Calculator
A full calculator, native on KeyOS
A basic-and-scientific calculator that runs natively on Passport Prime, showing KeyOS as a general-purpose app platform rather than a Bitcoin-only signer.
Last updated Jul 2026
Basic keypad · dark
Overview
A calculator app written from scratch for Passport Prime. It has two modes: a basic keypad, and a scientific mode with trigonometry, hyperbolic functions, powers and roots, logarithms, factorial, constants, a random generator, a 2nd-function shift, radian and degree switching, and a four-key memory. A running formula sits above the answer, and the whole interface tracks the system light and dark theme.
It exists to make a simple point for developers: Passport Prime is a general-purpose computer, not only a signing device. There is no Bitcoin, no networking, and no secret material here, just a native Rust and Slint application built with the public Foundation SDK, driven end to end through the foundation CLI and the KeyOS simulator.
What it does
- Basic mode: digits, decimal, sign flip, percent, backspace, an AC / C clear that adapts to context, and the four operators.
- Scientific mode: sin/cos/tan, sinh/cosh/tanh, x², x³, xʸ, eˣ, 10ˣ, 1/x, √, ³√, ʸ√, ln, log, x!, π, e, EE, and a random generator.
- 2nd-function shift exposes inverse trig and related alternates; a Rad / Deg toggle sets the angle unit for every trig call.
- Four-key memory (mc, m+, m−, mr) plus parenthesis support for grouped expressions.
- A live formula line renders above the large answer, so you see the whole expression as you build it, then the result on equals.
- Light and dark palettes follow the KeyOS system theme automatically; the custom key colours are defined once and recolour on the fly.
- Per-keypress performance is logged (calc, sync, and total microseconds) to keep the UI responsive on device.
Technical breakdown
How the proof-of-concept is built, for developers evaluating the platform.
The expression engine
src/calculator.rs holds the whole calculator with no external math dependencies. Input is modelled as a stream of typed pieces (PieceKind: number, decimal, exponent, operator, parenthesis, function, constant, postfix), which is both rendered as the on-screen formula and evaluated on equals. It carries answer state, a just-evaluated flag for chaining, memory, and a small deterministic random generator, so behaviour is fully host-testable off-device.
UI in Slint
ui/app.slint composes the interface from a couple of reusable components (a rounded CalcButton and an icon variant for backspace) laid out over basic and scientific keypads and a mode toggle. A CalcPalette global defines every key colour for light and dark in one place; the orange operator keys, muted function keys, and adaptive text all read from it. The backspace glyph is a single SVG recoloured at runtime via Slint colorize, so it inverts cleanly between themes.
Theming and platform
main.rs boots through the SDK app_minimal! macro and wires a single Callbacks.input(string) channel from every key back into the Rust model, then syncs only the properties that changed. Theming uses foundation-themes: include_theme! pulls in the compiled app theme and apply_theme! pushes the palette into the Slint Theme global, with a subscription that re-applies whenever the system switches between light and dark.
Dig into the source
README, architecture notes, and the wire protocol live in the repo.