fix(core): prevent observer trigger because of grab cursor

fixes #6423

Author: nolimits4web

src/core/grab-cursor/setGrabCursor.js

@@ -7,6 +7,14 @@ export default function setGrabCursor(moving) {
   )
     return;
   const el = swiper.params.touchEventsTarget === 'container' ? swiper.el : swiper.wrapperEl;
+  if (swiper.isElement) {
+    swiper.__preventObserver__ = true;
+  }
   el.style.cursor = 'move';
   el.style.cursor = moving ? 'grabbing' : 'grab';
+  if (swiper.isElement) {
+    requestAnimationFrame(() => {
+      swiper.__preventObserver__ = false;
+    });
+  }
 }

src/core/grab-cursor/unsetGrabCursor.js

@@ -3,5 +3,13 @@ export default function unsetGrabCursor() {
   if ((swiper.params.watchOverflow && swiper.isLocked) || swiper.params.cssMode) {
     return;
   }
+  if (swiper.isElement) {
+    swiper.__preventObserver__ = true;
+  }
   swiper[swiper.params.touchEventsTarget === 'container' ? 'el' : 'wrapperEl'].style.cursor = '';
+  if (swiper.isElement) {
+    requestAnimationFrame(() => {
+      swiper.__preventObserver__ = false;
+    });
+  }
 }

src/core/modules/observer/observer.js

@@ -10,10 +10,12 @@ export default function Observer({ swiper, extendParams, on, emit }) {
       // The observerUpdate event should only be triggered
       // once despite the number of mutations.  Additional
       // triggers are redundant and are very costly
+      if (swiper.__preventObserver__) return;
       if (mutations.length === 1) {
         emit('observerUpdate', mutations[0]);
         return;
       }
+
       const observerUpdate = function observerUpdate() {
         emit('observerUpdate', mutations[0]);
       };