Merge remote-tracking branch 'upstream/master' into image-ext

Also make faster by removing much loadCell calls.

addons/addon-image/README.md

@@ -98,7 +98,7 @@ terminal.loadAddon(imageAddon);
   Set by default, change it with `{iipSupport: true}`.
 
   The IIP implementation has the following features / restrictions (sequence will silently fail for unmet conditions):
-  - Supported formats: PNG, JPEG, GIF and QOI
+  - Supported formats: PNG, JPEG, GIF, QOI, WEBP and AVIF
   - No animation support.
   - Image type hinting is not supported (always deducted from data header).
   - File download is not supported.
@@ -112,6 +112,13 @@ terminal.loadAddon(imageAddon);
   - ReportCellSize sequence is supported.
   - Hi-res display support is currently limited (image gets blurred).
 
+- **Note on IIP image format support**  
+  For all image formats except QOI the addon only does the dimension extraction and leaves
+  the image decoding to the underlying browser engine. Note that some formats are implemented
+  and enabled with different constraints by browser vendors, especially newer formats
+  (e.g. under Firefox you might need to change the setting _image.avif.compliance_strictness_ to 0
+  to get broader AVIF support).
+
 - **Kitty Graphics Support (TGP)**  
   Set by default, change it with `{kittySupport: true}`.
 

addons/addon-image/src/IIPHandler.ts

@@ -39,7 +39,6 @@ export class IIPHandler implements IOscHandler, IResetHandler {
   private _header: IHeaderFields = DEFAULT_HEADER;
   private _dec: Base64Decoder;
   private _qoiDec: QoiDecoder;
-  private _metrics = UNSUPPORTED_TYPE;
   private _isMultipart = false;
   private _abortMulti = false;
 
@@ -63,7 +62,6 @@ export class IIPHandler implements IOscHandler, IResetHandler {
 
   public start(): void {
     this._aborted = false;
-    this._metrics  = UNSUPPORTED_TYPE;
     this._hp.reset();
   }
 
@@ -120,14 +118,14 @@ export class IIPHandler implements IOscHandler, IResetHandler {
 
     if (seqType === SequenceType.REPORTCELLSIZE) {
       // OSC 1337 ; ReportCellSize=[height];[width];[scale] ST
-      let width = CELL_SIZE_DEFAULT.width;
-      let height = CELL_SIZE_DEFAULT.height;
+      let w = CELL_SIZE_DEFAULT.width;
+      let h = CELL_SIZE_DEFAULT.height;
       if (this._renderer.dimensions) {
-        width = this._renderer.dimensions.css.canvas.width / this._coreTerminal.cols;
-        height = this._renderer.dimensions.css.canvas.height / this._coreTerminal.rows;
+        w = this._renderer.dimensions.css.canvas.width / this._coreTerminal.cols;
+        h = this._renderer.dimensions.css.canvas.height / this._coreTerminal.rows;
       }
       const scale = this._coreTerminal._core._coreBrowserService?.dpr ?? 1;
-      const report = `\x1b]1337;ReportCellSize=${height.toFixed(3)};${width.toFixed(3)};${scale.toFixed(3)}\x1b\\`;
+      const report = `\x1b]1337;ReportCellSize=${h.toFixed(3)};${w.toFixed(3)};${scale.toFixed(3)}\x1b\\`;
       this._coreTerminal.input(report, false);
       return true;
     }
@@ -154,17 +152,24 @@ export class IIPHandler implements IOscHandler, IResetHandler {
 
     // early exit condition chain
     let cond: number | boolean;
+    let metrics = UNSUPPORTED_TYPE;
     if (cond = success) {
       if (cond = !this._dec.end()) {
-        this._metrics = imageType(this._dec.data8);
-        if (cond = this._metrics.mime !== 'unsupported') {
-          w = this._metrics.width;
-          h = this._metrics.height;
+        metrics = imageType(this._dec.data8);
+        if (cond = metrics.mime !== 'unsupported') {
+          w = metrics.width;
+          h = metrics.height;
           if (cond = w && h && w * h < this._opts.pixelLimit) {
             [w, h] = this._resize(w, h).map(Math.floor);
             cond = w && h && w * h < this._opts.pixelLimit;
+          } else {
+            console.warn(`IIP: image dimension issue ${metrics.width}x${metrics.height}`);
           }
+        } else {
+          console.warn('IIP: unsupported image type');
         }
+      } else {
+        console.warn('IIP: error during BASE64 decoding');
       }
     }
     if (!cond) {
@@ -173,7 +178,7 @@ export class IIPHandler implements IOscHandler, IResetHandler {
     }
 
     let blob: Blob | ImageData;
-    if (this._metrics.mime === 'image/qoi') {
+    if (metrics.mime === 'image/qoi') {
       const data = this._qoiDec.decode(this._dec.data8);
       blob = new ImageData(
         new Uint8ClampedArray(data.buffer, data.byteOffset, data.byteLength),
@@ -190,13 +195,17 @@ export class IIPHandler implements IOscHandler, IResetHandler {
         return true;
       }
     } else {
-      blob = new Blob([this._dec.data8], { type: this._metrics.mime });
+      blob = new Blob([this._dec.data8], { type: metrics.mime });
     }
     this._dec.release();
     return createImageBitmap(blob, { resizeWidth: w, resizeHeight: h })
       .then(bm => {
         this._storage.addImage(bm);
         return true;
+      })
+      .catch(e => {
+        console.warn(`IIP: decoding error ${metrics.mime} ${metrics.width}x${metrics.height}`, e);
+        return true;
       });
   }
 

addons/addon-image/src/IIPMetrics.test.ts

@@ -32,6 +32,28 @@ const TEST_IMAGES: [string, IMetrics][] = [
   ['agfa-makernotes.jpg', { mime: 'image/jpeg', width: 8, height: 8 }],
   ['sony-alpha-6000.jpg', { mime: 'image/jpeg', width: 6000, height: 4000 }],
   ['dice.qoi', { mime: 'image/qoi', width: 800, height: 600 }],
+  // VP8
+  ['1.webp', { mime: 'image/webp', width: 550, height: 368 }],
+  ['2.webp', { mime: 'image/webp', width: 550, height: 404 }],
+  ['3.webp', { mime: 'image/webp', width: 1280, height: 720 }],
+  ['4.webp', { mime: 'image/webp', width: 1024, height: 772 }],
+  ['5.webp', { mime: 'image/webp', width: 1024, height: 752 }],
+  // VP8X
+  ['1_webp_a.webp', { mime: 'image/webp', width: 400, height: 301 }],
+  ['2_webp_a.webp', { mime: 'image/webp', width: 386, height: 395 }],
+  ['3_webp_a.webp', { mime: 'image/webp', width: 800, height: 600 }],
+  ['4_webp_a.webp', { mime: 'image/webp', width: 421, height: 163 }],
+  ['5_webp_a.webp', { mime: 'image/webp', width: 300, height: 300 }],
+  // VP8L
+  ['1_webp_ll.webp', { mime: 'image/webp', width: 400, height: 301 }],
+  ['2_webp_ll.webp', { mime: 'image/webp', width: 386, height: 395 }],
+  ['3_webp_ll.webp', { mime: 'image/webp', width: 800, height: 600 }],
+  ['4_webp_ll.webp', { mime: 'image/webp', width: 421, height: 163 }],
+  ['5_webp_ll.webp', { mime: 'image/webp', width: 300, height: 300 }],
+  // some AVIF test images
+  ['fox.profile2.12bpc.yuv444.odd-width.odd-height.avif', { mime: 'image/avif', width: 1203, height: 799 }],
+  ['hato.profile0.8bpc.yuv420.avif', { mime: 'image/avif', width: 3082, height: 2048 }],
+  ['kimono.crop.avif', { mime: 'image/avif', width: 722, height: 1024 }],
 ];
 
 

addons/addon-image/src/IIPMetrics.ts

@@ -4,7 +4,7 @@
  */
 
 
-export type ImageType = 'image/png' | 'image/jpeg' | 'image/gif' | 'image/qoi' | 'unsupported' | '';
+export type ImageType = 'image/png' | 'image/jpeg' | 'image/gif' | 'image/qoi' | 'image/webp' | 'image/avif' | 'unsupported' | '';
 
 export interface IMetrics {
   mime: ImageType;
@@ -19,16 +19,16 @@ export const UNSUPPORTED_TYPE: IMetrics = {
 };
 
