I have created an Acrobat DC PlugIn which creates a toolbar. The icon for the toolbar initially shows up correctly, but on subsequent mouse clicks of the icon, it turns black. I cannot find any significant documentation on the AVToolBarSetIcon function and am going by one or two samples I have seen. I am not sure what the two images in AVToolBarSetIcon should be. It doesn't seem to matter what the second one is though. The code is shown here:
This is poorly documented or poorly implemented, I am not sure which. Do you do anything with the PDF icon file after closing it? My experience is that Acrobat takes a lock to prevent the close, and continues to try to read it after you close it.