For this specific example I am using demo/ToolBar.py and changing one of the Button’s Bitmaps for the wx.ART_LIST_VIEW bitmap from the ArtProvider. In Version 4.0.7.Post2 the background was “transparent”; I have now upgraded to version 4.1.1 and now half of the background is black. I have tried adding a mask, but to no avail. Any light on the matter would help. I have found this here, but I don’t know if it has to do with the issue.
Update: Seems like I can only upload one image.
Update2: This is on a Windows 10 Machine Using Python 3.5