New circular tree view

[westram]

Provide a circular dendrogram treeview (similar to attached picture).

Possible implementation:

• create a new transforming device
• use normal dendrogram draw routines on that device

Needed transformations:

dendrogram	→	circular
horizontal line		straight line from center towards tip
vertical line		circle segment concentrical to origin
diagonal line		arc segment (complicated; slow)
text		displaced similar to traditional radial view
polygones		correct would be filled arc-figure. possible
fixed sized markers		<keep>

Expected problems:

• distance between tips and bracket will depend on text-displacement and on current zoom

Possible settings - quite unclear what makes sense :

• size of inner/outer radius. Implicates
  • "horizontal" zoom of dendrogram, ie. length of branches
  • vertical zoom (ie. branch-distance)
• amount of circle used (eg. display as half-circle )
• root-direction (would allow rotation)

---

blocked by: #729
related: #130 #578

[westram]

Milestone renamed