Layout & Styling

Kael uses GPU-accelerated flexbox (powered by Taffy) with a Tailwind-inspired API. Every style is a method call on a Div.

Flexbox layout

#![allow(unused)]
fn main() {
div().flex().flex_row().gap_2()
    .child(div().child("Left"))
    .child(div().child("Right"))

div().flex().flex_col().gap_4()
    .child(div().child("Top"))
    .child(div().child("Bottom"))
}

Alignment

#![allow(unused)]
fn main() {
div().flex()
    .items_center()
    .justify_center()
    .justify_between()
    .items_start()
    .items_end()
}

Flex sizing

#![allow(unused)]
fn main() {
div().flex_1()
div().flex_grow()
div().flex_shrink_0()
div().flex_none()
}

Switch a container to CSS Grid with .grid(), define tracks with .grid_cols(n) / .grid_rows(n), and place children with .col_span(n) / .row_span(n) (or .col_span_full() / .row_span_full()). .gap_*() sets the gutters:

#![allow(unused)]
fn main() {
div()
    .grid()
    .grid_cols(5)
    .grid_rows(5)
    .gap_1()
    .child(div().row_span(1).col_span_full().child("Header"))
    .child(div().col_span(1).row_span(3).child("Sidebar"))
    .child(div().col_span(3).row_span(3).child("Content"))
    .child(div().col_span(1).row_span(3).child("Aside"))
    .child(div().row_span(1).col_span_full().child("Footer"))
}

See examples/grid_layout.rs for a full “holy grail” layout.

Sizing

#![allow(unused)]
fn main() {
div().w(px(200.0)).h(px(100.0))

div().w_full()
div().h_full()
div().size_full()

div().size_8()
div().w_12()
div().h_6()

div().min_w(px(200.0)).max_w(px(600.0))
}

Spacing

#![allow(unused)]
fn main() {
div().p_4()
div().px_3()
div().py_2()
div().pt_1()
div().pl(px(20.0))

div().m_4()
div().mx_auto()
div().mt_2()

div().flex().gap_2()
div().flex().gap_4()
}

Colors

#![allow(unused)]
fn main() {
div().bg(rgb(0x1E1E1E))
div().text_color(rgb(0xFFFFFF))
div().border_color(rgb(0x3C3C3C))

div().bg(rgba(0x00000080))

div().bg(kael::red())
div().bg(kael::blue())
div().bg(kael::white())
div().bg(kael::black())

use kael::hsla;
div().bg(hsla(210.0 / 360.0, 1.0, 0.5, 1.0))
}

Borders

#![allow(unused)]
fn main() {
div().border_1()
div().border_2()
div().border_t_1()
div().border_b_1()
div().border_l_1()
div().border_r_1()
div().border_color(rgb(0x3C3C3C))
div().border_dashed()
}

Corners

#![allow(unused)]
fn main() {
div().rounded_sm()
div().rounded_md()
div().rounded_lg()
div().rounded_full()
div().rounded(px(8.0))
}

By default, rounded corners use continuous (squircle) rounding to match SwiftUI’s RoundedRectangle shape on macOS. Use .circular_corners() to opt into the legacy pure quarter-circle look:

#![allow(unused)]
fn main() {
div().rounded(px(8.0)).circular_corners()
}

Shadows

#![allow(unused)]
fn main() {
div().shadow_sm()
div().shadow_md()
div().shadow_lg()
div().shadow_xl()
}

Typography

#![allow(unused)]
fn main() {
div()
    .text_xs()
    .text_sm()
    .text_base()
    .text_lg()
    .text_xl()
    .text_2xl()
    .text_3xl()

div().font_weight(FontWeight::BOLD)
div().font_family(".SystemUIFont")
}

Overflow and scrolling

Control how content behaves when it exceeds the element bounds:

#![allow(unused)]
fn main() {
div().overflow_hidden()
div().overflow_x_scroll()
div().overflow_y_scroll()
div().overflow_y_auto()
    .id("scroll-container")
}

When using overflow_y_scroll() or overflow_y_auto() with a ScrollHandle, Kael automatically renders a macOS-style scrollbar thumb when content overflows. No extra widget is needed:

#![allow(unused)]
fn main() {
let scroll_handle = ScrollHandle::new();

div()
    .id("my-scrollable")
    .overflow_y_scroll()
    .track_scroll(&scroll_handle)
    .child(long_content)
}

The auto-scrollbar appears only when content exceeds the viewport and tracks the scroll position automatically. To keep scrollbars visible at all times (instead of auto-hiding after idle):

#![allow(unused)]
fn main() {
let scroll_handle = ScrollHandle::new().always_show_scrollbars();
}

For custom scrollbar styling, use the explicit scroll_bar() widget instead (see Lists & Data).

Positioning

#![allow(unused)]
fn main() {
div().relative()
    .child(
        div().absolute()
            .top(px(10.0))
            .right(px(10.0))
            .child("Badge")
    )
}

Opacity

#![allow(unused)]
fn main() {
div().opacity(0.5)
}

Cursor

#![allow(unused)]
fn main() {
div().cursor_pointer()
div().cursor_default()
}

Conditional styling with `.when()`

#![allow(unused)]
fn main() {
div()
    .when(self.is_selected, |this| {
        this.bg(rgb(0x2563eb)).text_color(rgb(0xffffff))
    })
    .when(!self.is_selected, |this| {
        this.bg(rgb(0xffffff)).text_color(rgb(0x000000))
    })
}

Kael Documentation