Editor: Undo/Redo system for the GUI Editor

[ivan-mogilko]

Having Undo/Redo in the GUI editor is quite wanted by the users. Unfortunately there's none.

This task suggests coding an abstract Undo/Redo system in the Editor first, and then a specialized implementation for the GUI Editor.

There's a ticket #2321 which discusses how to write such a Undo/Redo system, having Room Editor as an example. Please refer to it for explanation and comments on how such system could be done. It does not matter much whether a Room or GUI editor will receive this first, but IMO both should have a common foundation.

[ericoporto]

The big issue here is how to handle things that happen through property grid, there would be a need for some generic way for everything there somehow, so changes there go to the main undo-redo stack.

Edit: today without undo/redo my system is actually just using git. When I think about AGS, it's hard to think about things separated, I think all things that affect the project state would need to somehow go through an undo/redo system. I don't know how this would actually work memory wise.

[ivan-mogilko]

The big issue here is how to handle things that happen through property grid, there would be a need for some generic way for everything there somehow, so changes there go to the main undo-redo stack.

There's PropertyChanged virtual method in both EditorComponent and EditorContentPanel classes. I don't remember details of how it works by heart, but I think it's reliable.