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mapbox-gl-rtl-text.js

An Emscripten port of a subset of the functionality of International Components for Unicode (ICU) necessary for Mapbox GL JS to support right to left text rendering. Supports the Arabic and Hebrew languages, which are written right-to-left. Mapbox Studio loads this plugin by default.

Requires mapbox-gl-js (version 0.32.1 and up).

A map that requires Arabic names should at a minimum install the mapbox-gl-rtl-text plugin. To display the actual place names, the map could use a specially modified style, manipulate the style at runtime, or install the mapbox-gl-language plugin for convenience. The mapbox-gl-language plugin displays Arabic name data (among other languages), while the mapbox-gl-rtl-text plugin adds support for displaying Arabic names.

Using mapbox-gl-rtl-text

mapbox-gl-rtl-text exposes two functions:

applyArabicShaping(unicodeInput)

Takes an input string in "logical order" (i.e. characters in the order they are typed, not the order they will be displayed) and replaces Arabic characters with the "presentation form" of the character that represents the appropriate glyph based on the character's location within a word.

processBidirectionalText(unicodeInput, lineBreakPoints)

Takes an input string with characters in "logical order", along with a set of chosen line break points, and applies the Unicode Bidirectional Algorithm to the string. Returns an ordered set of lines with characters in "visual order" (i.e. characters in the order they are displayed, left-to-right). The algorithm will insert mandatory line breaks (\n etc.) if they are not already included in lineBreakPoints.

mapbox-gl-rtl-text.js is built to be loaded directly by Mapbox GL JS using:

mapboxgl.setRTLTextPlugin('mapbox-gl-rtl-text.js');

You can use ICU JS directly:

import rtlText from '@mapbox/mapbox-gl-rtl-text';
const {applyArabicShaping, processBidirectionalText} = await rtlText;

const arabicString = "سلام";
const shapedArabicText = applyArabicShaping(arabicString);
const readyForDisplay = processBidirectionalText(shapedArabicText, []);

Building mapbox-gl-rtl-text

• Running npm start will spin up a local server to test the plugin in a browser.
• Running npm test will run unit tests in test.js.
• Running npm run build:icu will rebuild ICU WASM module:
  • Download Emscripten SDK Docker Image
  • Compile ushape_wrapper.c and ubidi_wrapper.c to LLVM bytecode
  • Generate ./src/icu.wasm.js, exposing bytecode sources as WASM module

Deploying mapbox-gl-rtl-text

npm test
npm version {patch|minor|major}
git push --follow-tags

mbx env
VERSION=v$(node -p "require('./package.json').version")
aws s3 cp --acl public-read --content-type application/javascript mapbox-gl-rtl-text.js s3://mapbox-gl-js/plugins/mapbox-gl-rtl-text/v$VERSION/mapbox-gl-rtl-text.js
mbx npm publish