 export function imageType(d: Uint8Array): IMetrics {
-  if (d.length < 24) {
+  if (d.length < 32) {
     return UNSUPPORTED_TYPE;
   }
-  const d32 = new Uint32Array(d.buffer, d.byteOffset, 6);
+  const d32 = new Uint32Array(d.buffer, d.byteOffset, 8);
   // PNG: 89 50 4E 47 0D 0A 1A 0A (8 first bytes == magic number for PNG)
   // + first chunk must be IHDR
   if (d32[0] === 0x474E5089 && d32[1] === 0x0A1A0A0D && d32[3] === 0x52444849) {
     return {
       mime: 'image/png',
-      width: d[16] << 24 | d[17] << 16 | d[18] << 8 | d[19],
+      width:  d[16] << 24 | d[17] << 16 | d[18] << 8 | d[19],
       height: d[20] << 24 | d[21] << 16 | d[22] << 8 | d[23]
     };
   }
@@ -41,7 +41,7 @@ export function imageType(d: Uint8Array): IMetrics {
   if (d32[0] === 0x38464947 && (d[4] === 0x37 || d[4] === 0x39) && d[5] === 0x61) {
     return {
       mime: 'image/gif',
-      width: d[7] << 8 | d[6],
+      width:  d[7] << 8 | d[6],
       height: d[9] << 8 | d[8]
     };
   }
@@ -49,13 +49,71 @@ export function imageType(d: Uint8Array): IMetrics {
   if (d32[0] === 0x66696F71) {
     return {
       mime: 'image/qoi',
-      width: d[4] << 24 | d[5] << 16 | d[6] << 8 | d[7],
+      width:  d[4] << 24 | d[5] << 16 | d[6] << 8 | d[7],
       height: d[8] << 24 | d[9] << 16 | d[10] << 8 | d[11]
     };
   }
+  // WEBP: RIFF | xxxx | WEBP | VP8x
+  if (d32[0] === 0x46464952 && d32[2] === 0x50424557 && (d32[3] & 0xFFFFFF) === 0x385056) {
+    switch (d[15]) {
+      case 0x58:  // Extended WebP VP8X --> "X"
+        return {
+          mime: 'image/webp',
+          width:  (d[24] | d[25] << 8 | d[26] << 16) + 1,
+          height: (d[27] | d[28] << 8 | d[29] << 16) + 1
+        };
+      case 0x4C:  // Lossless WebP VP8L --> "L"
+        if (d[20] !== 0x2f) return UNSUPPORTED_TYPE;
+        const dim = d[21] | d[22] << 8 | d[23] << 16 | d[24] << 24;
+        return {
+          mime: 'image/webp',
+          width:  (dim        & 0x3FFF) + 1,
+          height: (dim >>> 14 & 0x3FFF) + 1
+        };
+      case 0x20:  // Lossy WebP VP8  --> " "
+        if (d[23] !== 0x9d || d[24] !== 0x01 || d[25] !== 0x2a) return UNSUPPORTED_TYPE;
+        return {
+          mime: 'image/webp',
+          width:  (d[26] | d[27] << 8) & 0x3FFF,
+          height: (d[28] | d[29] << 8) & 0x3FFF
+        };
+    }
+    return UNSUPPORTED_TYPE;
+  }
+  // AVIF: Box size | ftyp | avif/avis
+  if (d32[1] === 0x70797466 && (d32[2] === 0x66697661 || d32[2] === 0x73697661)) {
+    let pos = -1;
+    // search for ispe box within first 1024 bytes
+    const limit = Math.min(d.length - 16, 1024);
+    for (let i = 8; i < limit; i++) {
+      // scan for ispe
+      if (d[i] === 0x69 && d[i + 1] === 0x73 && d[i + 2] === 0x70 && d[i + 3] === 0x65) {
+        pos = i;
+        break;
+      }
+    }
+    if (pos !== -1) {
+      // dimensions are in BE at +8 (width) at +12 (height)
+      const width =
+        d[pos +  8] << 24 |
+        d[pos +  9] << 16 |
+        d[pos + 10] <<  8 |
+        d[pos + 11];
+      const height =
+        d[pos + 12] << 24 |
+        d[pos + 13] << 16 |
+        d[pos + 14] <<  8 |
+        d[pos + 15];
+      if (width > 0 && height > 0) {
+        return { mime: 'image/avif', width, height };
+      }
+    }
+    return UNSUPPORTED_TYPE;
+  }
   return UNSUPPORTED_TYPE;
 }
 
+
 function jpgSize(d: Uint8Array): [number, number] {
   const len = d.length;
   let i = 4;

addons/addon-image/src/ImageStorage.ts

@@ -346,52 +346,44 @@ export class ImageStorage implements IDisposable {
     const placeholderCalls: { col: number, row: number, count: number }[] = [];
 
     // walk all cells in viewport and collect tiles found
-    // Note: We check extended directly (not just HAS_EXTENDED flag)
-    // because text writes clear the BG flag but leave image tile data intact.
-    // This lets top-layer images survive text overwrites (kitty C=1 behavior).
     for (let row = start; row <= end; ++row) {
       const line = buffer.lines.get(row + buffer.ydisp);
       if (!line) return;
-      const workCell = this._workCell;
       for (let col = 0; col < cols; ++col) {
-        line.loadCell(col, workCell);
-        const e = workCell.hasExtendedAttrs() && workCell.extended.payload;
-        if (!(e instanceof ImageTileInfo)) {
-          continue;
-        }
-        const imageId = e.imageId;
-        if (imageId === undefined || imageId === -1) {
-          continue;
-        }
-        const imgSpec = this._images.get(imageId);
-        if (e.tileId !== -1) {
-          const startTile = e.tileId;
-          const startCol = col;
-          let count = 1;
-          /**
-           * merge tiles to the right into a single draw call, if:
-           * - not at end of line
-           * - cell has same image id
-           * - cell has consecutive tile id
-           * Also check _extendedAttrs directly for cells where text cleared HAS_EXTENDED.
-           */
-          while (++col < cols) {
-            line.loadCell(col, workCell);
-            const nextE = workCell.hasExtendedAttrs() && workCell.extended.payload;
-            if (!(nextE instanceof ImageTileInfo) || !nextE || nextE.imageId !== imageId || nextE.tileId !== startTile + count) {
-              break;
-            }
-            count++;
+        const e = line.getExtended(col)?.payload;
+        if (e instanceof ImageTileInfo) {
+          const imageId = e.imageId;
+          if (imageId === undefined || imageId === -1) {
+            continue;
           }
-          col--;
-          if (imgSpec) {
-            if (imgSpec.actual) {
-              drawCalls.push({ imgSpec, tileId: startTile, col: startCol, row, count });
+          const imgSpec = this._images.get(imageId);
+          if (e.tileId !== -1) {
+            const startTile = e.tileId;
+            const startCol = col;
+            let count = 1;
+            /**
+             * merge tiles to the right into a single draw call, if:
+             * - not at end of line
+             * - cell has same image id
+             * - cell has consecutive tile id
+             */
+            while (++col < cols) {
+              const nextE = line.getExtended(col)?.payload;
+              if (!(nextE instanceof ImageTileInfo) || nextE.imageId !== imageId || nextE.tileId !== startTile + count) {
+                break;
+              }
+              count++;
             }
-          } else if (this._opts.showPlaceholder) {
-            placeholderCalls.push({ col: startCol, row, count });
+            col--;
+            if (imgSpec) {
+              if (imgSpec.actual) {
+                drawCalls.push({ imgSpec, tileId: startTile, col: startCol, row, count });
+              }
+            } else if (this._opts.showPlaceholder) {
+              placeholderCalls.push({ col: startCol, row, count });
+            }
+            this._fullyCleared = false;
           }
-          this._fullyCleared = false;
         }
       }
     }
@@ -428,15 +420,10 @@ export class ImageStorage implements IDisposable {
     const buffer = this._terminal._core.buffer;
     const rows = buffer.lines.length;
     const oldCol = this._viewportMetrics.cols - 1;
-    const workCell = this._workCell;
     for (let row = 0; row < rows; ++row) {
       const line = buffer.lines.get(row)!;
-      line.loadCell(oldCol, workCell);
-      if (workCell.hasExtendedAttrs()) {
-        const e = workCell.extended.payload;
-        if (!(e instanceof ImageTileInfo)) {
-          continue;
-        }
+      const e = line.getExtended(oldCol)?.payload;
+      if (e instanceof ImageTileInfo) {
         const imageId = e.imageId;
         if (imageId === undefined || imageId === -1) {
           continue;
@@ -480,8 +467,8 @@ export class ImageStorage implements IDisposable {
   public getImageAtBufferCell(x: number, y: number): HTMLCanvasElement | undefined {
     const buffer = this._terminal._core.buffer;
     const line = buffer.lines.get(y);
-    if (line && line.loadCell(x, this._workCell).hasExtendedAttrs()) {
-      const e = this._workCell.extended.payload;
+    if (line) {
+      const e = line.getExtended(x)?.payload;
       if (e instanceof ImageTileInfo && e.imageId && e.imageId !== -1) {
         const orig = this._images.get(e.imageId)?.orig;
         if (window.ImageBitmap && orig instanceof ImageBitmap) {
@@ -500,8 +487,8 @@ export class ImageStorage implements IDisposable {
   public extractTileAtBufferCell(x: number, y: number): HTMLCanvasElement | undefined {
     const buffer = this._terminal._core.buffer;
     const line = buffer.lines.get(y);
-    if (line && line.loadCell(x, this._workCell).hasExtendedAttrs()) {
-      const e = this._workCell.extended.payload;
+    if (line) {
+      const e = line.getExtended(x)?.payload;
       if (e instanceof ImageTileInfo && e.imageId && e.imageId !== -1 && e.tileId !== -1) {
         const spec = this._images.get(e.imageId);
         if (spec) {
@@ -552,7 +539,7 @@ export class ImageStorage implements IDisposable {
       workCell.extended.payload = new ImageTileInfo(imageId, tileId);
       return;
     }
-    // fall-through: always create new ExtendedAttrsImage entry
+    // fall-through: always create new ExtendedAttrs entry
     const extattr = workCell.extended.clone();
     extattr.payload = new ImageTileInfo(imageId, tileId);
     workCell.extended = extattr;
@@ -574,16 +561,12 @@ export class ImageStorage implements IDisposable {
       if (!line) {
         continue;
       }
-      const workCell = this._workCell;
       for (let x = 0; x < this._terminal.cols; ++x) {
-        line.loadCell(x, workCell);
-        if (workCell.hasExtendedAttrs()) {
-          const payload = workCell.extended.payload;
-          if (payload instanceof ImageTileInfo) {
-            const spec = this._images.get(payload.imageId);
-            if (spec) {
-              spec.tileCount++;
-            }
+        const payload = line.getExtended(x)?.payload;
+        if (payload instanceof ImageTileInfo) {
+          const spec = this._images.get(payload.imageId);
+          if (spec) {
+            spec.tileCount++;
           }
         }
       }

addons/addon-image/test/ImageAddon.test.ts

@@ -435,6 +435,15 @@ test.describe('ImageAddon', () => {
       });
     }
   });
+
+  test.describe('text overwrite removes tiles', () => {
+    test('sixel', async () => {
+      await assertTextClearsTiles(SIXEL_SEQ_0);
+    });
+    test('iip', async () => {
+      await assertTextClearsTiles(TESTDATA_IIP[0][0]);
+    });
+  });
 });
 
