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//! Segmented control with a liquid selection blob: the glass pill behind the
//! selected segment runs its leading and trailing edges on different springs,
//! so it stretches like a droplet while traveling and settles round. Touching
//! it lifts the indicator into a magnifying glass lens that follows the finger
//! across the segments (the reference control swipes, it doesn't just tap).
use crate::material::{Glass, GlassDynamics, GlassMorph, LiquidModifierExt, LiquidShape};
use crate::motion::LiquidMotion;
use crate::theme::{liquid_colors, liquid_typography};
use cranpose_animation::{animateFloatAsState, spring};
use cranpose_core::{mutableStateOf, remember};
use cranpose_foundation::{PointerEventKind, PointerId};
use cranpose_macros::composable;
use cranpose_services::{default_haptics, HapticFeedback};
use cranpose_ui::text::{FontWeight, SpanStyle, TextStyle};
use cranpose_ui::widgets::{
Box, BoxSpec, BoxWithConstraints, BoxWithConstraintsScope, Row, RowSpec, Text,
};
use cranpose_ui::{Modifier, PointerInputScope, Size};
use cranpose_ui_graphics::{Brush, Color, CornerRadii, GlassSurfaceProfile, GraphicsLayer};
use cranpose_ui_layout::Alignment;
use std::rc::Rc;
const SEGMENT_HEIGHT: f32 = 36.0;
const TRACK_PADDING: f32 = 2.0;
/// How far the interaction lens pokes past the track vertically.
const LENS_OVERFLOW: f32 = 8.0;
/// Glass node span beyond the lens shape (rim glow + bulge live here).
const LENS_PAD: f32 = 10.0;
/// Pointer travel below this is a tap, not a swipe.
const TAP_SLOP: f32 = 4.0;
fn plain_indicator_alpha(lens_progress: f32) -> f32 {
((0.18 - lens_progress) / 0.16).clamp(0.0, 1.0)
}
fn segment_lens_left(pointer_x: f32, segment_width: f32, count: usize) -> f32 {
(pointer_x - segment_width * 0.5).clamp(0.0, segment_width * (count.saturating_sub(1)) as f32)
}
/// A segmented control. `labels` are equal-width segments; `selected` is the
/// active index; `on_select` receives the committed index. Segments tap AND
/// swipe: dragging slides the indicator with the finger as a glass lens.
#[composable]
#[allow(non_snake_case)]
pub fn LiquidSegmentedControl(
modifier: Modifier,
labels: Vec<String>,
selected: usize,
on_select: impl Fn(usize) + 'static,
) {
let colors = liquid_colors();
let typography = liquid_typography();
let count = labels.len().max(1);
let selected = selected.min(count - 1);
let on_select: Rc<dyn Fn(usize)> = Rc::new(on_select);
let labels = Rc::new(labels);
let pressed = remember(|| mutableStateOf(false)).with(|s| *s);
let track_fill = colors.fill;
let track = Modifier::empty()
.height(SEGMENT_HEIGHT + TRACK_PADDING * 2.0)
.draw_behind(move |scope| {
scope.draw_round_rect(
Brush::solid(track_fill),
CornerRadii::uniform((SEGMENT_HEIGHT + TRACK_PADDING * 2.0) * 0.5),
);
});
Box(track.then(modifier), BoxSpec::default(), move || {
let labels = Rc::clone(&labels);
let typography = typography.clone();
let on_select = Rc::clone(&on_select);
BoxWithConstraints(Modifier::empty().padding(TRACK_PADDING), move |scope| {
let labels = Rc::clone(&labels);
let typography = typography.clone();
let on_select = Rc::clone(&on_select);
let total_width = scope.constraints().max_width.max(1.0);
let segment_width = total_width / count as f32;
let selected_x = segment_width * selected as f32;
let lens_axis = crate::motion::remember_liquid_drag_axis(selected_x);
lens_axis.settle_to(selected_x, LiquidMotion::glide());
let lens_x = lens_axis.value();
// The resting indicator belongs to controlled state. The
// interaction lens has a separate direct-drag axis: it reads the
// raw pointer while held and only springs after release.
let leading = animateFloatAsState(
selected_x,
LiquidMotion::blob_leading(),
"segmented-leading",
);
let trailing = animateFloatAsState(
selected_x + segment_width,
LiquidMotion::blob_trailing(),
"segmented-trailing",
);
// Lens presence: up while touched, lingering decay on release
// (the indicator stays liquid through the settle flight).
