gizmo-ui — experimental

Flexbox layout and pointer hit-testing for the Gizmo engine's ECS.

This crate draws nothing. It has no renderer dependency and no graphics code. If you are here looking for a UI toolkit, read the next two sections before you spend an afternoon on it.

What works

Two systems, registered by gizmo_ui::register(&mut world, &mut schedule) or by the UiPlugin (app feature):

27 unit tests cover exactly that: layout write-back (including ancestor-offset accumulation), the POD-Style → engine-style conversion, node lifecycle, the hit-test predicate, and the interaction state machine.

use gizmo_ui::prelude::*;

// Layout + interaction on a bare World/Schedule — no gizmo-app required.
// `register` also registers the component types and inserts `UiContext`.
gizmo_ui::register(&mut world, &mut schedule);

let button = world.spawn_bundle(ButtonBundle {
    style: Style {
        width: Val::Px(120.0),
        height: Val::Percent(10.0),   // CSS scale: 10% of the parent
        padding: UiRect::all(Val::Px(8.0)),
        ..Default::default()
    },
    ..Default::default()
});

schedule.run(&mut world, dt);
// `button`'s `Node` now holds the computed box and `Interaction` the pointer
// state. Turning those into pixels is your job — see "What does not work".

Style is our own type

taffy does the layout maths, but it is an implementation detail: no taffy type is reachable through this crate's API. Style is plain old data — Val lengths (Auto / Px / Percent, on the CSS 0..=100 percent scale), UiRects, and a flexbox subset — and it is converted to a taffy style in exactly one function, inside UiContext.

Before 0.9 Style was a newtype that deref'd to taffy::style::Style, and the prelude glob-re-exported taffy's style and geometry modules. That made a third-party type part of the public API, and it forced two unsafe impl Send/Sync on the component, because taffy::Style is structurally !Send. Both are gone.

The properties Style does not model — CSS Grid, overflow, box_sizing, direction, text_align, float/clear, intrinsic sizing keywords and calc() — are listed in the type's rustdoc.

What does not work

• No text rendering. No Text component, no font loading, no glyph rasterisation — not in this crate and not in gizmo-renderer. This is the single largest missing piece, and the reason for the "experimental" label.
• No drawing of any kind. No vertices, no draw calls, no renderer integration. BackgroundColor is stored on the entity and read by nothing in the workspace.
• No CSS Grid. Style covers flexbox and block layout only. taffy's grid algorithm is compiled in but unreachable — there is no way to say display: grid or to describe a track template.
• No z-order or occlusion. The hit-test is a flat loop, so overlapping elements all report Hovered.
• No click/focus events, keyboard handling, scrolling, clipping or text input. Interaction is recomputed each frame; it is state, not an event stream.
• A UI entity whose Parent is not itself a styled UI entity gets no layout pass at all. (Read from the code; no test covers it.)

Use this if / use something else if

Use gizmo-ui if you want the engine to solve box geometry and hover/press state and you will do the drawing yourself — read Node and BackgroundColor in your own pass.

If you want a HUD that is visible on screen today, use the egui integration in gizmo-engine (egui feature, and editor on top of it). It renders, text included, and it does not go through this crate.

Note: gizmo-engine enables its ui feature by default, so these types show up in gizmo::prelude::* unasked. That is not evidence anything is being drawn.

Özet (TR)

Bu crate hiçbir şey çizmez. Yaptığı iki şey var: taffy ile flexbox yerleşimi hesaplayıp Node'a mutlak pencere koordinatı olarak yazmak, ve fare konumunu Node kutularıyla test edip Interaction durumunu güncellemek. İkisi de 27 birim testiyle kaplı. Metin render'ı yok — ne burada, ne gizmo-renderer'da; "deneysel" etiketinin sebebi budur. Ekranda görünen bir HUD istiyorsan gizmo-engine'in egui özelliğini kullan.

Style artık taffy'nin tipi değil, kendi POD tipimiz (Val / UiRect); taffy public API'de hiç görünmüyor ve component'teki iki unsafe impl Send/Sync kalktı. Yüzde değerleri CSS ölçeğinde (Val::Percent(50.0) = %50). CSS Grid modellenmiyor.

Status

Experimental in the 0.x sense. Nothing here is deprecated or scheduled for removal; the label describes how much of a UI toolkit this is, not its lifespan. Expect the component set to change when rendering lands.

License

MIT OR Apache-2.0, same as the rest of the workspace.