📐 ShaftSchematic

ShaftSchematic is an Android application for rapidly modeling marine prop-shaft assemblies and exporting clean, dimensioned drawings as PDFs. It supports multi-segment shafts with bodies, tapers, threads, and liners.

This tool is built for machinists, shipyards, repair techs, and engineering teams that need fast, clear shaft visualizations without CAD overhead.

✨ Current Features Real-Time Shaft Modeling

Add Bodies, Tapers, Threads, and Liners

Components rendered with:

Bodies & liners as closed rectangles

Tapers as true 4-point polygons

Threads as dimensioned segments

Live preview that masks the centerline underneath occupied spans

Preview Styling (on-screen only)

Preview colors configurable via Settings (presets + Custom theme palette)

Black/White Only mode for drafting-style preview

Clean Editing Workflow

Incremental component creation (in the order you build the shaft)

Unit switching (mm / inch) with DataStore persistence

Grid visibility persistence (DataStore)

Validation nudges when component total length doesn't match overall length

Delete + Undo (v1)

Tap trash icon → segment is removed instantly

Snackbar with Undo restores it in the correct order and position

Multi-step undo buffer (up to 10 deletes)

PDF Export

One-page, landscape technical drawing

Includes:

Component labels

Major/minor grid

Centerline rules

Dimensioning and callouts

Reliable system-document picker integration (SAF)

Portrait UI

The editor UI is locked to portrait orientation (landscape is currently disabled).

Session Tools

Clear All → resets to a clean shaft

Dynamic layout that shows advanced sections only when components exist

📂 Project Structure

app/
└─ com.android.shaftschematic/
   ├─ MainActivity.kt (single-activity host)
   ├─ data/
   │   ├─ SettingsStore.kt → DataStore persistence
   │   └─ ShaftRepository / ShaftFileRepository → JSON I/O
   ├─ model/
   │   ├─ ShaftSpec.kt → root aggregate (mm)
   │   ├─ Body, Taper, Threads, Liner → component models
   │   └─ Segment.kt → shared interface
   ├─ pdf/
   │   ├─ ShaftPdfComposer.kt → PDF export engine
   │   └─ render/, dim/, notes/ → dimension & annotation rendering
   ├─ ui/
   │   ├─ drawing/
   │   │   ├─ compose/ShaftDrawing.kt → preview wrapper
   │   │   └─ render/ → ShaftLayout, ShaftRenderer, GridRenderer
   │   ├─ screen/ → ShaftScreen, AddComponentDialogs
   │   ├─ input/ → ShaftMetaSection, NumberField
   │   ├─ viewmodel/ → ShaftViewModel, factory
   │   └─ nav/ → AppNav, routing
   ├─ util/
   │   ├─ UnitSystem.kt → mm/inch conversions
   │   └─ Parsing.kt, TaperParser.kt → input parsing
   └─ settings/ → PdfPrefs configuration

🔧 Requirements

Android Studio Koala or newer

Kotlin 2.2.20 (with Compose compiler plugin)

Jetpack Compose (Material3) via BOM 2024.09.00

DataStore Preferences 1.1.1

Coroutines 1.8+

Min SDK 28, Target SDK 36

Dependencies (gradle/libs.versions.toml):

[versions]
kotlin = "2.2.20"
composeBom = "2024.09.00"
datastore = "1.1.1"

[libraries]
androidx-compose-bom = { group = "androidx.compose", name = "compose-bom", version.ref = "composeBom" }
androidx-datastore-preferences = { module = "androidx.datastore:datastore-preferences", version.ref = "datastore" }

🚀 Build & Run

Clone repository

Open in Android Studio

Let Gradle sync

Run on a device or emulator

📘 Usage Guide

Set the overall shaft length

Press the ➕ Add Component FAB

Add bodies, tapers, threads, or liners in physical build order

Switch units anytime (top bar dropdown)

Export to PDF from the top-right icon

Use ⋮ → Clear All to reset the layout

Component ordering honors a persisted/explicit component order when provided. Otherwise, components are ordered by their physical starting X-position.

🧠 Persistence

Unit preference persists via DataStore (default unit + grid visibility)

Document state: JSON save/load via Storage Access Framework (SAF)

Versioned JSON envelope preserves unit preference and lock state per-document

Thread pitch normalization: auto-populates both pitchMm and tpi when either is present

🛠️ Roadmap Active

Component highlighting in preview (tap-to-select)

Better precision input (fractions, 4–6 decimals)

Liner dimension rendering improvements

Next Sprints

Inline "+ Add here" between segments

Tap-to-edit directly from the preview

Autosave/drafts system

PDF dimension clarity improvements

Overlap detection and warnings

Web/Multi-platform port (concept phase)

📄 License

Pending — private/closed until final licensing decision.

📜 Changelog

See CHANGELOG.md for version history. Latest entries include rendering updates, UI cleanups, validation improvements, and the new Delete/Undo system.