Background, yesterday a thunderstorm caused a power failure when I had several modified buffers in Geany 2.0 (actually LSP but same thing) and Vscode. After power came back on (8 hours later ... its was a _big_ storm) the system recovered fine, thanks ext4, Geany opened the right files thanks to regular saves of the session, but as expected at the last state I had saved them, so I have to figure out where I was up to and redo changes since that save. Vscode on the other hand opened the buffers at pretty much the state at the power failure (might have lost a few characters of the one I was editing at the time, but hard to tell, anyway not much) and of course marked them as modified again. I didn't think to check if the undo/redo list was restored as well.

It seems to me that it might be possible to add this as an extra function in the save actions plugin and this issue is to record a reminder. I have not examined things in detail, but I realised a couple of important things:

1. the buffer can be saved in UTF-8, and just restored directly to Scintilla, 2. just some metadata needs to be saved as well to restore the document state and then the buffer can be saved under a hash or some other unique name, no problems with replicating the directory tree 3. no need for all the complex save and load that applies to the actual files.

Havn't examined if all the metadata can be restored by a plugin, but should only need minimal extra if not already possible. I doubt a plugin can stop the session loading the saved file, but if it overwrites Scintilla after the file is loaded at least a undo will be recorded so the Scintilla deltas functionality could be used to show whats different.

An alternative is to save the undo list instead of the buffer and replay it from the last save (but I'm not sure if absolutely everything is put in the undo list).