# Objective

Fixes #56136.

The issue was initially reported while an agent was generating code.
Later reports reproduced it during manual editing and with AI disabled,
ruling out the agent as the cause.

At fractional display scales, the editor's right-click context menu
could fail to appear at specific discrete scroll positions. Scrolling
one line at a time could make the menu alternate between hidden and
visible, even when its anchor remained within the viewport.



## Solution

The editor-specific changes in #54728 started pixel-snapping the
vertical scroll position used by `EditorElement` to derive and render
visible rows. However, `Editor::display_to_pixel_point` continued using
the raw scroll position for its visibility check and vertical
projection.

When a downward pixel snap crossed an integer display-row boundary,
`EditorElement` treated the preceding row as the visible range start.
`display_to_pixel_point` then rejected that row as being above the raw
viewport. Mouse context menu layout returned early before inspecting the
actual clicked anchor, leaving the menu state present without rendering
its element.

This change applies the same line-height and display-scale pixel
snapping in `display_to_pixel_point`. Its visibility check and
coordinate projection now use the coordinate space actually rendered by
the editor.

A test-support-only scale-factor setter was also added so GPUI tests can
exercise fractional display scaling without depending on the host
display.

## Testing

Added a GPUI regression test using 100 plain-text lines so the editor
can scroll. The test uses a `1.25` scale factor and a `14px` font with
`1.3` relative line height. The resulting `18.2px` line height is
rounded to `18px`, producing exactly `22.5` device pixels per row.

At a raw scroll position of one row, midpoint-toward-zero snapping maps
`22.5` device pixels to `22`, or approximately `0.978` rows. This
reproduces the old boundary mismatch where the snapped visible range
starts at row zero while the raw visibility check starts at row one.

The test pins these values with precondition assertions. Row five and an
in-bounds click keep the actual source visible, while checking the
rendered bounds of the `Copy` item ensures the test does not pass merely
because menu state was created.

Manually verified that scrolling from the start of a document no longer
makes the context menu alternate between hidden and visible.

## 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

## Showcase

Before:


https://github.com/user-attachments/assets/e14c030f-1587-4172-aed2-fecfbfcb65ed


After:



https://github.com/user-attachments/assets/3080db1e-46eb-4e20-a619-b1608f233668



---

Release Notes:

- Fixed editor right-click context menus intermittently failing to
appear at certain scroll positions.