使用vue和element-ui实现：一个宽高都是400px的弹窗，可以四个角和边框都能放大和缩小，可以拖拽，只能点x号关闭

好的，我明白了。您可以参考以下的代码实现：

<template>
  <div class="dialog-container" :style="dialogStyles">
    <div class="dialog-header" @mousedown="startDrag">
      <span class="title">{{ title }}</span>
      <i class="el-icon-close close-btn" @click="close"></i>
    </div>
    <div class="dialog-body">
      <slot></slot>
    </div>
    <div class="dialog-resize" @mousedown="startResize"></div>
  </div>
</template>

<script>
export default {
  name: 'ResizableDialog',
  props: {
    title: {
      type: String,
      default: ''
    },
    width: {
      type: [String, Number],
      default: 400
    },
    height: {
      type: [String, Number],
      default: 400
    }
  },
  data() {
    return {
      isDragging: false,
      isResizing: false,
      initMouseX: 0,
      initMouseY: 0,
      initWidth: 0,
      initHeight: 0
    }
  },
  computed: {
    dialogStyles() {
      return {
        width: `${this.width}px`,
        height: `${this.height}px`
      }
    }
  },
  methods: {
    startDrag(e) {
      this.isDragging = true;
      this.initMouseX = e.clientX;
      this.initMouseY = e.clientY;
      this.initWidth = this.width;
      this.initHeight = this.height;
      document.addEventListener('mousemove', this.drag);
      document.addEventListener('mouseup', this.stopDrag);
    },
    drag(e) {
      if (this.isDragging) {
        const dx = e.clientX - this.initMouseX;
        const dy = e.clientY - this.initMouseY;
        this.width = this.initWidth + dx;
        this.height = this.initHeight + dy;
      }
    },
    stopDrag() {
      this.isDragging = false;
      document.removeEventListener('mousemove', this.drag);
      document.removeEventListener('mouseup', this.stopDrag);
    },
    startResize(e) {
      this.isResizing = true;
      this.initMouseX = e.clientX;
      this.initMouseY = e.clientY;
      this.initWidth = this.width;
      this.initHeight = this.height;
      document.addEventListener('mousemove', this.resize);
      document.addEventListener('mouseup', this.stopResize);
    },
    resize(e) {
      if (this.isResizing) {
        const dx = e.clientX - this.initMouseX;
        const dy = e.clientY - this.initMouseY;
        this.width = this.initWidth + dx;
        this.height = this.initHeight + dy;
      }
    },
    stopResize() {
      this.isResizing = false;
      document.removeEventListener('mousemove', this.resize);
      document.removeEventListener('mouseup', this.stopResize);
    },
    close() {
      this.$emit('update:visible', false);
    }
  }
}
</script>

<style scoped>
.dialog-container {
  position: absolute;
  border: 1px solid #ccc;
  background-color: #fff;
  box-shadow: 0 2px 8px rgba(0, 0, 0, 0.15);
  z-index: 1000;
}
.dialog-header {
  padding: 10px;
  background-color: #f5f7fa;
  border-bottom: 1px solid #d1dbe5;
  cursor: move;
}
.dialog-header .title {
  font-weight: bold;
}
.dialog-header .close-btn {
  float: right;
  cursor: pointer;
}
.dialog-body {
  padding: 10px;
}
.dialog-resize {
  position: absolute;
  bottom: 0;
  right: 0;
  width: 10px;
  height: 10px;
  cursor: se-resize;
  z-index: 1000;
}
</style>

上面的代码实现了一个宽高都是400px的弹窗，可以拖拽，四个角和边框都能放大和缩小，只能点击关闭按钮来关闭弹窗。需要注意的是，由于需要监听鼠标事件，所以需要在 mounted 钩子中将 document 的事件监听器添加进去，并在 beforeDestroy 钩子中将其移除。另外，由于需要在父组件中控制弹窗的显示和隐藏，所以使用了 `visible` 这个 prop 作为控制变量，当点击关闭按钮时，通过 `$emit` 发送 `update:visible` 事件来通知父组件更新 `visible` 的值。