Feat：鼠标滚轮缩放时默认以鼠标当前位置为中心进行缩放，可以通过配置关闭该特性

simple-mind-map/src/constants/defaultOptions.js

@@ -14,6 +14,8 @@ export const defaultOpt = {
   themeConfig: {},
   // 放大缩小的增量比例
   scaleRatio: 0.2,
+  // 鼠标缩放是否以鼠标当前位置为中心点，否则以画布中心点
+  mouseScaleCenterUseMousePosition: true,
   // 最多显示几个标签
   maxTag: 5,
   // 导出图片时的内边距

simple-mind-map/src/core/view/View.js

@@ -60,29 +60,37 @@ class View {
     })
     // 放大缩小视图
     this.mindMap.event.on('mousewheel', (e, dir, event, isTouchPad) => {
+      let {
+        customHandleMousewheel,
+        mousewheelAction,
+        mouseScaleCenterUseMousePosition,
+        mousewheelMoveStep
+      } = this.mindMap.opt
+      // 是否自定义鼠标滚轮事件
       if (
-        this.mindMap.opt.customHandleMousewheel &&
-        typeof this.mindMap.opt.customHandleMousewheel === 'function'
+        customHandleMousewheel &&
+        typeof customHandleMousewheel === 'function'
       ) {
-        return this.mindMap.opt.customHandleMousewheel(e)
+        return customHandleMousewheel(e)
       }
-      if (
-        this.mindMap.opt.mousewheelAction === CONSTANTS.MOUSE_WHEEL_ACTION.ZOOM
-      ) {
+      // 鼠标滚轮事件控制缩放
+      if (mousewheelAction === CONSTANTS.MOUSE_WHEEL_ACTION.ZOOM) {
+        let cx = mouseScaleCenterUseMousePosition ? e.clientX : undefined
+        let cy = mouseScaleCenterUseMousePosition ? e.clientY : undefined
         switch (dir) {
           // 鼠标滚轮，向上和向左，都是缩小
           case CONSTANTS.DIR.UP:
           case CONSTANTS.DIR.LEFT:
-            this.narrow(e.clientX, e.clientY)
+            this.narrow(cx, cy)
             break
           // 鼠标滚轮，向下和向右，都是放大
           case CONSTANTS.DIR.DOWN:
           case CONSTANTS.DIR.RIGHT:
-            this.enlarge(e.clientX, e.clientY)
+            this.enlarge(cx, cy)
             break
         }
-      } else {
-        let step = this.mindMap.opt.mousewheelMoveStep
+      } else {// 鼠标滚轮事件控制画布移动
+        let step = mousewheelMoveStep
         if (isTouchPad) {
           step = 5
         }