From 0d8f08ab9b435f0c16aa24fa0e2e9f99fdd738ab Mon Sep 17 00:00:00 2001
From: msidolphin <msidolphin@outlook.com>
Date: Thu, 27 Jan 2022 17:10:44 +0800
Subject: [PATCH] perf(components): [el-scrollbar] prevent re-render when
 scrolling (#5670)

* perf(components): [el-scrollbar] prevent re-render when scrolling

* chore: improve code
---
 packages/components/scrollbar/index.ts        |   2 +-
 packages/components/scrollbar/src/bar.ts      |  26 ++-
 packages/components/scrollbar/src/bar.vue     | 203 +++---------------
 .../components/scrollbar/src/scrollbar.vue    |  23 +-
 packages/components/scrollbar/src/thumb.ts    |  14 ++
 packages/components/scrollbar/src/thumb.vue   | 194 +++++++++++++++++
 6 files changed, 263 insertions(+), 199 deletions(-)
 create mode 100644 packages/components/scrollbar/src/thumb.ts
 create mode 100644 packages/components/scrollbar/src/thumb.vue

diff --git a/packages/components/scrollbar/index.ts b/packages/components/scrollbar/index.ts
index 7d9bafef97..1e829330b4 100644
--- a/packages/components/scrollbar/index.ts
+++ b/packages/components/scrollbar/index.ts
@@ -7,4 +7,4 @@ export default ElScrollbar
 
 export * from './src/util'
 export * from './src/scrollbar'
-export * from './src/bar'
+export * from './src/thumb'
diff --git a/packages/components/scrollbar/src/bar.ts b/packages/components/scrollbar/src/bar.ts
index f8bd75dabd..5dd090572a 100644
--- a/packages/components/scrollbar/src/bar.ts
+++ b/packages/components/scrollbar/src/bar.ts
@@ -2,13 +2,25 @@ import { buildProps } from '@element-plus/utils/props'
 import type { ExtractPropTypes } from 'vue'
 
 export const barProps = buildProps({
-  vertical: Boolean,
-  size: String,
-  move: Number,
-  ratio: {
-    type: Number,
-    required: true,
+  always: {
+    type: Boolean,
+    default: true,
+  },
+  width: {
+    type: String,
+    default: '',
+  },
+  height: {
+    type: String,
+    default: '',
+  },
+  ratioX: {
+    type: Number,
+    default: 1,
+  },
+  ratioY: {
+    type: Number,
+    default: 1,
   },
-  always: Boolean,
 } as const)
 export type BarProps = ExtractPropTypes<typeof barProps>
diff --git a/packages/components/scrollbar/src/bar.vue b/packages/components/scrollbar/src/bar.vue
index 0951ac6c80..e0252fdc44 100644
--- a/packages/components/scrollbar/src/bar.vue
+++ b/packages/components/scrollbar/src/bar.vue
@@ -1,193 +1,42 @@
 <template>
-  <transition name="el-scrollbar-fade">
-    <div
-      v-show="always || visible"
-      ref="instance"
-      :class="['el-scrollbar__bar', 'is-' + bar.key]"
-      @mousedown="clickTrackHandler"
-    >
-      <div
-        ref="thumb"
-        class="el-scrollbar__thumb"
-        :style="thumbStyle"
-        @mousedown="clickThumbHandler"
-      ></div>
-    </div>
-  </transition>
+  <thumb :move="moveX" :ratio="ratioX" :size="width" :always="always" />
+  <thumb
+    :move="moveY"
+    :ratio="ratioY"
+    :size="height"
+    vertical
+    :always="always"
+  />
 </template>
-
 <script lang="ts">
-import {
-  computed,
-  defineComponent,
-  inject,
-  onBeforeUnmount,
-  ref,
-  toRef,
-} from 'vue'
-import { useEventListener, isClient } from '@vueuse/core'
-import { scrollbarContextKey } from '@element-plus/tokens'
-import { throwError } from '@element-plus/utils/error'
-import { BAR_MAP, renderThumbStyle } from './util'
-
+import { defineComponent, ref } from 'vue'
+import Thumb from './thumb.vue'
 import { barProps } from './bar'
 
