Re: Quick question on Glib style/design

[muppet <scott asofyet org>]

On Aug 4, 2004, at 1:57 AM, Jan Kratochvil wrote:

> On Wed, 04 Aug 2004 04:21:31 +0200, muppet wrote:
> ...
> > not quite.  notice that most gtk+ constructors return GtkWidget*?
>
> I do not much understand why. GLib functions expect C type of the most 
> far ancestor type they need to access to be as general as possible. 
> They usually return the most far descendant class they create. Just 
> why GTK+ has a style where the constructor gtk_button_new() returns 
> (GtkWidget *) and not its native class (GtkButton *)? It is not much 
> systematic this way.

i'm getting a bit out of my depth here, as i didn't design the API (/me 
looks at the devs) and all i can do is wave my hands around a lot, but 
there are reasons.

if the style factory methods returned the most-descended class, you'd 
be unable to have private style types or even style factories.  when i 
create a GtkStyle, it's returned as a GtkStyle and i deal with it as a 
GtkStyle, but it's actually a BlueCurveStyle.  same thing for the 
GdkPixbufLoaders.

i'm sure there are historical reasons, too; wasn't GtkWidget the root 
of the hierarchy in The Old Days?



--
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