let lens_settling = !lens_axis.is_dragging() && (lens_x - selected_x).abs() > 1.0;
let lens_target = if pressed.get() || lens_settling {
1.0
} else {
0.0
};
let lens_progress = animateFloatAsState(
lens_target,
if pressed.get() {
spring(0.9, 1400.0)
} else {
spring(1.0, 170.0)
},
"segmented-lens",
);
let indicator_color = if colors.is_dark {
Color::from_rgba_u8(90, 90, 96, 240)
} else {
Color::WHITE
};
let lens_for_indicator = lens_progress;
let indicator = Modifier::empty()
.size(Size::new(segment_width, SEGMENT_HEIGHT))
.graphics_layer(move || {
let lead = leading.get();
let trail = trailing.get().max(lead + 1.0);
GraphicsLayer {
translation_x: lead,
scale_x: ((trail - lead) / segment_width.max(1.0)).max(0.01),
// The plain fill hides while the lens is up.
alpha: plain_indicator_alpha(lens_for_indicator.get()),
// Scale from the leading edge so translation stays exact.
transform_origin: cranpose_ui_graphics::TransformOrigin {
pivot_fraction_x: 0.0,
pivot_fraction_y: 0.5,
},
..Default::default()
}
})
.draw_behind(move |scope| {
scope.draw_round_rect(
Brush::solid(indicator_color),
CornerRadii::uniform(SEGMENT_HEIGHT * 0.5),
);
});
Box(indicator, BoxSpec::default(), || {});
// Labels row on top of the indicator. The cells keep button
// semantics (robot/a11y); pointer handling lives on the swipe
// surface below.
Row(Modifier::empty(), RowSpec::default(), move || {
for (index, label) in labels.iter().enumerate() {
let is_selected = index == selected;
let style = TextStyle {
span_style: SpanStyle {
color: Some(if is_selected {
colors.label
} else {
colors.secondary_label
}),
font_weight: Some(if is_selected {
FontWeight::SEMI_BOLD
} else {
FontWeight::MEDIUM
}),
..typography.subheadline.span_style.clone()
},
..typography.subheadline.clone()
};
let label_for_semantics = label.clone();
let cell = Modifier::empty()
.size(Size::new(segment_width, SEGMENT_HEIGHT))
.semantics(move |config| {
config.is_button = true;
config.is_clickable = true;
config.content_description = Some(label_for_semantics.clone());
});
let label = label.clone();
Box(
cell,
BoxSpec::default().content_alignment(Alignment::CENTER),
move || {
Text(label.clone(), Modifier::empty(), style.clone());
},
);
}
});
// Swipe/tap surface across the whole control.
let gesture = Modifier::empty()
.size(Size::new(total_width, SEGMENT_HEIGHT))
.pointer_input(selected, {
let on_select = Rc::clone(&on_select);
let lens_axis = Rc::clone(&lens_axis);
move |scope: PointerInputScope| {
let on_select = Rc::clone(&on_select);
let lens_axis = Rc::clone(&lens_axis);
async move {
scope
.await_pointer_event_scope(|await_scope| async move {
let mut down_x = 0.0f32;
let mut active_pointer = Option::<PointerId>::None;
loop {
let event = await_scope.await_pointer_event().await;
match event.kind {
PointerEventKind::Down if active_pointer.is_none() => {
active_pointer = Some(event.id);
down_x = event.position.x;
pressed.set(true);
lens_axis.begin(
segment_lens_left(
event.position.x,
segment_width,
count,
),
event.time_ms,
);
default_haptics()
.perform(HapticFeedback::Selection);
event.consume();
}
PointerEventKind::Move
if active_pointer == Some(event.id) =>
{
lens_axis.move_to(
segment_lens_left(
event.position.x,
segment_width,
count,
),
event.time_ms,
);
event.consume();
}
PointerEventKind::Up
if active_pointer == Some(event.id) =>
{
active_pointer = None;
pressed.set(false);
let travelled =
(event.position.x - down_x).abs() > TAP_SLOP;
let position = if travelled {
event.position.x
} else {
down_x
};
let index =
((position / segment_width).floor().max(0.0)
as usize)
.min(count - 1);
lens_axis.release_to(
segment_width * index as f32,
event.time_ms,
LiquidMotion::glide(),
);
default_haptics()
.perform(HapticFeedback::ImpactLight);
on_select(index);
event.consume();
}
PointerEventKind::Cancel
if active_pointer == Some(event.id) =>
{
active_pointer = None;
pressed.set(false);
lens_axis.release_to(
selected_x,
event.time_ms,
LiquidMotion::glide(),
);
event.consume();
}
_ => {}
}
}
})
.await;
}
}
});
Box(gesture, BoxSpec::default(), || {});
// The interaction lens riding the indicator: a glass capsule that
// magnifies the label under it and bulges along the travel.