 /**
@@ -472,3 +481,20 @@ async function getOrigSize(id: number): Promise<[number, number]> {
 async function getImageAtBufferCell(x: number, y: number): Promise<string | undefined> {
   return ctx.page.evaluate<any>(`window.imageAddon.getImageAtBufferCell(${x}, ${y})?.toDataURL('image/png')`);
 }
+
+async function hasTileAtBufferCell(x: number, y: number): Promise<boolean> {
+  return ctx.page.evaluate(`!!window.imageAddon.extractTileAtBufferCell(${x}, ${y})`);
+}
+
+async function assertTextClearsTiles(imageSeq: string): Promise<void> {
+  await ctx.proxy.write('\x1b[H' + imageSeq);
+  await pollFor(ctx.page, '!!window.imageAddon.extractTileAtBufferCell(5, 1)', true);
+  ok(await hasTileAtBufferCell(0, 1));
+  await ctx.proxy.write('\x1b[2;6H#######');
+  for (let x = 5; x < 12; x++) {
+    strictEqual(await hasTileAtBufferCell(x, 1), false);
+  }
+  ok(await hasTileAtBufferCell(0, 1));
+  ok(await hasTileAtBufferCell(13, 1));
+  ok(((await ctx.page.evaluate('window.term.buffer.active.getLine(1).translateToString(true)')) as string).includes('#######'));
+}

addons/addon-image/test/KittyGraphics.test.ts

@@ -2213,6 +2213,21 @@ test.describe('Kitty Graphics Protocol', () => {
       await pollFor(ctx.page, 'window._imageAddedCount', 2);
     });
   });
+
+  test.describe('text overwrite removes tiles', () => {
+    test('a=T placement', async () => {
+      await ctx.proxy.write(`\x1b[H\x1b_Ga=T,f=100;${KITTY_MULTICOLOR_200X100_BASE64}\x1b\\`);
+      await pollFor(ctx.page, '!!window.imageAddon.extractTileAtBufferCell(5, 1)', true);
+      ok(await hasTileAtBufferCell(0, 1));
+      await ctx.proxy.write('\x1b[2;6H#######');
+      for (let x = 5; x < 12; x++) {
+        strictEqual(await hasTileAtBufferCell(x, 1), false);
+      }
+      ok(await hasTileAtBufferCell(0, 1));
+      ok(await hasTileAtBufferCell(13, 1));
+      ok(((await ctx.page.evaluate('window.term.buffer.active.getLine(1).translateToString(true)')) as string).includes('#######'));
+    });
+  });
 });
 
 /**
@@ -2262,3 +2277,7 @@ async function getPixels(col: number, row: number, x: number, y: number, w: numb
     return Array.from(ctx2d.getImageData(x, y, w, h).data);
   }, [col, row, x, y, w, h]);
 }
+
+async function hasTileAtBufferCell(x: number, y: number): Promise<boolean> {
+  return ctx.page.evaluate(`!!window.imageAddon.extractTileAtBufferCell(${x}, ${y})`);
+}

addons/addon-webgl/src/customGlyphs/CustomGlyphRasterizer.test.ts

@@ -0,0 +1,54 @@
+/**
+ * Copyright (c) 2026 The xterm.js authors. All rights reserved.
+ * @license MIT
+ */
+
+import { assert } from 'chai';
+import { createPatternCanvas } from './CustomGlyphRasterizer';
+
+describe('CustomGlyphRasterizer', () => {
+  describe('createPatternCanvas', () => {
+    it('prefers an offscreen canvas without using the DOM canvas factory', () => {
+      const expectedCanvas = {} as OffscreenCanvas;
+      const calls: string[] = [];
+
+      const canvas = createPatternCanvas(
+        2,
+        3,
+        (width, height) => {
+          calls.push(`offscreen:${width}x${height}`);
+          return expectedCanvas;
+        },
+        () => {
+          calls.push('dom');
+          return {} as HTMLCanvasElement;
+        }
+      );
+
+      assert.deepEqual({ canvas, calls }, {
+        canvas: expectedCanvas,
+        calls: ['offscreen:2x3']
+      });
+    });
+
+    it('uses the main-realm DOM canvas factory when OffscreenCanvas is unavailable', () => {
+      const expectedCanvas = {} as HTMLCanvasElement;
+      const calls: string[] = [];
+
+      const canvas = createPatternCanvas(
+        4,
+        5,
+        undefined,
+        (width, height) => {
+          calls.push(`dom:${width}x${height}`);
+          return expectedCanvas;
+        }
+      );
+
+      assert.deepEqual({ canvas, calls }, {
+        canvas: expectedCanvas,
+        calls: ['dom:4x5']
+      });
+    });
+  });
+});

addons/addon-webgl/src/customGlyphs/CustomGlyphRasterizer.ts

@@ -8,6 +8,29 @@ import type { ILogService } from 'common/services/Services';
 import { customGlyphDefinitions } from './CustomGlyphDefinitions';
 import { CustomGlyphDefinitionType, CustomGlyphScaleType, CustomGlyphVectorType, type CustomGlyphDefinitionPart, type CustomGlyphPathDrawFunctionDefinition, type CustomGlyphPatternDefinition, type ICustomGlyphSolidOctantBlockVector, type ICustomGlyphVectorShape } from './Types';
 
+type PatternCanvas = HTMLCanvasElement | OffscreenCanvas;
+type PatternCanvasFactory = (width: number, height: number) => PatternCanvas;
+
+const createOffscreenPatternCanvas: PatternCanvasFactory | undefined = typeof OffscreenCanvas === 'undefined'
+  ? undefined
+  : (width, height) => new OffscreenCanvas(width, height);
+
+const createDomPatternCanvas: PatternCanvasFactory = (width, height) => {
+  const canvas = document.createElement('canvas');
+  canvas.width = width;
+  canvas.height = height;
+  return canvas;
+};
+
+export function createPatternCanvas(
+  width: number,
+  height: number,
+  offscreenCanvasFactory: PatternCanvasFactory | undefined = createOffscreenPatternCanvas,
+  domCanvasFactory: PatternCanvasFactory = createDomPatternCanvas
+): PatternCanvas {
+  return offscreenCanvasFactory?.(width, height) ?? domCanvasFactory(width, height);
+}
+
 /**
  * Try drawing a custom block element or box drawing character, returning whether it was
  * successfully drawn.
@@ -458,9 +481,9 @@ function drawPatternChar(
   if (!pattern) {
     const width = charDefinition[0].length;
     const height = charDefinition.length;
-    const tmpCanvas = ctx.canvas.ownerDocument.createElement('canvas');
-    tmpCanvas.width = width;
-    tmpCanvas.height = height;
+    // The atlas canvas can be adopted into another document, so temporary resources must not use
+    // its mutable ownerDocument.
+    const tmpCanvas = createPatternCanvas(width, height);
     const tmpCtx = throwIfFalsy(tmpCanvas.getContext('2d'));
     const imageData = new ImageData(width, height);
 

addons/addon-webgl/test/WebglCustomGlyphs.test.ts

@@ -0,0 +1,77 @@
+/**
+ * Copyright (c) 2026 The xterm.js authors. All rights reserved.
+ * @license MIT
+ */
+
+import test, { expect } from '@playwright/test';
+import { platform } from 'os';
+import { ITestContext, createTestContext, openTerminal } from '../../../test/playwright/TestUtils';
+
+interface ITestRendererWithAtlasCanvas {
+  readonly _charAtlas?: {
+    readonly _tmpCanvas?: HTMLCanvasElement;
+  };
+}
+
+async function writeAndWaitForRender(ctx: ITestContext, data: string): Promise<void> {
+  const renderPromise = new Promise<void>(resolve => {
+    const disposable = ctx.proxy.onRender(() => {
+      disposable.dispose();
+      resolve();
+    });
+  });
+  await ctx.proxy.write(data);
+  await renderPromise;
+}
+
+test.describe('WebGL custom glyphs', () => {
+  if (platform() === 'linux') {
+    test.skip(({ browserName }) => browserName === 'firefox' || browserName === 'webkit');
+  }
+
+  test('pattern glyphs render after the terminal is adopted into another document', async ({ browser }) => {
+    const ctx = await createTestContext(browser);
+    const errors: string[] = [];
+    const onError = (error: Error): void => { errors.push(error.message); };
+    ctx.page.on('pageerror', onError);
+    try {
+      await openTerminal(ctx);
+      await ctx.page.evaluate(`
+        window.addon = new window.WebglAddon({ customGlyphs: true });
+        window.term.loadAddon(window.addon);
+      `);
+      await ctx.page.evaluate(() => {
+        const frame = document.createElement('iframe');
+        document.body.appendChild(frame);
+        const auxiliaryDocument = frame.contentDocument;
+        if (!auxiliaryDocument?.body || !window.term.element) {
+          throw new Error('Auxiliary document and terminal element must be available');
+        }
+        const renderer = window.term._core?._renderService?._renderer?.value as ITestRendererWithAtlasCanvas | undefined;
+        const atlasCanvas = renderer?._charAtlas?._tmpCanvas;
+        if (!atlasCanvas) {
+          throw new Error('Texture atlas canvas must be available');
+        }
+        // Model the atlas state after an uncached glyph has attached the measurement canvas.
+        window.term.element.appendChild(atlasCanvas);
+        auxiliaryDocument.body.appendChild(window.term.element);
+        if (atlasCanvas.ownerDocument !== auxiliaryDocument) {
+          throw new Error('Texture atlas canvas must be adopted into the auxiliary document');
+        }
+        auxiliaryDocument.createElement = () => {
+          throw new Error('Not allowed to create elements in the auxiliary document');
+        };
+      });
+
+      await writeAndWaitForRender(ctx, '\u2591');
+      await writeAndWaitForRender(ctx, 'X');
+
+      const line = await ctx.page.evaluate(() => window.term.buffer.active.getLine(0)?.translateToString(true));
+      expect(errors, `renderer must not create pattern canvases in the auxiliary document: ${errors[0] ?? ''}`).toEqual([]);
+      expect(line).toBe('\u2591X');
+    } finally {
+      ctx.page.off('pageerror', onError);
+      await ctx.page.close();
+    }
+  });
+});

demo/client/components/window/addonImageWindow.ts

@@ -67,6 +67,8 @@ export class AddonImageWindow extends BaseWindow implements IControlWindow {
     dlIip.appendChild(dtIip);
     this._addDdWithButton(dlIip, 'image-demo3', 'palette (png File)');
     this._addDdWithButton(dlIip, 'image-demo4', 'dice (qoi MultipartFile)');
+    this._addDdWithButton(dlIip, 'image-demo5', 'rose (webp File)');
+    this._addDdWithButton(dlIip, 'image-demo6', 'kimono (avif MultipartFile)');
     container.appendChild(dlIip);
 
