Multiple checkbox un/checking works/doesn't work/sort-of-works according to exact selection

[David Gowers]

The F12/Shift-F12 commands, when applied to a multiple-checkbox selection, succeed, fail, or partially succeed in different contexts, with no obvious logic behind it.

To demonstrate this,
create a new wiki page with the following checkboxes (including the indicated nesting level)

* 1
 * a
 * b
 * c
* 2
 * d
 * e
 * f
* g
* h
* i

Now:

1. Select ghi, press F12. Nothing happens. Press Shift-F12. Nothing happens.
2. Select def, press F12 -- d, e, f, and 2 are checked (correctly, afaics). Reselect and Press Shift+F12 -- d, e, f, and 2 are X-checked (also correctly)
3. Select b, c, 2. Press F12 to check them, then reselect, followed by Shift+F12 to X-check them. Both of these work correctly.
4. Select 1, a. Press F12 to check them. Instead, b and c are checked. Uncheck them. Now reselect and press Shift+F12. Instead, b and c are X-checked. Reselect again, and press F12 to check them. Nothing happens.
5. Uncheck all checked boxes. Now select b,c,2. Press F12 to check them; They (b,c,2,d,e,f) are all checked correctly, Reselect and press Shift+F12. They (b,c,2) are all X-checked correctly. [Reselect and press F12], twice, to uncheck them. They are all unchecked correctly
6. Uncheck all checked boxes. Select 1,a,b,c,2. Hit F12. 2,d,e,f are correctly checked, but 1,a,b,c are not. Uncheck all selected boxes, reselect, and hit Shift+F12. 2,d,e,f are correctly X-checked, but 1,a,b,c are not.
7. Uncheck all checked boxes. Select all checkboxes. Hit F12. g,h,i are correctly checked, but 1,a,b,c,2,d,e,f are not.

In summary:

* un/checking multiple boxes at the top level does not work at all.
* un/checking multiple boxes at lower levels works
* un/checking multiple boxes at multiple levels:
 * if the first selected box is at top level, the only affected boxes are those lower level boxes which should be unaffected.
 * if the first selected box is not at top level, all selected boxes are appropriately modified.
 * if the selection ends in multiple top-level checkboxes, these will be the only affected checkboxes, all others will be ignored.

Versions
* PyGTK 2.24.0
* GTK 2.24.27
* Zim 0.62+ (bzr r742)