-const COMPONENT_NAME = 'Bar'
 export default defineComponent({
-  name: COMPONENT_NAME,
+  components: {
+    Thumb,
+  },
   props: barProps,
-
   setup(props) {
-    const scrollbar = inject(scrollbarContextKey)
-    if (!scrollbar)
-      throwError(COMPONENT_NAME, 'can not inject scrollbar context')
+    const moveX = ref(0)
+    const moveY = ref(0)
+    const GAP = 4 // top 2 + bottom 2 of bar instance
 
-    const instance = ref<HTMLDivElement>()
-    const thumb = ref<HTMLDivElement>()
+    const handleScroll = (wrap: HTMLDivElement) => {
+      if (wrap) {
+        const offsetHeight = wrap.offsetHeight - GAP
+        const offsetWidth = wrap.offsetWidth - GAP
 
-    const barStore = ref({})
-    const visible = ref(false)
-
-    let cursorDown = false
-    let cursorLeave = false
-    let onselectstartStore:
-      | ((this: GlobalEventHandlers, ev: Event) => any)
-      | null = isClient ? document.onselectstart : null
-
-    const bar = computed(
-      () => BAR_MAP[props.vertical ? 'vertical' : 'horizontal']
-    )
-
-    const thumbStyle = computed(() =>
-      renderThumbStyle({
-        size: props.size,
-        move: props.move,
-        bar: bar.value,
-      })
-    )
-
-    const offsetRatio = computed(
-      () =>
-        // offsetRatioX = original width of thumb / current width of thumb / ratioX
-        // offsetRatioY = original height of thumb / current height of thumb / ratioY
-        // instance height = wrap height - GAP
-        instance.value![bar.value.offset] ** 2 /
-        scrollbar.wrapElement![bar.value.scrollSize] /
-        props.ratio /
-        thumb.value![bar.value.offset]
-    )
-
-    const clickThumbHandler = (e: MouseEvent) => {
-      // prevent click event of middle and right button
-      e.stopPropagation()
-      if (e.ctrlKey || [1, 2].includes(e.button)) return
-
-      window.getSelection()?.removeAllRanges()
-      startDrag(e)
-
-      const el = e.currentTarget as HTMLDivElement
-      if (!el) return
-      barStore.value[bar.value.axis] =
-        el[bar.value.offset] -
-        (e[bar.value.client] - el.getBoundingClientRect()[bar.value.direction])
+        moveY.value = ((wrap.scrollTop * 100) / offsetHeight) * props.ratioY
+        moveX.value = ((wrap.scrollLeft * 100) / offsetWidth) * props.ratioX
+      }
     }
 