     // Kitty demos
@@ -173,11 +175,15 @@ export class AddonImageWindow extends BaseWindow implements IControlWindow {
     document.getElementById('image-demo2')!.addEventListener('click',
       sixelDemo('https://raw.githubusercontent.com/jerch/node-sixel/master/testfiles/test2.sixel'));
     document.getElementById('image-demo3')!.addEventListener('click',
-      iipDemo('https://raw.githubusercontent.com/jerch/node-sixel/master/palette.png'));
+      iipDemo('https://raw.githubusercontent.com/xtermjs/xterm.js/master/addons/addon-image/fixture/palette.png'));
     document.getElementById('image-demo4')!.addEventListener('click',
-      iipDemoMulti('https://raw.githubusercontent.com/jerch/xterm-wasm-parts/master/fixtures/qoi/dice.qoi'));
+      iipDemoMulti('https://raw.githubusercontent.com/xtermjs/xterm.js/master/addons/addon-image/fixture/testimages/dice.qoi'));
+    document.getElementById('image-demo5')!.addEventListener('click',
+      iipDemo('https://raw.githubusercontent.com/xtermjs/xterm.js/master/addons/addon-image/fixture/testimages/1_webp_a.webp'));
+    document.getElementById('image-demo6')!.addEventListener('click',
+      iipDemoMulti('https://raw.githubusercontent.com/xtermjs/xterm.js/master/addons/addon-image/fixture/testimages/kimono.crop.avif'));
     document.getElementById('image-demo-kitty1')!.addEventListener('click',
-      kittyDemo('https://raw.githubusercontent.com/jerch/node-sixel/master/palette.png'));
+      kittyDemo('https://raw.githubusercontent.com/xtermjs/xterm.js/master/addons/addon-image/fixture/palette.png'));
 
     // demo for image retrieval API
     this._terminal.element!.addEventListener('click', (ev: MouseEvent) => {

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

@@ -6,16 +6,14 @@
 import jsdom = require('jsdom');
 import { assert } from 'chai';
 import { DomRendererRowFactory } from './DomRendererRowFactory';
-import { NULL_CELL_CODE, NULL_CELL_WIDTH, NULL_CELL_CHAR, DEFAULT_ATTR, FgFlags, BgFlags, Attributes, UnderlineStyle } from '../../../common/buffer/Constants';
+import { DEFAULT_ATTR, FgFlags, BgFlags, Attributes, UnderlineStyle } from '../../../common/buffer/Constants';
 import { BufferLine, DEFAULT_ATTR_DATA } from '../../../common/buffer/BufferLine';
-import { BufferLineStringCache } from '../../../common/buffer/BufferLineStringCache';
 import { IBufferLine } from '../../../common/buffer/Types';
 import { CellData } from '../../../common/buffer/CellData';
 import { MockCoreService, MockDecorationService, MockOptionsService, createCellData, NULL_CELL_DATA } from '../../../common/TestUtils.test';
 import { MockCharacterJoinerService, MockCoreBrowserService, MockThemeService } from '../../TestUtils.test';
 import { TestWidthCache } from './WidthCache.test';
 
-const TEST_STRING_CACHE = new BufferLineStringCache();
 
 describe('DomRendererRowFactory', () => {
   let dom: jsdom.JSDOM;
@@ -517,7 +515,7 @@ describe('DomRendererRowFactory', () => {
   }
 
   function createEmptyLineData(cols: number): IBufferLine {
-    const lineData = new BufferLine(TEST_STRING_CACHE, cols);
+    const lineData = new BufferLine(cols);
     for (let i = 0; i < cols; i++) {
       lineData.setCell(i, NULL_CELL_DATA);
     }

src/browser/services/CharacterJoinerService.test.ts

@@ -7,12 +7,10 @@ import { assert } from 'chai';
 import { ICharacterJoinerService } from './Services';
 import { CharacterJoinerService } from './CharacterJoinerService';
 import { BufferLine } from '../../common/buffer/BufferLine';
-import { BufferLineStringCache } from '../../common/buffer/BufferLineStringCache';
 import { IBufferLine } from '../../common/buffer/Types';
 import { CellData } from '../../common/buffer/CellData';
 import { MockBufferService, createCellData } from '../../common/TestUtils.test';
 
-const TEST_STRING_CACHE = new BufferLineStringCache();
 
 describe('CharacterJoinerService', () => {
   let service: ICharacterJoinerService;
@@ -25,7 +23,7 @@ describe('CharacterJoinerService', () => {
     lines.set(2, lineData([['a -> b -', 0xFFFFFFFF], ['> c -> d', 0]]));
 
     lines.set(3, lineData([['no joined ranges']]));
-    lines.set(4, new BufferLine(TEST_STRING_CACHE, 0));
+    lines.set(4, new BufferLine(0));
     lines.set(5, lineData([['a', 0x11111111], [' -> b -> c -> '], ['d', 0x22222222]]));
     const line6 = lineData([['wi']]);
     line6.resize(line6.length + 1, createCellData(0, '￥', 2));
@@ -270,7 +268,7 @@ describe('CharacterJoinerService', () => {
 type IPartialLineData = ([string] | [string, number]);
 
 function lineData(data: IPartialLineData[]): IBufferLine {
-  const tline = new BufferLine(TEST_STRING_CACHE, 0);
+  const tline = new BufferLine(0);
   for (let i = 0; i < data.length; ++i) {
     const line = data[i][0];
     const attr = (data[i][1] || 0) as number;

src/browser/services/SelectionService.test.ts

@@ -9,13 +9,11 @@ import { SelectionModel } from '../selection/SelectionModel';
 import { IBuffer, IBufferLine } from '../../common/buffer/Types';
 import { MockBufferService, MockOptionsService, MockCoreService, MockMouseStateService, createCellData } from '../../common/TestUtils.test';
 import { BufferLine } from '../../common/buffer/BufferLine';
-import { BufferLineStringCache } from '../../common/buffer/BufferLineStringCache';
 import { IBufferService, IOptionsService } from '../../common/services/Services';
 import { MockCoreBrowserService, MockMouseService, MockRenderService } from '../TestUtils.test';
 import { CellData } from '../../common/buffer/CellData';
 import { IRenderService } from './Services';
 
-const TEST_STRING_CACHE = new BufferLineStringCache();
 
 class TestSelectionService extends SelectionService {
   constructor(
@@ -60,7 +58,7 @@ describe('SelectionService', () => {
   });
 
   function stringToRow(text: string): IBufferLine {
-    const result = new BufferLine(TEST_STRING_CACHE, text.length);
+    const result = new BufferLine(text.length);
     for (let i = 0; i < text.length; i++) {
       result.setCell(i, createCellData(0, text.charAt(i), 1));
     }
@@ -68,7 +66,7 @@ describe('SelectionService', () => {
   }
 
   function stringArrayToRow(chars: string[]): IBufferLine {
-    const line = new BufferLine(TEST_STRING_CACHE, chars.length);
+    const line = new BufferLine(chars.length);
     chars.map((c, idx) => line.setCell(idx, createCellData(0, c, 1)));
     return line;
   }
@@ -123,7 +121,7 @@ describe('SelectionService', () => {
         [0, 'o', 1, 'o'.charCodeAt(0)],
         [0, 'o', 1, 'o'.charCodeAt(0)]
       ];
-      const line = new BufferLine(TEST_STRING_CACHE, data.length);
+      const line = new BufferLine(data.length);
       for (let i = 0; i < data.length; ++i) line.setCell(i, CellData.fromCharData(data[i]));
       buffer.lines.set(0, line);
       // Ensure wide characters take up 2 columns

src/common/Event.ts

@@ -27,11 +27,13 @@ export class Emitter<T> {
       }
 
       const entry = { fn: listener, thisArgs };
+      this._listeners = this._listeners.slice();
       this._listeners.push(entry);
 
       const result = toDisposable(() => {
         const idx = this._listeners.indexOf(entry);
         if (idx !== -1) {
+          this._listeners = this._listeners.slice();
           this._listeners.splice(idx, 1);
         }
       });
@@ -50,23 +52,16 @@ export class Emitter<T> {
   }
 
   public fire(event: T): void {
-    if (this._disposed) {
+    if (this._disposed || !this._listeners.length) {
       return;
     }
-    switch (this._listeners.length) {
-      case 0: return;
-      case 1: {
-        const { fn, thisArgs } = this._listeners[0];
-        fn.call(thisArgs, event);
-        return;
-      }
-      default: {
-        // Snapshot listeners to allow modifications during iteration (2+ listeners)
-        const listeners = this._listeners.slice();
-        for (const { fn, thisArgs } of listeners) {
-          fn.call(thisArgs, event);
-        }
-      }
+    if (this._listeners.length === 1) {
+      this._listeners[0].fn.call(this._listeners[0].thisArgs, event);
+      return;
+    }
+    const listeners = this._listeners;
+    for (let i = 0, len = listeners.length; i < len; ++i) {
+      listeners[i].fn.call(listeners[i].thisArgs, event);
     }
   }
 

src/common/buffer/Buffer.test.ts

@@ -8,24 +8,14 @@ import { Buffer } from './Buffer';
 import { CircularList } from '../CircularList';
 import { MockOptionsService, MockBufferService, MockLogService, createCellData } from '../TestUtils.test';
 import { BufferLine, DEFAULT_ATTR_DATA } from './BufferLine';
-import { BufferLineStringCache } from './BufferLineStringCache';
 import { CellData } from './CellData';
-import { ExtendedAttrs } from './AttributeData';
+
 
 const INIT_COLS = 80;
 const INIT_ROWS = 24;
 const INIT_SCROLLBACK = 1000;
-const TEST_STRING_CACHE = new BufferLineStringCache();
 
