DEV Community: anoop p

What I Shipped This Month Building Invoiso (v3.4.2)

anoop p — Tue, 31 Mar 2026 13:50:27 +0000

One of the best things about working on Invoiso, a free offline invoice and billing tool available for Windows and Linux operating systems, has been “building in public.” This month has been particularly fruitful as a mix of long-pending features, quality-of-life enhancements, and critical bug fixes were included.

All Changes in v3.4.2 👇

🔗 GitHub · Website · Download

💡 The Focus This Month

This release is all about:

More flexibility in invoicing
Better real-world usage
Smoother payments and workflows

🌍 Multi-Currency Support

One of the most requested features is finally here.

Create invoices in different currencies:

INR · USD · EUR · GBP · JPY · AED · SGD · AUD · CAD · JMD

Each invoice locks in the currency at creation time, maintaining historical data’s accuracy.

Why is multi-currency support important?
If you work with clients across borders, you know how annoying currency conversions can be.

🧾 Per Item Tax Rates

Tax rate is now set per item.

Tax rate is no longer set at the invoice level.

Why is per item tax rate useful?

Mixed GST items
Different tax rates for different service/product types

This makes things more similar to real-world usage.

💸 UPI QR Code on Invoices

A significant feature update for users in India.

Enter your UPI ID in settings
A QR code is automatically added on every invoice you create in PDF format

Clients can also scan and pay instantly using GPay, PhonePe, or Paytm. There is no need to type anything or get confused.

🔁 Invoice Cloning

Creating similar invoices was a tedious task. This feature lets you clone an invoice and use it as a starting point.

A small feature, a big time saver.

📦 Bulk Actions

You can select multiple invoices and perform actions on them in bulk.

More efficiency, less clicks.

💳 Payment Tracking & Receipts

This was a big feature.

Mark invoices as Paid / Partially Paid / Unpaid
Track payment history
Generate downloadable PDF payment receipts

This feature alone makes Invoiso not just an invoice generator, but a basic invoicing system.

🔐 Role-Based Access Control (RBAC)

This feature is for those who work in teams.

Set admin and user roles
Set access level for each user

This feature will pave the way for more user-based features.

🧭 Invoice Type Indicator

The invoice type is also visible on the invoice list and dashboard. There is no need to click on an invoice to know its type.

A small feature, a big time saver.

🖥️ Ubuntu 24.04 LTS Support

Linux users, rejoice! Builds are tested and working on Ubuntu 24.04 LTS.

🎨 UI/UX Improvements

Redesigned: PDF Settings, Company Info, and Software Info screens
Fixed: annoying bug where search fields lost focus on fast typing
General layout and visual polish on screens
Fixed ₹ symbol rendering incorrectly in generated PDFs
Fixed database connection dropping after backup restore
Fixed window resizing issues on Linux
Updated Windows app icon (all sizes: 16, 32, 48, 256px)

📊 What I Learned

Some observations and insights from this release cycle:

Small UX issues matter more than missing features.
The search field focus bug was reported most. More than any missing feature. Fixing UX issues is important.

Payments are core, not optional.
Tracking and receipts are a big part of any payment process. This is a game-changer for the product. Should have done this earlier.

Speed of iteration > perfection.
Shipping is important. Consistency is key. Will improve and iterate soon.

🔮 What's Next?

Exploring next for Invoiso:

Improving reporting & analytics
Improving payment workflows
Improving invoice customization options

🙌 Feedback Welcome

If you have tried Invoiso or have any thoughts on it:

How are you using Invoiso?
What is missing?
What is clunky?

Add a comment below or open an issue on GitHub. I read all of them.

Invoiso is free, open source, and runs entirely offline. No account required. No data leaves your device.

Thanks for reading! More updates soon! 🚀

I built a free Android soundboard that works with a External keyboard

anoop p — Wed, 25 Mar 2026 11:29:40 +0000

A few months ago I needed a simple soundboard for a live session. I wanted to trigger audio clips from a Bluetooth/External keyboard connected to my Android phone - just press a key, hear the sound, instantly.

