agg_gui/widgets/

primitives.rs

//! Primitive layout widgets: Stack, Padding, SizedBox. (Spacer/Separator → `spacers`.)

use crate::draw_ctx::DrawCtx;
use crate::event::{Event, EventResult};
use crate::geometry::{Rect, Size};
use crate::layout_props::{resolve_fit_or_stretch, HAnchor, Insets, VAnchor, WidgetBase};
use crate::widget::Widget;

// ---------------------------------------------------------------------------
// Stack — overlays children at the same position (first = back, last = front)
// ---------------------------------------------------------------------------

/// Stacks children on top of each other.
///
/// Paint order: first child is drawn first (furthest back). The last child
/// appears on top. Hit testing also follows paint order (reverse).
///
/// Children added with [`add`](Stack::add) are stretched to fill the stack's
/// area (the classic behaviour). Children added with
/// [`add_aligned`](Stack::add_aligned) are laid out at their *natural* size
/// and positioned within the stack using their own `h_anchor` / `v_anchor`
/// (plus margin) — like a floating overlay panel. Because an aligned child's
/// bounds only cover the panel itself, pointer events outside it fall through
/// to the stretched layer(s) beneath, so an aligned control panel doesn't
/// block interaction with a full-bleed background child.
pub struct Stack {
    bounds: Rect,
    children: Vec<Box<dyn Widget>>,
    /// Parallel to `children`: `true` = placed at natural size by anchor
    /// (overlay), `false` = stretched to fill (default).
    aligned: Vec<bool>,
    base: WidgetBase,
}

impl Stack {
    pub fn new() -> Self {
        Self {
            bounds: Rect::default(),
            children: Vec::new(),
            aligned: Vec::new(),
            base: WidgetBase::new(),
        }
    }

    /// Add a child stretched to fill the stack's full area.
    pub fn add(mut self, child: Box<dyn Widget>) -> Self {
        self.children.push(child);
        self.aligned.push(false);
        self
    }

    /// Add a floating child laid out at its natural size and positioned by
    /// its `h_anchor` / `v_anchor` (respecting margin). Points outside the
    /// child fall through to lower layers.
    pub fn add_aligned(mut self, child: Box<dyn Widget>) -> Self {
        self.children.push(child);
        self.aligned.push(true);
        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 Stack {
    fn default() -> Self {
        Self::new()
    }
}

impl Widget for Stack {
    fn type_name(&self) -> &'static str {
        "Stack"
    }
    fn bounds(&self) -> Rect {
        self.bounds
    }
    fn set_bounds(&mut self, b: Rect) {
        self.bounds = b;
    }
    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 widget_base(&self) -> Option<&WidgetBase> {
        Some(&self.base)
    }
    fn widget_base_mut(&mut self) -> Option<&mut WidgetBase> {
        Some(&mut self.base)
    }
    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 {
        for idx in 0..self.children.len() {
            if self.aligned.get(idx).copied().unwrap_or(false) {
                let child = &mut self.children[idx];
                // Measure natural size, then re-layout at that size so nested
                // content (e.g. a FlexColumn) places its children within the
                // box we actually assign rather than the full stack height.
                let desired = child.layout(available);
                // Margins are logical units — DPI is applied once at the App
                // paint boundary, never during layout.
                let m = child.margin();
                // The margin slot bounds the child even when its own max_size
                // doesn't: an overlay must keep its margins on a viewport
                // narrower than max_size, not go full-bleed off the edges.
                let slot_w = (available.width - m.left - m.right).max(0.0);
                let slot_h = (available.height - m.top - m.bottom).max(0.0);
                let w = desired
                    .width
                    .clamp(child.min_size().width, child.max_size().width)
                    .min(slot_w);
                let h = desired
                    .height
                    .clamp(child.min_size().height, child.max_size().height)
                    .min(slot_h);
                child.layout(Size::new(w, h));

                let ha = child.h_anchor();
                let x = if ha.contains(HAnchor::RIGHT) && !ha.contains(HAnchor::LEFT) {
                    (available.width - m.right - w).max(0.0)
                } else if ha.contains(HAnchor::CENTER) && !ha.is_stretch() {
                    m.left + (available.width - m.left - m.right - w) * 0.5
                } else {
                    m.left
                };

