UI Toolkit Companion

Unity's UI Toolkit Debugger lives in the editor. The moment a layout misbehaves on a phone — or only in a signed release build — the tooling stops at the edge of the device.

UI Toolkit Companion puts the debugger inside your game. Press F8 in any build that carries it: the element tree, every resolved style property, the four boxes of the layout model drawn over the element, and a picker that finds what is actually under your finger.

Then it fills in the rest of what UI Toolkit does not give you.

THE DEBUGGER, WHEREVER YOUR GAME RUNS

Element tree of every live panel, filtered by name, type or class. Pick by tapping the screen. Every resolved property, updating while the game runs. Margin, border, padding and content drawn over the selection. Live edits: hide, make invisible, outline, clear inline styles. Opens on F8 or four fingers, under either input backend, and is compiled out of release builds unless you tick it in.

TYPED VIEWS FROM YOUR UXML

A partial class beside each watched .uxml, with a field per named element, a Bind and a Validate that names whatever went missing. A file you can read and step into — not a source generator that takes every generated symbol in the project down with it when it breaks.

BINDINGS WITHOUT REFLECTION

Observables, observable lists that say which row changed, and commands that carry their own can-run. One Binder holds every subscription and releases them all at once. No property paths, no reflection: it survives managed stripping under IL2CPP, and a renamed member is a compile error rather than a binding that quietly stops working.

WHAT USS DOES NOT HAVE

Box shadow from a single nine-sliced texture — one draw call at any size, and exact rather than banded. Draw order that sorts the drawing without touching the tree. Aspect ratio, text that shrinks to fit, and alignment to whole pixels for pixel art.

CONTROLS UI TOOLKIT LACKS

Accordion, a tooltip that works in a build (VisualElement.tooltip is drawn by the editor and shows nothing in a player), toasts that clear themselves, and a modal stack whose scrim stops a click reaching the screen behind it.

GAMEPAD AND KEYBOARD FOCUS

Directional focus decided by geometry, wired by hand where the geometry reads it wrong, and held inside a region so the stick cannot walk out of a dialog onto the screen it is covering.

WHAT YOU GET

Full C# source. No DLL, no third-party code, no additional package required. 355 tests, run against Unity 6000.4 and 6000.6. A sample: a ship loadout screen built with the package, carrying two planted layout faults for the debugger to find in a minute. Works with every render pipeline. IL2CPP and managed stripping are safe.

USS+, A PREPROCESSOR

A .ussx file compiles to an ordinary .uss beside it, rebuilt on every save. Nesting with &, @tokens and $name resolved while compiling, calc() worked out at compile time, @scope, the inset and size shorthands, and @use for a shared palette. Errors name the line you wrote. @breakpoint and gap are the two USS cannot express at all: each compiles to something plain and is finished by one line of C#.

COMING FROM uGUI

A window that reads a Canvas and writes a .uxml with a stylesheet beside it. Nothing in the scene is touched. Anchors and stretching become the USS edges that behave the same way, including the flip from counting up to counting down. What it cannot carry it lists, with the path and the reason.

PANEL PREVIEW AND TOKENS

UI Builder shows a layout at the size of its own canvas, not the size the panel runs at. Panel Preview asks a PanelSettings what it would do on a chosen screen and lays the markup out at that point size. Token Palette lists every $token in the project with a swatch.