tachyonfx

tachyonfx is a ratatui library for creating shader-like effects in terminal UIs. It provides a collection of stateful effects that can enhance the visual appeal of terminal applications through color transformations, animations, and complex effect combinations.

Installation

Add tachyonfx to your Cargo.toml:

tachyonfx = "0.9.2"

Core Concepts

Effects and State

Effects in tachyonfx are stateful objects that evolve over time. When you create an effect, it typically maintains:

• An internal timer or flag tracking progress
• Effect-specific state (like transition progress)
• Configuration (like styling, directions, or interpolation methods)

// Create the effect once
let mut fade_effect = fx::fade_to_fg(Color::Red, Duration::from_millis(1000));

// In your render loop:
loop {
    widget.render(area, buf);
    
    // Process the same effect each frame, updating its state
    fade_effect.process(frame_duration, buf, area);
    // Or use the helper trait:
    // frame.render_effect(&mut fade_effect, area, frame_duration);
}

Effects and Widgets

Effects in tachyonfx operate on terminal cells after widgets have been rendered to the screen. When an effect is applied, it modifies properties of the already-rendered cells - like their colors, characters, or visibility. This means the typical flow is:

1. Render your widget to the screen
2. Apply effects to transform the rendered content

Types of Effects

The library includes a variety of effects, loosely categorized as follows:

Color Effects

• fade_from: Fades from the specified background and foreground colors
• fade_from_fg: Fades the foreground color from a specified color.
• fade_to: Fades to the specified background and foreground colors.
• fade_to_fg: Fades the foreground color to a specified color.
• hsl_shift: Changes the hue, saturation, and lightness of the foreground and background colors.
• hsl_shift_fg: Shifts the foreground color by the specified hue, saturation, and lightness over the specified duration.
• term256_colors: Downsamples to 256 color mode.

Text/Character Effects

• coalesce: The reverse of dissolve, coalesces text over the specified duration.
• dissolve: Dissolves the current text over the specified duration.
• slide_in: Applies a directional sliding in effect to terminal cells.
• slide_out: Applies a directional sliding out effect to terminal cells.
• sweep_in: Sweeps in from the specified color.
• sweep_out: Sweeps out to the specified color.

Timing and Control Effects

• consume_tick: Consumes a single tick.
• never_complete: Makes an effect run indefinitely.
• ping_pong: Plays the effect forwards and then backwards.
• prolong_start: Extends the start of an effect by a specified duration.
• prolong_end: Extends the end of an effect by a specified duration.
• repeat: Repeats an effect indefinitely or for a specified number of times or duration.
• repeating: Repeats the effect indefinitely.
• sleep: Pauses for a specified duration.
• timed_never_complete: Creates an effect that runs indefinitely but has an enforced duration.
• with_duration: Wraps an effect and enforces a duration on it.

Geometry Effects

• translate: Moves the effect area by a specified amount.
• translate_buf: Copies the contents from an aux buffer, moving it by a specified amount.
• resize_area: Resizes the area of the wrapped effect.

Combination Effects

• parallel: Runs effects in parallel, all at the same time. Reports completion once all effects have completed.
• sequence: Runs effects in sequence, one after the other. Reports completion once the last effect has completed.

Other Effects

• effect_fn: Creates custom effects from user-defined functions, operating over CellIterator.
• effect_fn_buf: Creates custom effects from functions, operating over Buffer.
• offscreen_buffer: Wraps an existing effect and redirects its rendering to a separate buffer.

Additional effects can be created by implementing the Shader trait.

EffectTimer and Interpolations

Most effects are driven by an EffectTimer that controls their duration and interpolation. It allows for precise timing and synchronization of visual effects within your application.

fx::dissolve(EffectTimer::from_ms(500, BounceOut))
fx::dissolve((500, BounceOut)) // shorthand for the above
fx::dissolve(500)              // linear interpolation

Cell Selection and Area

Effects can be applied to specific cells in the terminal UI, allowing for targeted visual modifications and animations.

// only apply to cells with `Light2` foreground color
fx::sweep_in(Direction::UpToDown, 15, 0, Dark0, timer)
    .with_cell_selection(CellFilter::FgColor(Light2.into()))

CellFilters can be combined to form complex selection criteria.

// apply effect to cells on the outer border of the area
let margin = Margin::new(1, 1);
let border_text = CellFilter::AllOf(&[
    CellFilter::Outer(margin),
    CellFilter::Text
]);

prolong_start(duration, fx::fade_from(Dark0, Dark0, (320, QuadOut)),
    .with_cell_selection(border_text)

Features

• sendable: Enables the Send trait for effects, shaders, and associated parameters. This allows effects to be safely transferred across thread boundaries. Note that enabling this feature requires all Shader implementations to be Send, which may impose additional constraints on custom shader implementations.
• std-duration: Uses std::time::Duration instead of a custom 32-bit duration type.

Examples

Example: minimal

cargo run --release --example=minimal 

Example: tweens

cargo run --release --example=tweens 

Example: basic-effects

cargo run --release --example=basic-effects 

Example: open-window

cargo run --release --example=open-window  

Example: fx-chart

A demo of the EffectTimelineWidget showcasing the composition of effects. The widget is a "plain" widget without any effects as part of its rendering. The effects are instead applied after rendering the widget.

cargo run --release --example=fx-chart