Implement some form of lazy loading of large files.
Not sure if I should report to GtkSourceView5 but I had the sadistic idea to throw a 1.5GB JSON file in it to see how it would handle it and I'm sorry for doing that honestly. Anyhow, it grew to 4.1GB and wrote 9.2GB on my disk after a few minutes of loading which is already better than previously crashing but I just decided to spare it (and myself) because I knew it just wasn't gonna happen.
Is this unreasonable to do to a text editor? Yes.
Anyhow, I think there should be some kind of lazy loading to avoid this worst case scenario.