build-ui

Create a src/ui.tsx file with a React-ECS component using UiEntity, Label, and Button, then call ReactEcsRenderer.setUiRenderer with virtualWidth 1920 and virtualHeight 1080 from a setupUi() function invoked in main(). The root UiEntity should use width and height of 100%.

UI event handlers receive no pointer coordinates, so track movement with PrimaryPointerInfo.screenDelta accumulated in a system, divided by the UI scale factor. Render a full-screen pointer-blocking overlay only while dragging to catch the release, and add stepper buttons for mobile where screenDelta is always zero.

The most common cause is a missing setupUi() call in main() or a missing setUiRenderer call inside it. Also check that the root component does not return null on first render and that the file uses the .tsx extension.

No, React hooks are not available in Decentraland React-ECS. Use module-level variables for state; the UI renderer re-renders every frame, so changes to those variables are reflected immediately.

Text intrinsic sizing is engine-dependent: the Bevy explorer measures rendered text while the Unity explorer gives unset Label dimensions zero size, causing overlap and collapsed panels. Give every Label an explicit width and height, and never use emoji, which the Unity explorer cannot render.

Use TextShape with Billboard for 3D text floating in the world, such as labels above NPCs or objects. Use React-ECS only for 2D screen-space overlays like scoreboards, menus, and dialogs.