feat: Add position-by to tooltip and popover. (close #410)

Author: wxsms

src/mixins/popup.mixin.js

@@ -38,6 +38,10 @@ export default {
       type: null,
       default: 'body'
     },
+    positionBy: {
+      type: null,
+      default: null
+    },
     transition: {
       type: Number,
       default: 150
@@ -195,7 +199,7 @@ export default {
       const popup = this.$refs.popup
       /* istanbul ignore else */
       if (popup) {
-        setTooltipPosition(popup, this.triggerEl, this.placement, this.autoPlacement, this.appendTo, this.viewport)
+        setTooltipPosition(popup, this.triggerEl, this.placement, this.autoPlacement, this.appendTo, this.positionBy, this.viewport)
         popup.offsetHeight
       }
     },

src/utils/dom.utils.js

@@ -219,19 +219,19 @@ export function isAvailableAtPosition (trigger, popup, placement) {
   return top && right && bottom && left
 }
 
-export function setTooltipPosition (tooltip, trigger, placement, auto, appendTo, viewport) {
+export function setTooltipPosition (tooltip, trigger, placement, auto, appendTo, positionBy, viewport) {
   if (!isElement(tooltip) || !isElement(trigger)) {
     return
   }
   const isPopover = tooltip && tooltip.className && tooltip.className.indexOf('popover') >= 0
   let containerScrollTop
   let containerScrollLeft
-  if (!isExist(appendTo) || appendTo === 'body') {
+  if (!isExist(appendTo) || appendTo === 'body' || positionBy === 'body') {
     const doc = document.documentElement
     containerScrollLeft = (window.pageXOffset || doc.scrollLeft) - (doc.clientLeft || 0)
     containerScrollTop = (window.pageYOffset || doc.scrollTop) - (doc.clientTop || 0)
   } else {
-    const container = getElementBySelectorOrRef(appendTo)
+    const container = getElementBySelectorOrRef(positionBy || appendTo)
     containerScrollLeft = container.scrollLeft
     containerScrollTop = container.scrollTop
   }