Fix #5960: a narrow part of a variable-width stroke paints over a wide part only where they overlap

With a width profile, every slice of a stroke gradient (along or across)
reached as far as the stroke is wide anywhere. Where the stroke crosses
or runs close by itself, the later, narrower part painted a square of
its colour over the wider part beside it, clipped only to the whole
outline. Each rib now reaches as far as the stroke is wide there and on
its way to the next points (each side of a profile stays between its
widths at a span's points); for a dashed stroke, as wide as it gets
within a cap's reach, since caps and dots reach along the path.

docs/target-app-parity.md

@@ -1,6 +1,6 @@
 # Parity with Adobe Illustrator
 
-> **Last reviewed:** 2026-10-10 · **Last updated:** 2026-11-07 · **Change:** minor (Tools stays beside the canvas with left-side panels; new gradients follow document color mode; scores and estimates unchanged) · **Target:** Adobe Illustrator 2026 (30.x; public release notes through 30.7, August 2026; Units › East Asian Type acts, with Q and Ha units; scores unchanged; Selection QoL: marquee modes and visible feedback, #5313; SVG CSS classes survive export and repeated import in all four styling modes (#2480); current-main integration retains event attributes and scripts; the canvas keeps selection outlines and anchors between frames; Indian-language hyphenation review and license allowlist, #4947; Stroke gradients: an arrowhead aligned to the tip is painted to the corners of its base, #5964; Drop Shadow and glow dialogs: spinner arrows, #5367, #5368; Stroke Weight Up and Down shortcuts, #5797; Hindi catalog and contributor loanword preferences; full wording review in progress; Properties in Edit Artboards: a Transform section with the reference point above the Artboards section, #5219; the Control bar's Stroke: and Opacity: links scrub their fields, #4088; an image zoomed in on is separated, colorized or proofed only where it shows (#4155); a document's first frame renders on the render worker, so opening a heavy file no longer freezes the window, #4155; Control bar Paragraph section with type selected, #5372; translating unchanged type reuses its glyph and character-stroke outlines; scores and estimates unchanged) · **Target:** Adobe Illustrator 2026 (30.x; public release notes through 30.7, August 2026)
+> **Last reviewed:** 2026-10-10 · **Last updated:** 2026-11-07 · **Change:** minor (Stroke gradients: where a variable-width stroke crosses or runs close by itself, a narrow part no longer paints over a wide part beside it, #5960; the canvas keeps selection outlines and anchors between frames; Indian-language hyphenation review and license allowlist, #4947; Stroke gradients: an arrowhead aligned to the tip is painted to the corners of its base, #5964; Drop Shadow and glow dialogs: spinner arrows, #5367, #5368; Stroke Weight Up and Down shortcuts, #5797; Hindi catalog and contributor loanword preferences; full wording review in progress; Properties in Edit Artboards: a Transform section with the reference point above the Artboards section, #5219; the Control bar's Stroke: and Opacity: links scrub their fields, #4088; an image zoomed in on is separated, colorized or proofed only where it shows (#4155); a document's first frame renders on the render worker, so opening a heavy file no longer freezes the window, #4155; Control bar Paragraph section with type selected, #5372; translating unchanged type reuses its glyph and character-stroke outlines; scores and estimates unchanged) · **Target:** Adobe Illustrator 2026 (30.x; public release notes through 30.7, August 2026)
 
 ## Feature submission evidence
 
@@ -34,6 +34,7 @@ Artboard Options forwards the active Artboard tool's Scale Artwork with Artboard
 | 2026-11-03 | minor | Docked Tools stays between left-side panels and the canvas; redocking accepts canvas and window edges. Requested layout choice; scores and estimates unchanged. |
 | 2026-11-02 | minor | Selection QoL: saved marquee modes, screen drag direction with a 3 px dead zone, and translated mode/E feedback (#5313); VectorCraft addition, scores and estimates unchanged. |
 | 2026-11-07 | minor | The canvas keeps selection outlines, anchors and handles between frames, so an idle frame with a large selection redraws them as one mesh; scores and estimates unchanged |
+| 2026-11-07 | minor | Stroke gradients along or across a variable-width stroke: where the stroke crosses or runs close by itself, a narrow part paints over a wide part only where the two overlap, instead of in a square as wide as the stroke gets anywhere (#5960). Each slice reaches as far as the stroke is wide there (for a dashed stroke, wherever a cap or dot can reach). Tests: `stroke::tests_gradient::a_narrow_pass_over_a_wide_one_paints_only_where_they_overlap`, `a_narrow_pass_beside_a_wide_one_leaves_its_edge_alone`. Scores and estimates unchanged. |
 | 2026-11-07 | minor | Indian-language hyphenation (#4947): eleven MIT-licensed pattern sets, with grapheme and shaping-cluster protection in both composers and existing paragraph limits. Assamese and Sanskrit are selectable; Sanskrit automatic patterns remain pending an allowlisted source. Scores and estimates unchanged. |
 | 2026-11-06 | minor | Stroke gradients: an arrowhead whose tip sits on the end of a long straight leg is painted by the gradient to the corners of its base. The slices that reach across a head now run to the end of its reach instead of narrowing towards the next corner (#5964). Test: `stroke::tests_gradient::slices_cover_an_arrowhead_on_a_long_straight_leg`. Scores and estimates unchanged. |
 | 2026-11-06 | minor | Width profiles: the width between two width points follows a smooth curve instead of a straight line, so a stroke no longer kinks at each width point (#5714). Each side is a monotone cubic through its points: flat at a widest or narrowest point, never past either point of a span; stacked points still step. Straight runs are sampled between width points to the drawing tolerance. Scores and estimates unchanged. |