Crate repose_ui 

Views, Modifiers, and Layout

Repose UI is built around three core ideas:

• View: an immutable description of a UI node.
• Modifier: layout, styling, and interaction hints attached to a View.
• Layout + paint: a separate pass (layout_and_paint) that turns the View tree into a Scene + hit regions using the Taffy layout engine.

Views

A View is a lightweight value that describes what to show, not how it is rendered. It is cheap to create and you are expected to rebuild the entire view tree on each frame:

use repose_core::*;
use repose_ui::*;

fn Counter(count: i32, on_inc: impl Fn() + 'static) -> View {
    Column(Modifier::new().padding(16.0)).child((
        Text(format!("Count = {count}")),
        Button("Increment".into_children(), on_inc),
    ))
}

Internally, a View has:

• id: ViewId — assigned during composition/layout.
• kind: ViewKind — which widget it is (Text, Button, ScrollV, etc.).
• modifier: Modifier — layout/styling/interaction metadata.
• children: Vec<View> — owned child views.

Views are pure data: they do not hold state or references into platform APIs. State lives in signals / remember_* and platform integration happens in the runner (repose-platform).

Modifiers

Modifier describes how a view participates in layout and hit‑testing:

• Size hints: size, width, height, min_size, max_size, fill_max_size, fill_max_width, fill_max_height.
• Box model: padding, padding_values.
• Visuals: background, background_brush, border, clip_rounded, alpha, transform.
• Flex / grid: flex_grow, flex_shrink, flex_basis, align_self, justify_content, align_items, grid, grid_span.
• Positioning: absolute(), offset(..) for overlay / Stack / FABs.
• Interaction: clickable(), pointer callbacks, on_scroll, semantics.
• Custom paint: painter (used by repose-canvas).

Example:

use repose_core::*;
use repose_ui::*;

fn CardExample() -> View {
    Surface(
        Modifier::new()
            .padding(16.0)
            .background(theme().surface)
            .border(1.0, theme().outline, 8.0)
            .clip_rounded(8.0),
        Text("Hello, Repose!"),
    )
}

Modifiers are merged into a Taffy Style inside layout_and_paint. Most values are specified in density‑independent pixels (dp) and converted to physical pixels (px) using the current Density local.

Layout

Layout is a pure function:

pub fn layout_and_paint(
    root: &View,
    size_px: (u32, u32),
    textfield_states: &HashMap<u64, Rc<RefCell<TextFieldState>>>,
    interactions: &Interactions,
    focused: Option<u64>,
) -> (Scene, Vec<HitRegion>, Vec<SemNode>);

It:

1. Clones the root View and assigns stable ViewIds.
2. Builds a parallel Taffy tree and computes layout for the given window size.
3. Walks the tree to:
   • Emit SceneNodes for visuals (rects, text, images, scrollbars, etc.).
   • Build HitRegions for input routing (clicks, pointer events, scroll).
   • Build SemNodes for accessibility / semantics.

Row, Column, Stack, Grid, ScrollV and ScrollXY are all special ViewKinds that map into Taffy styles and additional paint/hit logic.

Because layout + paint are separate from the platform runner, you can reuse the same UI code on desktop, Android, and other platforms.

Re-exports

pub use textfield::TextArea;

pub use textfield::TextField;

pub use textfield::TextFieldState;

Modules

anim

anim_ext

gestures

layout

lazy

navigation

overlay

scroll

Scroll model

textfield

TextField model

windowing

Structs

Interactions

Traits

ImageExt

IntoChildren

TextStyle

Method styling

ViewExt

Extension trait for child building

Functions

Box

Button

Checkbox

Column

Grid

Image

LinearProgress

OverlayHost

ProgressBar

RadioButton

RangeSlider

Row

ScrollDeprecated

Slider

Space

Spacer

Stack

Surface

Switch

Text

layout_and_paint

Layout and paint with TextField state injection (Taffy 0.9 API)