Every app I found was either subscription-based, required an account, or didn't support physical keyboards at all. So I built CTunes.

What CTunes does

CTunes maps keyboard keys (A-Z and 0-9) to audio files on your device. Tap the on-screen button or press the physical key — the sound plays immediately.

That's the whole pitch. 36 keys. Any audio file. Zero lag.

Try it

I'd love feedback — especially from anyone who uses soundboards for live performance, streaming, or teaching. What features would make this more useful for your workflow?

Core features

Key mapping — pick any audio file from your device and assign it to a key
Dual input — works with on-screen taps and physical Bluetooth keyboards
18-color palette — each key gets a unique color so you can read the board at a glance
Import / Export — your entire layout serialises to a single JSON file
Persistent storage — mappings survive reboots and reinstalls via SQLite + takePersistableUriPermission()
Free — ad-supported, no subscription, no sign-in, works fully offline

The tech stack

CTunes is a native Android app written in Java (yes, Java — not Kotlin). Here's how the main pieces fit together:

Architecture

Single-module project, Activities only
No Fragments, no Navigation component
SQLite via a hand-rolled SQLiteOpenHelper
SharedPreferences for UI settings (grid size, column count, keyboard visibility)

Audio playback


java
// A new MediaPlayer is created per keypress
// The previous one is released first to avoid leaks
if (currentPlayer != null) {
    currentPlayer.release();
}
MediaPlayer mp = MediaPlayer.create(this, uri);
if (mp != null) {
    mp.setOnCompletionListener(MediaPlayer::release);
    mp.start();
    currentPlayer = mp;
}

I Built an Android App Because Android Kept Deleting My Clipboard

anoop p — Thu, 19 Mar 2026 04:52:06 +0000

Here's something that has happened to all of us.

You copy a link. Then you copy someone's phone number. You go to paste the link - and it's gone. Replaced by the phone number. Android only remembers the last thing you copied. That's it. One item. Always.

I kept running into this. Copying a piece of text, copying something else on top of it, then needing the first thing back with no way to get it. I'd go back to the original source, find it again, copy it again. Every time. It was a small annoyance, but it happened constantly.

So I built CopyDuo

What CopyDuo Does

CopyDuo runs quietly in the background and saves everything you copy - up to 50 items. Whenever you need something you copied earlier, you open the app, find it in the list, and tap it to copy it back to your clipboard.

That's it. No accounts. No cloud. No internet connection. Your clipboard history stays on your device, private and instant.

It also handles something I found genuinely annoying about other clipboard apps: duplicates. If you copy the same text twice, CopyDuo stores it only once. Your history stays clean.

Why This Problem Is Harder to Solve Than It Looks

When I started building this, I thought it would be straightforward - just listen for clipboard changes and save them to a local database. Simple, right?

Not quite.

Android 12 Made Background Services Much Harder

To capture clipboard items when the app isn't open, I needed a background service - a piece of code that keeps running even when you're not actively using the app. On older Android versions, this was manageable.

On Android 12 and above, Google introduced strict restrictions on background services. Apps can no longer just run freely in the background. There are limits on when a service can start, and if you don't handle it correctly, the system kills your service entirely - meaning you miss clipboard items.

Getting this right took significant work. CopyDuo uses a foreground service (the kind Android officially supports for long-running tasks) with a persistent notification. This keeps the service alive reliably without fighting the system - and without draining your battery.

On New Devices, Apps Can't Read Your Clipboard in the Background

This one genuinely surprised me.

Starting with Android 10, Google added a privacy restriction: apps can only read clipboard data when they are actively in use - meaning they're the foreground app the user is currently interacting with. A background service can't silently read your clipboard anymore.

This is actually a good privacy decision. You don't want random apps reading everything you copy in the background. But it created a real problem for a clipboard manager.

I had to find another way.

The solution: a button in the notification panel.

