A Counter class that follows the specification outlined at https://www.w3.org/TR/css-lists-3/#auto-numbering.

The CounterStyle class represents styles that can be used to generate a text representation of the given counter's value (such as a 'iv' for 4, or 'β' for 2).

See https://www.w3.org/TR/css-counter-styles-3/#counter-styles for more details.

Getting started

Getting started is simple:

dependencies:
  list_counter: ^1.0.2

Usage

void main() {
  final counter = Counter('named_counter'); //You can also start a counter at a specific integer value with Counter('name', VALUE);
  final listStyle = PredefinedCounterStyle.upperRoman;
  
  counter.increment(); // Adds 1 to the counter
  print(listStyle.generateMarkerContent(counter.value));
  // Prints "I. "
 
  counter.increment(2021); // Now the counter is at 2022
  print(listStyle.generateMarkerContent(conter.value));
  // Prints "MMXXII. "
 
  // Optionally, you can just print the result of the algorithm without any suffixes:
  print(listStyle.generateCounterContent(counter.value));
  // Prints "MMXXII"
}

Predefined Counter Styles

A lengthy list of predefined counter styles is included!

Some of the most basic include:

  • PredefinedCounterStyle.decimal (A simple ordered list)
  • PredefinedCounterStyle.disc (A simple bulleted/unordered list)
  • PredefinedCounterStyle.circle (A bulleted list with open circles)
  • PredefinedCounterStyle.square (A bulleted list with square bullets)
  • PredefinedCounterStyle.lowerAlpha (a, b, c, ..., z, aa, ab)

As well as dozens of language-specific number/alphabet systems, such as:

  • PredefinedCounterStyle.cjkDecimal (〇 一 二 三 四 五 六 七 八 九 ...)
  • PredefinedCounterStyle.cambodian (០ ១ ២ ៣ ៤ ៥ ៦ ៧ ៨ ៩ ...)
  • PredefinedCounterStyle.katakana (ア イ ウ エ オ カ キ ク ...)
  • PredefinedCounterStyle.koreanHangulFormal (일천일백일십일, etc.)
  • PredefinedCounterStyle.simpChineseFormal (壹仟壹佰壹拾壹, etc.)

See https://www.w3.org/TR/css-counter-styles-3/#predefined-counters for the full list.

Custom Counter Styles

Or, you can define your own style:

// Sample additive style taken from https://www.w3.org/TR/css-counter-styles-3/#additive-system
final diceStyle = CounterStyle.define(
  name: 'dice-style',
  system: System.additive,
  additiveSymbols: {6: '⚅', 5: '⚄', 4: '⚃', 3: '⚂', 2: '⚁', 1: '⚀'},
  suffix: " ",
);

diceStyle will then produce lists that look like:

⚀  One
⚁  Two
⚂  Three
...
⚅⚄  Eleven
⚅⚅  Twelve
⚅⚅⚀  Thirteen

Using the CounterStyleRegistry

If wanted, you can also dynamically manage a library of CounterStyles using the static CounterStyleRegistry. It is automatically filled with all the predefined styles.

Here's how it can be used:

void main() {
  // Optionally register your own styles:
  CounterStyleRegistry.register(myCustomStyle);
  // You can also overwrite any of the predefined styles:
  CounterStyleRegistry.register(customDisc); 
  // customDisc Has name "disc" to overwrite the default style in the registry
  
  // Elsewhere...
  
  // Lookup your custom style by its name to use it:
  CounterStyleRegistry.lookup('my-custom-style');
  // or lookup a predefined style:
  CounterStyleRegistry.lookup('ethiopic-numeric');
  
  // Optionally...
  CounterStyleRegistry.remove('my-custom-style');
}

Libraries

list_counter