[alosslessdev]

Fixes #1786.

The Draw tab's live stroke preview now uses the selected pen's colour and thickness, so the line under the pointer is the ink that will be committed — the highlighter preview is a thick yellow line, not a thin blue one.

What changed

• crates/ui-egui/src/grid.rs: the in-progress stroke is painted with session.draw_color and session.draw_width (falling back to 2 pt when no width has been set).
• ink_color: parses #RRGGBB into a painter colour, defaulting to pen blue on bad input; no panics.
• A UI test (crates/ui-egui/tests/draw_preview.rs) drives a pointer drag with a red 8 pt pen and asserts the painted path carries exactly that colour and width.

Control order, labels and menus are unchanged; they are separate PRs (#1783, #1784, #1785). Cut from main, independent of #1767/#1187.

Verification

• cargo fmt --all -- --check
• cargo clippy -p gridcraft-ui-egui --all-targets -- -D warnings
• cargo test -p gridcraft-ui-egui (full crate suite, including the new preview test)
• docs/ui-parity.md revision history updated; contributors/people.toml entry per AGENTS.md

[alosslessdev]

Round-trip test: Excel 16.0 (Build 20430) ↔ GridCraft @ 7b3d09e

Result: this PR's preview change is fine, but Excel pen strokes do not round-trip through main's XLSX reader. An existing PR already owns that fix, so I stopped before opening a duplicate.

What Excel writes

A 0.35 mm red pen stroke drawn with Excel's Draw tab (blank workbook, SaveAs .xlsx) contains:

• xl/ink/ink1.xml — InkML: brush #E71224, width 0.035 cm; trace 5 1 24575,'-4'0'0,"1420"536"0,513 195 0,-71-27-8191 (X/Y in 1/1000 cm, with first/second differences, per InkML §3.2).
• xl/drawings/drawing1.xml — mc:AlternateContent → mc:Choice → xdr:contentPart r:id (relationship type customXml) plus an mc:Fallback.
• xl/media/image1.png — the raster fallback.

Excel → GridCraft

gridcraft-cli info excel-ink-red.xlsx --json reports:

"images": 1,
"shapes": 0

The stroke is imported from the fallback PNG as a picture, not as editable ink, so Ink to Shape cannot act on it. Saving from GridCraft writes the picture back; Excel reopens a picture, not ink.

GridCraft → Excel

draw.pen {color:"#D13B2F", width:8} + draw.stroke saved to .xlsx opens in Excel repair-free with one object (135 × 43.2 pt), but as a freeform shape (Shapes.Count = 1, Type = 5), not an Ink content part (Type = 23). Excel's resave keeps a shape, not InkML.

Duplicate

#1187 ("Draw: typed ink, Excel InkML and Draw with Trackpad") already implements this: crates/xlsx/src/inkml.rs parses the same difference-encoded traces and brush units, and writes InkML behind mc:AlternateContent with a DrawingML fallback and tests. The fix belongs in #1187; no new PR was opened. #551 is closed. The "external Excel rendering and repair-free opening remain unverified" note in docs/file-format-parity.md is now half-verified: Excel opens the current DrawingML ink repair-free, but not as editable ink.

This PR

cargo test -p gridcraft-ui-egui --test draw_preview passes. One minor preview/commit mismatch: the preview paints draw_width as a float, while draw.stroke rounds the width to an integer (stored in the fill red channel), so 1.5 pt previews at 1.5 but commits at 2. Independent of the round-trip issue.

I stopped before the all-pens/eraser matrix because #1187 already owns the InkML work.

[alosslessdev]

Closing in favour of #1187, which shares stroke_shape() between the preview and draw.stroke and covers #1786. The Excel/InkML round-trip findings above remain the evidence for #1187's crates/xlsx/src/inkml.rs work.