Daniel Imms
8712f8067d
1. processLookahead/BacktrackPosition created separate entry objects for each glyph at each position (O(N^M) with N glyphs, M positions). Now all glyphs at a position share one entry object. 2. cloneEntry, cloneTree, flattenEntry, and mergeTreeEntry could infinitely recurse or duplicate work on shared/cyclic references. Added visited/merged tracking maps to cache results. Note that parsing CommitMono locks up the renderer for some time still so there is still a performance issue here, this fixes the OOM though. This was mostly defensive generated code since the codebase is unfamiliar to me. Fixes #5570
@xterm/addon-ligatures
Add support for programming ligatures to xterm.js when running in environments with access to Node.js APIs (such as Electron).
Requirements
- Node.js 8.x or higher (present in Electron 1.8.3 or higher)
- xterm.js 4.0.0 or higher using the default canvas renderer
Install
npm install --save @xterm/addon-ligatures
Usage
import { Terminal } from '@xterm/xterm';
import { LigaturesAddon } from '@xterm/addon-ligatures';
const terminal = new Terminal();
const ligaturesAddon = new LigaturesAddon();
terminal.open(containerElement);
terminal.loadAddon(ligaturesAddon);
How It Works
In a browser environment, font ligature information is read directly by the web browser and used to render text correctly without any intervention from the developer. As of version 3, xterm.js uses the canvas to render characters individually, resulting in a significant performance boost. However, this means that it can no longer lean on the browser to determine when to draw font ligatures.
This package locates the font file on disk for the font currently in use by the terminal and parses the ligature information out of it (via the font-ligatures package). As text is rendered in xterm.js, this package annotates it with the locations of ligatures, allowing xterm.js to render it correctly.
Since this package depends on being able to find and resolve a system font from disk, it has to have system access that isn't available in the web browser. As a result, this package is mainly useful in environments that combine browser and Node.js runtimes (such as Electron).
Fallback Ligatures
When ligatures cannot be fetched from the environment, a set of "fallback" ligatures is used to get the most common ligatures working. These fallback ligatures can be customized with options passed to LigatureAddon.constructor.
Fonts
This package makes use of the following fonts for testing:
- Fira Code - Licensed under the OFL by Nikita Prokopov, Mozilla Foundation with reserved names Fira Code, Fira Mono, and Fira Sans
- Iosevka - Licensed under the OFL by Belleve Invis with reserved name Iosevka