Allows to define how disabled buttons should be rendered
in case no own image set is available for it.
The following values are possible:
Shape-
Draws only a B/W shape to show the disabled status.
Grid-
Draw a light grid in front of the image.
FullGrid-
Draw a full grid.
Sunny-
Converts the image into a greyscale image and
displays it.
Blend-
The disabled image is somehow blended. It requires a true
color image with an active alpha channel and a system capable
to render it.
BlendGray-
As the above, but rendered as gray.
This overwrites the user preferences and so must be used
wisely. If in doubt, don't use it.