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Project @thi.ng/text-canvas

text-canvas

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This project is part of the @thi.ng/umbrella monorepo.

About

Text based canvas, drawing, tables with arbitrary formatting (incl. ANSI/HTML).

Status

ALPHA - bleeding edge / work-in-progress

Search or submit any issues for this package

Installation

yarn add @thi.ng/text-canvas
// ES module
<script type="module" src="https://unpkg.com/@thi.ng/text-canvas?module" crossorigin></script>

// UMD
<script src="https://unpkg.com/@thi.ng/text-canvas/lib/index.umd.js" crossorigin></script>

Package sizes (gzipped, pre-treeshake): ESM: 5.83 KB / CJS: 6.16 KB / UMD: 5.88 KB

Dependencies

Usage examples

Several demos in this repo's /examples directory are using this package.

A selection:

ScreenshotDescriptionLive demoSource
3D wireframe textmode demoDemoSource
Textmode image warping w/ 16bit color outputDemoSource

API

Generated API docs

Canvas creation

const c = canvas(width, height, format?, style?);

Format identifiers

The text canvas stores all characters in a Uint32Array with the lower 16 bits used for the UTF-16 code and the upper 16 bits for abitrary formatting data. The package provides its own format IDs which are tailored for the bundled ANSI & HTML formatters, but users are free to choose use any other system (but then will also need to implement a custom string formatter impl).

The default format ID layout is as shown:

format bit layout

Most drawing functions accept an optional format arg, but a default format can also be set via setFormat(canvas, formatID).

The following built-in format IDs are only compatible with these formatters:

  • FMT_ANSI16
  • FMT_HTML_INLINE_CSS
  • FMT_HTML_TACHYONS

Custom formatters are discussed further below:

Colors

These color IDs MUST be prefixed with either FG_ (foreground) or BG_ (background):

  • BLACK
  • RED
  • GREEN
  • YELLOW
  • BLUE
  • MAGENTA
  • CYAN
  • GRAY
  • WHITE
  • LIGHT_GRAY
  • LIGHT_RED
  • LIGHT_GREEN
  • LIGHT_YELLOW
  • LIGHT_BLUE
  • LIGHT_MAGENTA
  • LIGHT_CYAN

Variations

  • BOLD
  • DIM
  • UNDERLINE

Combined formats

Format IDs can be combined via the binary OR operator (|), e.g.:

setFormat(canvas, FG_BLACK | BG_LIGHT_CYAN | BOLD | UNDERLINE);

String conversion format presets

Canvas-to-string conversion is completely customizable via the StringFormat interface and the following presets are supplied:

  • FMT_ANSI16 - translate built-in format IDs to 4bit ANSI escape sequences
  • FMT_ANSI256 - uses all 16 format bits for fg & bg colors (ANSI esc sequences)
  • FMT_ANSI_RAW - verbatim use of format IDs to ANSI sequences
  • FMT_HTML_INLINE_CSS - HTML <span> elements with inline CSS
  • FMT_HTML_TACHYONS - HTML <span> elements with Tachyons CSS class names
// Terminal
console.log(toString(canvas, FMT_ANSI16));
// or
console.log(toString(canvas, FMT_ANSI256));

// Browser
const el = document.createElement("pre");
el.innerHTML = toString(canvas, FMT_HTML_TACHYONS);

256 color ANSI format

If targeting this output format, all 16 bits available for formatting information are used to encode 2x 8bit foreground/background colors. Therefore, none of the above mentioned preset color names and/or any additional formatting flags (e.g. bold, underline etc.) cannot be used. Instead, use the format256() function to compute a format ID based on given FG, BG colors.

// deep purple on yellow bg
textLine(canvas, 1, 1, "hello color!", format256(19, 226));

ANSI256 color pallette

Source: Wikipedia

16bit color HTML format

Similar to the above custom ANSI format, here all available 16 bits are used to store color information, in the standard RGB565 format (5bits red, 6bits green, 5bits blue). This also means, only either the text or background color can be controlled and no other formatting flag (bold, underline etc.) are available.

const el = document.createElement("pre");
// format and assign text colors
el.innerHTML = toString(canvas, FMT_HTML_565());

// assign bg colors
el.innerHTML = toString(canvas, FMT_HTML_565("background"));

Ad-hoc formatting of strings

String formatters can also be used in an ad-hoc manner, without requiring any of the other text canvas functionality.

