# Objective

When you make a line selection in a row that is long enough to multiple
lines long while wrapped the selection box will disappear when the
cursor (or just origin of the line selection goes off screen).


## Solution

The when you are in line selection mode the `SelectionsCollection` just
enables `line_mode`, instead of storing the whole ranges of those line
selections, so the Anchor of the selection is a single point.
`disjoint_in_range` filters all the disjoint selections of the
collection to fit inside some range, this is used to render the
selection boxes on screen. `disjoint_in_range` had no special case for
`line_mode` causing it to filter on the point instead of the bounds of
the selection.

My fix is too add a case for `line_mode` that changes the filtering
`Anchor` -> `Point` and then only filters on the row. Then use the
proper bounds of the selection with that:
```rust
        let (start_ix, end_ix) = if self.line_mode {
            let start_row = range.start.to_point(buffer).row;
            let end_row = range.end.to_point(buffer).row;
            let start_ix = self
                .disjoint
                .partition_point(|probe| probe.end.to_point(buffer).row < start_row);
            let end_ix = self
                .disjoint
                .partition_point(|probe| probe.start.to_point(buffer).row <= end_row);
            (start_ix, end_ix)
        } else {
        ...
```

## Testing

Before:


https://github.com/user-attachments/assets/a443de39-53d7-4ee4-b3af-d3be99ca1fcf

After:


https://github.com/user-attachments/assets/18c1c7ef-45cc-4dc8-9a8b-241252c376ab

I also added some tests `disjoint_in_range_line_mode_matches_whole_row`,
being the one that really tests this behavior. the other two are just
for `disjoint_in_range`

I am using macOS 27.0 Beta (26A5368g), but I noticed this bug before
upgrading.

## Self-Review Checklist:

- [x] I've reviewed my own diff for quality, security, and reliability
- [x] Unsafe blocks (if any) have justifying comments
- [x] The content adheres to Zed's UI standards
([UX/UI](https://github.com/zed-industries/zed/blob/main/CONTRIBUTING.md#uiux-checklist)
and
[icon](https://github.com/zed-industries/zed/blob/main/crates/icons/README.md)
guidelines)
- [x] Tests cover the new/changed behavior
- [x] Performance impact has been considered and is acceptable

---

Release Notes:

- editor: Fixed bug where selection boxes wouldn't render when the
cursor was offscreen.