Custom Editor Mode

Types

UEdMode

Base class for all editor modes.

Misc Entry points

• Get the FTabManager representing the Editor Modes with FLevelEditorModule::GetLevelEditorTabManager
  • Snippet: FLevelEditorModule& LevelEditorModule = FModuleManager::GetModuleChecked<FLevelEditorModule>("LevelEditor") and TSharedPtr<FTabManager> LevelEditorTabManager = LevelEditorModule.GetLevelEditorTabManager().
• Get FEditorModeTools with SLevelEditor::GetEditorModeManager or GLevelEditorModeTools.
• Get FEditorModeRegistry with the static Get method.

Editor Mode Anatomy

Each mode has a Toolkit and commands.

Add custom Editor Mode

• See Sample Tools Editor Mode plugin which is very small and contains an example on how to implement a new editor mode in UE5+.

But basically you make a subclass of UEdMode and FModeToolkit in a editor module. As well as a TCommand class that you will register in your module.

In your toolkit class implement GetInlineContent so show a widget in the empty panel.

Engine Registration of Editor Modes

When FCoreDelegates::OnAllModuleLoadingPhasesComplete is broadcasted UAssetEditorSubsystem::RegisterEditorModes is run.

This will iterate all UEdMode objects. After a few checks and if the mode isn’t already registrated, we add it to the EditorModes array.

FEditorModeRegistry::CreateMode is used for legacy modes going through ULegacyEdModeWrapper::CreateLegacyMode.

Engine Creation Editor Mode

When SLevelEditor::RefreshEditorModeCommands is called and will handle mapping actions which triggers SLevelEditor::ToggleEditorMode on editor UI click.

Engine Changing Editor Mode flow

When switching Editor Mode SLevelEditor::ToggleEditorMode is called with the mode ID. This will eventually call FEditorModeTools::ActivateMode

FEditorModeTools holds an array of currently active editor modes (See ActiveScriptableModes and IsModeActive/GetActiveScriptableMode).

If it can’t “recycle” the mode that needs to be activated, it will call UAssetEditorSubsystem::CreateEditorModeWithToolsOwner, which looks an internal EditorModes array.

It the mode was changed EditorModeIDChangedEvent delegate is broadcasted.