history

Preview-area per-axis wheel zoom

id: LK-20260709-preview-area-per-axis-wheel-zoom
date: 2026-07-09
sequence: 44
type: feat
compatibility: compatible
component: `labkit.ui` | `5.0.3 -> 5.0.4`
scope: Preview-area per-axis wheel zoom

Context

The preview area applied the same two-dimensional wheel zoom to every registered axes. That was appropriate for an image or main plot, but awkward for a narrow histogram or color-scale axes: horizontal zoom changed a dimension whose layout was meant to remain fixed.

Decision and rationale

Let a preview-area definition choose xy, x, or y wheel zoom for each axes. Preserve xy as the default so existing apps keep their behavior, while side axes can opt into only the dimension that carries data.

Changes

• labkit.ui 5.0.3 -> 5.0.4

• Added a scrollZoomAxes preview-area layout option so apps can declare whether each preview axis should mouse-wheel zoom in xy, x, or y.
• Preview-area side axes can now remain horizontally stable while still allowing app-selected vertical wheel zoom.

User and data impact

A histogram or temperature scale could remain horizontally stable while still supporting vertical exploration. Main images and plots continued to zoom in both dimensions unless their app explicitly chose another mode.

Compatibility and migration

• Existing preview areas keep default xy wheel zoom unless they opt into another per-axis setting.

Validation

The commit extended UI layout unit tests and axes-workbench GUI coverage for the default and per-axis modes. The exact historical command was not recorded.

Evidence

• Mainline commit 3c143eb.

Known limitations and follow-up

The option controlled wheel navigation only. Toolbar zoom, pan, linked axes, and app-specific limit policies remained separate concerns.