button themes

["Shawn T. Amundson" <amundson CompleteIS com>]

Here are my thoughts on the button stuff so far...

If a shaped button is made, what extra work is involved in making
it react correctly (so if you can't press where the button is
transparent).  Is that just a matter of feeding the transparent
part as a mask to X to create the shaped window and like magic it 
is done?  (sorry, not played with anything like that before...)

Assuming it is simple to do this, how much overhead is produced
if we allow multiple shapes per button, one for each state?  Will 
it even be practical to allow a button to change shape?

-

A button should not know anything about it's child
widget.  Therefore, the last step that is on the web page now
doesn't make sense to the toolkit.  Instead, it belongs in 
GNOME stock someplace, not GTK.  I suggest we start breaking 
these up now for clarity.

-

It seems to me that we want will want to have some other 
faster method for creating parts of themes instead of only
pixmaps.  For example, we could have one theme that just
changes how reliefs are drawn by specifying the drawing
color and lines:

color #FFFFFF 
drawline 0,0 to 0,-1
...

This way we could define a fully motif/win95/mac without
the overhead of pixmaps.  This would allow us to have some
standard themes as well if we can do this in a efficient fashion.

Basically all the above would be done by replacing the draw
function with a function that knew how to work with the special
info once it was read in and such.

The syntax of a button would be in a gtkbutton.theme file.

Images then would just be a special entry in this file:

image "button.ppm"

Of course the file would be broken up into the available
states like:

[state normal]
image "button.ppm"
...
[state pressed]
image "button.ppm"
...

All other attributes would be defined in these files as well.
Perhaps distributed in tar files like E's theme balls.  It would
be nice perhaps to make some way to compile them into a library
if that would speed things up.

-

So where does the prototype code start?  I think we start with
defining what needs to change for gtkobject (if anything), 
gtkwidget, gtkcontainer, and gtkbutton.

My initial feelings are:

gtkobject: not much if anything
gtkwidget: a lot of things, including the interface to setting
           the current theme
gtkcontainer: some issues, most trivial
gtkbutton: no external interface changes, but core changes

Core new functions:

gtk_widget_set_theme(widget, theme);
gtk_container_set_theme(container, theme);

Calling gtk_widget_set_theme should only change the current
widget.  gtk_container_set_theme should propogate down through
all the children and call gtk_widget_set_theme.  So changing an
entire window would take nothing more than:

gtk_container_set_theme(window, theme);

The question then becomes how the widgets know how to get the
theme information.  First we need to initialize the theme 
into memory:

gtk_theme_set_path("/usr/local/lib/gtk/themes:/opt/gnome/themes/gtk");
gtk_theme_load("57chevy");

We will assume for now that works like magic and found all 
the files and such.  We need a couple more functions for
working with loaded themes (note - more than one theme can
be loaded at once to allow switching at runtime).

gtk_theme_unload("57chevy");
gtk_theme_refresh("57chevy");

To work with the unload/refresh commands we may wish to 
keep track of a couple of things - such as which widgets
think they can use the things being unloaded or refreshed.
To do this, widgets should be able to register themselves
as using the theme:

gtk_theme_register_widget("57chevy", widget);
gtk_theme_unregister_widget("57chevy", widget);

Note, we can optimise this by registering only a container:

gtk_theme_register_container("57chevy", container);
gtk_theme_unregister_container("57chevy", container);

This will allow us to notify widgets when they can no longer
use a theme or when they should redraw because the theme
has been refreshed.

Ok, lets go back to gtk_widget_set_theme().  When called, the
widget asks the theme manager what functions it should use for
doing various things like drawing - defaults to these will be
defined as they are now.

func = gtk_theme_get_draw_function("57chevy", "gtkbutton");
widget->draw_func = func;

Ok, discuss.

--
Shawn T. Amundson		Complete Internet Solutions
Senior Systems Administrator	Minneapolis, Minnesota, USA
amundson@CompleteIS.com		http://www.CompleteIS.com/~amundson

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