eng-pad/PROJECT_PLAN.md

PROJECT_PLAN.md — eng-pad Implementation Steps

This file tracks all implementation steps. Check off steps as they are completed and log them in PROGRESS.md.

Phase 0: Project Documents

• 0.1: Create DESIGN.md
• 0.2: Create PROJECT_PLAN.md (this file)
• 0.3: Create PROGRESS.md
• 0.4: Update CLAUDE.md with build commands and source tree

Phase 1: Project Skeleton + Data Layer

• 1.1: Generate Android project with Gradle
  • build.gradle.kts (root), app/build.gradle.kts, settings.gradle.kts
  • Kotlin, Compose, Room KSP, minSdk 30, compileSdk/targetSdk 36
• 1.2: Configure gradle/libs.versions.toml version catalog
  • Compose BOM, Room, Navigation, Lifecycle, Coroutines
• 1.3: Configure linting (app/build.gradle.kts Android Lint config)
• 1.4: Define Room entities
  • data/model/Notebook.kt, Page.kt, Stroke.kt, PageSize.kt
• 1.5: Implement type converters
  • data/db/Converters.kt — FloatArray ↔ ByteArray
• 1.6: Define DAOs
  • data/db/NotebookDao.kt, PageDao.kt, StrokeDao.kt
• 1.7: Define Room database
  • data/db/EngPadDatabase.kt
• 1.8: Implement repositories
  • data/repository/NotebookRepository.kt, PageRepository.kt
• 1.9: Unit tests
  • test/.../data/StrokeBlobTest.kt — blob roundtrip
  • test/.../data/PageSizeTest.kt — page size enum
• Verify: ./gradlew build — PASSED (build + test + lint)

Phase 2: Notebook List Screen

• 2.1: Set up MainActivity with Compose and NavHost
  • MainActivity.kt, ui/navigation/NavGraph.kt, ui/theme/Theme.kt
• 2.2: Implement NotebookListViewModel
  • ui/notebooks/NotebookListViewModel.kt
• 2.3: Implement NotebookListScreen
  • ui/notebooks/NotebookListScreen.kt — list, create dialog, delete confirmation
• 2.4: Auto-create page 1 on notebook creation
  • In NotebookRepository.create()
• 2.5: Navigation: tap notebook → page list (stub screen)
• Verify: ./gradlew build — PASSED (build + test + lint)

Phase 3: Canvas — Basic Drawing

• 3.1: Implement PadCanvasView — stylus event handling
  • ui/editor/PadCanvasView.kt — onTouchEvent, getHistoricalX/Y
• 3.2: Stroke rendering — Path/Paint, backing bitmap (1/4 resolution)
• 3.3: Grid drawing — 60pt spacing, drawn on screen only
• 3.4: Coordinate transform — canonical ↔ screen via Matrix
• 3.5: Implement CanvasState
  • ui/editor/CanvasState.kt — zoom, pan, active tool, pen widths
• 3.6: Implement EditorViewModel
  • ui/editor/EditorViewModel.kt — load/save strokes from Room
• 3.7: Implement EditorScreen + toolbar
  • ui/editor/EditorScreen.kt, ui/editor/Toolbar.kt
• 3.8: Wire navigation — notebook list → pages → editor (pages auto-navigates to first page)
• Verify: ./gradlew build — PASSED (build + test + lint). Manual on-device test pending.

Phase 4: Zoom and Pan

• 4.1: ScaleGestureDetector for pinch-to-zoom (0.5×–4×) with focal-point zoom
• 4.2: Finger drag for pan with pointer tracking
• 4.3: Input routing — TOOL_TYPE_STYLUS → draw, TOOL_TYPE_FINGER → zoom/pan
• Verify: ./gradlew build — PASSED. Manual on-device test pending.

Phase 5: Eraser

• 5.1: Eraser mode in CanvasState (already defined in Phase 3)
• 5.2: Hit testing — bounding box pre-filter (expanded by 42pt radius)
• 5.3: Stroke deletion + backing bitmap rebuild + DB sync
• Verify: ./gradlew build — PASSED. Manual test pending.

Phase 6: Undo/Redo

• 6.1: UndoableAction interface + AddStrokeAction, DeleteStrokeAction
  • undo/UndoableAction.kt, undo/StrokeActions.kt
• 6.2: UndoManager — undo/redo stacks, depth 50
  • undo/UndoManager.kt
• 6.3: Integrated with EditorViewModel + toolbar (undo/redo buttons)
• 6.4: Unit tests — 9 tests in UndoManagerTest.kt
• Verify: ./gradlew build — PASSED (19 tests total)

Phase 7: Selection — Move, Copy, Delete

• 7.1: Selection mode — rectangle selection via stylus drag
• 7.2: Visual feedback — blue highlight on selected strokes, dashed selection rect
• 7.3: Operations — delete, drag-to-move, copy (toolbar buttons appear on selection)
• 7.4: Undo integration — DeleteMultipleStrokesAction, MoveStrokesAction, CopyStrokesAction
• Verify: ./gradlew build — PASSED

Phase 8: Multi-Page Navigation

• 8.1: PageListScreen with page grid (aspect-ratio cards)
  • ui/pages/PageListScreen.kt, PageListViewModel.kt
• 8.2: Add new page FAB
• 8.3: NavGraph updated — pages route shows PageListScreen, tap page → editor
• Verify: ./gradlew build — PASSED

Phase 9: PDF Export

• 9.1: PdfExporter — Android PdfDocument API with 300→72 DPI scaling
  • ui/export/PdfExporter.kt
• 9.2: Share via Intent.ACTION_SEND + FileProvider
  • res/xml/file_provider_paths.xml already configured in Phase 1
• 9.3: Export button (PDF) in editor toolbar
• Verify: ./gradlew build — PASSED. Manual PDF verification pending.

Phase 10: Polish

• 10.1: E-ink optimizations — minimize animations, high contrast
• 10.2: Auto-save zoom/pan state per page
• 10.3: Empty states, error handling, delete confirmations
• 10.4: Performance profiling on target devices