inspect-runtime

Inspect a running app

From Engine 2.23, every app announces itself to a hook at globalThis[Symbol.for('playcanvas.inspector')]. Read live state through it instead of adding window.app or debug code to the app.

Attach

• Resolve scripts/devtools-hook.js relative to this skill and inject it as an init script that runs before any page script. A hook defined later misses existing apps; reload instead.
• Page code then reads globalThis.__playcanvasApps, a Map from each live app to { version, revision, protocol }. app.init() adds the entry and app.destroy() removes it.
• The script chains a hook defined before it, such as a devtools extension's.
• No entry means the Engine predates 2.23, the hook loaded late, or the app set devtools: false. The Engine swallows errors thrown by the hook.
• In 2.23.0 only the debug build (playcanvas/debug, build/playcanvas.dbg.*) announces apps; the default import never calls the hook. Later 2.23 patches fix every build.

Read state

• Read after frameend, so values reflect a rendered frame.
• Return plain numbers and strings to the caller, not Engine objects.
• Useful reads: app.root.findByName() and findByTag(), world positions and meshInstance.aabb, app.stats.drawCallCount and frameTime, and entity.anim.baseLayer.activeState.
• Pause with app.timeScale = 0; update still runs with a zero dt. Step one frame by restoring the scale, then zeroing it again on the next frameend.
• Revert anything you change to take a measurement.

Inspector panel

@playcanvas/inspector adds a panel for people: new Inspector(app) shows the hierarchy, assets, materials, shaders, textures, render targets, frame graph, and physics. It must import the app's own playcanvas package, so add it only to development builds. It draws over the canvas and applies view overrides, so destroy it before verify-pixels captures. Stepping through draws needs the debug build.