type: task id: GRAPH_LIBRARY-ADD_COORDINATED_SCALE_DOMAINS_FOR_COMPARABLE_CHARTS title: Add coordinated scale domains for comparable charts description: Capture follow-on work for dashboard- or group-level shared scale domain control so comparable charts can coordinate quantitative axes without manual per-chart overrides. milestone: m1-ft-analytics-analyst-pilot owner: data-viz-designer-engineer status: not_started priority: p2

Add coordinated scale domains for comparable charts

Superseded (2026-03-27). This narrowly scoped follow-on was consolidated into Consolidate semantic chart defaults and rendering control-surface follow-ons so the active backlog carries one M2 umbrella task instead of many M1 leaf items. Keep the notes below as reference detail, not as a separately scheduled task.

Problem

Capture follow-on work for dashboard- or group-level shared scale domain control so comparable charts can coordinate quantitative axes without manual per-chart overrides.

Context

During M1 structure-lab work, we noticed that neighboring bar charts with the same Revenue y-axis were each auto-scaling independently. That makes side-by-side comparison harder and pushes authors toward manual per-chart y_scale.domain overrides.

Today Dataface appears to support only per-chart scale control, for example:

settings.y_scale.domain: [...]
settings.x_scale.domain: [...]

What is missing is a system-level way to say that a set of comparable charts should coordinate their quantitative domains.

Relevant files and surfaces:

examples/playground/faces/labs/m1-structure-bars-lines-lab.yml
dataface/core/render/chart/standard_renderer.py
dataface/core/render/chart/vega_lite_types.py
dataface/core/render/chart/DESIGN.md

Note: - m1-structure-bars-lines-lab.yml was a March 26, 2026 session artifact from the parallel codex/m1-structure-lab branch. If it is not on main yet when this task is picked up, treat it as historical repro context rather than a guaranteed in-repo dependency.

This came up specifically in a row of vertical bar charts, but the capability should likely generalize to other comparable chart groups and small multiples.

Possible Solutions

Keep relying on manual per-chart domain overrides. This works for isolated authored examples but is brittle, repetitive, and does not scale as a product behavior.
Add ad hoc lab-only helpers that stamp the same domain onto sibling charts. This could help in playgrounds, but it would still avoid the real product surface and risks creating one-off semantics.
Recommended: add a dashboard/group-level coordinated scale domain feature. Let authors declare that a set of comparable charts should share a quantitative domain, and have the renderer/compile pipeline compute or apply that domain consistently.

Plan

Clarify the right ownership layer for coordinated domains: dashboard row, chart group, or explicit comparable-series group.
Decide whether the feature should support: - explicit authored domains - automatic union/max-based coordinated domains - both
Prototype the smallest useful surface for standard charts.
Preserve authored per-chart overrides as the strongest precedence.
Add regression coverage with side-by-side comparable charts.

Implementation Progress

Not started.

March 26, 2026 notes:

Confirmed there is no obvious row-level/dashboard-level shared-domain surface today.
Confirmed that current control is chart-local via settings.x_scale / settings.y_scale.
Decided not to paper over the issue with manual lab overrides because the goal is to reason at a systems level.

QA Exploration

N/A for now. This task has not been implemented yet.

[ ] QA exploration completed (or N/A for non-UI tasks)

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