fix(fabric.Object) unnecessary cache invalidation, ISSUE-7157 (#7183)

src/shapes/object.class.js

@@ -930,6 +930,17 @@
      * @return {Object} object with scaleX and scaleY properties
      */
     getObjectScaling: function() {
+      // if the object is a top level one, on the canvas, we go for simple aritmetic
+      // otherwise the complex method with angles will return approximations and decimals
+      // and will likely kill the cache when not needed
+      // https://github.com/fabricjs/fabric.js/issues/7157
+      if (!this.group) {
+        return {
+          scaleX: this.scaleX,
+          scaleY: this.scaleY,
+        };
+      }
+      // if we are inside a group total zoom calculation is complex, we defer to generic matrices
       var options = fabric.util.qrDecompose(this.calcTransformMatrix());
       return { scaleX: Math.abs(options.scaleX), scaleY: Math.abs(options.scaleY) };
     },