-    const clickTrackHandler = (e: MouseEvent) => {
-      if (!thumb.value || !instance.value || !scrollbar.wrapElement) return
-
-      const offset = Math.abs(
-        (e.target as HTMLElement).getBoundingClientRect()[bar.value.direction] -
-          e[bar.value.client]
-      )
-      const thumbHalf = thumb.value[bar.value.offset] / 2
-      const thumbPositionPercentage =
-        ((offset - thumbHalf) * 100 * offsetRatio.value) /
-        instance.value[bar.value.offset]
-
-      scrollbar.wrapElement[bar.value.scroll] =
-        (thumbPositionPercentage *
-          scrollbar.wrapElement[bar.value.scrollSize]) /
-        100
-    }
-
-    const startDrag = (e: MouseEvent) => {
-      e.stopImmediatePropagation()
-      cursorDown = true
-      document.addEventListener('mousemove', mouseMoveDocumentHandler)
-      document.addEventListener('mouseup', mouseUpDocumentHandler)
-      onselectstartStore = document.onselectstart
-      document.onselectstart = () => false
-    }
-
-    const mouseMoveDocumentHandler = (e: MouseEvent) => {
-      if (!instance.value || !thumb.value) return
-      if (cursorDown === false) return
-
-      const prevPage = barStore.value[bar.value.axis]
-      if (!prevPage) return
-
-      const offset =
-        (instance.value.getBoundingClientRect()[bar.value.direction] -
-          e[bar.value.client]) *
-        -1
-      const thumbClickPosition = thumb.value[bar.value.offset] - prevPage
-      const thumbPositionPercentage =
-        ((offset - thumbClickPosition) * 100 * offsetRatio.value) /
-        instance.value[bar.value.offset]
-      scrollbar.wrapElement[bar.value.scroll] =
-        (thumbPositionPercentage *
-          scrollbar.wrapElement[bar.value.scrollSize]) /
-        100
-    }
-
-    const mouseUpDocumentHandler = () => {
-      cursorDown = false
-      barStore.value[bar.value.axis] = 0
-      document.removeEventListener('mousemove', mouseMoveDocumentHandler)
-      document.removeEventListener('mouseup', mouseUpDocumentHandler)
-      restoreOnselectstart()
-      if (cursorLeave) visible.value = false
-    }
-
-    const mouseMoveScrollbarHandler = () => {
-      cursorLeave = false
-      visible.value = !!props.size
-    }
-
-    const mouseLeaveScrollbarHandler = () => {
-      cursorLeave = true
-      visible.value = cursorDown
-    }
-
-    onBeforeUnmount(() => {
-      restoreOnselectstart()
-      document.removeEventListener('mouseup', mouseUpDocumentHandler)
-    })
-
-    const restoreOnselectstart = () => {
-      if (document.onselectstart !== onselectstartStore)
-        document.onselectstart = onselectstartStore
-    }
-
-    useEventListener(
-      toRef(scrollbar, 'scrollbarElement'),
-      'mousemove',
-      mouseMoveScrollbarHandler
-    )
-    useEventListener(
-      toRef(scrollbar, 'scrollbarElement'),
-      'mouseleave',
-      mouseLeaveScrollbarHandler
-    )
-
     return {
-      instance,
-      thumb,
-      bar,
-      thumbStyle,
-      visible,
-      clickTrackHandler,
-      clickThumbHandler,
+      handleScroll,
+      moveX,
+      moveY,
     }
   },
 })
diff --git a/packages/components/scrollbar/src/scrollbar.vue b/packages/components/scrollbar/src/scrollbar.vue
index 8d86ef8c27..aeab296bdd 100644
--- a/packages/components/scrollbar/src/scrollbar.vue
+++ b/packages/components/scrollbar/src/scrollbar.vue
@@ -20,14 +20,14 @@
       </component>
     </div>
     <template v-if="!native">
-      <bar :move="moveX" :ratio="ratioX" :size="sizeWidth" :always="always" />
       <bar
-        :move="moveY"
-        :ratio="ratioY"
-        :size="sizeHeight"
-        vertical
+        ref="barRef"
+        :height="sizeHeight"
+        :width="sizeWidth"
         :always="always"
-      />
+        :ratio-x="ratioX"
+        :ratio-y="ratioY"
+      ></bar>
     </template>
   </div>
 </template>
@@ -69,6 +69,7 @@ export default defineComponent({
 
     const sizeWidth = ref('0')
     const sizeHeight = ref('0')
+    const barRef = ref()
     const moveX = ref(0)
     const moveY = ref(0)
     const ratioY = ref(1)
@@ -85,13 +86,7 @@ export default defineComponent({
 
     const handleScroll = () => {
       if (wrap$.value) {
-        const offsetHeight = wrap$.value.offsetHeight - GAP
-        const offsetWidth = wrap$.value.offsetWidth - GAP
-
-        moveY.value =
-          ((wrap$.value.scrollTop * 100) / offsetHeight) * ratioY.value
-        moveX.value =
-          ((wrap$.value.scrollLeft * 100) / offsetWidth) * ratioX.value
+        barRef.value?.handleScroll(wrap$.value)
 
