Here is the brief status report on the graph-world-2 branch and
related issues.
1. Terry appears to be right that by default all iterators should
avoid nodes reached by back links. In effect, this projects a graph
onto a legacy Leo outline. This is an important Aha.
2. Yesterday I revised the drawTree and drawChildren methods in the qt
gui plugin. This draws nodes properly (in most cases). The guiding
principle: back links are never followed, except that all ancestors of
the current position are drawn.
This works when making this tree:
- A
- A
Pressing Alt-RightArrow from the second node shows:
- A
- A
- A
etc.
>From the last shown node, pressing Alt-UpArrow then shows
- A
- A
BTW, All copies of A show the '+' box, indicating more children.
3. However, moving a cloned child node left does not work. The reason
is clear. In the tree world, moving a node left means unlinking the
node and relinking it as a child of its grandparent. But this is
wrong if its parent is also its grandparent. This problem is solvable,
but it requires new code in Leo's core.
Summary
Points 1 and 2 show that general graphs can be drawn by projecting
them onto a legacy Leo outline. We ignore all back links in the
drawing code, except those links that are parents of the current
position.
Point 3 shows that Leo's core must change to handle new special cases
arising only in the graph world. These special cases should be
manageable, but there is no telling no how many there might be.
In short, the graph world appears feasible, but it can hardly be
called a simple project. I shall experiment further, but I make no
promises about finishing this project in a timely manner.
Edward
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