NeoCalc Desktop (The "Why Do We Exist" Fork)

Originally created as a simple calculator to teach kids how to program. It was simple. It was pure. It added 2 and 2 and got 4.

But then I came along. I saw a perfectly functional teaching tool and thought, "You know what this needs? Unnecessary complexity and a bad attitude." So I forked it, injected it with Rust, and stripped it of its innocence.

Features

• Rust Backend: Powered by neocalc-core via UniFFI for high performance and safety.
• Fraction Support: Toggle between precise fractional (e.g., 1/2) and decimal (e.g., 0.5) outputs in Settings.
• 4 Calculator Modes: Standard, Scientific, Programming, and Financial.
• Responsive Layout: Optimized for desktop resizing.
• Theming Engine: Import your own .css themes (GTK-compatible).
• Dark Mode: By default, because we respect your eyes.

Flatpak

You can install downloading the flatpak from the release page and running:

flatpak install ./neocalc.flatpak

Flatpak Repository (Auto-Updates)

To receive automatic updates, add the repository:

flatpak remote-add --user --if-not-exists neocalc https://niltonperimneto.github.io/neocalc/repo
flatpak install neocalc com.niltonperimneto.neocalc

Installation

If you really want to verify that mass times acceleration equals force (or merely a headache):

# Don't ask me why ABI3 is involved.
PYO3_USE_ABI3_FORWARD_COMPATIBILITY=1 cargo run --manifest-path desktop/Cargo.toml

Theming Guide: How to Create Custom Themes

NeoCalc supports custom themes defined in simple .css files. These themes are compatible with the original GTK version of the app.

How to Import a Theme

1. Create a .css file (e.g., my-cool-theme.css).
2. Open NeoCalc.
3. Go to Settings or Theme Manager.
4. Select "Import Theme" and choose your .css file.

CSS Format

The theme parser looks for specific @define-color lines. Format: @define-color KEY #HEXCODE;

Theme Keys Reference

Key	Description
Window Colors
window_bg_color	Main background color of the app.
window_fg_color	Default text color.
Number Buttons
card_bg_color	Background for number buttons (0-9).
card_fg_color	Text color for numbers.
Operator Buttons
warning_bg_color	Background for operators (+, -, /, x).
warning_fg_color	Text color for operators.
Function Buttons
headerbar_bg_color	Background for functions (Sin, Cos, Log).
headerbar_fg_color	Text color for functions.
Accent / Equals
accent_bg_color	The "Equals" (=) button background.
accent_fg_color	Text on the Equals button.
Destructive
destructive_bg_color	Delete / Clear button background.
destructive_fg_color	Delete / Clear button text.

Example Theme (dracula.css)

@define-color window_bg_color #282a36;
@define-color window_fg_color #f8f8f2;

@define-color headerbar_bg_color #44475a;
@define-color headerbar_fg_color #f8f8f2;

@define-color card_bg_color #6272a4;
@define-color card_fg_color #f8f8f2;

@define-color accent_bg_color #bd93f9;
@define-color accent_fg_color #282a36;

@define-color warning_bg_color #ffb86c;
@define-color warning_fg_color #282a36;

@define-color destructive_bg_color #ff5555;
@define-color destructive_fg_color #282a36;

Styling Specific Components

You can style specific parts of the UI using standard CSS selectors.

Calculator Grid Buttons

The buttons in the keypad use the .calc-grid-button class.

.calc-grid-button {
    background-color: #313244;
    color: #cdd6f4;
    border: 1px solid #45475a;
}

.calc-grid-button:hover {
    background-color: #45475a;
}

.calc-grid-button:active {
    background-color: @accent_bg_color;
    color: @accent_fg_color;
}

Accented Buttons

Operators often use the .accent class.

.calc-grid-button.accent {
    background-color: @accent_bg_color;
    color: @accent_fg_color;
}

.calc-grid-button.accent:hover {
    filter: brightness(1.1);
}

Sidebar

The sidebar (history/variables) uses .sidebar.

.sidebar {
    background-color: @headerbar_bg_color;
    border-right: 1px solid @headerbar_border_color;
}

Building (For the Masochists)

So you want a standalone binary to cherish forever? Fine.

1. Install Prerequisites: You need Rust, GTK4, and Python development headers. Consult your distro's wiki for the specific incantations.
2. Compile:

   PYO3_USE_ABI3_FORWARD_COMPATIBILITY=1 cargo build --release --manifest-path desktop/Cargo.toml

3. Locate the Artifact: The binary neocalc_runner (or launcher) awaits you in target/release/. It needs to be run from the root directory so it can find the python folder.

Versioning Scheme

We use a Date-Based Versioning scheme to keep things fresh:

vYEAR.MONTH-REVISION

• YEAR: The current year (e.g., 2025).
• MONTH: The current month (e.g., 12).
• REVISION: An incrementing number for releases within that month (e.g., 1, 2, 5).

Safety Notice

This calculator assumes no liability for failed math exams or existential crises triggered by its output.

License

All the code is licensed under the GPLv3 license. You can check under LICENSE file for more details.