When CopyDuo is running, it shows a persistent notification. That notification has a "SAVE TEXT" button. When you tap it, the app briefly comes to the foreground, reads your current clipboard content, saves it, and steps back. It's a one-tap action that takes less than a second.

It's not the invisible magic I originally wanted, but it works reliably on every Android version - including the latest ones - without any workarounds that could break with future updates.

What It Looks Like in Practice

Your day-to-day usage looks like this:

You copy something → CopyDuo saves it automatically (on older devices) or you tap the notification button (on newer devices)
You copy something else on top of it → no problem, both are saved
Ten minutes later you need the first thing → open CopyDuo, tap it, done

The list shows your most recent 50 items. You can delete individual ones or clear everything at once.

Another Way to Save: the Text Selection Menu

While working around the Android 10+ clipboard restriction, I found another clean solution that fits even more naturally into how people actually use their phones.

When you long-press any text in any app — a browser, a PDF reader, a messaging app — Android shows a floating toolbar with options like Copy, Cut, and Share. CopyDuo adds its own button to that menu: "Save to CopyDuo".

Select any text → tap Save to CopyDuo → it's in your history. No need to copy first. No need to open the notification. No steps in between.

This works everywhere Android shows the text selection menu. Reading an article and want to save a quote? Select it, tap Save to CopyDuo. Found a useful command in a tutorial? Same flow.

Between the notification button and the text selection action, CopyDuo covers every scenario — whether you're copy-pasting quickly or deliberately saving something you just read.

Why I Kept It Offline

A lot of productivity apps want your data in the cloud. Sync across devices, access from anywhere - it sounds convenient.

But your clipboard is where passwords live. Phone numbers. Bank account details. Private messages. One-time codes. The idea of that data leaving your device and sitting on someone's server made me uncomfortable - and I figured it would make you uncomfortable too.

CopyDuo has no internet permission. It physically cannot send your data anywhere. Everything is stored locally using a lightweight on-device database, and it never leaves your phone.

Download CopyDuo

It's free on the Google Play Store.

Get CopyDuo on Google Play →

Works on Android 8.0 and above. No account required. No subscription.

If you've ever lost something you copied, give it a try. It solves exactly one problem - but it solves it well.

I Built a Free, Offline Invoice App with Flutter - No Cloud, No Subscription, No BS

anoop p — Thu, 12 Mar 2026 15:48:17 +0000

Every time I needed to invoice a client, I ran into the same wall: every decent invoice tool either locks your data in the cloud, wants a monthly subscription, or both. I just wanted something that works offline, keeps my data on my machine, and doesn't cost me anything.

So I built it.

Invoiso is a free, open-source desktop invoice app for Windows and Linux. No account. No internet. No recurring fee. Just a binary you run on your machine.

Why Flutter for a Desktop App?

Flutter is usually talked about in the context of mobile. But Flutter's desktop support has matured a lot - and it gave me a few things I really wanted:

One codebase for Windows and Linux - I didn't want to maintain separate projects.
A rich widget ecosystem - building forms, data tables, and PDF previews is fast.
Dart's type safety - for a data-heavy app with models, migrations, and services, it helps.

The build output is a native binary - no Electron, no Chromium, no 300 MB runtime. The Linux AppImage is lean and starts instantly.

The Stack

Layer	Tech
Framework	Flutter 3.x (Dart)
Database	SQLite via `sqflite` + `sqflite_common_ffi`
State Management	Riverpod
PDF Generation	`pdf` + `printing`
QR Codes	`qr`
CSV Export	`csv`
Window Management	`window_manager`
File Picker	`file_picker`

SQLite with sqflite_common_ffi is the key piece for desktop. The mobile sqflite package doesn't work on Linux/Windows - sqflite_common_ffi wraps the native SQLite library and exposes the same API, so the transition is seamless. All data lives in a single .db file the user controls.

