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frontend/node_modules/rc-virtual-list/es/hooks/useScrollDrag.js

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+import raf from "rc-util/es/raf";
+import * as React from 'react';
+function smoothScrollOffset(offset) {
+  return Math.floor(Math.pow(offset, 0.5));
+}
+export function getPageXY(e, horizontal) {
+  var obj = 'touches' in e ? e.touches[0] : e;
+  return obj[horizontal ? 'pageX' : 'pageY'] - window[horizontal ? 'scrollX' : 'scrollY'];
+}
+export default function useScrollDrag(inVirtual, componentRef, onScrollOffset) {
+  React.useEffect(function () {
+    var ele = componentRef.current;
+    if (inVirtual && ele) {
+      var mouseDownLock = false;
+      var rafId;
+      var _offset;
+      var stopScroll = function stopScroll() {
+        raf.cancel(rafId);
+      };
+      var continueScroll = function continueScroll() {
+        stopScroll();
+        rafId = raf(function () {
+          onScrollOffset(_offset);
+          continueScroll();
+        });
+      };
+      var clearDragState = function clearDragState() {
+        mouseDownLock = false;
+        stopScroll();
+      };
+      var onMouseDown = function onMouseDown(e) {
+        // Skip if element set draggable
+        if (e.target.draggable || e.button !== 0) {
+          return;
+        }
+        // Skip if nest List has handled this event
+        var event = e;
+        if (!event._virtualHandled) {
+          event._virtualHandled = true;
+          mouseDownLock = true;
+        }
+      };
+      var onMouseMove = function onMouseMove(e) {
+        if (mouseDownLock) {
+          var mouseY = getPageXY(e, false);
+          var _ele$getBoundingClien = ele.getBoundingClientRect(),
+            top = _ele$getBoundingClien.top,
+            bottom = _ele$getBoundingClien.bottom;
+          if (mouseY <= top) {
+            var diff = top - mouseY;
+            _offset = -smoothScrollOffset(diff);
+            continueScroll();
+          } else if (mouseY >= bottom) {
+            var _diff = mouseY - bottom;
+            _offset = smoothScrollOffset(_diff);
+            continueScroll();
+          } else {
+            stopScroll();
+          }
+        }
+      };
+      ele.addEventListener('mousedown', onMouseDown);
+      ele.ownerDocument.addEventListener('mouseup', clearDragState);
+      ele.ownerDocument.addEventListener('mousemove', onMouseMove);
+      ele.ownerDocument.addEventListener('dragend', clearDragState);
+      return function () {
+        ele.removeEventListener('mousedown', onMouseDown);
+        ele.ownerDocument.removeEventListener('mouseup', clearDragState);
+        ele.ownerDocument.removeEventListener('mousemove', onMouseMove);
+        ele.ownerDocument.removeEventListener('dragend', clearDragState);
+        stopScroll();
+      };
+    }
+  }, [inVirtual]);
+}