I just noticed, that ProjExtStates can not store strings with \0-bytes. Means, they will be cut at the very first \0.
Example:
Code:
reaper.SetProjExtState(0, "extname", "key", "Oh, Sweet child \0 mine...")
A,B=reaper.GetProjExtState(0, "extname", "key")
I tried to store the content of image-files(png, jpg) into ProjExtStates to add them later on to the metadata of my mp3. However, as pngs/jpgs use \0 in them, the data is not complete and therefore not useable anymore.
Tested in Reaper 6.61x64 and Reaper 6.59x64 on Windows 7