While working on a different bug I noticed that FilterGrid would occasionally not render properly when backed by LimitProxyModel.
To give you an example:
$ bzr branch -r657 lp:~unity-team/unity8/unity8-fix-filtergrid
tests/qmltests/Components/tst_FilterGrid
Wraps the fakeModel with LimitProxyModel, and sets that on the filterGrid as the backing model.
$ make -C builddir tryFilterGrid
Consdering collapsedRowCount: 2, columns: 3, now select "model count limit" value
4 (4 items shown, 3+1), then
1 (1 item shown), then
4 (*3* items shown, 3+0) -- second row should show one more item.
Note that "rowsWhenCollapsed" displays value of 2, which would be correct (that would be the actual value of collapsedRowCount).
Now select:
3 (3 items shown), then
4 (*4* items shown, 3+1) -- only now the behavior is correct!
In other words, items displayed on the second row seem to "kick in" only after model grows while it previously filled up the whole first row (or, for that matter, you could generalize to the last row being visible in the FilterGrid, smaller than collapsedRowCount).
As you see, changing the count of items in the model should not affect how many items FilterGrid shows (/renders). And even though rowsWhenCollapsed is calculated correctly, items are missing. Try selecting "model count limit" to 1, then 7. You'll only see 3. If you, however, set 3, then 7, you'll see 6!
Karni is this still happening/important as to have a bug open?