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Overview

TerminalBackend renders a Scene to an ANSI/Unicode string for terminal display. It uses:
  • Braille characters (U+2800–U+28FF) for circles and diagonal lines
  • Box-drawing characters for axes and grid lines
  • Full-block characters (█) for filled rectangles
  • ANSI 24-bit color for all elements
This backend is always available and requires no feature flags.

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Usage

use kuva::backend::terminal::TerminalBackend;
use kuva::render::render::Scene;

let scene = /* your Scene */;
let backend = TerminalBackend::new(80, 24);
let output = backend.render_scene(&scene);
print!("{}", output);

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Constructor

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new

Creates a new terminal backend with specified dimensions.
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cols
usize
required
Number of terminal character columns (typically 80-200)
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rows
usize
required
Number of terminal character rows (typically 24-60)
Returns: TerminalBackend Example: 
let backend = TerminalBackend::new(120, 40);

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Methods

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render_scene

Renders a Scene to an ANSI/Unicode string.
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scene
&Scene
required
The scene to render
Returns: String - ANSI string with color codes and Unicode graphics Example: 
let output = backend.render_scene(&scene);
print!("{}", output);

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Rendering Layers

The terminal backend renders in three layers (front-to-back):
  1. char_grid - Filled rectangles (█) and text characters
  2. line_char_grid - Box-drawing characters for axes/ticks
  3. braille - Dot-matrix characters for circles and diagonal lines

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Coordinate Mapping

Scene coordinates are mapped to terminal coordinates:
  • Braille resolution: 2×4 dots per character cell
  • Character resolution: 1×1 character per cell
  • Box-drawing uses bitmask encoding (TOP=1, RIGHT=2, BOTTOM=4, LEFT=8)

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Features

  • Horizontal/vertical lines: Rendered with box-drawing characters (─, │, ┼, etc.)
  • Diagonal lines: Rendered with Bresenham algorithm on braille grid
  • Circles: Filled using braille dots
  • Filled paths: Scanline-filled with braille dots (for Sankey, pie slices)
  • Text: Rendered directly with character grid
  • Rotated labels: Collision-avoided stacking for readability

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Auto-detection

Terminal dimensions can be auto-detected: 
use kuva::render::layout::Layout;

let layout = Layout::auto_from_plots(&plots)
    .with_term_rows(40);  // Override rows if needed

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CLI Usage

The CLI supports terminal output with --terminal: 
kuva scatter data.tsv --x x --y y --terminal

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Limitations

  • UpSetPlot is not supported in terminal mode
  • No font size control (uses monospace terminal font)
  • Limited color resolution compared to image formats
  • Text rotation is approximated

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Source

src/backend/terminal.rs

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