urwid / urwid / 37013991564

91%

push

github

Bound ListBox scans and hold the ListBox weakly (#1383)

f0b1e11 made calculate_visible quadratic in the number of 0-height
widgets. Separately, wrapping bodies of 0-height widgets hung the
scrolling keys, page up, page down and end raised ListBoxError on
bodies ending in 0-height widgets, and the body's "modified" handler
kept every ListBox alive with its walker.

- _SeenPositions tracks visited positions in a set and falls back to
  a list compared with == once a position cannot be hashed, since
  walker positions only promise ==.
- calculate_visible and render's short-body check use it instead of
  a list and a frozenset.
- Up, down, page up and page down stop when a (position, row offset)
  pair repeats, so a cycle of the body that adds no rows ends.
- Page down clamps its fallback offset to the last row, as page up
  already does, and bottom valign keeps a 0-height focus on the last
  row.
- The fell-short step of page up and page down never focuses a
  0-height widget.
- The "modified" handler holds the ListBox weakly and goes away with
  it; the deque walker tests expect the unbound ListBox._invalidate.

| what | avg time before | avg time after | percent change |
| --- | --- | --- | --- |
| urwid.ListBox.calculate_visible (1000 0-row widgets) | 4.51 ms | 0.92 ms | -79.6% |
| urwid.ListBox.calculate_visible (4000 0-row widgets) | 61.21 ms | 3.77 ms | -93.8% |
| urwid.ListBox.calculate_visible (16000 0-row widgets) | 994.59 ms | 15.80 ms | -98.4% |

4577 of 5508 branches covered (83.1%)

Branch coverage included in aggregate %.

46 of 46 new or added lines in 1 file covered. (100.0%)

11506 of 13133 relevant lines covered (87.61%)

9.79 hits per line