Each windowing system has its own visual and technical properties. Hence, developing applications cross-platform is difficult. The simplest approach would be to use a virtual Operational System on-top of the host system. Such an application differs dramatically from the surrounding Operational System. To incorporate a theming engine into such a virtual Operational System helps to overcome the worst alienation.

Of course, theming toolkits do not always have a virtual Operational System or a virtual machine. What I wrote about virtual Operational System is fairly right for these toolkits, too.

In the case of Linux® X11 a literal »Theming War« has been fought between toolkit contenders to become dominant on that platform. This conflict is still in progress, despite of pressure from Computer Owners to end this devastating contest.

Tk itself does not deploy themes for the various supported platforms, and lost ground on X11 to theming toolkits. Tile is the first theming engine for Tk, and might steady Tk in the enduring theming age.