent to the class IsWidget Button approach. Axel.