Bug 1774330: Only return ancestors from ChildAtPoint r=eeejay

Differential Revision: https://phabricator.services.mozilla.com/D160849

accessible/ipc/RemoteAccessibleBase.cpp

@@ -380,12 +380,16 @@ Accessible* RemoteAccessibleBase<Derived>::ChildAtPoint(
             MOZ_ASSERT(innerDoc->IsDoc());
             // Search the embedded document's viewport cache so we return the
             // deepest descendant in that embedded document.
-            return innerDoc->ChildAtPoint(aX, aY,
+            Accessible* deepestAcc = innerDoc->ChildAtPoint(
-                                          EWhichChildAtPoint::DeepestChild);
+                aX, aY, EWhichChildAtPoint::DeepestChild);
+            MOZ_ASSERT(!deepestAcc || deepestAcc->IsRemote());
+            lastMatch = deepestAcc ? deepestAcc->AsRemote() : nullptr;
+            break;
           }
           // If there is no embedded document, the iframe itself is the deepest
           // descendant.
-          return acc;
+          lastMatch = acc;
+          break;
         }
 
         if (acc == this) {
@@ -417,6 +421,12 @@ Accessible* RemoteAccessibleBase<Derived>::ChildAtPoint(
   if (!lastMatch && Bounds().Contains(aX, aY)) {
     return this;
   }
+  // If we end up with a match that is not in the ancestor chain
+  // of the accessible this call originated on, we should ignore it.
+  // This can happen when the aX, aY given are outside `this`.
+  if (lastMatch && !IsDoc() && !IsAncestorOf(lastMatch)) {
+    return nullptr;
+  }
 
   return lastMatch;
 }

accessible/tests/browser/hittest/browser_test_general.js

@@ -129,3 +129,76 @@ addAccessibleTask(
     iframeAttrs: { style: "width: 600px; height: 600px; padding: 10px;" },
   }
 );
+
+addAccessibleTask(
+  `
+  <div id="container">
+    <h1 id="a">A</h1><h1 id="b">B</h1>
+  </div>
+  `,
+  async function(browser, accDoc) {
+    const a = findAccessibleChildByID(accDoc, "a");
+    const b = findAccessibleChildByID(accDoc, "b");
+    const dpr = await getContentDPR(browser);
+    // eslint-disable-next-line no-unused-vars
+    const [x, y, w, h] = Layout.getBounds(a, dpr);
+    // The point passed below will be made relative to `b`, but
+    // we'd like to test a point within `a`. Pass `a`s negative
+    // width for an x offset. Pass zero as a y offset,
+    // assuming the headings are on the same line.
+    await testChildAtPoint(dpr, -w, 0, b, null, null);
+  },
+  {
+    iframe: true,
+    remoteIframe: true,
+    // Ensure that all hittest elements are in view.
+    iframeAttrs: { style: "width: 600px; height: 600px; padding: 10px;" },
+  }
+);
+
+addAccessibleTask(
+  `
+  <style>
+    div {
+      width: 50px;
+      height: 50px;
+      position: relative;
+    }
+
+    div > div {
+      width: 30px;
+      height: 30px;
+      position: absolute;
+      opacity: 0.9;
+    }
+  </style>
+  <div id="a" style="background-color: orange;">
+    <div id="aa" style="background-color: purple;"></div>
+  </div>
+  <div id="b" style="background-color: yellowgreen;">
+    <div id="bb" style="top: -30px; background-color: turquoise"></div>
+  </div>`,
+  async function(browser, accDoc) {
+    const a = findAccessibleChildByID(accDoc, "a");
+    const aa = findAccessibleChildByID(accDoc, "aa");
+    const dpr = await getContentDPR(browser);
+    // eslint-disable-next-line no-unused-vars
+    const [_, y, w] = Layout.getBounds(a, dpr);
+    // test upper left of `a`
+    await testChildAtPoint(dpr, 1, 1, a, aa, aa);
+    // test upper right of `a`
+    await testChildAtPoint(dpr, w - 1, 1, a, a, a);
+    // test just outside upper left of `a`
+    await testChildAtPoint(dpr, 1, y - 1, a, null, null);
+    if (isCacheEnabled) {
+      // test halfway down/left of `a`
+      await testChildAtPoint(dpr, 1, Math.round(y / 2), a, null, null);
+    }
+  },
+  {
+    iframe: false,
+    remoteIframe: false,
+    // Ensure that all hittest elements are in view.
+    iframeAttrs: { style: "width: 600px; height: 600px; padding: 10px;" },
+  }
+);

accessible/tests/browser/hittest/head.js

@@ -37,7 +37,7 @@ function getChildAtPoint(container, x, y, findDeepestChild) {
   } catch (e) {
     // Failed to get child at point.
   }
-
+  info("could not get child at point");
   return null;
 }
 
@@ -45,19 +45,31 @@ async function testChildAtPoint(dpr, x, y, container, child, grandChild) {
   const [containerX, containerY] = Layout.getBounds(container, dpr);
   x += containerX;
   y += containerY;
+  let actual = null;
   await untilCacheIs(
-    () => getChildAtPoint(container, x, y, false),
+    () => {
+      actual = getChildAtPoint(container, x, y, false);
+      return actual;
+    },
     child,
     `Wrong direct child accessible at the point (${x}, ${y}) of ${CommonUtils.prettyName(
       container
-    )}, sought ${child ? roleToString(child.role) : "unknown"}`
+    )}, sought ${CommonUtils.prettyName(
+      child
+    )} and got ${CommonUtils.prettyName(actual)}`
   );
+  actual = null;
   await untilCacheIs(
-    () => getChildAtPoint(container, x, y, true),
+    () => {
+      actual = getChildAtPoint(container, x, y, true);
+      return actual;
+    },
     grandChild,
     `Wrong deepest child accessible at the point (${x}, ${y}) of ${CommonUtils.prettyName(
       container
-    )}, sought ${grandChild ? roleToString(grandChild.role) : "unknown"}`
+    )}, sought ${CommonUtils.prettyName(
+      grandChild
+    )} and got ${CommonUtils.prettyName(actual)}`
   );
 }
 
@@ -78,14 +90,14 @@ async function hitTest(browser, container, child, grandChild) {
     child,
     `Wrong direct child accessible at the point (${x}, ${y}) of ${CommonUtils.prettyName(
       container
-    )}, sought ${child ? roleToString(child.role) : "unknown"}`
+    )}, sought ${CommonUtils.prettyName(child)}`
   );
   await untilCacheIs(
     () => getChildAtPoint(container, x, y, true),
     grandChild,
     `Wrong deepest child accessible at the point (${x}, ${y}) of ${CommonUtils.prettyName(
       container
-    )}, sought ${grandChild ? roleToString(grandChild.role) : "unknown"}`
+    )}, sought ${CommonUtils.prettyName(grandChild)}`
   );
 }