server: gui elements

[blobject]

Define representations of:

• windows
• frames
• tags
• marks
• rules: new, snapping
• selection: what to focus (and to occlude), where to move, to what to adhere
• adhesion: tab, pile, concat
• occlusion: overlapping, hiding, visibility transition
• focus: changes in look, showing of name, index, position, order, input, output, frame, view
• transition: focus, visibility

Decouple the data to be represented and the representation itself, so that other gui clients (eg. tk) can jump in and consume the data. But some representations will have to be drawn by the server natively, eg. borders around windows/frames and indications of adhesion.