-class TestBuffer extends Buffer {
-  public getStringCache(): BufferLineStringCache {
-    return (this as unknown as { _stringCache: BufferLineStringCache })._stringCache;
-  }
-
-  public getStringCacheClearTimeout(): unknown {
-    return (this.getStringCache() as unknown as { _clearTimeout: { value: unknown } })._clearTimeout.value;
-  }
-}
+class TestBuffer extends Buffer {}
 
 describe('Buffer', () => {
   let optionsService: MockOptionsService;
@@ -1202,7 +1192,7 @@ describe('Buffer', () => {
 
   describe ('translateBufferLineToString', () => {
     it('should handle selecting a section of ascii text', () => {
-      const line = new BufferLine(TEST_STRING_CACHE, 4);
+      const line = new BufferLine(4);
       line.setCell(0, createCellData(0, 'a', 1));
       line.setCell(1, createCellData(0, 'b', 1));
       line.setCell(2, createCellData(0, 'c', 1));
@@ -1214,7 +1204,7 @@ describe('Buffer', () => {
     });
 
     it('should handle a cut-off double width character by including it', () => {
-      const line = new BufferLine(TEST_STRING_CACHE, 3);
+      const line = new BufferLine(3);
       line.setCell(0, createCellData(0, '語', 2));
       line.setCell(1, createCellData(0, '', 0));
       line.setCell(2, createCellData(0, 'a', 1));
@@ -1225,7 +1215,7 @@ describe('Buffer', () => {
     });
 
     it('should handle a zero width character in the middle of the string by not including it', () => {
-      const line = new BufferLine(TEST_STRING_CACHE, 3);
+      const line = new BufferLine(3);
       line.setCell(0, createCellData(0, '語', 2));
       line.setCell(1, createCellData(0, '', 0));
       line.setCell(2, createCellData(0, 'a', 1));
@@ -1242,7 +1232,7 @@ describe('Buffer', () => {
     });
 
     it('should handle single width emojis', () => {
-      const line = new BufferLine(TEST_STRING_CACHE, 2);
+      const line = new BufferLine(2);
       line.setCell(0, createCellData(0, '😁', 1));
       line.setCell(1, createCellData(0, 'a', 1));
       buffer.lines.set(0, line);
@@ -1255,7 +1245,7 @@ describe('Buffer', () => {
     });
 
     it('should handle double width emojis', () => {
-      const line = new BufferLine(TEST_STRING_CACHE, 2);
+      const line = new BufferLine(2);
       line.setCell(0, createCellData(0, '😁', 2));
       line.setCell(1, createCellData(0, '', 0));
       buffer.lines.set(0, line);
@@ -1266,7 +1256,7 @@ describe('Buffer', () => {
       const str2 = buffer.translateBufferLineToString(0, true, 0, 2);
       assert.equal(str2, '😁');
 
-      const line2 = new BufferLine(TEST_STRING_CACHE, 3);
+      const line2 = new BufferLine(3);
       line2.setCell(0, createCellData(0, '😁', 2));
       line2.setCell(1, createCellData(0, '', 0));
       line2.setCell(2, createCellData(0, 'a', 1));
@@ -1277,99 +1267,6 @@ describe('Buffer', () => {
     });
   });
 
-  describe('line string cache cleanup', () => {
-    it('should clear shared cache entries with a single timer', () => {
-      const originalSetTimeout = globalThis.setTimeout;
-      const originalClearTimeout = globalThis.clearTimeout;
-      const originalDateNow = Date.now;
-      let timeoutId = 0;
-      let now = 0;
-      const clearedTimeouts: number[] = [];
-      const scheduledTimeouts = new Map<number, { delay: number, fire: () => void }>();
-      (globalThis as any).setTimeout = ((handler: (...args: any[]) => void, timeout?: number) => {
-        const id = ++timeoutId;
-        scheduledTimeouts.set(id, {
-          delay: timeout ?? 0,
-          fire: () => {
-            scheduledTimeouts.delete(id);
-            handler();
-          }
-        });
-        return id as ReturnType<typeof setTimeout>;
-      }) as typeof setTimeout;
-      (globalThis as any).clearTimeout = ((id: ReturnType<typeof setTimeout>) => {
-        const numericId = id as unknown as number;
-        clearedTimeouts.push(numericId);
-        scheduledTimeouts.delete(numericId);
-      }) as typeof clearTimeout;
-      Date.now = () => now;
-      try {
-        buffer.fillViewportRows();
-        buffer.lines.get(0)!.setCell(0, createCellData(0, 'a', 1));
-        buffer.lines.get(1)!.setCell(0, createCellData(0, 'b', 1));
-
-        assert.equal(buffer.translateBufferLineToString(0, false), `a${' '.repeat(INIT_COLS - 1)}`);
-        assert.equal(buffer.translateBufferLineToString(1, false), `b${' '.repeat(INIT_COLS - 1)}`);
-
-        const cache = buffer.getStringCache();
-        assert.equal(cache.entries.size, 2);
-        assert.ok(buffer.getStringCacheClearTimeout() !== undefined);
-        assert.equal(scheduledTimeouts.size, 1);
-        assert.equal([...scheduledTimeouts.values()][0].delay, 15000);
-        const initialTimerCreationCount = timeoutId;
-
-        now = 5000;
-        assert.equal(buffer.translateBufferLineToString(0, false), `a${' '.repeat(INIT_COLS - 1)}`);
-        assert.equal(timeoutId, initialTimerCreationCount);
-        assert.equal(scheduledTimeouts.size, 1);
-        assert.deepEqual(clearedTimeouts, []);
-
-        now = 15000;
-        [...scheduledTimeouts.values()][0].fire();
-        assert.equal(timeoutId, initialTimerCreationCount + 1);
-        assert.ok(buffer.getStringCacheClearTimeout() !== undefined);
-        assert.equal(scheduledTimeouts.size, 1);
-        assert.equal([...scheduledTimeouts.values()][0].delay, 5000);
-
-        now = 20000;
-        [...scheduledTimeouts.values()][0].fire();
-
-        assert.equal(cache.entries.size, 0);
-        assert.equal(buffer.getStringCacheClearTimeout(), undefined);
-
-        assert.equal(buffer.translateBufferLineToString(0, false), `a${' '.repeat(INIT_COLS - 1)}`);
-        assert.equal(cache.entries.size, 1);
-      } finally {
-        Date.now = originalDateNow;
-        globalThis.setTimeout = originalSetTimeout;
-        globalThis.clearTimeout = originalClearTimeout;
-      }
-    });
-
-    it('should reset line string cache state on clear and resize', () => {
-      buffer.fillViewportRows();
-      buffer.lines.get(0)!.setCell(0, createCellData(0, 'a', 1));
-      buffer.translateBufferLineToString(0, false);
-
-      const cache = buffer.getStringCache();
-      assert.equal(cache.entries.size, 1);
-      assert.ok(buffer.getStringCacheClearTimeout() !== undefined);
-
-      buffer.clear();
-      assert.equal(cache.entries.size, 0);
-      assert.equal(buffer.getStringCacheClearTimeout(), undefined);
-
-      buffer.fillViewportRows();
-      buffer.lines.get(0)!.setCell(0, createCellData(0, 'b', 1));
-      buffer.translateBufferLineToString(0, false);
-      assert.equal(cache.entries.size, 1);
-
-      buffer.resize(INIT_COLS - 1, INIT_ROWS);
-      assert.equal(cache.entries.size, 0);
-      assert.equal(buffer.getStringCacheClearTimeout(), undefined);
-    });
-  });
-
   describe('memory cleanup after shrinking', () => {
     it('should realign memory from idle task execution', async () => {
       buffer.fillViewportRows();

src/common/buffer/Buffer.ts

@@ -10,7 +10,6 @@ import { ICharset } from '../Types';
 import { IAttributeData, IBuffer, IBufferLine, ICellData } from './Types';
 import { ExtendedAttrs } from './AttributeData';
 import { BufferLine, DEFAULT_ATTR_DATA } from './BufferLine';
-import { BufferLineStringCache } from './BufferLineStringCache';
 import { getWrappedLineTrimmedLength, reflowLargerApplyNewLayout, reflowLargerCreateNewLayout, reflowLargerGetLinesToRemove, reflowSmallerGetNewLineLengths } from './BufferReflow';
 import { CellData } from './CellData';
 import { NULL_CELL_CHAR, NULL_CELL_CODE, NULL_CELL_WIDTH, WHITESPACE_CELL_CHAR, WHITESPACE_CELL_CODE, WHITESPACE_CELL_WIDTH } from './Constants';
@@ -52,7 +51,6 @@ export class Buffer extends Disposable implements IBuffer {
   private _isClearing: boolean = false;
   private _memoryCleanupQueue: InstanceType<typeof IdleTaskQueue>;
   private _memoryCleanupPosition = 0;
-  private readonly _stringCache: BufferLineStringCache;
 
   constructor(
     private _hasScrollback: boolean,
@@ -70,7 +68,6 @@ export class Buffer extends Disposable implements IBuffer {
     this._memoryCleanupQueue = new IdleTaskQueue(this._logService);
     this._register(toDisposable(() => this._memoryCleanupQueue.clear()));
     this._register(toDisposable(() => this.clearAllMarkers()));
-    this._stringCache = this._register(new BufferLineStringCache());
   }
 
   public getNullCell(attr?: IAttributeData): ICellData {
@@ -100,7 +97,7 @@ export class Buffer extends Disposable implements IBuffer {
   }
 
   public getBlankLine(attr: IAttributeData, isWrapped?: boolean): IBufferLine {
-    return new BufferLine(this._stringCache, this._bufferService.cols, this.getNullCell(attr), isWrapped);
+    return new BufferLine(this._bufferService.cols, this.getNullCell(attr), isWrapped);
   }
 
   public get hasScrollback(): boolean {
@@ -145,7 +142,6 @@ export class Buffer extends Disposable implements IBuffer {
    * Clears the buffer to its initial state, discarding all previous data.
    */
   public clear(): void {
-    this._stringCache.clear();
     this.ydisp = 0;
     this.ybase = 0;
     this.y = 0;
@@ -164,7 +160,6 @@ export class Buffer extends Disposable implements IBuffer {
   public resize(newCols: number, newRows: number): void {
     // store reference to null cell with default attrs
     const nullCell = this.getNullCell(DEFAULT_ATTR_DATA);
-    this._stringCache.clear();
 
