Move WidthCache measure container to helper container

src/browser/Terminal.ts

@@ -561,7 +561,7 @@ export class Terminal extends CoreTerminal implements ITerminal {
   }
 
   private _createRenderer(): IRenderer {
-    return this._instantiationService.createInstance(DomRenderer, this.element!, this.screenElement!, this._viewportElement!, this.linkifier2);
+    return this._instantiationService.createInstance(DomRenderer, this._document!, this.element!, this.screenElement!, this._viewportElement!, this._helperContainer!, this.linkifier2);
   }
 
   /**

src/browser/renderer/dom/DomRenderer.ts

@@ -47,9 +47,11 @@ export class DomRenderer extends Disposable implements IRenderer {
   public readonly onRequestRedraw = this.register(new EventEmitter<IRequestRedrawEvent>()).event;
 
   constructor(
+    private readonly _document: Document,
     private readonly _element: HTMLElement,
     private readonly _screenElement: HTMLElement,
     private readonly _viewportElement: HTMLElement,
+    private readonly _helperContainer: HTMLElement,
     private readonly _linkifier2: ILinkifier2,
     @IInstantiationService instantiationService: IInstantiationService,
     @ICharSizeService private readonly _charSizeService: ICharSizeService,
@@ -59,12 +61,12 @@ export class DomRenderer extends Disposable implements IRenderer {
     @IThemeService private readonly _themeService: IThemeService
   ) {
     super();
-    this._rowContainer = document.createElement('div');
+    this._rowContainer = this._document.createElement('div');
     this._rowContainer.classList.add(ROW_CONTAINER_CLASS);
     this._rowContainer.style.lineHeight = 'normal';
     this._rowContainer.setAttribute('aria-hidden', 'true');
     this._refreshRowElements(this._bufferService.cols, this._bufferService.rows);
-    this._selectionContainer = document.createElement('div');
+    this._selectionContainer = this._document.createElement('div');
     this._selectionContainer.classList.add(SELECTION_CLASS);
     this._selectionContainer.setAttribute('aria-hidden', 'true');
 
@@ -96,7 +98,7 @@ export class DomRenderer extends Disposable implements IRenderer {
       this._dimensionsStyleElement.remove();
     }));
 
-    this._widthCache = new WidthCache(document);
+    this._widthCache = new WidthCache(this._document, this._helperContainer);
     this._widthCache.setFont(
       this._optionsService.rawOptions.fontFamily,
       this._optionsService.rawOptions.fontSize,
@@ -130,7 +132,7 @@ export class DomRenderer extends Disposable implements IRenderer {
     }
 
     if (!this._dimensionsStyleElement) {
-      this._dimensionsStyleElement = document.createElement('style');
+      this._dimensionsStyleElement = this._document.createElement('style');
       this._screenElement.appendChild(this._dimensionsStyleElement);
     }
 
@@ -150,7 +152,7 @@ export class DomRenderer extends Disposable implements IRenderer {
 
   private _injectCss(colors: ReadonlyColorSet): void {
     if (!this._themeStyleElement) {
-      this._themeStyleElement = document.createElement('style');
+      this._themeStyleElement = this._document.createElement('style');
       this._screenElement.appendChild(this._themeStyleElement);
     }
 
@@ -276,7 +278,7 @@ export class DomRenderer extends Disposable implements IRenderer {
   private _refreshRowElements(cols: number, rows: number): void {
     // Add missing elements
     for (let i = this._rowElements.length; i <= rows; i++) {
-      const row = document.createElement('div');
+      const row = this._document.createElement('div');
       this._rowContainer.appendChild(row);
       this._rowElements.push(row);
     }
@@ -330,7 +332,7 @@ export class DomRenderer extends Disposable implements IRenderer {
     }
 
     // Create the selections
-    const documentFragment = document.createDocumentFragment();
+    const documentFragment = this._document.createDocumentFragment();
 
     if (columnSelectMode) {
       const isXFlipped = start[0] > end[0];
@@ -362,7 +364,7 @@ export class DomRenderer extends Disposable implements IRenderer {
    * @param colEnd The end columns.
    */
   private _createSelectionElement(row: number, colStart: number, colEnd: number, rowCount: number = 1): HTMLElement {
-    const element = document.createElement('div');
+    const element = this._document.createElement('div');
     element.style.height = `${rowCount * this.dimensions.css.cell.height}px`;
     element.style.top = `${row * this.dimensions.css.cell.height}px`;
     element.style.left = `${colStart * this.dimensions.css.cell.width}px`;

src/browser/renderer/dom/DomRendererRowFactory.test.ts

@@ -14,8 +14,8 @@ import { MockCoreService, MockDecorationService, MockOptionsService } from 'comm
 import { MockCharacterJoinerService, MockCoreBrowserService, MockThemeService } from 'browser/TestUtils.test';
 import { TestWidthCache } from 'browser/renderer/dom/WidthCache.test';
 
-
-const EMPTY_WIDTH = new TestWidthCache(new jsdom.JSDOM('').window.document);
+const dom = new jsdom.JSDOM('');
+const EMPTY_WIDTH = new TestWidthCache(dom.window.document, dom.window.document.createElement('div'));
 
 
 describe('DomRendererRowFactory', () => {

src/browser/renderer/dom/WidthCache.test.ts

@@ -36,7 +36,8 @@ function castf32(v: number): number {
 describe('WidthCache', () => {
   let wc: TestWidthCache;
   beforeEach(() => {
-    wc = new TestWidthCache(new jsdom.JSDOM('').window.document);
+    const dom = new jsdom.JSDOM('');
+    wc = new TestWidthCache(dom.window.document, dom.window.document.createElement('div'));
     wc.setFont('monospace', 15, 'normal', 'bold');
   });
   describe('cache invalidation', () => {

src/browser/renderer/dom/WidthCache.ts

@@ -45,25 +45,28 @@ export class WidthCache implements IDisposable {
   private _container: HTMLDivElement;
   private _measureElements: HTMLSpanElement[] = [];
 
-  constructor(_document: Document) {
+  constructor(_document: Document, _helperContainer: HTMLElement) {
     this._container = _document.createElement('div');
-    this._container.style.position = 'absolute';
-    this._container.style.top = '-50000px';
-    this._container.style.width = '50000px';
+    this._container.classList.add('xterm-width-cache-measure-container');
+    this._container.setAttribute('aria-hidden', 'true');
     // SP should stack in spans
     this._container.style.whiteSpace = 'pre';
     // avoid undercuts in non-monospace fonts from kerning
     this._container.style.fontKerning = 'none';
 
     const regular = _document.createElement('span');
+    regular.classList.add('xterm-char-measure-element');
 
     const bold = _document.createElement('span');
+    bold.classList.add('xterm-char-measure-element');
     bold.style.fontWeight = 'bold';
 
     const italic = _document.createElement('span');
+    italic.classList.add('xterm-char-measure-element');
     italic.style.fontStyle = 'italic';
 
     const boldItalic = _document.createElement('span');
+    boldItalic.classList.add('xterm-char-measure-element');
     boldItalic.style.fontWeight = 'bold';
     boldItalic.style.fontStyle = 'italic';
 
@@ -74,7 +77,7 @@ export class WidthCache implements IDisposable {
     this._container.appendChild(italic);
     this._container.appendChild(boldItalic);
 
-    _document.body.appendChild(this._container);
+    _helperContainer.appendChild(this._container);
 
     this.clear();
   }