[tgrushka]

Summary

This PR fixes #2515 (erratic cursor movement in magnifier when Zoomed view moves mode is To keep pointer centered -- ZoomMovement::Centered).

Please see the issue for full description and screen recording.

By changing the coordinate calculations in ZoomState::update_focal_point from i32 to f64, we avoid:

• truncating integer division that results in miscalculation of the focal point;
• potential other edge cases related to the same issue.

Tagging @Drakulix and @leviport , thanks for your help with my last PR!

Screen recording of fix

Attached in comment...

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[tgrushka]

Here is my test recording of fix.

recording-1782858918_downscaled.mp4

[leviport]

This fix is working great, thanks!

Before:

Kooha-2026-06-30-16-32-39.webm

After:

Kooha-2026-06-30-19-10-18.webm

[Drakulix]

LGTM. Thanks!