                // Y-up: BOTTOM = low Y, TOP = high Y.
                let va = child.v_anchor();
                let y = if va.contains(VAnchor::TOP) && !va.contains(VAnchor::BOTTOM) {
                    (available.height - m.top - h).max(0.0)
                } else if va.contains(VAnchor::CENTER) && !va.is_stretch() {
                    m.bottom + (available.height - m.bottom - m.top - h) * 0.5
                } else {
                    m.bottom
                };

                child.set_bounds(Rect::new(x, y, w, h));
            } else {
                let child = &mut self.children[idx];
                child.layout(available);
                child.set_bounds(Rect::new(0.0, 0.0, available.width, available.height));
            }
        }

        // Bring-to-front pass — **after** children.layout on purpose.
        //
        // A raise can be requested from two places:
        //   1. Widget input handlers (e.g. `Window::on_event` firing on a
        //      MouseDown inside the window — "click to raise").  These run
        //      BEFORE the frame's layout pass, so the flag is already set
        //      by the time we get here.
        //   2. Widget `layout()` itself (e.g. `Window` detects the
        //      `visible_cell` false→true rising edge at layout time, so
        //      toggling a demo on from the sidebar raises its window).
        //      These set the flag DURING this very layout pass.
        //
        // Draining the flags AFTER children.layout catches both cases in
        // the same frame — no one-frame visual delay.  The reactive-mode
        // event loop only renders once per event, so a one-frame delay
        // means the raise is invisible until the next unrelated event
        // arrives, which is what the user reported (sidebar-opened windows
        // appearing in the back).
        let mut i = 0;
        let mut raised: Vec<(Box<dyn Widget>, bool)> = Vec::new();
        while i < self.children.len() {
            if self.children[i].take_raise_request() {
                let child = self.children.remove(i);
                // `aligned` can be shorter than `children` when the tree is
                // mutated through `children_mut()` (e.g. the app pushes a
                // full-canvas overlay directly, or reorders windows for
                // z-order restore). Mirror the read path's tolerance above
                // (`self.aligned.get(idx).unwrap_or(false)`) instead of
                // assuming a strict 1:1 length — otherwise a raise landing on
                // the overhang index panics in `Vec::remove`.
                let aligned = if i < self.aligned.len() {
                    self.aligned.remove(i)
                } else {
                    false
                };
                raised.push((child, aligned));
                // Don't advance `i` — the list just shortened.
            } else {
                i += 1;
            }
        }
        for (r, a) in raised {
            self.children.push(r);
            self.aligned.push(a);
        }

        available
    }

    fn paint(&mut self, _ctx: &mut dyn DrawCtx) {}

    fn on_event(&mut self, _: &Event) -> EventResult {
        EventResult::Ignored
    }
}

// ---------------------------------------------------------------------------
// Padding — wraps one child with per-side insets
// ---------------------------------------------------------------------------

/// Surrounds a single child with configurable per-side padding.
pub struct Padding {
    bounds: Rect,
    children: Vec<Box<dyn Widget>>,
    base: WidgetBase,
    insets: Insets,
}

impl Padding {
    /// Explicit per-side padding.
    pub fn new(insets: Insets, child: Box<dyn Widget>) -> Self {
        Self {
            bounds: Rect::default(),
            children: vec![child],
            base: WidgetBase::new(),
            insets,
        }
    }

    /// Uniform padding on all four sides.
    pub fn uniform(amount: f64, child: Box<dyn Widget>) -> Self {
        Self::new(Insets::all(amount), child)
    }