         emit('scroll', {
           scrollTop: wrap$.value.scrollTop,
@@ -170,7 +165,7 @@ export default defineComponent({
       scrollbar$,
       wrap$,
       resize$,
-
+      barRef,
       moveX,
       moveY,
       ratioX,
diff --git a/packages/components/scrollbar/src/thumb.ts b/packages/components/scrollbar/src/thumb.ts
new file mode 100644
index 0000000000..005d6043af
--- /dev/null
+++ b/packages/components/scrollbar/src/thumb.ts
@@ -0,0 +1,14 @@
+import { buildProps } from '@element-plus/utils/props'
+import type { ExtractPropTypes } from 'vue'
+
+export const thumbProps = buildProps({
+  vertical: Boolean,
+  size: String,
+  move: Number,
+  ratio: {
+    type: Number,
+    required: true,
+  },
+  always: Boolean,
+} as const)
+export type ThumbProps = ExtractPropTypes<typeof thumbProps>
diff --git a/packages/components/scrollbar/src/thumb.vue b/packages/components/scrollbar/src/thumb.vue
new file mode 100644
index 0000000000..f10c4cd92a
--- /dev/null
+++ b/packages/components/scrollbar/src/thumb.vue
@@ -0,0 +1,194 @@
+<template>
+  <transition name="el-scrollbar-fade">
+    <div
+      v-show="always || visible"
+      ref="instance"
+      :class="['el-scrollbar__bar', 'is-' + bar.key]"
+      @mousedown="clickTrackHandler"
+    >
+      <div
+        ref="thumb"
+        class="el-scrollbar__thumb"
+        :style="thumbStyle"
+        @mousedown="clickThumbHandler"
+      ></div>
+    </div>
+  </transition>
+</template>
+
+<script lang="ts">
+import {
+  computed,
+  defineComponent,
+  inject,
+  onBeforeUnmount,
+  ref,
+  toRef,
+} from 'vue'
+import { useEventListener, isClient } from '@vueuse/core'
+import { scrollbarContextKey } from '@element-plus/tokens'
+import { throwError } from '@element-plus/utils/error'
+import { BAR_MAP, renderThumbStyle } from './util'
+
+import { thumbProps } from './thumb'
+
+const COMPONENT_NAME = 'Thumb'
+export default defineComponent({
+  name: COMPONENT_NAME,
+  props: thumbProps,
+
+  setup(props) {
+    const scrollbar = inject(scrollbarContextKey)
+    if (!scrollbar)
+      throwError(COMPONENT_NAME, 'can not inject scrollbar context')
+
+    const instance = ref<HTMLDivElement>()
+    const thumb = ref<HTMLDivElement>()
+
+    const thumbState = ref({})
+    const visible = ref(false)
+
+    let cursorDown = false
+    let cursorLeave = false
+    let originalOnSelectStart:
+      | ((this: GlobalEventHandlers, ev: Event) => any)
+      | null = isClient ? document.onselectstart : null
+
+    const bar = computed(
+      () => BAR_MAP[props.vertical ? 'vertical' : 'horizontal']
+    )
+
+    const thumbStyle = computed(() =>
+      renderThumbStyle({
+        size: props.size,
+        move: props.move,
+        bar: bar.value,
+      })
+    )
+
+    const offsetRatio = computed(
+      () =>
+        // offsetRatioX = original width of thumb / current width of thumb / ratioX
+        // offsetRatioY = original height of thumb / current height of thumb / ratioY
+        // instance height = wrap height - GAP
+        instance.value![bar.value.offset] ** 2 /
+        scrollbar.wrapElement![bar.value.scrollSize] /
+        props.ratio /
+        thumb.value![bar.value.offset]
+    )
+
+    const clickThumbHandler = (e: MouseEvent) => {
+      // prevent click event of middle and right button
+      e.stopPropagation()
+      if (e.ctrlKey || [1, 2].includes(e.button)) return
+
