Show Arrows at snippets tab bar only when needed

browser/main/Detail/SnippetNoteDetail.js

@@ -93,6 +93,7 @@ class SnippetNoteDetail extends React.Component {
           this.refs['code-' + index].reload()
         })
         if (this.refs.tags) this.refs.tags.reset()
+        this.setState(this.getArrowsState())
       })
     }
   }
@@ -340,7 +341,7 @@ class SnippetNoteDetail extends React.Component {
     const snippetIndex = this.state.snippetIndex >= snippets.length
       ? snippets.length - 1
       : this.state.snippetIndex
-    this.setState({ note, snippetIndex }, () => {
+    this.setState(Object.assign({ note, snippetIndex }, this.getArrowsState()), () => {
       this.save()
       this.refs['code-' + this.state.snippetIndex].reload()
     })
@@ -515,15 +516,22 @@ class SnippetNoteDetail extends React.Component {
 
   moveTabBarBy (x) {
     this.allTabs.addEventListener('transitionend', () => {
-      this.setState({
+      this.setState(this.getArrowsState())
-        enableRightArrow: this.allTabs.offsetLeft !== this.visibleTabs.offsetWidth - this.allTabs.offsetWidth,
-        enableLeftArrow: this.allTabs.offsetLeft !== 0
-      })
     }, {once: true})
 
     this.allTabs.style.left = `${x}px`
   }
 
+  getArrowsState () {
+    const allTabs = this.allTabs
+    const visibleTabs = this.visibleTabs
+    const showArrows = visibleTabs.offsetWidth < allTabs.offsetWidth
+    const enableRightArrow = allTabs.offsetLeft !== visibleTabs.offsetWidth - allTabs.offsetWidth
+    const enableLeftArrow = allTabs.offsetLeft !== 0
+
+    return {showArrows, enableRightArrow, enableLeftArrow}
+  }
+
   addSnippet () {
     const { note } = this.state
 
@@ -534,12 +542,14 @@ class SnippetNoteDetail extends React.Component {
     }])
     const snippetIndex = note.snippets.length - 1
 
-    this.setState({
+    this.setState(Object.assign({
       note,
       snippetIndex
-    }, () => {
+    }, this.getArrowsState()), () => {
+      if (this.state.showArrows) {
         const newLeft = this.visibleTabs.offsetWidth - this.allTabs.offsetWidth
         this.moveTabBarBy(newLeft)
+      }
       this.refs['tab-' + snippetIndex].startRenaming()
     })
   }