     // count bufferlines with overly big memory to be cleaned afterwards
     let dirtyMemoryLines = 0;
@@ -199,7 +194,7 @@ export class Buffer extends Disposable implements IBuffer {
             if (this._optionsService.rawOptions.windowsPty.backend !== undefined || this._optionsService.rawOptions.windowsPty.buildNumber !== undefined) {
               // Just add the new missing rows on Windows as conpty reprints the screen with its
               // view of the world. Once a line enters scrollback for conpty it remains there
-              this.lines.push(new BufferLine(this._stringCache, newCols, nullCell, false));
+              this.lines.push(new BufferLine(newCols, nullCell, false));
             } else {
               if (this.ybase > 0 && this.lines.length <= this.ybase + this.y + addToY + 1) {
                 // There is room above the buffer and there are no empty elements below the line,
@@ -213,7 +208,7 @@ export class Buffer extends Disposable implements IBuffer {
               } else {
                 // Add a blank line if there is no buffer left at the top to scroll to, or if there
                 // are blank lines after the cursor
-                this.lines.push(new BufferLine(this._stringCache, newCols, nullCell, false));
+                this.lines.push(new BufferLine(newCols, nullCell, false));
               }
             }
           }
@@ -354,7 +349,7 @@ export class Buffer extends Disposable implements IBuffer {
         }
         if (this.lines.length < newRows) {
           // Add an extra row at the bottom of the viewport
-          this.lines.push(new BufferLine(this._stringCache, newCols, nullCell, false));
+          this.lines.push(new BufferLine(newCols, nullCell, false));
         }
       } else {
         if (this.ydisp === this.ybase) {

src/common/buffer/BufferLine.test.ts

@@ -4,19 +4,16 @@
  */
 import { NULL_CELL_CHAR, NULL_CELL_WIDTH, NULL_CELL_CODE, DEFAULT_ATTR, Content, UnderlineStyle, BgFlags, Attributes, FgFlags } from './Constants';
 import { BufferLine } from './BufferLine';
-import { BufferLineStringCache } from './BufferLineStringCache';
 import { CellData } from './CellData';
 import { CharData, IBufferLine, ICellData } from './Types';
 import { assert } from 'chai';
 import { AttributeData } from './AttributeData';
 import { createCellData, NULL_CELL_DATA, extendedAttributes } from '../TestUtils.test';
 
-const TEST_STRING_CACHE = new BufferLineStringCache();
-
 
 class TestBufferLine extends BufferLine {
   constructor(cols: number, fillCellData?: ICellData, isWrapped: boolean = false) {
-    super(TEST_STRING_CACHE, cols, fillCellData, isWrapped);
+    super(cols, fillCellData, isWrapped);
   }
 
   public get combined(): {[index: number]: string} {
@@ -24,19 +21,19 @@ class TestBufferLine extends BufferLine {
   }
 
   public get cachedString(): string | undefined {
-    return this._getStringCacheEntry(false)?.value;
+    return this._cacheValid ? this._cache : undefined;
   }
 
   public set cachedString(value: string | undefined) {
-    this._getStringCacheEntry(true)!.value = value;
+    this._cache = value ?? '';
   }
 
   public get isCachedStringTrimmed(): boolean {
-    return this._getStringCacheEntry(false)?.isTrimmed ?? false;
+    return this._cacheTrimmed;
   }
 
   public set isCachedStringTrimmed(value: boolean) {
-    this._getStringCacheEntry(true)!.isTrimmed = value;
+    this._cacheTrimmed = value;
   }
 
   public toArray(): CharData[] {

src/common/buffer/BufferLine.ts

@@ -8,7 +8,6 @@ import { AttributeData } from './AttributeData';
 import { CellData } from './CellData';
 import { Attributes, BgFlags, CHAR_DATA_ATTR_INDEX, CHAR_DATA_CHAR_INDEX, CHAR_DATA_WIDTH_INDEX, Content, NULL_CELL_CHAR, NULL_CELL_CODE, NULL_CELL_WIDTH, WHITESPACE_CELL_CHAR } from './Constants';
 import { stringFromCodePoint } from '../input/TextDecoder';
-import { StringBuilder } from '../StringBuilder';
 
 // Buffer memory layout:
 //
@@ -37,24 +36,20 @@ const enum Cell {
   BG = 2  // currently unused
 }
 
+
+interface IExtendedAttrsExt extends IExtendedAttrs {
+  _ext: number;
+  _urlId: number;
+}
+
+
 export const DEFAULT_ATTR_DATA = Object.freeze(new AttributeData());
 
 // Work variables to avoid garbage collection
 let $startIndex = 0;
 const $workCell = new CellData();
-const $translateToStringBuilder = new StringBuilder();
+const $extended = DEFAULT_ATTR_DATA.extended.clone() as IExtendedAttrsExt;
 
-export interface IBufferLineStringCacheEntry {
-  value: string | undefined;
-  isTrimmed: boolean;
-  generation: number;
-}
-
-export interface IBufferLineStringCache {
-  generation: number;
-  allocateEntry(): IBufferLineStringCacheEntry;
-  touch?(): void;
-}
 
 /**
  * Typed array based bufferline implementation.
@@ -77,11 +72,14 @@ export class BufferLine implements IBufferLine {
   protected _combined: {[index: number]: string} = {};
   /** Sparse cache; only read when `HAS_EXTENDED` is set in `_data`. */
   protected _extendedAttrs: {[index: number]: IExtendedAttrs | undefined} = {};
-  protected _stringCacheEntryRef: WeakRef<IBufferLineStringCacheEntry> | undefined;
   public length: number;
 
+  /** line text cache */
+  protected _cacheValid = false;
+  protected _cache: string = '';
+  protected _cacheTrimmed = false;
+
   constructor(
-    protected readonly _stringCache: IBufferLineStringCache,
     cols: number,
     fillCellData?: ICellData,
     public isWrapped: boolean = false
@@ -118,7 +116,7 @@ export class BufferLine implements IBufferLine {
    * @deprecated
    */
   public set(index: number, value: CharData): void {
-    this._invalidateStringCache();
+    this._cacheValid = false;
     this._data[index * Constants.CELL_INDICIES + Cell.FG] = value[CHAR_DATA_ATTR_INDEX];
     if (value[CHAR_DATA_CHAR_INDEX].length > 1) {
       this._combined[index] = value[1];
@@ -210,21 +208,30 @@ export class BufferLine implements IBufferLine {
     } else {
       cell.combinedData = '';
     }
-    if (cell.bg & BgFlags.HAS_EXTENDED) {
-      cell.extended = this._extendedAttrs[index]!;
-    } else {
-      // Do not mutate cell.extended in place: it may still reference this line's map entry from a
-      // prior loadCell into a reused CellData (e.g. $workCell during insert/delete).
-      cell.extended = DEFAULT_ATTR_DATA.extended.clone();
-    }
+    cell.extended = this.getExtended(index);
     return cell;
   }
 
+  public getExtended(index: number): IExtendedAttrs {
+    $startIndex = index * Constants.CELL_INDICIES;
+    if (this._data[$startIndex + Cell.BG] & BgFlags.HAS_EXTENDED) {
+      return this._extendedAttrs[index]!;
+    }
+    // Do not mutate cell.extended in place: it may still reference this line's map entry from a
+    // prior loadCell into a reused CellData (e.g. $workCell during insert/delete).
+    // We use $extended as blueprint and reset the internals
+    // mimicking the ctor to avoid a new allocation.
+    $extended._ext = 0;
+    $extended._urlId = 0;
+    $extended.payload = undefined;
+    return $extended;
+  }
+
   /**
    * Set data at `index` to `cell`.
    */
   public setCell(index: number, cell: ICellData): void {
-    this._invalidateStringCache();
+    this._cacheValid = false;
     if (cell.content & Content.IS_COMBINED_MASK) {
       this._combined[index] = cell.combinedData;
     }
@@ -242,13 +249,14 @@ export class BufferLine implements IBufferLine {
    * it gets an optimized access method.
    */
   public setCellFromCodepoint(index: number, codePoint: number, width: number, attrs: IAttributeData): void {
-    this._invalidateStringCache();
+    this._cacheValid = false;
     if (attrs.bg & BgFlags.HAS_EXTENDED) {
       this._extendedAttrs[index] = attrs.extended;
     }
-    this._data[index * Constants.CELL_INDICIES + Cell.CONTENT] = codePoint | (width << Content.WIDTH_SHIFT);
-    this._data[index * Constants.CELL_INDICIES + Cell.FG] = attrs.fg;
-    this._data[index * Constants.CELL_INDICIES + Cell.BG] = attrs.bg;
+    const $idx = index * Constants.CELL_INDICIES;
+    this._data[$idx + Cell.CONTENT] = codePoint | (width << Content.WIDTH_SHIFT);
+    this._data[$idx + Cell.FG] = attrs.fg;
+    this._data[$idx + Cell.BG] = attrs.bg;
   }
 
