Add Launch Cancellation Support for Plugins

📋 Summary

Add an official way for plugins to cancel a game launch before it begins.

❗ Problem

Plugin developers can currently respond to game launch events, but there is no clear supported way to stop a launch from continuing.

This forces developers to rely on unsafe workarounds, such as temporarily changing launch settings or redirecting the launch to a dummy application. These workarounds can be fragile and may risk altering a user’s emulator or game configuration.

💡 Proposal

Add a supported launch cancellation option to the plugin API.

When a plugin runs before a game or additional app launches, it should be able to safely cancel that launch and optionally provide a reason that can be shown to the user.

🧩 Use Cases

• A plugin blocks launching when required files are missing

• A plugin prevents launch until a custom confirmation prompt is accepted

• A parental control or playtime plugin cancels launches based on rules

• A plugin checks dependencies before allowing an emulator to start

📦 Benefits

• Makes launch-related plugins safer

• Prevents accidental changes to emulator or game configuration

• Gives plugin developers a clean supported workflow

• Improves reliability for custom launch validation tools

• Helps users understand why a launch was stopped

⚠️ Considerations

The cancellation design should avoid breaking existing plugins. It may be better to add a new cancellable launch event or launch arguments object rather than changing existing plugin behavior directly. Cancellation should work consistently in both LaunchBox and Big Box.