Deprecate fast scroll modifier as it's no longer possible

Not possible via the component we import. We could add this but I
doubt it was being used anyway.

demo/client.ts

@@ -437,12 +437,13 @@ function initOptions(term: Terminal): void {
     'logger',
     'theme',
     'windowOptions',
-    'windowsPty'
+    'windowsPty',
+    // Deprecated
+    'fastScrollModifier'
   ];
   const stringOptions = {
     cursorStyle: ['block', 'underline', 'bar'],
     cursorInactiveStyle: ['outline', 'block', 'bar', 'underline', 'none'],
-    fastScrollModifier: ['none', 'alt', 'ctrl', 'shift'],
     fontFamily: null,
     fontWeight: ['normal', 'bold', '100', '200', '300', '400', '500', '600', '700', '800', '900'],
     fontWeightBold: ['normal', 'bold', '100', '200', '300', '400', '500', '600', '700', '800', '900'],

src/browser/Viewport.ts

@@ -41,7 +41,6 @@ export class Viewport extends Disposable {
     super();
 
     // TODO: Support smooth scroll
-    // TODO: Support fastScrollModifier?
 
     this._scrollableElement = this.register(new DomScrollableElement(screenElement, {
       vertical: ScrollbarVisibility.Auto,

src/common/services/Services.ts

@@ -219,6 +219,7 @@ export interface ITerminalOptions {
   disableStdin?: boolean;
   documentOverride?: any | null;
   drawBoldTextInBrightColors?: boolean;
+  /** @deprecated No longer supported */
   fastScrollModifier?: 'none' | 'alt' | 'ctrl' | 'shift';
   fastScrollSensitivity?: number;
   fontSize?: number;

typings/xterm-headless.d.ts

@@ -83,6 +83,8 @@ declare module '@xterm/headless' {
 
     /**
      * The modifier key hold to multiply scroll speed.
+     * @deprecated This option is no longer available and will always use alt. Setting this will be
+     * ignored.
      */
     fastScrollModifier?: 'none' | 'alt' | 'ctrl' | 'shift';
 

typings/xterm.d.ts

@@ -109,11 +109,13 @@ declare module '@xterm/xterm' {
 
     /**
      * The modifier key hold to multiply scroll speed.
+     * @deprecated This option is no longer available and will always use alt. Setting this will be
+     * ignored.
      */
     fastScrollModifier?: 'none' | 'alt' | 'ctrl' | 'shift';
 
     /**
-     * The scroll speed multiplier used for fast scrolling.
+     * The scroll speed multiplier used for fast scrolling when `Alt` is held.
      */
     fastScrollSensitivity?: number;