webview: sample click(selector) stability from distinct rAF callbacks

src/runtime/webview/ChromeBackend.h

@@ -277,27 +277,37 @@
 // passed as JSON-escaped arguments at the end — avoids Chrome's
 // callFunctionOn dance for one string + one number.
 //
-// The predicate: attached + has size + in viewport + stable for 2 frames
-// + elementFromPoint at center returns the element (not obscured). Returns
-// the center coords as [cx, cy]; throws on timeout.
+// The predicate: attached + has size + in viewport + stable across two
+// distinct animation frames + elementFromPoint at center returns the element
+// (not obscured). Returns the center coords as [cx, cy]; throws on timeout.
+//
+// Every sample is taken after an `await rAF`, and a match only counts when
+// the rAF timestamp advanced, so a just-started animation cannot look stable
+// at its from-keyframe (Playwright's _checkElementIsStable does the same).
+// The rAF wait races a setTimeout bound to the deadline so the timeout
+// contract holds when the renderer is not producing frames.
 constexpr ASCIILiteral kActionabilityIIFE = R"js((async (sel, timeout) => {
 const deadline = performance.now() + timeout;
-let last;
+let last, lastT;
 for (;;) {
+  const t = await new Promise(f => {
+    const id = setTimeout(f, Math.max(0, deadline - performance.now()));
+    requestAnimationFrame(t => { clearTimeout(id); f(t); });
+  });
+  if (performance.now() > deadline) throw "timeout waiting for '" + sel + "' to be actionable";
   const el = document.querySelector(sel);
   if (el) {
     const r = el.getBoundingClientRect();
     const cx = r.left + r.width / 2, cy = r.top + r.height / 2;
     if (r.width > 0 && r.height > 0 && cx >= 0 && cy >= 0 && cx < innerWidth && cy < innerHeight) {
-      if (last && last.l === r.left && last.t === r.top && last.w === r.width && last.h === r.height) {
+      if (last && t !== lastT && last.l === r.left && last.t === r.top && last.w === r.width && last.h === r.height) {
         const hit = document.elementFromPoint(cx, cy);
         if (hit === el || el.contains(hit)) return [cx, cy];
       }
       last = { l: r.left, t: r.top, w: r.width, h: r.height };
     } else last = undefined;
   } else last = undefined;
-  if (performance.now() > deadline) throw "timeout waiting for '" + sel + "' to be actionable";
-  await new Promise(f => requestAnimationFrame(f));
+  lastT = t;
 }
 }))js"_s;
 

src/runtime/webview/WebViewHost.cpp

@@ -351,30 +351,42 @@ void WebViewHost::doNativeClick(float x, float y, uint8_t button, uint8_t modifi
 // page-side via callAsyncJavaScript: — WebKit awaits the returned Promise.
 // One IPC roundtrip regardless of how many frames the poll takes.
 //
-// The predicate: attached + has size + in viewport + stable for 2 frames +
-// elementFromPoint at center returns the element or a descendant (not
-// obscured). Returns "cx,cy" on success; throws on timeout.
+// The predicate: attached + has size + in viewport + stable across two
+// distinct animation frames + elementFromPoint at center returns the element
+// or a descendant (not obscured). Returns "cx,cy" on success; throws on
+// timeout.
+//
+// Every sample is taken after an `await rAF`, and a match only counts when
+// the rAF timestamp advanced, so a just-started animation cannot look stable
+// at its from-keyframe (Playwright's _checkElementIsStable does the same).
+// The rAF wait races a setTimeout bound to the deadline so the timeout
+// contract holds when the renderer is not producing frames (headless WK
+// without a display driver).
 //
 // Arguments `sel` and `timeout` are passed via the arguments: NSDictionary,
 // not string-interpolated — the selector can contain any characters.
 static constexpr const char* kActionabilityJS = R"js(
 const deadline = performance.now() + timeout;
-let last;
+let last, lastT;
 for (;;) {
+  const t = await new Promise(f => {
+    const id = setTimeout(f, Math.max(0, deadline - performance.now()));
+    requestAnimationFrame(t => { clearTimeout(id); f(t); });
+  });
+  if (performance.now() > deadline) throw "timeout waiting for '" + sel + "' to be actionable";
   const el = document.querySelector(sel);
   if (el) {
     const r = el.getBoundingClientRect();
     const cx = r.left + r.width / 2, cy = r.top + r.height / 2;
     if (r.width > 0 && r.height > 0 && cx >= 0 && cy >= 0 && cx < innerWidth && cy < innerHeight) {
-      if (last && last.l === r.left && last.t === r.top && last.w === r.width && last.h === r.height) {
+      if (last && t !== lastT && last.l === r.left && last.t === r.top && last.w === r.width && last.h === r.height) {
         const hit = document.elementFromPoint(cx, cy);
         if (hit === el || el.contains(hit)) return cx + "," + cy;
       }
       last = { l: r.left, t: r.top, w: r.width, h: r.height };
     } else last = undefined;
   } else last = undefined;
-  if (performance.now() > deadline) throw "timeout waiting for '" + sel + "' to be actionable";
-  await new Promise(f => requestAnimationFrame(f));
+  lastT = t;
 }
 )js";
 