+      window.getSelection()?.removeAllRanges()
+      startDrag(e)
+
+      const el = e.currentTarget as HTMLDivElement
+      if (!el) return
+      thumbState.value[bar.value.axis] =
+        el[bar.value.offset] -
+        (e[bar.value.client] - el.getBoundingClientRect()[bar.value.direction])
+    }
+
+    const clickTrackHandler = (e: MouseEvent) => {
+      if (!thumb.value || !instance.value || !scrollbar.wrapElement) return
+
+      const offset = Math.abs(
+        (e.target as HTMLElement).getBoundingClientRect()[bar.value.direction] -
+          e[bar.value.client]
+      )
+      const thumbHalf = thumb.value[bar.value.offset] / 2
+      const thumbPositionPercentage =
+        ((offset - thumbHalf) * 100 * offsetRatio.value) /
+        instance.value[bar.value.offset]
+
+      scrollbar.wrapElement[bar.value.scroll] =
+        (thumbPositionPercentage *
+          scrollbar.wrapElement[bar.value.scrollSize]) /
+        100
+    }
+
+    const startDrag = (e: MouseEvent) => {
+      e.stopImmediatePropagation()
+      cursorDown = true
+      document.addEventListener('mousemove', mouseMoveDocumentHandler)
+      document.addEventListener('mouseup', mouseUpDocumentHandler)
+      originalOnSelectStart = document.onselectstart
+      document.onselectstart = () => false
+    }
+
+    const mouseMoveDocumentHandler = (e: MouseEvent) => {
+      if (!instance.value || !thumb.value) return
+      if (cursorDown === false) return
+
+      const prevPage = thumbState.value[bar.value.axis]
+      if (!prevPage) return
+
+      const offset =
+        (instance.value.getBoundingClientRect()[bar.value.direction] -
+          e[bar.value.client]) *
+        -1
+      const thumbClickPosition = thumb.value[bar.value.offset] - prevPage
+      const thumbPositionPercentage =
+        ((offset - thumbClickPosition) * 100 * offsetRatio.value) /
+        instance.value[bar.value.offset]
+      scrollbar.wrapElement[bar.value.scroll] =
+        (thumbPositionPercentage *
+          scrollbar.wrapElement[bar.value.scrollSize]) /
+        100
+    }
+
+    const mouseUpDocumentHandler = () => {
+      cursorDown = false
+      thumbState.value[bar.value.axis] = 0
+      document.removeEventListener('mousemove', mouseMoveDocumentHandler)
+      document.removeEventListener('mouseup', mouseUpDocumentHandler)
+      restoreOnselectstart()
+      if (cursorLeave) visible.value = false
+    }
+
+    const mouseMoveScrollbarHandler = () => {
+      cursorLeave = false
+      visible.value = !!props.size
+    }
+
+    const mouseLeaveScrollbarHandler = () => {
+      cursorLeave = true
+      visible.value = cursorDown
+    }
+
+    onBeforeUnmount(() => {
+      restoreOnselectstart()
+      document.removeEventListener('mouseup', mouseUpDocumentHandler)
+    })
+
+    const restoreOnselectstart = () => {
+      if (document.onselectstart !== originalOnSelectStart)
+        document.onselectstart = originalOnSelectStart
+    }
+
+    useEventListener(
+      toRef(scrollbar, 'scrollbarElement'),
+      'mousemove',
+      mouseMoveScrollbarHandler
+    )
+    useEventListener(
+      toRef(scrollbar, 'scrollbarElement'),
+      'mouseleave',
+      mouseLeaveScrollbarHandler
+    )
+
+    return {
+      instance,
+      thumb,
+      bar,
+      thumbStyle,
+      visible,
+      clickTrackHandler,
+      clickThumbHandler,
+    }
+  },
+})
+</script>