stickman/docs/specs/phase_9_prop_editor_round7.md

Phase 9 Prop Editor — Round 7 (Two-Tone Halo Selection)

Status: implemented (2026-09-19; direct follow-up on the Round 6 selection-contrast fix).

Source: one user feedback point — the Round 6 contrast approach did not fix the reported case.

Diagnosis

Round 6 made the selection color adaptive to the selected shape's fill (dark on light fills, white on dark fills). That solves "white shape selected on a dark canvas" but not the reported case: a shape sitting in front of a white shape — the selection outline, bounding box, rotation dot, and scale crosses extend beyond the selected shape onto the white shape behind it, so a white (or fill-mismatched) selection still blends into the white background. Fill-based contrast fundamentally cannot know what is behind the shape.

Fix

Every selection element now uses a two-tone halo: a dark backing pass (SELECTION_HALO_COLOR, black at 0.85 alpha, ~2 px wider) drawn first, then a bright core pass (SELECTION_CORE_COLOR, white, the original width) on top. The pair is visible on any background — the dark halo separates the bright core from light/white surroundings, and the bright core separates it from dark surroundings. Applied to:

• the selection polyline over the shape outline,
• the bounding box (dark 3.5/zoom pass + white 1.5/zoom pass),
• the rotation dot (dark ring at radius + 2, white dot at radius),
• the four scale crosses (dark 3.5 pass + white 1.5 pass),
• vertex handles in Reshape mode (a 1.5 px dark ring behind each handle).

The Round 6 contrast_color_for helper was removed. SELECTION_COLOR/GIZMO_COLOR were replaced by SELECTION_CORE_COLOR/SELECTION_HALO_COLOR.

Changes

Target	Change
scripts/editors/prop/prop_canvas.gd	Halo constants; two-pass drawing for selection polyline, bbox, rotation dot, scale crosses, vertex handles; contrast_color_for removed.
tests/test_prop_editor_canvas.gd	_test_selection_contrast replaced by _test_selection_halo (halo is dark, core is bright).

Verification

• --check-only clean; all five suites green (file 68, theme 53, canvas 100, thumb 10, round3 21).
• Manual F6: select a dark shape in front of a white shape, and a white shape in front of a white shape — the outline/box/dot/crosses must be visible in both; repeat in Reshape mode for the vertex handles.