   /**
@@ -258,7 +266,7 @@ export class BufferLine implements IBufferLine {
    * by the previous `setDataFromCodePoint` call, we can omit it here.
    */
   public addCodepointToCell(index: number, codePoint: number, width: number): void {
-    this._invalidateStringCache();
+    this._cacheValid = false;
     let content = this._data[index * Constants.CELL_INDICIES + Cell.CONTENT];
     if (content & Content.IS_COMBINED_MASK) {
       // we already have a combined string, simply add
@@ -285,7 +293,7 @@ export class BufferLine implements IBufferLine {
   }
 
   public insertCells(pos: number, n: number, fillCellData: ICellData): void {
-    this._invalidateStringCache();
+    this._cacheValid = false;
     pos %= this.length;
 
     // handle fullwidth at pos: reset cell one to the left if pos is second cell of a wide char
@@ -313,7 +321,7 @@ export class BufferLine implements IBufferLine {
   }
 
   public deleteCells(pos: number, n: number, fillCellData: ICellData): void {
-    this._invalidateStringCache();
+    this._cacheValid = false;
     pos %= this.length;
     if (n < this.length - pos) {
       for (let i = 0; i < this.length - pos - n; ++i) {
@@ -340,7 +348,7 @@ export class BufferLine implements IBufferLine {
   }
 
   public replaceCells(start: number, end: number, fillCellData: ICellData, respectProtect: boolean = false): void {
-    this._invalidateStringCache();
+    this._cacheValid = false;
     // full branching on respectProtect==true, hopefully getting fast JIT for standard case
     if (respectProtect) {
       if (start && this.getWidth(start - 1) === 2 && !this.isProtected(start - 1)) {
@@ -380,7 +388,7 @@ export class BufferLine implements IBufferLine {
    * excess memory (true after shrinking > Constants.CLEANUP_THRESHOLD).
    */
   public resize(cols: number, fillCellData: ICellData): boolean {
-    this._invalidateStringCache();
+    this._cacheValid = false;
     if (cols === this.length) {
       return this._data.length * 4 * Constants.CLEANUP_THRESHOLD < this._data.buffer.byteLength;
     }
@@ -440,7 +448,7 @@ export class BufferLine implements IBufferLine {
 
   /** fill a line with fillCharData */
   public fill(fillCellData: ICellData, respectProtect: boolean = false): void {
-    this._invalidateStringCache();
+    this._cacheValid = false;
     // full branching on respectProtect==true, hopefully getting fast JIT for standard case
     if (respectProtect) {
       for (let i = 0; i < this.length; ++i) {
@@ -458,8 +466,7 @@ export class BufferLine implements IBufferLine {
   }
 
   /** alter to a full copy of line  */
-  public copyFrom(line: BufferLine): void {
-    this._invalidateStringCache();
+  public copyFrom(line: BufferLine, blank?: boolean): void {
     if (this.length !== line.length) {
       this._data = new Uint32Array(line._data);
     } else {
@@ -467,16 +474,29 @@ export class BufferLine implements IBufferLine {
       this._data.set(line._data);
     }
     this.length = line.length;
-    this._copySparseMapsFrom(line);
+    if (blank) {
+      // a blank line may never hold combined or extended attrs,
+      // thus we can skip handling them
+      this._combined = {};
+      this._extendedAttrs = {};
+    } else {
+      this._copySparseMapsFrom(line);
+    }
+    this._cache = '';
+    this._cacheValid = false;
     this.isWrapped = line.isWrapped;
   }
 
   /** create a new clone */
-  public clone(): IBufferLine {
-    const newLine = new BufferLine(this._stringCache, 0, undefined, false);
+  public clone(blank?: boolean): IBufferLine {
+    const newLine = new BufferLine(0, undefined, false);
     newLine._data = new Uint32Array(this._data);
     newLine.length = this.length;
-    newLine._copySparseMapsFrom(this);
+    if (!blank) {
+      // a blank line may never hold combined or extended attrs,
+      // thus we can skip handling them
+      newLine._copySparseMapsFrom(this);
+    }
     newLine.isWrapped = this.isWrapped;
     return newLine;
   }
@@ -500,7 +520,7 @@ export class BufferLine implements IBufferLine {
   }
 
   public copyCellsFrom(src: BufferLine, srcCol: number, destCol: number, length: number, applyInReverse: boolean): void {
-    this._invalidateStringCache();
+    this._cacheValid = false;
     const srcData = src._data;
     if (applyInReverse) {
       for (let cell = length - 1; cell >= 0; cell--) {
@@ -534,17 +554,13 @@ export class BufferLine implements IBufferLine {
    * returned string, the corresponding entries in `outColumns` will have the same column number.
    */
   public translateToString(trimRight?: boolean, startCol?: number, endCol?: number, outColumns?: number[]): string {
-    const isCanonicalRequest = (startCol === undefined || startCol === 0) && endCol === undefined && outColumns === undefined;
-    if (isCanonicalRequest) {
-      this._stringCache.touch?.();
-    }
-    const stringCacheEntry = isCanonicalRequest ? this._getStringCacheEntry(false) : undefined;
-    if (isCanonicalRequest && stringCacheEntry?.value !== undefined) {
+    const isCanonical = (startCol === undefined || startCol === 0) && endCol === undefined && outColumns === undefined;
+    if (isCanonical && this._cacheValid) {
       if (trimRight) {
-        return stringCacheEntry.isTrimmed ? stringCacheEntry.value : stringCacheEntry.value.trimEnd();
+        return this._cacheTrimmed ? this._cache : this._cache.trimEnd();
       }
-      if (!stringCacheEntry.isTrimmed) {
-        return stringCacheEntry.value;
+      if (!this._cacheTrimmed) {
+        return this._cache;
       }
     }
     startCol = startCol ?? 0;
@@ -555,12 +571,12 @@ export class BufferLine implements IBufferLine {
     if (outColumns) {
       outColumns.length = 0;
     }
-    $translateToStringBuilder.reset();
+    const cellContents: string[] = [];
     while (startCol < endCol) {
       const content = this._data[startCol * Constants.CELL_INDICIES + Cell.CONTENT];
       const cp = content & Content.CODEPOINT_MASK;
       const chars = (content & Content.IS_COMBINED_MASK) ? this._combined[startCol] : (cp) ? stringFromCodePoint(cp) : WHITESPACE_CELL_CHAR;
-      $translateToStringBuilder.append(chars);
+      cellContents.push(chars);
       if (outColumns) {
         for (let i = 0; i < chars.length; ++i) {
           outColumns.push(startCol);
@@ -571,39 +587,15 @@ export class BufferLine implements IBufferLine {
     if (outColumns) {
       outColumns.push(startCol);
     }
-    const result = $translateToStringBuilder.toString();
-    $translateToStringBuilder.reset();
-    if (isCanonicalRequest) {
-      const cacheEntry = this._getStringCacheEntry(true)!;
-      cacheEntry.value = result;
-      cacheEntry.isTrimmed = !!trimRight;
+    const result = cellContents.join('');
+    if (isCanonical) {
+      this._cache = result;
+      this._cacheValid = true;
+      this._cacheTrimmed = !!trimRight;
     }
     return result;
   }
 
-  protected _getStringCacheEntry(createIfNeeded: boolean): IBufferLineStringCacheEntry | undefined {
-    const cachedEntry = this._stringCacheEntryRef?.deref();
-    if (cachedEntry) {
-      if (cachedEntry.generation === this._stringCache.generation) {
-        return cachedEntry;
-      }
-    }
-    if (!createIfNeeded) {
-      return undefined;
-    }
-    const cacheEntry = this._stringCache.allocateEntry();
-    this._stringCacheEntryRef = new WeakRef(cacheEntry);
-    return cacheEntry;
-  }
-
-  private _invalidateStringCache(): void {
-    const cacheEntry = this._getStringCacheEntry(false);
-    if (cacheEntry) {
-      cacheEntry.value = undefined;
-      cacheEntry.isTrimmed = false;
-    }
-  }
-
   /** Copy sparse map entries for a single cell when `_data` flags require them. */
   private _copyCellMapsFrom(src: BufferLine, srcCol: number, destCol: number): void {
     const srcStart = srcCol * Constants.CELL_INDICIES;

src/common/buffer/BufferLineStringCache.ts

@@ -1,69 +0,0 @@
-/**
- * Copyright (c) 2026 The xterm.js authors. All rights reserved.
- * @license MIT
- */
-
-import type { IBufferLineStringCache, IBufferLineStringCacheEntry } from './BufferLine';
-import { disposableTimeout } from '../Async';
-import { Disposable, MutableDisposable, toDisposable, type IDisposable } from '../Lifecycle';
-
-const enum Constants {
-  CACHE_TTL_MS = 15000
-}
-
-export class BufferLineStringCache extends Disposable implements IBufferLineStringCache {
-  public generation: number = 0;
-  public readonly entries: Set<IBufferLineStringCacheEntry> = new Set();
-  private readonly _clearTimeout = this._register(new MutableDisposable<IDisposable>());
-  private _lastAccessTimestamp: number = 0;
-
-  constructor() {
-    super();
-    this._register(toDisposable(() => this.entries.clear()));
-  }
-
-  public touch(): void {
-    this._scheduleClear();
-  }
-
-  public allocateEntry(): IBufferLineStringCacheEntry {
-    const entry: IBufferLineStringCacheEntry = {
-      value: undefined,
-      isTrimmed: false,
-      generation: this.generation
-    };
-    this.entries.add(entry);
-    this._scheduleClear();
-    return entry;
-  }
-
-  public clear(): void {
-    this._clearTimeout.clear();
-    this._lastAccessTimestamp = 0;
-    this.generation++;
-    for (const entry of this.entries) {
-      entry.value = undefined;
-      entry.isTrimmed = false;
-    }
-    this.entries.clear();
-  }
-
-  private _scheduleClear(): void {
-    this._lastAccessTimestamp = Date.now();
-    if (this._clearTimeout.value) {
-      return;
-    }
-    this._scheduleClearTimeout(Constants.CACHE_TTL_MS);
-  }
-
-  private _scheduleClearTimeout(timeoutMs: number): void {
-    this._clearTimeout.value = disposableTimeout(() => {
-      const elapsed = Date.now() - this._lastAccessTimestamp;
-      if (elapsed >= Constants.CACHE_TTL_MS) {
-        this.clear();
-        return;
-      }
-      this._scheduleClearTimeout(Constants.CACHE_TTL_MS - elapsed);
-    }, timeoutMs);
-  }
-}

src/common/buffer/BufferReflow.test.ts

@@ -5,18 +5,16 @@
 import { assert } from 'chai';
 import { CircularList } from '../CircularList';
 import { BufferLine } from './BufferLine';
-import { BufferLineStringCache } from './BufferLineStringCache';
 import { CellData } from './CellData';
 import { NULL_CELL_CHAR, NULL_CELL_WIDTH, NULL_CELL_CODE } from './Constants';
 import { reflowLargerGetLinesToRemove, reflowSmallerGetNewLineLengths } from './BufferReflow';
 import { IBufferLine } from './Types';
 