Project Structure

lib/
├── main.dart
├── common.dart          # Shared enums and data classes
├── constants.dart       # UI constants
├── database/            # SQLite helpers and CRUD services
├── models/              # Invoice, Customer, Product, ...
├── providers/           # Riverpod state providers
├── screens/             # All UI screens
├── services/            # PDF generation, CSV/PDF export
├── backup/              # Backup and restore logic
└── utils/               # Logger, formatters, error handler

The database layer follows a service pattern - each entity (invoices, customers, products) has its own service class wrapping raw SQL. Migrations are handled manually in database_helper.dart with a version counter.

Interesting Technical Bits

1. PDF Generation with Three Templates

PDF output is generated using the pdf package (not a web renderer - actual vector PDF). I built three templates: Classic, Modern, and Minimal - each with a distinct layout and color scheme.

The tricky part was making the layout adaptive to variable-length item lists, long product descriptions, and optional sections (GST, UPI QR, logo). The pdf package has its own layout model (similar to Flutter widgets but without hot reload - so a lot of trial and error).

2. UPI Payment QR Code on Invoices

For Indian users, I added UPI QR code embedding. When a UPI ID is configured in settings, the PDF generation encodes a upi://pay?pa={upi_id}&am={total} URI into a QR code using the qr package and renders it directly in the PDF footer. Clients can scan it with GPay, PhonePe, or Paytm to pay instantly.

3. Multi-Currency with Per-Invoice Snapshots

Currency is selected globally in settings, but each invoice stores its own currency_code and currency_symbol at creation time. This means if you change your default currency later, old invoices still display correctly. A simple but important detail - got it wrong the first time and had to add a DB migration.

Speaking of migrations: I maintain a DB_VERSION constant and a chain of _upgradeDbV{n} functions. Each upgrade is additive (new columns with defaults, new tables) - no destructive changes.

4. Backup and Restore

The backup feature is a plain file copy of the SQLite .db file to a user-chosen directory. Restore reverses it. Simple, robust, and the user owns the backup file - they can put it on a USB drive, copy it to another machine, or commit it to their own repo.

Features at a Glance

PDF invoices - one-click generation in Classic, Modern, or Minimal templates
Invoices and Quotations - with color-coded tracking
Invoice cloning - duplicate any document with one click
Bulk actions - multi-select to export CSV, generate PDFs, or delete
UPI QR code - embedded scannable payment QR in every PDF
GST ready - GSTIN fields, HSN codes, per-item or global tax rate
Multi-currency - INR, USD, EUR, GBP, JPY, AED, SGD, AUD, CAD, JMD
Customer and product management - full CRUD with search and pagination
Soft delete / Trash - recoverable deleted invoices
CSV export - for spreadsheets or accounting software
Backup and restore - one-click, local file
Security - login with brute-force protection and session timeout
100% offline - zero network calls, ever

Download

Platform	Format
Windows	`.exe` installer
Linux	`.AppImage` (portable)
Linux	`.deb` package

Grab the latest from the Download page.

Build from Source

git clone https://github.com/Anooppandikashala/invoiso.git
cd invoiso
flutter pub get

# Run in debug mode
flutter run -d linux    # or -d windows

# Release build
flutter build linux --release
flutter build windows --release

Prerequisites: Flutter SDK >= 3.3.3. On Linux you'll also need clang, cmake, ninja-build, and libgtk-3-dev.

What's Next

There's a solid list of planned features:

Invoice status tracking (Paid / Unpaid / Overdue / Draft) - the biggest gap right now
Due dates and payment terms (Net 7, Net 30, etc.)
Payment recording with partial payment support
Recurring invoices for retainers and subscriptions
Revenue reports with date range filters
Dark mode
Global search across invoices, customers, and products
GST report export in GSTR-1 compatible format (for Indian users)

If any of these interests you, contributions are welcome.

Contributing

Fork the repo
Create a branch: git checkout -b feature/your-feature
Open a pull request

Bug reports and feature requests go in GitHub Issues.

The whole thing is MIT licensed. If it saves you time or money, great - that's the point. If you want to help make it better, even better.

GitHub: github.com/Anooppandikashala/invoiso
Website: anooppandikashala.github.io/invoisoapp