// create & use a HTML formatter
defFormat(FMT_HTML_INLINE_CSS, FG_LIGHT_RED | BG_GRAY)("hello")
// "<span style="color:#f55;background:#555;">hello</span>"

// create & use an ANSI formatter
defFormat(FMT_ANSI16, FG_LIGHT_RED | BG_GRAY)("hello")
// "\x1B[91;100mhello\x1B[0m"

// ANSI syntax sugar (same result as above)
defAnsi16(FG_LIGHT_RED | BG_GRAY)("hello")
// "\x1B[91;100mhello\x1B[0m"

Furthermore, defFormatPresets() can be used to create formatting functions for all 16 preset foreground color IDs for a given string format strategy:

const ansi = defFormatPresets(FMT_ANSI16);

`${ansi.green("hello")} ${ansi.lightRed("world")}!`;
// '\x1B[32mhello\x1B[0m \x1B[91mworld\x1B[0m!'

const html = defFormatPresets(FMT_HTML_TACHYONS);

`${html.green("hello")} ${html.lightRed("world")}!`;
// '<span class="dark-green ">hello</span> <span class="red ">world</span>!'

Stroke styles

Built-in style presets:

  • STYLE_ASCII
  • STYLE_THIN
  • STYLE_THIN_ROUNDED
  • STYLE_DASHED
  • STYLE_DASHED_ROUNDED
  • STYLE_DOUBLE

Functions:

  • beginStyle(canvas, style)
  • endStyle(canvas)

Clipping

All drawing operations are constrained to the currently active clipping rect (by default full canvas). The canvas maintains a stack of such clipping regions, each newly pushed one being intersected with the previous top-of-stack rect:

  • beginClip(canvas, x, y, w, h) - push new clip rect
  • endClip(canvas) - restore previous clip rect
┌──────────────────┐
│ A                │
│         ╔════════╗─────────┐
│         ║        ║         │
│         ║ A & B  ║         │
│         ║        ║         │
└─────────╚════════╝         │
          │                B │
          └──────────────────┘

Drawing functions

  • line

  • hline

  • vline

  • circle

  • clear

  • fillRect

  • strokeRect

Image functions

  • blit
  • resize
  • extract
  • scrollV
  • image

Text functions

  • textLine
  • textLines
  • textColumn
  • textBox

Bars & bar charts

The following are string builders only, draw result via text functions:

  • barHorizontal
  • barVertical
  • barChartHStr
  • barChartVStr

Tables

Tables support individual column width, automatic (or user defined) row heights, cell padding, as well as global and per-cell formats and the following border style options:

Border styleResult
Border.ALLtable
Border.NONEtable
Border.Htable
Border.Vtable
Border.FRAMEtable
Border.FRAME_Htable
Border.FRAME_Vtable
import { repeatedly } from "@thi.ng/transducers";
import * as tc from "@thi.ng/text-canvas";

// generate 20 random values
const data = repeatedly(() => Math.random(), 20)
// format as bar chart string
const chart = tc.barChartHStr(4, data, 0, 1);

// create text canvas
const canvas = new tc.Canvas(64, 20);

// create table
tc.table(
    canvas,
    0,
    0,
    {
        // column defs
        cols: [{ width: 4 }, { width: 20 }, { width: 8 }],
        // default cell format
        format: tc.FG_BLACK | tc.BG_LIGHT_CYAN,
        // default format for header cells (1st row)
        formatHead: tc.FG_RED | tc.BG_LIGHT_CYAN | tc.BOLD | tc.UNDERLINE,
        // border line style
        style: tc.STYLE_DASHED_ROUNDED,
        // border mode
        border: tc.Border.ALL,
        // internal cell padding [h,v]
        padding: [1, 0]
    },
    // table contents (row major)
    // each cell either a string or RawCell object
    [
        ["ID", "Main", "Comment"],
        [
            "0001",
            { body: chart, format: tc.FG_BLUE | tc.BG_LIGHT_CYAN },
            "This is a test!"
        ],
        ["0002", "Random data plot", "Word wrapped content"],
        ["0003", { body: "More details...", height: 4 }, ""]
    ]
);

// output as ANSI formatted string
console.log(tc.toString(canvas, tc.FMT_ANSI16));

For even more detailed control, tables can also be pre-initialized prior to creation of the canvas via initTable() and then drawn via drawTable(). The initTable function returns an object also containing the computed table size (width, height keys) which can then be used to create a canvas with the required size...

