$ show marijnz/unity-toolbar-extender
This is a Unity Editor extension package that injects custom GUI into Unity's toolbar via reflection. The core library (ToolbarExtender.cs) exposes two static lists of Action delegates (LeftToolbarGUI and RightToolbarGUI) that users populate in InitializeOnLoad static constructors. The companion ToolbarCallback.cs handles the low-level reflection hooking, with version-specific code paths for Unity 2018 through Unity 6.3 (which uses UI Toolkit docks instead of IMGUI). Two example implementations demonstrate usage: a scene switcher with numbered buttons and a scene view focuser toggle that persists state via EditorPrefs. The architecture is minimal but effective; the library has no external dependencies beyond the Unity Editor API and is distributed as a UPM package. The code is well-structured for its niche, though it remains inherently fragile due to its reliance on Unity's internal API reflection.
The LLM identified 2 files worth highlighting for reuse:
Provides the public API for extending the toolbar via static lists of Action delegates (LeftToolbarGUI and RightToolbarGUI). It calculates precise screen positions to carve out space left and right of the built-in toolbar controls, then renders each registered handler inside GUILayout areas. The code is version-aware (different spacing for different Unity versions) and cleanly separates the rendering logic from the hooking mechanism. Extracting this into another project would require copying the entire file and the ToolbarCallback.cs it depends on, but the pattern of exposing static action lists for editor customization is directly reusable.
Handles the low-level hooking into Unity's internal toolbar rendering using reflection. For Unity 6.3+, it bypasses a deprecation warning by using EditorApplication.update polling to find the MainToolbarWindow and injecting VisualElement docks. For earlier versions, it attaches to the IMGUIContainer's m_OnGUIHandler. This file demonstrates a pragmatic approach to dealing with breaking Unity API changes across versions, and its conditional compilation blocks are well organized. The pattern of polling for ScriptableObject persistence and reattaching after layout changes is a reusable technique for any Editor extension that needs to piggyback on internal UI.