retrocalc

A retro Windows 3.1–styled calculator for your desktop — the standard-view CALC.EXE you remember, rebuilt as a small, crisp, density-independent window with the saudade GUI toolkit (the same toolkit behind retrofetch and control-panel).

It has everything the classic standard view had: the four operators, square root, percent, reciprocal, sign flip, the full memory register (MC / MR / MS / M+), Backspace / CE / C, and Edit ▸ Copy / Paste — all with perfect keyboard and mouse support. Like the original, it uses immediate-execution arithmetic (no operator precedence), so $2 + 3 \times 4 =$ is 20, not 14.

Installation

cargo install retrocalc

Run

After instalation:

retrocalc  

Or, after cloning the source code:

cargo run --release

The calculator opens straight away; the keypad takes focus, so you can start typing immediately.

Keyboard

Everything is reachable from the keyboard:

Key(s)	Action
0–9	enter a digit
. or ,	decimal point
+ - * /	add / subtract / multiply / divide
Enter or =	equals (press again to repeat)
Backspace	delete the last digit
Delete	CE — clear the current entry
Esc	C — clear everything
%	percent
r	reciprocal (1/x)
@ or q	square root
Ctrl+C / Ctrl+V	copy / paste the displayed number
Ctrl+L / Ctrl+R	memory clear / recall (MC / MR)
Ctrl+M / Ctrl+P	memory store / add (MS / M+)

The sign-flip key (+/-) is on the keypad — click it with the mouse. A little M lights up next to the keypad whenever the memory register holds a value.

Mouse

Click any key. The buttons behave like real Win 3.1 push buttons: press to arm, drag off to cancel (the key pops back up), drag back to re-arm, release inside to fire.

How it fits together

• engine.rs is the pure calculator state machine — all of the arithmetic and none of the pixels, exhaustively unit-tested.
• keypad.rs is a single custom Widget: it paints the readout and the coloured key grid (blue digits, maroon functions, just like the original) and turns pointer / key presses into engine calls.
• main.rs assembles the window — a Column with a menu bar, the keypad, and a shared "About" Dialog overlay.
• A headless test suite (cargo test) drives the engine and the widget through saudade's MockBackend

License

MIT