Description of the Issue

When Doc Switcher is set in vertical mode on the left side it inherits the background color of the editor. But, in certain cases, it doesn't appear to repaint when it should. This gives the doc switcher the same light grey background as the title bar. Happens in Windows 10 when the user switches to task view.

Steps to Reproduce the Issue

1. Open Notepad++
2. Switch to Task View ( Windows Button + Tab )
3. Exit Task View

Expected Behavior

The doc switcher should repaint the background upon refocus.

Actual Behavior

Appears the doc switcher does not repaint, producing the light grey background of the title bar.

Debug Information

Notepad++ v7.2.2 (32-bit)
Build time : Nov 27 2016 - 16:31:07
Path : C:\Program Files (x86)\Notepad++\notepad++.exe
Admin mode : OFF
Local Conf mode : OFF
OS : Windows 10
Plugins : AutoSave.dll mimeTools.dll NppConverter.dll NppExport.dll NppFTP.dll PluginManager.dll