    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 Widget for Padding {
    fn type_name(&self) -> &'static str {
        "Padding"
    }
    fn bounds(&self) -> Rect {
        self.bounds
    }
    fn set_bounds(&mut self, b: Rect) {
        self.bounds = b;
    }
    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 widget_base(&self) -> Option<&WidgetBase> {
        Some(&self.base)
    }
    fn widget_base_mut(&mut self) -> Option<&mut WidgetBase> {
        Some(&mut self.base)
    }
    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 p = &self.insets;
        let inner = Size::new(
            (available.width - p.left - p.right).max(0.0),
            (available.height - p.top - p.bottom).max(0.0),
        );
        if let Some(child) = self.children.first_mut() {
            let desired = child.layout(inner);
            // In Y-up coordinates: origin of the child content is at (left, bottom).
            child.set_bounds(Rect::new(p.left, p.bottom, desired.width, desired.height));
        }
        // Report total size including insets.
        let content_w = self.children.first().map_or(0.0, |c| c.bounds().width);
        let content_h = self.children.first().map_or(0.0, |c| c.bounds().height);
        Size::new(content_w + p.left + p.right, content_h + p.top + p.bottom)
    }

    fn paint(&mut self, _ctx: &mut dyn DrawCtx) {}

    fn on_event(&mut self, _: &Event) -> EventResult {
        EventResult::Ignored
    }
}

// ---------------------------------------------------------------------------
// SizedBox — forces specific width and/or height, with anchor-aware child placement
// ---------------------------------------------------------------------------

/// Forces a specific size on its optional child.
///
/// If `width` or `height` is `None`, the available size on that axis is passed
/// through unchanged.  The child is placed within the box using its own
/// `h_anchor` and `v_anchor`, respecting its `margin`.
pub struct SizedBox {
    bounds: Rect,
    children: Vec<Box<dyn Widget>>,
    base: WidgetBase,
    pub width: Option<f64>,
    pub height: Option<f64>,
}

impl SizedBox {
    pub fn new() -> Self {
        Self {
            bounds: Rect::default(),
            children: Vec::new(),
            base: WidgetBase::new(),
            width: None,
            height: None,
        }
    }

    pub fn with_width(mut self, w: f64) -> Self {
        self.width = Some(w);
        self
    }
    pub fn with_height(mut self, h: f64) -> Self {
        self.height = Some(h);
        self
    }

    pub fn with_child(mut self, child: Box<dyn Widget>) -> Self {
        self.children.clear();
        self.children.push(child);
        self
    }

    /// Create a fixed-size empty box (gap / spacer with exact dimensions).
    pub fn fixed(width: f64, height: f64) -> Self {
        Self::new().with_width(width).with_height(height)
    }

    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 SizedBox {
    fn default() -> Self {
        Self::new()
    }
}

impl Widget for SizedBox {
    fn type_name(&self) -> &'static str {
        "SizedBox"
    }
    fn bounds(&self) -> Rect {
        self.bounds
    }
    fn set_bounds(&mut self, b: Rect) {
        self.bounds = b;
    }
    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 widget_base(&self) -> Option<&WidgetBase> {
        Some(&self.base)
    }
    fn widget_base_mut(&mut self) -> Option<&mut WidgetBase> {
        Some(&mut self.base)
    }
    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
    }

    /// Mirror the height [`layout`] resolves to, so an ancestor
    /// `Window::with_tight_content_fit` measures the box correctly instead
    /// of the trait-default `0`:
    /// - explicit `with_height` → that height;
    /// - else a child → the child's required height plus its vertical margin;
    /// - else (a pure horizontal spacer) → `0`.
    fn measure_min_height(&self, available_w: f64) -> f64 {
        if let Some(h) = self.height {
            return h;
        }
        if let Some(child) = self.children.first() {
            let m = child.margin();
            let w = self.width.unwrap_or(available_w);
            let slot_w = (w - m.left - m.right).max(0.0);
            return (child.measure_min_height(slot_w) + m.vertical())
                .clamp(self.base.min_size.height, self.base.max_size.height);
        }
        self.base.min_size.height
    }

