Add failing repro: atlas page overflow crashes GlyphRenderer.render

GlyphRenderer sizes its GL texture array and fragment-shader sampler array to exactly TextureAtlas.maxAtlasPages at construction, but _createNewPage pushes past that cap whenever a 4-page same-size merge is impossible (heterogeneous sizes, e.g. 1024+512+512+512). The next render throws TypeError: Cannot read properties of undefined (reading 'version') and rendering freezes — the single-terminal breakage vector for long heavy-CLI sessions (vscode#322756). The test builds the renderer with maxAtlasPages=4 (same code path as the production 8/16/32 values), churns distinct glyphs, and asserts no pageerror, pages.length <= texture capacity, and an intact pinned header. RED today: 4x TypeError from GlyphRenderer.render.
2026-07-04 12:58:33 -07:00
parent 32fdce592b
commit 8481bfd8dd
1 changed files with 109 additions and 0 deletions
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+/**
+ * Copyright (c) 2025 The xterm.js authors. All rights reserved.
+ * @license MIT
+ *
+ * Reproduces the single-terminal WebGL crash/garble when the texture atlas
+ * page count overflows TextureAtlas.maxAtlasPages (vscode#322756 class).
+ *
+ * GlyphRenderer sizes its GL texture array and fragment-shader sampler array
+ * to exactly maxAtlasPages at construction time, but TextureAtlas._createNewPage
+ * pushes past that cap whenever a 4-page same-size merge is impossible (e.g. a
+ * heterogeneous mix like 1024+512+512+512). The next GlyphRenderer.render then
+ * throws "Cannot read properties of undefined (reading 'version')" and cells
+ * reference sampler indexes the shader does not have, freezing/garbling the
+ * terminal. Long heavy-CLI sessions hit this in production; the test makes it
+ * fast by building the renderer with a small cap (the same code path as the
+ * production 8/16/32 values).
+ *
+ * Chromium only (additive scope; Firefox/WebKit WebGL broken in CI, xtermjs#5854).
+ */
+import test, { expect } from '@playwright/test';
+import { ITestContext, createTestContext, openTerminal } from '../../../test/playwright/TestUtils';
+import {
+  captureRowSignatures,
+  expectSignatureMatches,
+  loadWebglStrict,
+  setMaxAtlasPages,
+  writeAndWaitForRender
+} from '../../../test/playwright/RendererTestUtils';
+import { generateUniqueGlyphFlood } from '../../../test/playwright/SyntheticTui';
+
+const HEADER = ' OVERFLOW_REF_0123456789';
+const HEADER_COLS = [1, 2, 3, 4, 5, 6, 7, 8, 9, 10];
+
+test.describe('atlas page overflow (#322756 class)', () => {
+  test.skip(({ browserName }) => browserName !== 'chromium');
+  test.describe.configure({ timeout: 60000 });
+
+  test('renderer survives the atlas exceeding maxAtlasPages-sized textures', async ({ browser }) => {
+    const ctx: ITestContext = await createTestContext(browser);
+    const errors: string[] = [];
+    const onError = (e: Error): void => { errors.push(e.message); };
+    ctx.page.on('pageerror', onError);
+    try {
+      // Bootstrap: create a throwaway WebGL terminal so the TextureAtlas class
+      // statics exist, then lower the page cap. openTerminal() disposes the old
+      // terminal (and its atlas), so the next WebGL renderer is CONSTRUCTED
+      // with the small cap: its GL texture array and fragment-shader sampler
+      // array have exactly 4 entries, faithfully mirroring production where
+      // they always equal maxAtlasPages.
+      await openTerminal(ctx, { cols: 80, rows: 24 });
+      await loadWebglStrict(ctx);
+      await setMaxAtlasPages(ctx, 4);
+      await openTerminal(ctx, { cols: 80, rows: 24 });
+      await loadWebglStrict(ctx);
+
+      const atlasTexturesLength = await ctx.page.evaluate(() =>
+        (window as any).term._core._renderService._renderer.value._glyphRenderer.value._atlasTextures.length);
+      expect(atlasTexturesLength, 'renderer must be built with the lowered page cap').toBe(4);
+
+      // Pinned header in the alt buffer; body churns distinct CJK glyphs below
+      // (cursor-positioned, no trailing linefeed on the bottom row -> no scroll).
+      await writeAndWaitForRender(ctx, `\x1b[?1049h\x1b[H${HEADER}`);
+      const reference = await captureRowSignatures(ctx, 1, HEADER_COLS);
+      await ctx.page.locator('#terminal-container .xterm-screen').screenshot({ path: 'out-esbuild-test/playwright/overflow-before.png' });
+
+      const glyphsPerChunk = 23 * 40 - 1;
+      for (let c = 0; c < 16; c++) {
+        // Plain write + short wait instead of waiting for a render event: once
+        // the overflow crash fires, render events stop arriving and a render
+        // wait would hang the test instead of failing it.
+        await ctx.proxy.write('\x1b[2;1H' + generateUniqueGlyphFlood(glyphsPerChunk, 80, c * glyphsPerChunk));
+        await ctx.page.waitForTimeout(50);
+      }
+      await ctx.page.waitForTimeout(300);
+      await ctx.page.locator('#terminal-container .xterm-screen').screenshot({ path: 'out-esbuild-test/playwright/overflow-after.png' });
+
+      const state = await ctx.page.evaluate(() => {
+        const renderer = (window as any).term._core._renderService._renderer.value;
+        return {
+          pages: renderer._charAtlas.pages.length,
+          atlasTextures: renderer._glyphRenderer.value._atlasTextures.length
+        };
+      });
+      console.error('[overflow] pages=', state.pages, 'atlasTextures=', state.atlasTextures, 'pageErrors=', errors.length, errors[0] ?? '');
+
+      // Contract: the page count must never exceed the renderer's texture and
+      // sampler capacity, and rendering must never throw.
+      expect(errors, `GlyphRenderer must not crash when the atlas is saturated: ${errors[0] ?? ''}`).toEqual([]);
+      expect(state.pages, 'atlas page count must stay within the renderer texture capacity').toBeLessThanOrEqual(state.atlasTextures);
+
+      // The untouched header must still render correctly after the churn.
+      const after = await captureRowSignatures(ctx, 1, HEADER_COLS);
+      for (let i = 0; i < HEADER_COLS.length; i++) {
+        expectSignatureMatches(after[i], reference[i], 14, `header col ${HEADER_COLS[i]} corrupted after atlas saturation`);
+      }
+    } finally {
+      ctx.page.off('pageerror', onError);
+      // Restore the default so a lowered cap can never leak into other tests.
+      await ctx.page.evaluate(() => {
+        const renderer = (window as any).term._core._renderService._renderer.value;
+        const atlas = renderer?._charAtlas;
+        if (atlas) {
+          (atlas.constructor as any).maxAtlasPages = undefined;
+        }
+      }).catch(() => { /* page may already be unusable after a crash */ });
+      await ctx.page.close();
+    }
+  });
+});