For convenience, the tableCanvas() function can be used to combine these steps and to create an auto-sized canvas with the rendered table as content.

3D wireframe cube example

       ┌───┐
  ┌──────────────────────┐
  │ @thi.ng/text-canvas  │
  │ wireframe cube       │++++++++++
  │                      │          +++++++++++    ┌───┐
  │ x: 0.42              │                     ++++│ 6 │
  │ y: 0.30              │        ┌───┐ ++++++++   └───┘
  └──────────────────────┘++++++++│ 7 │+           +
           +         └───┘        └───┘            +
            +          +           +              +
            +          +           +              +
             +         +           +             +
             +         +          +              +
             +          +         +              +
              +         +         +             +
              +         +         +             +
               +        +        ┌───┐         +
               +         +      +│ 3 │         +
                +       ┌───┐+++ └───┘        +
                +       │ 0 │       +         +
                 +      └───┘        +        +
                 +       +            +      +
                 +       +             +     +
                  +     +               +   +
                  +     +                +  +
                   +    +                 ┌───┐
                   +    +                 │ 2 │
                    +   +               ++└───┘
                    +   +            +++
                     + +           ++
                     + +        +++
                      ++      ++

Code for this above example output (CLI version):

import * as geom from "@thi.ng/geom";
import * as mat from "@thi.ng/matrices";
import * as tc from "@thi.ng/text-canvas";

const W = 64;
const H = 32;

// create text canvas
const canvas = new tc.Canvas(W, H, tc.BG_BLACK, tc.STYLE_THIN);

// cube corner vertices
const cube = geom.vertices(geom.center(geom.aabb(1))!);

// edge list (vertex indices)
const edges = [
    [0, 1], [1, 2], [2, 3], [3, 0], [4, 5], [5, 6],
    [6, 7], [7, 4], [0, 4], [1, 5], [2, 6], [3, 7]
];

// animated parameters
let rotx = 0;
let roty = 0;

// 3D transformation matrices
const view = mat.lookAt([], [0, 0, 1], [0, 0, 0], [0, 1, 0]);
const proj = mat.perspective([], 90, W / H, 0.1, 10);
const viewp = mat.viewport([], 0, W, H, 0);

setInterval(() => {
    tc.clear(canvas, true);
    // model rotation matrix
    const model = mat.concat(
        [],
        mat.rotationX44([], rotx += 0.01),
        mat.rotationY44([], roty += 0.03)
    );
    // combined model-view-projection matrix
    const mvp = mat.concat([], proj, view, model);
    // draw cube instances
    // project 3D points to 2D viewport (canvas coords)
    const pts = cube.map((p) => mat.project3([], mvp, viewp, p)!);
    // draw cube edges
    for (let e of edges) {
        const a = pts[e[0]];
        const b = pts[e[1]];
        tc.line(canvas, a[0], a[1], b[0], b[1], "+", tc.FG_WHITE | tc.BG_RED);
    }
    // draw vertex labels
    canvas.format = tc.FG_WHITE | tc.BG_BLUE;
    for (let i = 0; i < 8; i++) {
        const p = pts[i];
        tc.textBox(canvas, p[0] - 1, p[1] - 1, 5, 3, ` ${i} `);
    }
    tc.textBox(
        canvas,
        2, 1, 24, -1,
        `@thi.ng/text-canvas wireframe cube\n\nx: ${rotx.toFixed(2)}\ny: ${roty.toFixed(2)}`,
        {
            format: tc.FG_BLACK | tc.BG_LIGHT_CYAN,
            padding: [1, 0]
        }
    );
    // draw canvas
    console.clear();
    // output as ANSI formatted string
    console.log(tc.toString(canvas, tc.FMT_ANSI16));
    // output as plain text
    // console.log(tc.toString(canvas));
}, 15);

Authors

Karsten Schmidt

If this project contributes to an academic publication, please cite it as:

@misc{thing-text-canvas,
  title = "@thi.ng/text-canvas",
  author = "Karsten Schmidt",
  note = "https://thi.ng/text-canvas",
  year = 2020
}

License

© 2020 - 2021 Karsten Schmidt // Apache Software License 2.0

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