    fn layout(&mut self, available: Size) -> Size {
        // Fall back to the available axis only for dimensions that haven't been
        // explicitly set AND don't have a child to size to; otherwise use the
        // child's natural size on that axis so the SizedBox reports a sensible
        // height when only a width was supplied (e.g. narrow DragValue wrapper).
        //
        // When neither height nor child is present (pure horizontal spacer,
        // e.g. `SizedBox::new().with_width(8.0)`), default the height to zero
        // so the spacer doesn't inflate the parent row/column to the full
        // available axis — which would otherwise push sibling widgets off
        // screen.
        let w = self.width.unwrap_or(available.width);
        let mut h = self.height.unwrap_or_else(|| {
            if self.children.is_empty() {
                0.0
            } else {
                available.height
            }
        });

        if let Some(child) = self.children.first_mut() {
            let m = child.margin();
            let slot_w = (w - m.left - m.right).max(0.0);
            let slot_h = (h - m.top - m.bottom).max(0.0);

            let desired = child.layout(Size::new(slot_w, slot_h));

            // If the caller didn't pin the height, shrink to the child's
            // natural height plus its vertical margin.
            if self.height.is_none() {
                h = (desired.height + m.vertical())
                    .clamp(self.base.min_size.height, self.base.max_size.height);
            }

            // Horizontal placement within the box (margin already limits slot).
            let h_anchor = child.h_anchor();
            let min_w = child.min_size().width;
            let max_w = child.max_size().width;
            let child_w = if h_anchor.is_stretch() {
                slot_w.clamp(min_w, max_w)
            } else if h_anchor == HAnchor::MAX_FIT_OR_STRETCH {
                resolve_fit_or_stretch(desired.width, slot_w, true).clamp(min_w, max_w)
            } else if h_anchor == HAnchor::MIN_FIT_OR_STRETCH {
                resolve_fit_or_stretch(desired.width, slot_w, false).clamp(min_w, max_w)
            } else {
                desired.width.clamp(min_w, max_w)
            };

            let child_x = if h_anchor.contains(HAnchor::RIGHT) && !h_anchor.contains(HAnchor::LEFT)
            {
                (w - m.right - child_w).max(0.0)
            } else if h_anchor.contains(HAnchor::CENTER) && !h_anchor.is_stretch() {
                m.left + (slot_w - child_w) * 0.5
            } else {
                m.left
            };

            // Vertical placement (Y-up: BOTTOM = low Y).
            let v_anchor = child.v_anchor();
            let min_h = child.min_size().height;
            let max_h = child.max_size().height;
            let child_h = if v_anchor.is_stretch() {
                slot_h.clamp(min_h, max_h)
            } else if v_anchor == VAnchor::MAX_FIT_OR_STRETCH {
                resolve_fit_or_stretch(desired.height, slot_h, true).clamp(min_h, max_h)
            } else if v_anchor == VAnchor::MIN_FIT_OR_STRETCH {
                resolve_fit_or_stretch(desired.height, slot_h, false).clamp(min_h, max_h)
            } else {
                desired.height.clamp(min_h, max_h)
            };

            // When a dimension is explicitly pinned, the child must fit —
            // otherwise a child whose `layout` ignores the slot budget (e.g.
            // `TextField` returning a font-derived natural height) paints
            // outside the SizedBox and clips into siblings above it.  Widgets
            // re-read `self.bounds` during paint, so shrinking here propagates
            // cleanly.
            let child_w = if self.width.is_some() {
                child_w.min(slot_w)
            } else {
                child_w
            };
            let child_h = if self.height.is_some() {
                child_h.min(slot_h)
            } else {
                child_h
            };

            let child_y = if v_anchor.contains(VAnchor::TOP) && !v_anchor.contains(VAnchor::BOTTOM)
            {
                (h - m.top - child_h).max(0.0)
            } else if v_anchor.contains(VAnchor::CENTER) && !v_anchor.is_stretch() {
                m.bottom + (slot_h - child_h) * 0.5
            } else {
                m.bottom
            };

            child.set_bounds(Rect::new(child_x, child_y, child_w, child_h));
        }

        Size::new(w, h)
    }

    fn paint(&mut self, _ctx: &mut dyn DrawCtx) {}

    fn on_event(&mut self, _: &Event) -> EventResult {
        EventResult::Ignored
    }
}