test/js/bun/webview/webview-chrome.test.ts

@@ -725,16 +725,26 @@ it("chrome: click(selector) waits for animation to stop", async () => {
     html(`
         <style>
           @keyframes slide { from { left: 0; } to { left: 100px; } }
-          #mover { position: fixed; top: 50px; width: 60px; height: 60px;
-                   animation: slide 80ms linear forwards; }
+          #mover { position: fixed; top: 50px; left: 0; width: 60px; height: 60px; }
         </style>
-        <button id=mover onclick="window.__hit=this.getBoundingClientRect().left">mv</button>
+        <body style="margin:0" onclick="(window.__x ||= []).push(event.clientX)">
+          <div id=mover></div>
+        </body>
       `),
   );
-  // Stable-for-2-frames check — the click lands after the animation stops.
-  await view.click("#mover");
-  const left = Number(await view.evaluate("String(__hit)"));
-  expect(left).toBe(100);
+  // Restart the animation immediately before each click(): the element reads
+  // left=0 both before the next render (no effect yet) and at t=0 of the
+  // animation, so a sync-then-rAF stability pair would match and click at
+  // the from-position. The loop covers frame-scheduling variance.
+  for (let i = 0; i < 5; i++) {
+    await view.evaluate(
+      `(m => { m.style.animation = 'none'; void m.offsetHeight; m.style.animation = 'slide 100ms linear forwards'; })(document.getElementById('mover'))`,
+    );
+    await view.click("#mover");
+  }
+  // The animation ends at left=100; the element is 60px wide, so every click
+  // lands at clientX=130 once the slide has settled.
+  expect(await view.evaluate("__x")).toEqual(Array(5).fill(130));
 });
 
 // --- scrollTo variants -----------------------------------------------------

test/js/bun/webview/webview.test.ts

@@ -557,17 +557,26 @@ itRendering("click(selector) waits for element to stop animating", async () => {
       encodeURIComponent(`
         <style>
           @keyframes slide { from { left: 0px; } to { left: 100px; } }
-          #mover { position: fixed; top: 50px; width: 60px; height: 60px;
-                   animation: slide 100ms linear forwards; }
+          #mover { position: fixed; top: 50px; left: 0; width: 60px; height: 60px; }
         </style>
-        <button id=mover onclick="window.__hit=this.getBoundingClientRect().left">mv</button>
+        <body style="margin:0" onclick="(window.__x ||= []).push(event.clientX)">
+          <div id=mover></div>
+        </body>
       `),
   );
-  // The stable-for-2-consecutive-frames check means we don't click until
-  // the animation stops. If we clicked mid-slide, __hit would be < 100.
-  await view.click("#mover");
-  const left = await view.evaluate("String(__hit)");
-  expect(Number(left)).toBe(100);
+  // Restart the animation immediately before each click(): the element reads
+  // left=0 both before the next render (no effect yet) and at t=0 of the
+  // animation, so a sync-then-rAF stability pair would match and click at
+  // the from-position. The loop covers frame-scheduling variance.
+  for (let i = 0; i < 5; i++) {
+    await view.evaluate(
+      `(m => { m.style.animation = 'none'; void m.offsetHeight; m.style.animation = 'slide 100ms linear forwards'; })(document.getElementById('mover'))`,
+    );
+    await view.click("#mover");
+  }
+  // The animation ends at left=100; the element is 60px wide, so every click
+  // lands at clientX=130 once the slide has settled.
+  expect(await view.evaluate("__x")).toEqual(Array(5).fill(130));
 });
 
 itRendering("click(selector) rejects on timeout when obscured", async () => {