uefn-python-tools

A growing collection of Python tools for UEFN. More will be added over time.

Verse Field Tool

tools/verse_field_tool.py — a standalone in-editor GUI (PySide6) for creating, managing, and MVVM-binding Verse-exposed variables ("Verse fields") on UEFN Widget Blueprints.

It's fully self-contained: it only needs unreal, the Python standard library, and PySide6. Run it inside UEFN via Tools > Execute Python Script….

First run installs PySide6 for you. A small progress window appears while it downloads (no console window, and a collapsible Console log if you want to watch pip), then the tool opens straight away — no UEFN restart and no need to run the script twice. If the install fails, the log expands automatically and a Retry button appears.

Auto-update. On launch the tool checks GitHub for a newer version (a tiny, fast check with a short timeout). If one exists it downloads and applies it on the spot, then opens the updated tool — no manual re-download. When you're already up to date or offline, the check is skipped instantly and the tool opens as normal. The current version and a link to the repo show in the tool's footer. Version starts at v1.0.

What it does

• Bind — bulk-bind a widget's Verse fields to engine widget properties (Text, ColorAndOpacity, RenderOpacity, …), to the Verse fields of embedded child-widget instances, or to button events (OnClicked, OnHovered, …), all at once.
• Event parameters — an event field can take one int, float, or logic parameter, and each binding carries its own value. Select ten buttons, type a starting number, and they bind to the same event field passing 1, 2, 3, … — so one Verse handler can tell which button called it.
• Create Fields — add Verse fields of any supported type (float, int, logic, string, message, color, color_alpha, material, texture, event), organized into categories.
• Manage Fields — edit a field's category or delete it. Deletion is crash-safe (a naive delete of a freshly-created field will crash UEFN; this tool handles it).

Why

Creating and binding Verse fields on a Widget Blueprint normally means memory-patching the editor by hand — error-prone and easy to crash UEFN. This tool wraps the whole create → patch → compile → verify → bind workflow behind a UI.

Event bindings can't be authored through the engine API at all (the next compile discards them), so the tool patches the saved .uasset directly and reloads it. That's pure Python — no external binary, no .NET dependency. Every byte it writes was verified against a real UE serializer until the output was identical to what the editor itself produces.

Limitations

Bindings that need a conversion function or node can't be created — do those in the editor UI. The tool only creates bindings where the source and destination types match directly, so anything requiring a conversion is either hidden from the target list or shown locked.

• ❌ texture → Brush and material → Brush use MVVM conversion nodes (MVVMK2Node_MakeBrushFromSoftTexture / ...SoftMaterial), which have no Python setter — creating one means synthesizing a wired multi-node EdGraph. These are the one case shown locked in the target list, as a signpost to go do them in the editor.
• ❌ logic → Visibility needs a conversion function (Conv_BoolToSlateVisibility) — Visibility is an enum, not a bool.
• ❌ int → float (e.g. RenderOpacity) is not implicit. It fails to compile with "a conversion function is required". Same-type only.
• ✅ Works without conversion: message/string → Text, color/color_alpha → ColorAndOpacity, float → RenderOpacity, logic → IsEnabled.
• ✅ The UEFN buttons (Loud / Quiet / Regular) expose their label as Text, so a message field binds straight to it — the same binding the editor's Text field makes. It's the button's only bindable property; the plain Custom Button has no Text at all.
• ✅ Field-to-field bindings work for every type, including texture. A parent field bound to an embedded child widget's same-type Verse field is plain property-to-property. The usual pattern: do the Brush conversion inside the child widget once, in the editor UI, then bulk-bind parent → child fields with this tool.

Other limits:

• Only Widget Blueprints. Bind targets cover the widget types UEFN actually exposes (TextBlock, Image, and the Loud/Quiet/Regular buttons); unbindable engine properties like ToolTipText are hidden.
• Category order can't be changed. It follows the order categories were first used, and the underlying array can't be safely patched. The order is cosmetic.
• Deleting a field also drops MVVM bindings that use it as a source.
• Memory offsets are probed at runtime rather than hardcoded, but a large engine update could still break them.

Reference

skills/uefn-verse-fields/ is a Claude Code skill documenting the underlying workflow, pin-type mapping, safe deletion, and which MVVM bindings can and cannot be scripted from Python — including every trap that will crash UEFN if done wrong.

⚠️ Warning

These tools memory-patch live UEFN editor state via ctypes, and event bindings rewrite the saved .uasset on disk. Use at your own risk, and save your work first. Every on-disk edit takes a timestamped backup to Saved/VerseBinderBackups/ first, and rolls back on failure.

Credits

Thanks to @Benjf29 (Benjamin Ferellec), who pointed us toward UAssetGUI — the lead that made the event-binding side of this possible.

---

Made with Claude AI, Yes it's AI Slop