"优化橡皮擦工具，你优化在哪" — the eraser already did segment erase, but
the radius was a hardcoded const with no size control and no whole-stroke
mode. Add both, OneNote/Notability-style:
- PenConfig: eraserRadius (0.005-0.1, default 0.02) + eraserWholeStroke
bool, with copyWith / JSON / setters.
- PenCanvas: uses widget.eraserRadius for the live hit area AND the cursor
preview (they stay in sync); eraserWholeStroke=true removes the whole
stroke on contact, false keeps the segment-split behavior.
- pen_editor threads both from PenConfig.
- pen-settings: new Eraser section — size slider + "Stroke Eraser" switch.
Tests: pen_eraser_mode_widget proves point-eraser keeps the untouched ends
while stroke-eraser deletes the whole stroke from the same pass.
flutter analyze: 0 issues.
Co-Authored-By: Claude Opus 4.8 (1M context) <noreply@anthropic.com>
"手写笔就是一个带压感的手指，没有特殊适配" — correct. The new editor fed
RAW LINEAR stylus pressure into perfect_freehand, and the pressureGamma
config (a slider in pen-settings) was read ONLY by that slider's UI and
NEVER applied to a stroke. Dead wiring, like the rest.
Wire it for real:
- PenCanvas applies PressureCurve(floor, gamma) at capture, so stored
pressure carries the feel and live + PDF export replay identically.
- Natural defaults: gamma 0.7 (light touches register more width, rnote/
OneNote-like) + floor 0.12 (thin strokes keep body, not scratchy).
- pen_editor threads PenConfig.pressureGamma into the canvas — the slider
now actually changes stroke width.
- pen_config: natural default + one-time migration of the legacy inert
gamma 1.0, guarded by a marker so a deliberate 1.0 still sticks.
Tests: pen_config_gamma_migration (4) + pressure_curve (6) pass; pen
widget regressions green. flutter analyze: 0 issues.
Co-Authored-By: Claude Opus 4.8 (1M context) <noreply@anthropic.com>
W1 — Custom pen width + pressure sensitivity (Saber-style):
- Root cause of "压感没用": perfect_freehand 1.0.4 IGNORES real stylus pressure
(hardcodes radius=size/2 when simulatePressure=false) — width never tracked pen
force. Upgraded perfect_freehand ^1.0.0 -> ^2.0.0 (honors real pressure); migrated
all 5 getStroke call sites to the 2.x API (PointVector / StrokeOptions / Offset).
- De-hardcoded `thinning` into `kDefaultPenThinning` (0.85), single source shared by
the on-screen painter and the PDF export path; exposed as PenConfig.pressureSensitivity
with a Pressure Sensitivity slider; live-applies via a config listener.
W3 — Native Windows pen plugin (tilt + barrel/eraser buttons):
- windows/runner/pen_channel.{h,cpp}: observe WM_POINTER at the TOP of MessageHandler
(before HandleTopLevelWindowProc, which Flutter uses to consume pen events), read
GetPointerPenInfo penFlags + tilt, stream over EventChannel('badnote/pen'); non-consuming.
- PenInputService: single latched hardware state (no Win32-pointerId<->event.pointer
correlation); graceful no-op off-Windows.
- pen_canvas maps barrel/inverted/eraser through PenConfig.sideButton/eraserEnd
(eraser/undo/toggleTool/pan) and captures tilt into PenPoint.tilt -> EditorPoint.tilt.
W2 — Zoom flicker: page raster isolated in its own RepaintBoundary (safe interim);
definitive crisp-on-zoom fix gated on the on-device root-cause probe (plan M3).
Plans: ralplan-consensus plan at docs/plans/2026-06-22-badnote-pen-polish.md
(Architect APPROVE-WITH-MUST-FIX M1-M4 + Critic ITERATE->APPROVE).
Tests: 58/58 pass incl. shared-thinning invariant + thinning-affects-outline +
tilt-adapter round-trip. flutter analyze clean; linux debug build OK.
Co-Authored-By: Claude Opus 4.8 (1M context) <noreply@anthropic.com>
