Extending GtkRange to support buffered region / GtkRange subclassing limitation

[Daniel Yek <dyek real com>]

Hi,

I subclassed GtkHScale and overrode expose_event virtual function and 
others to add additional functionality to the class. I called the parent 
classes's (particularly GtkRange's) expose_event implementation to draw the 
trough and slider. So far so good.

Due to the lack of support for "buffered region" in GtkRange for multimedia 
application, I'm trying to extend its implementation to add that support.

However, GtkRange is extremely inflexible (in my opinion, that is.) Its 
layout object is private, gtk_range_calc_layout() function is static, there 
is no class virtual functions for layout calculation, no virtual function 
for drawing of its parts -- its trough (I investigated GtkStyle, which 
can't provide a solution here), etc., making me thinking that my only way 
out is create my own GtkRange replacement. I cannot make use of part of 
GtkRange functionality because it won't let me. In my opinion, the layout 
object should be accessible to the subclass so that subclass can add 
drawing on top of the parts correctly whenever necessary.

This also meant that I need my own GtkScale and GtkHScale, even if I don't 
need to make any changes in these GtkRange subclasses.

Does anybody see other alternatives to maintaining private stack of 
GtkRange, GtkScale, and GtkHScale?

(Is a second rewrite of GtkRange warranted?)

Thanks.


--
Daniel Yek