The proper way to integrate self-made widgets with themes

[centipede takhis net]

Hello list.

I asked this question a few days ago at the generic gtk list, but
unfortunately did not get much of an answer. I'll figure I would try my
luck here instead...

------------------------------------

In the process of making a bunch of widgets I have stumbled upon this
issue: I need to paint various parts of my widget, but I would like to
make the color of the parts controlled by the theme. I.e. the properties I
want to deal with are extra, self-invented properties besides the usual
style properties. (Note: I am using PyGTK 2.12, GTK 2.10 on Arch Linux)

I have figured out how to manually load a theme-file accompanying my
application (by setting the environment variable GTK2_RC_FILES to ./gtkrc
before initializing gtk)
However I cannot insert my own property-names in such a file. The
following gives rise to a syntax error:

    # My Properties
    scalartrack_segment_handle_size = 5

Besides I wouldn't know how to get those properties out again so I can use
them in an expose event

So...
I am asking for the canonical way to implement new widgets and push the
choice of color, size and pixmap-overlays to the theme-designer. The
alternative is drawing with libcairo and using hardwired style properties.

------------------------------------

Then I answered my own question in part (but not enough) with this posting:

------------------------------------

Possible solution: Use the pixmap engine. It seems to support the "detail"
parameter, so I can specify many additional sections, one for each detail.
Example:
style "track"
{
  engine "pixmap"
  {
    image
    {
      function          = BOX
      recolorable       = TRUE
      detail            = "segment"
      file              = "Extra/track-segment-type1.png"
      border            = { 5, 5, 5, 5 }
      stretch           = TRUE
      orientation       = HORIZONTAL
    }
  }
}

.. This style will draw the image "Extra/track-segment-type1.png" when
invoked with this command (in PyGTK):

    self.styleTrack.paint_box (self.window, gtk.STATE_NORMAL,
gtk.SHADOW_IN, None, None, "segment", X,Y,W,H)



But still: How *should* I draw a theme'd box (using gtk_paint_box) in
colors different from what the theme has chosen for my GtkDrawingArea? Do
I have to modify_bg before each call to paint_box, and then reset it again
afterwards?

Remember that a widget can have several "details" which need not be in the
same color or style. It should not be necessary to make both a "Knob" and
"Trough" widget to make a scrollbar which paint two rectangles in
different colors.


Regards,
Rene Jensen, Denmark