if lens_progress.get() > 0.01 {
let lens_h = SEGMENT_HEIGHT + LENS_OVERFLOW;
let deformation_headroom =
crate::dynamics::STRETCH_MAX.max(1.0 / crate::dynamics::STRETCH_MIN);
let node_w = (segment_width + 4.0) * deformation_headroom
+ crate::dynamics::BULGE_MAX
+ LENS_PAD * 2.0;
let node_h =
lens_h * deformation_headroom + crate::dynamics::BULGE_MAX + LENS_PAD * 2.0;
let lens_for_layer = lens_progress;
let physics_axis = Rc::clone(&lens_axis);
let lens = Modifier::empty()
// required_size: taller than the track; the fixed-height
// host keeps the control's layout put.
.required_size(Size::new(node_w, node_h))
.offset(
(segment_width - node_w) * 0.5,
(SEGMENT_HEIGHT - node_h) * 0.5,
)
.graphics_layer(move || GraphicsLayer {
translation_x: lens_x,
alpha: (lens_for_layer.get() * 2.5).clamp(0.0, 1.0),
..Default::default()
})
.glass_effect_with(
Glass::lens()
.shape(LiquidShape::Capsule)
.tint(Color::rgba(1.0, 1.0, 1.0, 0.05))
.surface_profile(
GlassSurfaceProfile::lens()
.with_depth(6.8)
.expect("segmented surface depth is valid"),
)
.highlight(0.52)
.chromatic_aberration(2.4)
.displacement(24.0)
.content_recolor(colors.accent, 1.0)
.no_clip(),
move || {
let grow = lens_for_layer.get().clamp(0.0, 1.2);
let base_w = segment_width + 4.0 * grow;
let base_h = SEGMENT_HEIGHT + LENS_OVERFLOW * grow;
// Droplet law over the indicator ride
// (crate::dynamics): speed stretches the capsule
// along the travel, braking swells its front.
let pose = physics_axis.liquid_pose();
GlassDynamics {
morph: Some(GlassMorph {
node_size: (node_w, node_h),
primary: (node_w * 0.5, node_h * 0.5, base_w, base_h, -1.0),
shapes: Vec::new(),
glue: 0.0,
wobble_amplitude: 0.0,
wobble_phase: 0.0,
bulge_amplitude: pose.bulge_amplitude.min(6.0),
bulge_direction: pose.bulge_direction,
ellipse_blend: 0.0,
deformation: Some(pose.deformation()),
}),
surface_depth_boost: 0.18,
..Default::default()
}
},
);
Box(lens, BoxSpec::default(), || {});
}
});
});
}
#[cfg(test)]
mod tests {
use super::*;
#[test]
fn pointer_position_is_the_clamped_lens_center() {
let width = 100.0;
assert_eq!(segment_lens_left(50.0, width, 3), 0.0);
assert_eq!(segment_lens_left(150.0, width, 3), 100.0);
assert_eq!(segment_lens_left(250.0, width, 3), 200.0);
assert_eq!(segment_lens_left(-50.0, width, 3), 0.0);
assert_eq!(segment_lens_left(400.0, width, 3), 200.0);
}
#[test]
fn plain_indicator_stays_hidden_until_the_lens_is_almost_gone() {
assert_eq!(plain_indicator_alpha(1.0), 0.0);
assert_eq!(plain_indicator_alpha(0.5), 0.0);
assert_eq!(plain_indicator_alpha(0.2), 0.0);
assert!(plain_indicator_alpha(0.05) > 0.8);
assert_eq!(plain_indicator_alpha(0.0), 1.0);
}
}