fix(cli): check no longer calls a redrawn WebGL canvas a dead stretch (#6749)

* fix(cli): check no longer calls a redrawn WebGL canvas a dead stretch

* fix(cli): keep the seek comment under the line limit

packages/cli/src/commands/check.test.ts

@@ -2841,6 +2841,20 @@ describe("check pipeline", () => {
       expect(checkExitCode(strict.report)).toBe(0);
     });
 
+    it("seeks each craft frame with WebGL draws on, so a redrawn canvas reads as moving", async () => {
+      const driver = craftDriver();
+      await runScenario(driver);
+      const painted = new Set(
+        vi
+          .mocked(driver.seekGeometry)
+          .mock.calls.flatMap(([time, seek]) => (seek?.draws ? [time] : [])),
+      );
+      const sampled = vi.mocked(driver.collectCraftFrame!).mock.calls.map(([time]) => time);
+
+      expect(sampled.length).toBeGreaterThan(0);
+      expect(sampled.every((time) => painted.has(time))).toBe(true);
+    });
+
     it("re-measures a short line between dense samples before judging it", async () => {
       const driver = craftDriver();
       const { report } = await runScenario(driver);

packages/cli/src/utils/checkBrowser.chromium.test.ts

@@ -3,7 +3,7 @@ import puppeteer, { type Browser, type Page } from "puppeteer-core";
 import { createRequire } from "node:module";
 import { resolve } from "node:path";
 import { measuredInMotion, readContrastMotion } from "./contrastMotion.js";
-import { collectSeekClock } from "./checkBrowser.js";
+import { collectSeekClock, createPageDriver } from "./checkBrowser.js";
 
 const executablePath = process.env.PUPPETEER_EXECUTABLE_PATH;
 
@@ -119,6 +119,24 @@ describe.runIf(executablePath)("collectSeekClock in Chromium", () => {
     await page.close();
   });
 
+  it("skips a seek's WebGL draws unless the caller asks to paint them", async () => {
+    page = await browser.newPage();
+    await page.setContent(`<script>
+      window.draws = 0;
+      window.WebGLRenderingContext = function () {};
+      window.WebGLRenderingContext.prototype.drawArrays = () => { window.draws += 1; };
+      window.__hf = { seek: () => new window.WebGLRenderingContext().drawArrays() };
+    </script>`);
+    const driver = createPageDriver(page);
+    const drawn = () => page.evaluate(() => Reflect.get(window, "draws"));
+
+    await driver.seekGeometry(1);
+    expect(await drawn()).toBe(0);
+    await driver.seekGeometry(2, { draws: true });
+    expect(await drawn()).toBe(1);
+    await page.close();
+  });
+
   it("reports nothing on a page with no animations", async () => {
     page = await browser.newPage();
     await page.setContent("<body><h1>Hello</h1></body>");

packages/cli/src/utils/checkBrowser.ts

@@ -969,9 +969,12 @@ export function createPageDriver(
         screenshotFollows ? SCREENSHOT_SEEK_OPTIONS : AUDIT_SEEK_OPTIONS,
       );
     },
-    seekGeometry: async (time) => {
+    seekGeometry: async (time, { draws = false } = {}) => {
       clock.at(time);
-      await seekCompositionTimeline(page, time, DENSE_GEOMETRY_SEEK_OPTIONS);
+      const options = draws
+        ? { ...DENSE_GEOMETRY_SEEK_OPTIONS, skipWebglDraws: false }
+        : DENSE_GEOMETRY_SEEK_OPTIONS;
+      await seekCompositionTimeline(page, time, options);
     },
     collectLayout: (time, tolerance, layout) => collectLayout(page, time, tolerance, layout),
     collectOverlap: (time) => collectOverlap(page, time),

packages/cli/src/utils/checkPipeline.ts

@@ -759,7 +759,7 @@ async function collectMotionOverlapSamples(
     const craftTimes = buildCraftSampleTimes(grid.duration).filter((time) => time < grid.duration);
     for (const [index, time] of craftTimes.entries()) {
       progress(`craft frame at ${time}s`);
-      await driver.seekGeometry(time);
+      await driver.seekGeometry(time, { draws: true });
       collected.craftFrames.push(...(await collectCraftFrame(driver, time)));
       progress();
       report("craft", index + 1, craftTimes.length);
@@ -1583,7 +1583,7 @@ export async function runAuditGrid(
             noTimeline || sweepFindings.length > 0 || wholeCompositionKeepsMoving(plan.assertions),
         },
         async (time) => {
-          await driver.seekGeometry(time);
+          await driver.seekGeometry(time, { draws: true });
           if (!driver.collectCraftFrame) throw new Error("craft sampling unavailable");
           return driver.collectCraftFrame(time);
         },

packages/cli/src/utils/checkTypes.ts

@@ -262,8 +262,8 @@ export interface CheckAuditDriver {
   getCanvas(): Promise<Canvas>;
   findAmbiguousSelectors(selectors: string[]): Promise<AnchoredLayoutIssue[]>;
   seek(time: number, screenshotFollows?: boolean): Promise<void>;
-  /** Settle-free seek for the geometry-only dense content_overlap pass; only collectOverlap consumes it, and getBoundingClientRect is valid synchronously after setTime. */
-  seekGeometry(time: number): Promise<void>;
+  /** Settle-free seek for the dense passes; WebGL draws are skipped unless `draws` (a pass reading canvas pixels). */
+  seekGeometry(time: number, options?: { draws?: boolean }): Promise<void>;
   collectLayout(
     time: number,
     tolerance: number,