[REV] web: revert wrong fix on popper reposition

This reverts commit a9273ced.

The IntersectionObserver strategy it implements do not
fullfil properly its purpose.
It was a mistake trying to use this kind of observer as
it is specifically meant for a different use case than
the one we tried to solve in the first place.

Another fix should follow directly this revert commit.

Part-of: odoo/odoo#125048

addons/web/static/src/core/position/position_hook.js

@@ -242,20 +242,14 @@ export function usePosition(reference, options) {
     const { popper } = options;
     const popperRef = popper ? useRef(popper) : useComponent();
     const getReference = reference instanceof HTMLElement ? () => reference : reference;
-    let ref;
     const update = () => {
+        const ref = getReference();
         if (popperRef.el && ref) {
             reposition(ref, popperRef.el, options);
         }
     };
+    useEffect(update);
     const throttledUpdate = throttleForAnimation(update);
-    const referenceObserver = new IntersectionObserver(throttledUpdate);
-    useEffect(() => {
-        ref = getReference();
-        referenceObserver.observe(ref);
-        update();
-        return () => referenceObserver.disconnect();
-    });
     useExternalListener(document, "scroll", throttledUpdate, { capture: true });
     useExternalListener(window, "resize", throttledUpdate);
     onWillUnmount(throttledUpdate.cancel);

addons/web/static/tests/core/position_hook_tests.js

@@ -119,49 +119,31 @@ QUnit.test("can use a t-ref as popper", async (assert) => {
 
 QUnit.test("has no effect when component is destroyed", async (assert) => {
     const execRegisteredCallbacks = mockAnimationFrame();
-    const observer = new MutationObserver(() => assert.step("mutation observer called"));
+    const originalReference = reference;
+    reference = () => {
+        assert.step("reference called");
+        return originalReference;
+    };
+
     const popper = await mount(TestComp, { target: container });
-    observer.observe(popper.el, { attributes: true });
+    assert.verifySteps(["reference called"], "reference called when component mounted");
 
     triggerEvent(document, null, "scroll");
     await nextTick();
     assert.verifySteps([]);
-
     execRegisteredCallbacks();
-    await nextTick();
-    assert.verifySteps(["mutation observer called"], "mutation observer when document scrolled");
+    assert.verifySteps(["reference called"], "reference called when document scrolled");
 
     triggerEvent(document, null, "scroll");
     await nextTick();
-    assert.verifySteps([]);
-
     popper.destroy();
-    await nextTick();
-    assert.verifySteps([]);
-
     execRegisteredCallbacks();
-    await nextTick();
     assert.verifySteps(
         [],
-        "mutation observer not called even if scroll happened right before the component destroys"
+        "reference not called even if scroll happened right before the component destroys"
     );
 });
 
-QUnit.test("reposition popper when its reference moves", async (assert) => {
-    const popper = await mount(TestComp, { target: container });
-    const popBox1 = popper.el.getBoundingClientRect();
-    const spacer = document.createElement("div");
-    spacer.id = "foo";
-    spacer.style.height = "1px";
-    spacer.style.width = "100px";
-    container.prepend(spacer);
-    await nextTick();
-    const popBox2 = popper.el.getBoundingClientRect();
-    assert.strictEqual(popBox1.top, popBox2.top);
-    // spacer width * 0.5 because of flexbox style (justifyContent: center)
-    assert.strictEqual(popBox1.left, popBox2.left - spacer.offsetWidth * 0.5);
-});
-
 const getPositionTest = (position, positionToCheck) => {
     return async (assert) => {
         Object.assign(TestComp.popperOptions, { position });