The solution that comes to mind is that the graphical elements are backed by text for these purposes. Then, the graphical interface amounts to an editor for this meta-language.
Inevitably, that is what is attempted. But it doesn't solve the use cases I mentioned.
To take a diff for example, not only do you need to illustrate the diff version of (I drew a new line from here to here and made this other box green), you would also need to illustrate patches to textual details and how they related to the graphical code.
Maybe I can imagine a solution that could do that (at great expense). I cannot imagine the language being friendly enough that third-party compilers, IDEs, or static-analysis tools would be feasible.
To take a diff for example, not only do you need to illustrate the diff version of (I drew a new line from here to here and made this other box green), you would also need to illustrate patches to textual details and how they related to the graphical code.
Maybe I can imagine a solution that could do that (at great expense). I cannot imagine the language being friendly enough that third-party compilers, IDEs, or static-analysis tools would be feasible.