Display contexts

To deal with the customisation of components, Haggis uses an explicit environment. This environment, called DisplayContext or DC, is passed to every function that creates a component instance so that they can look up the needed customisation options from it.

The DisplayContext environment contains two components:

Window

the window the component is to be realised inside. The component creation functions can make use of this Window to access window system inexampleion, See section Window abstraction for more info.

Style

the Style is an hierarchical environment storing customisation inexampleion, in the form of (style option, value) pairs. (Both values are stored as strings). Component creating functions use it to look up resource values when created. The style values can be read from X11-like resource files, command-line or a function can add style options to the Style environment, See section Style environments for the full story.