type: task id: GRAPH_LIBRARY-INVESTIGATE_HORIZONTAL_BAR_ORIENTATION_PRESERVING_SEMANTIC_AXES title: Investigate horizontal bar orientation preserving semantic axes description: Investigate the bug where setting orientation horizontal on a bar chart mechanically swaps x and y semantics instead of preserving authored intent, leading to axes and titles that no longer match the data meaning. milestone: m1-ft-analytics-analyst-pilot owner: data-viz-designer-engineer status: not_started priority: p2

Investigate horizontal bar orientation preserving semantic axes

Superseded (2026-03-27).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

Investigate the bug where setting orientation horizontal on a bar chart mechanically swaps x and y semantics instead of preserving authored intent, leading to axes and titles that no longer match the data meaning.

Context

During M1 structure-lab work, we flipped a sparse age bar chart to orientation: horizontal and exposed a semantic bug in the standard renderer.

Authored chart:

type: bar
x: age
y: revenue
settings.orientation: horizontal

Observed result:

the chart title said "Horizontal Bar - 3 Marks (Age)"
but the rendered axes became:
horizontal axis = Revenue
vertical axis = Age

This indicates that the current horizontal-bar logic is performing a mechanical encoding swap instead of preserving authored semantic intent.

Relevant files:

examples/playground/faces/labs/m1-structure-bars-lines-lab.yml
dataface/core/render/chart/standard_renderer.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 available on main when this task is executed, recreate the repro in a fresh playground face.

Likely relevant implementation point:

_apply_horizontal_bar_orientation() in standard_renderer.py

Possible Solutions

Keep current behavior and require authors to think in Vega-Lite's swapped-axis terms. This is undesirable because it makes authored chart intent less semantic and more implementation-shaped.
Document orientation: horizontal as a low-level axis swap. This may clarify current behavior, but it still preserves the wrong product mental model.
Recommended: change horizontal-bar handling so authored semantic roles are preserved. Dataface should reason from "this is a horizontal bar chart" while preserving the intended measure/category meaning of x and y, rather than exposing a raw axis swap to authors.

Plan

Reproduce the bug in an isolated test.
Trace how orientation: horizontal currently transforms the encoding.
Define the intended authored semantics for horizontal bars.
Update the renderer to preserve semantic intent while still producing the correct Vega-Lite encoding.
Add regression coverage for titles, axis titles, and axis field meaning.

Implementation Progress

Not started.

March 26, 2026 notes:

The issue was observed live in the M1 structure lab.
We reverted the lab chart back to vertical so the current tuning surface remains semantically clean.
This task exists to investigate and fix the bug rather than normalize it.

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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