Support detailed ligatures and variants

Fixes #5284

addons/addon-ligatures/src/LigaturesAddon.ts

@@ -15,19 +15,22 @@ export interface ITerminalAddon {
 
 export class LigaturesAddon implements ITerminalAddon , ILigaturesApi {
   private readonly _fallbackLigatures: string[];
+  private readonly _fontFeatureSettings?: string;
 
   private _terminal: Terminal | undefined;
   private _characterJoinerId: number | undefined;
 
   constructor(options?: Partial<ILigatureOptions>) {
+    // Source: calt set from https://github.com/be5invis/Iosevka?tab=readme-ov-file#ligations
     this._fallbackLigatures = (options?.fallbackLigatures || [
       '<--', '<---', '<<-', '<-', '->', '->>', '-->', '--->',
       '<==', '<===', '<<=', '<=', '=>', '=>>', '==>', '===>', '>=', '>>=',
-      '<->', '<-->', '<--->', '<---->', '<=>', '<==>', '<===>', '<====>', '-------->',
-      '<~~', '<~', '~>', '~~>', '::', ':::', '==', '!=', '===', '!==',
-      ':=', ':-', ':+', '<*', '<*>', '*>', '<|', '<|>', '|>', '+:', '-:', '=:', ':>',
-      '++', '+++', '<!--', '<!---', '<***>'
+      '<->', '<-->', '<--->', '<---->', '<=>', '<==>', '<===>', '<====>', '::', ':::',
+      '<~~', '</', '</>', '/>', '~~>', '==', '!=', '/=', '~=', '<>', '===', '!==', '!===',
+      '<:', ':=', '*=', '*+', '<*', '<*>', '*>', '<|', '<|>', '|>', '+*', '=*', '=:', ':>',
+      '/*', '*/', '+++', '<!--', '<!---'
     ]).sort((a, b) => b.length - a.length);
+    this._fontFeatureSettings = options?.fontFeatureSettings;
   }
 
   public activate(terminal: Terminal): void {
@@ -36,7 +39,7 @@ export class LigaturesAddon implements ITerminalAddon , ILigaturesApi {
     }
     this._terminal = terminal;
     this._characterJoinerId = enableLigatures(terminal, this._fallbackLigatures);
-    terminal.element.style.fontFeatureSettings = '"liga" on, "calt" on';
+    terminal.element.style.fontFeatureSettings = this._fontFeatureSettings ?? '"calt" on';
   }
 
   public dispose(): void {

addons/addon-ligatures/src/Types.ts

@@ -5,4 +5,5 @@
 
 export interface ILigatureOptions {
   fallbackLigatures: string[];
+  fontFeatureSettings: string;
 }

addons/addon-ligatures/typings/addon-ligatures.d.ts

@@ -23,7 +23,10 @@ declare module '@xterm/addon-ligatures' {
     constructor(options?: Partial<ILigatureOptions>);
 
     /**
-     * Activates the addon
+     * Activates the addon. Note that if webgl is also being used, that addon
+     * should be reactivated after ligatures is activated in order to apply
+     * {@link ILigatureOptions.fontFeatureSettings} to the texture atlas.
+     *
      *
      * @param terminal The terminal the addon is being loaded in.
      */
@@ -40,19 +43,28 @@ declare module '@xterm/addon-ligatures' {
    */
   export interface ILigatureOptions {
     /**
-     * Fallback ligatures to use when the font access API is either not supported by the browser or
-     * access is denied. The default set of ligatures is taken from Iosevka's default "calt"
-     * ligation set: https://typeof.net/Iosevka/
+     * Fallback ligatures to use when the font access API is either not
+     * supported by the browser or access is denied. The default set of
+     * ligatures is taken from Iosevka's default "calt" ligation set:
+     * https://typeof.net/Iosevka/
      *
      * ```
      * <-- <--- <<- <- -> ->> --> --->
      * <== <=== <<= <= => =>> ==> ===> >= >>=
-     * <-> <--> <---> <----> <=> <==> <===> <====> -------->
-     * <~~ <~ ~> ~~> :: ::: == != === !==
-     * := :- :+ <* <*> *> <| <|> |> +: -: =: :>
-     * ++ +++ <!-- <!--- <***>
-     * ```
+     * <-> <--> <---> <----> <=> <==> <===> <====> :: :::
+     * <~~ </ </> /> ~~> == != /= ~= <> === !== !===
+     * <: := *= *+ <* <*> *> <| <|> |> +* =* =: :>
+     * /* <close block comment> +++ <!-- <!---
      */
     fallbackLigatures: string[]
+
+    /**
+     * The CSS `font-feature-settings` value to use for enabling ligatures. This
+     * also supports font variants for example with a value like
+     * `"calt" on, "ss03"`.
+     *
+     * The default value is `"calt" on`.
+     */
+    fontFeatureSettings: string;
   }
 }

addons/addon-webgl/src/GlyphRenderer.ts

@@ -238,9 +238,9 @@ export class GlyphRenderer extends Disposable {
 
     // Get the glyph
     if (chars && chars.length > 1) {
-      $glyph = this._atlas.getRasterizedGlyphCombinedChar(chars, bg, fg, ext, false);
+      $glyph = this._atlas.getRasterizedGlyphCombinedChar(chars, bg, fg, ext, false, this._terminal.element);
     } else {
-      $glyph = this._atlas.getRasterizedGlyph(code, bg, fg, ext, false);
+      $glyph = this._atlas.getRasterizedGlyph(code, bg, fg, ext, false, this._terminal.element);
     }
 
     $leftCellPadding = Math.floor((this._dimensions.device.cell.width - this._dimensions.device.char.width) / 2);