adjust the flex scale when close pane

src/pane-axis.coffee

@@ -83,6 +83,16 @@ class PaneAxis extends Model
     @children.splice(index, 0, child)
     @emitter.emit 'did-add-child', {child, index}
 
+  adjustFlexScale: ->
+    # get current total flex scale of children
+    total = 0
+    total += child.getFlexScale() for child in @children
+
+    needTotal = @children.length
+    # set every child's flex scale by the ratio
+    for child in @children
+      child.setFlexScale(needTotal * child.getFlexScale() / total)
+
   removeChild: (child, replacing=false) ->
     index = @children.indexOf(child)
     throw new Error("Removing non-existent child") if index is -1
@@ -90,6 +100,7 @@ class PaneAxis extends Model
     @unsubscribeFromChild(child)
 
     @children.splice(index, 1)
+    @adjustFlexScale()
     @emitter.emit 'did-remove-child', {child, index}
     @reparentLastChild() if not replacing and @children.length < 2
 
@@ -113,7 +124,9 @@ class PaneAxis extends Model
     @addChild(newChild, index + 1)
 
   reparentLastChild: ->
-    @parent.replaceChild(this, @children[0])
+    lastChild = @children[0]
+    lastChild.setFlexScale(@flexScale)
+    @parent.replaceChild(this, lastChild)
     @destroy()
 
   subscribeToChild: (child) ->

src/pane-resize-handle-element.coffee

@@ -13,8 +13,8 @@ class PaneResizeHandleElement extends HTMLElement
 
   resizeToFitContent: ->
     # clear flex-grow css style of both pane
-    @previousSibling.style.flexGrow = ''
-    @nextSibling.style.flexGrow = ''
+    @previousSibling.model.setFlexScale(1)
+    @nextSibling.model.setFlexScale(1)
 
   resizeStarted: (e)->
     e.stopPropagation()
@@ -30,8 +30,8 @@ class PaneResizeHandleElement extends HTMLElement
     [total * ratio1 / allRatio, total * ratio2 / allRatio]
 
   setFlexGrow: (prevSize, nextSize) ->
-    @prevModel = @previousSibling.getModel()
-    @nextModel = @nextSibling.getModel()
+    @prevModel = @previousSibling.model
+    @nextModel = @nextSibling.model
     totalScale = @prevModel.getFlexScale() + @nextModel.getFlexScale()
     flexGrows = @calcRatio(prevSize, nextSize, totalScale)
     @prevModel.setFlexScale flexGrows[0]