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//! `Container` — a rectangular box with optional background, border, and
//! padding that holds zero or more child widgets.
//!
//! Phase 4 child layout is a simple top-down vertical stack (bottom-most child
//! at `y = padding`, each subsequent child placed above the previous). Flex
//! layout arrives in Phase 5.
use crate::color::Color;
use crate::device_scale::device_scale;
use crate::draw_ctx::DrawCtx;
use crate::event::{Event, EventResult};
use crate::geometry::{Rect, Size};
use crate::layout_props::{HAnchor, Insets, VAnchor, WidgetBase};
use crate::widget::Widget;
/// A rectangular container widget.
///
/// Paints a background rounded-rect (optional border), then lets the framework
/// recurse into its children. Children are stacked bottom-to-top inside the
/// padding area.
pub struct Container {
bounds: Rect,
children: Vec<Box<dyn Widget>>,
base: WidgetBase,
pub background: Color,
pub border_color: Option<Color>,
pub border_width: f64,
pub corner_radius: f64,
pub inner_padding: Insets,
/// When `true`, `layout` returns the content's natural height + vertical
/// padding instead of the full available height. Off by default for
/// backward compatibility (callers that used `Container` as a fill-
/// parent decoration still work). Match egui's `Frame` by opting in.
pub fit_height: bool,
}
impl Container {
/// Create a transparent container with no border and default padding.
pub fn new() -> Self {
Self {
bounds: Rect::default(),
children: Vec::new(),
base: WidgetBase::new(),
background: Color::rgba(0.0, 0.0, 0.0, 0.0),
border_color: None,
border_width: 1.0,
corner_radius: 0.0,
inner_padding: Insets::ZERO,
fit_height: false,
}
}
/// Opt into content-fit height — [`layout`] returns
/// `content_height + vertical_padding` instead of the full
/// available height. Required when this `Container` sits inside
/// an auto-sized ancestor (e.g. `Window::with_auto_size(true)`),
/// which would otherwise pick up the full available height as
/// the container's preferred size and inflate the window.
pub fn with_fit_height(mut self, fit: bool) -> Self {
self.fit_height = fit;
self
}
/// Append a child widget.
pub fn add(mut self, child: Box<dyn Widget>) -> Self {
self.children.push(child);
self
}
pub fn with_background(mut self, color: Color) -> Self {
self.background = color;
self
}
pub fn with_border(mut self, color: Color, width: f64) -> Self {
self.border_color = Some(color);
self.border_width = width;
self
}
pub fn with_corner_radius(mut self, r: f64) -> Self {
self.corner_radius = r;
self
}
pub fn with_padding(mut self, p: f64) -> Self {
self.inner_padding = Insets::all(p);
self
}
pub fn with_inner_padding(mut self, p: Insets) -> Self {
self.inner_padding = p;
self
}
pub fn with_margin(mut self, m: Insets) -> Self {
self.base.margin = m;
self
}
pub fn with_h_anchor(mut self, h: HAnchor) -> Self {
self.base.h_anchor = h;
self
}
pub fn with_v_anchor(mut self, v: VAnchor) -> Self {
self.base.v_anchor = v;
self
}
pub fn with_min_size(mut self, s: Size) -> Self {
self.base.min_size = s;
self
}
pub fn with_max_size(mut self, s: Size) -> Self {
self.base.max_size = s;
self
}
}
impl Default for Container {
fn default() -> Self {
Self::new()
}
}
impl Widget for Container {
fn type_name(&self) -> &'static str {
"Container"
}
fn bounds(&self) -> Rect {
self.bounds
}
fn set_bounds(&mut self, bounds: Rect) {
self.bounds = bounds;
}
fn children(&self) -> &[Box<dyn Widget>] {
&self.children
}
fn children_mut(&mut self) -> &mut Vec<Box<dyn Widget>> {
&mut self.children
}
fn margin(&self) -> Insets {
self.base.margin
}
fn h_anchor(&self) -> HAnchor {
self.base.h_anchor
}
fn v_anchor(&self) -> VAnchor {
self.base.v_anchor
}
fn min_size(&self) -> Size {
self.base.min_size
}
fn max_size(&self) -> Size {
self.base.max_size
}
fn layout(&mut self, available: Size) -> Size {
let pad_l = self.inner_padding.left;
let pad_r = self.inner_padding.right;
let pad_t = self.inner_padding.top;
let pad_b = self.inner_padding.bottom;
let inner_w = (available.width - pad_l - pad_r).max(0.0);
// Stack children top-to-bottom (first child = visually highest).
// In Y-up coordinates, "top" = higher Y values.
// Start cursor at the top of the inner area; move it downward each step.
// Child margins are additive: top margin pushes the cursor down before
// placing the child; bottom margin is consumed after it.
let scale = device_scale();
let start_cursor = available.height - pad_t;
let mut cursor_y = start_cursor;
for child in self.children.iter_mut() {
let m = child.margin().scale(scale);
let avail_w = (inner_w - m.left - m.right).max(0.0);
let avail_h = (cursor_y - pad_b - m.top - m.bottom).max(0.0);
let desired = child.layout(Size::new(avail_w, avail_h));
// Top margin moves the cursor down before the child is placed.
cursor_y -= m.top;
let child_y = cursor_y - desired.height;
let child_bounds = Rect::new(
pad_l + m.left,
child_y,
desired.width.min(avail_w),
desired.height,
);
child.set_bounds(child_bounds);
// Bottom margin is consumed below the child.
cursor_y = child_y - m.bottom;
}
// Default: fill the full available area (legacy — many demo
// sites use `Container` as a decorated wrapper around content
// that should stretch). Opt in to content-fit via
// `with_fit_height(true)` — matches egui `Frame` semantics.
if self.fit_height {
let consumed_h = (start_cursor - cursor_y).max(0.0);
let natural_h = (consumed_h + pad_t + pad_b).min(available.height);
Size::new(available.width, natural_h)
} else {
Size::new(available.width, available.height)
}
}
fn paint(&mut self, ctx: &mut dyn DrawCtx) {
let w = self.bounds.width;
let h = self.bounds.height;
let r = self.corner_radius;
// Background
if self.background.a > 0.001 {
ctx.set_fill_color(self.background);
ctx.begin_path();
ctx.rounded_rect(0.0, 0.0, w, h, r);
ctx.fill();
}
// Border
if let Some(bc) = self.border_color {
ctx.set_stroke_color(bc);
ctx.set_line_width(self.border_width);
ctx.begin_path();
let inset = self.border_width * 0.5;
ctx.rounded_rect(
inset,
inset,
(w - self.border_width).max(0.0),
(h - self.border_width).max(0.0),
r,
);
ctx.stroke();
}
}
fn on_event(&mut self, _event: &Event) -> EventResult {
EventResult::Ignored
}
}