Event Handler Destroyer (EHD) is an add-on for GZDoom that destroys event handlers.
It has a very specific purpose: to allow transitioning to updated version of other add-ons without losing savegame progress.
Imagine if an add-on A updated from version 1.0 to version 2.0. Player has a saved game with Av1.0, but desires to continue playing with Av2.0. Av2.0 happens to be savefile-incompatible with Av1.0. What can we do?
In some cases, nothing. However, if A manifests itself only with Event Handlers, it's possible to destroy existing event handlers from Av1.0, load Av2.0, and Av2.0 will start working on new level.
Step by step guide:
- Have a saved game with Av1.0. Better to have it almost at the end of the level.
- Add EHD to load order.
- Load the saved game. EHD is compatible with existing savefiles.
- Open console, type
ehd_listto print all event handlers. - In the printed list, find all event handlers that belong to Av1.0.
- For each of the event handlers from Av1.0, use
ehd_destroycommand. - Av1.0 stops functioning.
- Save the game, quit GZDoom.
- Replace Av1.0 with Av2.0 in load order.
- Load the game saved in step 8.
- Finish the level.
- Av2.0 works.
Even if an add-on functions only event handlers, it may not expect those event handlers being destroyed, and therefore it may be not compatible with EHD.
EHD is created to aid updating Gearbox add-on (which supports EHD since v0.5), but with hope that it can be used for other add-ons too.
Event Handler Destroyer is a part of m8f's doctor's bag.