For programming and testing I'm abandoning Hosted on Windows in favor of Hosted on Linux and AROS Native. Hosted on Windows is very quirky! Firstly, the Snapshots don't work correctly. Secondly, and I'm sure there's more, the DataTypes System isn't working correctly either.
On Hosted on Windows when I compile and install a new version of a datatype in Sys:Classes/Datatypes and restart it should load it into the system and make it active. It doesn't. Instead it doesn't release the previous version of the datatype. It keeps using the older version.
I suspected that was the case so I deleted the dataype completely and restarted. It still worked to load and display images without the datatype!
On AROS Native however everything works as it should. When a new version of a datatype is copied to Sys:Classes/Datatypes on restart it gets loaded and becomes the active version instead.
Maybe the quirky behavior of the datatypes on Hosted on Windows is the primary reason I was struggling to display BMPX Alpha Transparency.