-const TEST_STRING_CACHE = new BufferLineStringCache();
 
 describe('BufferReflow', () => {
   describe('reflowSmallerGetNewLineLengths', () => {
     it('should return correct line lengths for a small line with wide characters', () => {
-      const line = new BufferLine(TEST_STRING_CACHE, 4);
+      const line = new BufferLine(4);
       line.set(0, [0, '汉', 2, '汉'.charCodeAt(0)]);
       line.set(1, [0, '', 0, 0]);
       line.set(2, [0, '语', 2, '语'.charCodeAt(0)]);
@@ -26,7 +24,7 @@ describe('BufferReflow', () => {
       assert.deepEqual(reflowSmallerGetNewLineLengths([line], 4, 2), [2, 2], 'line: 汉, 语');
     });
     it('should return correct line lengths for a large line with wide characters', () => {
-      const line = new BufferLine(TEST_STRING_CACHE, 12);
+      const line = new BufferLine(12);
       for (let i = 0; i < 12; i += 4) {
         line.set(i, [0, '汉', 2, '汉'.charCodeAt(0)]);
         line.set(i + 2, [0, '语', 2, '语'.charCodeAt(0)]);
@@ -48,7 +46,7 @@ describe('BufferReflow', () => {
       assert.deepEqual(reflowSmallerGetNewLineLengths([line], 12, 2), [2, 2, 2, 2, 2, 2], 'line: 汉, 语, 汉, 语, 汉, 语');
     });
     it('should return correct line lengths for a string with wide and single characters', () => {
-      const line = new BufferLine(TEST_STRING_CACHE, 6);
+      const line = new BufferLine(6);
       line.set(0, [0, 'a', 1, 'a'.charCodeAt(0)]);
       line.set(1, [0, '汉', 2, '汉'.charCodeAt(0)]);
       line.set(2, [0, '', 0, 0]);
@@ -62,14 +60,14 @@ describe('BufferReflow', () => {
       assert.deepEqual(reflowSmallerGetNewLineLengths([line], 6, 2), [1, 2, 2, 1], 'line: a, 汉, 语, b');
     });
     it('should return correct line lengths for a wrapped line with wide and single characters', () => {
-      const line1 = new BufferLine(TEST_STRING_CACHE, 6);
+      const line1 = new BufferLine(6);
       line1.set(0, [0, 'a', 1, 'a'.charCodeAt(0)]);
       line1.set(1, [0, '汉', 2, '汉'.charCodeAt(0)]);
       line1.set(2, [0, '', 0, 0]);
       line1.set(3, [0, '语', 2, '语'.charCodeAt(0)]);
       line1.set(4, [0, '', 0, 0]);
       line1.set(5, [0, 'b', 1, 'b'.charCodeAt(0)]);
-      const line2 = new BufferLine(TEST_STRING_CACHE, 6, undefined, true);
+      const line2 = new BufferLine(6, undefined, true);
       line2.set(0, [0, 'a', 1, 'a'.charCodeAt(0)]);
       line2.set(1, [0, '汉', 2, '汉'.charCodeAt(0)]);
       line2.set(2, [0, '', 0, 0]);
@@ -84,7 +82,7 @@ describe('BufferReflow', () => {
       assert.deepEqual(reflowSmallerGetNewLineLengths([line1, line2], 6, 2), [1, 2, 2, 2, 2, 2, 1], 'lines: a, 汉, 语, ba, 汉, 语, b');
     });
     it('should work on lines ending in null space', () => {
-      const line = new BufferLine(TEST_STRING_CACHE, 5);
+      const line = new BufferLine(5);
       line.set(0, [0, '汉', 2, '汉'.charCodeAt(0)]);
       line.set(1, [0, '', 0, 0]);
       line.set(2, [0, '语', 2, '语'.charCodeAt(0)]);
@@ -102,7 +100,7 @@ describe('BufferReflow', () => {
     function createWrappedLines(chars: string): CircularList<IBufferLine> {
       const lines = new CircularList<IBufferLine>(chars.length);
       for (let i = 0; i < chars.length; i++) {
-        const line = new BufferLine(TEST_STRING_CACHE, 1);
+        const line = new BufferLine(1);
         line.set(0, [0, chars[i], 1, chars.charCodeAt(i)]);
         line.isWrapped = i > 0;
         lines.push(line);

src/common/buffer/BufferSet.test.ts

@@ -82,45 +82,4 @@ describe('BufferSet', () => {
       assert.equal(bufferSet.alt.markers.length, 0);
     });
   });
-
-  describe('lifecycle', () => {
-    it('should dispose previous buffers on reset', () => {
-      const oldNormal = bufferSet.normal as any;
-      oldNormal.lines.get(0)!.setCell(0, createCellData(0, 'a', 1));
-      oldNormal.translateBufferLineToString(0, false);
-
-      const oldCache = oldNormal._stringCache;
-      assert.equal(oldCache.entries.size, 1);
-      assert.notEqual(oldCache._clearTimeout.value, undefined);
-
-      bufferSet.reset();
-
-      assert.notEqual(bufferSet.normal, oldNormal);
-      assert.equal(oldCache.entries.size, 0);
-      assert.equal(oldCache._clearTimeout.value, undefined);
-    });
-
-    it('should dispose both buffers when disposed', () => {
-      const normal = bufferSet.normal as any;
-      normal.lines.get(0)!.setCell(0, createCellData(0, 'a', 1));
-      normal.translateBufferLineToString(0, false);
-
-      bufferSet.activateAltBuffer();
-      const alt = bufferSet.alt as any;
-      alt.lines.get(0)!.setCell(0, createCellData(0, 'b', 1));
-      alt.translateBufferLineToString(0, false);
-
-      const normalCache = normal._stringCache;
-      const altCache = alt._stringCache;
-      assert.notEqual(normalCache._clearTimeout.value, undefined);
-      assert.notEqual(altCache._clearTimeout.value, undefined);
-
-      bufferSet.dispose();
-
-      assert.equal(normalCache.entries.size, 0);
-      assert.equal(altCache.entries.size, 0);
-      assert.equal(normalCache._clearTimeout.value, undefined);
-      assert.equal(altCache._clearTimeout.value, undefined);
-    });
-  });
 });

src/common/buffer/Types.ts

@@ -132,8 +132,8 @@ export interface IBufferLine {
   resize(cols: number, fill: ICellData): boolean;
   cleanupMemory(): number;
   fill(fillCellData: ICellData, respectProtect?: boolean): void;
-  copyFrom(line: IBufferLine): void;
-  clone(): IBufferLine;
+  copyFrom(line: IBufferLine, blank?: boolean): void;
+  clone(blank?: boolean): IBufferLine;
   getTrimmedLength(): number;
   getNoBgTrimmedLength(): number;
   translateToString(trimRight?: boolean, startCol?: number, endCol?: number, outColumns?: number[]): string;
@@ -147,6 +147,7 @@ export interface IBufferLine {
   getCodePoint(index: number): number;
   isCombined(index: number): number;
   getString(index: number): string;
+  getExtended(index: number): IExtendedAttrs;
 }
 
 export interface IMarker extends IDisposable {

src/common/services/BufferService.ts

@@ -86,12 +86,12 @@ export class BufferService extends Disposable implements IBufferService {
       // Insert the line using the fastest method
       if (bottomRow === buffer.lines.length - 1) {
         if (willBufferBeTrimmed) {
-          buffer.lines.recycle().copyFrom(newLine);
+          buffer.lines.recycle().copyFrom(newLine, true);
         } else {
-          buffer.lines.push(newLine.clone());
+          buffer.lines.push(newLine.clone(true));
         }
       } else {
-        buffer.lines.splice(bottomRow + 1, 0, newLine.clone());
+        buffer.lines.splice(bottomRow + 1, 0, newLine.clone(true));
       }
 
       // Only adjust ybase and ydisp when the buffer is not trimmed
@@ -113,7 +113,7 @@ export class BufferService extends Disposable implements IBufferService {
       // scrollback, instead we can just shift them in-place.
       const scrollRegionHeight = bottomRow - topRow + 1 /* as it's zero-based */;
       buffer.lines.shiftElements(topRow + 1, scrollRegionHeight - 1, -1);
-      buffer.lines.set(bottomRow, newLine.clone());
+      buffer.lines.set(bottomRow, newLine.clone(true));
     }
 
     // Move the viewport to the bottom of the buffer unless the user is

src/common/services/DecorationService.ts

@@ -214,7 +214,7 @@ export class DecorationLineCache extends Disposable {
   }
 
   private _handleBufferLinesTrim(amount: number): void {
-    if (amount <= 0) {
+    if (amount <= 0 || !this._decorationsByLine.size) {
       return;
     }
     const newMap = new Map<number, IInternalDecoration[]>();