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// Copyright 2022 The Druid Authors.
//
// Licensed under the Apache License, Version 2.0 (the "License");
// you may not use this file except in compliance with the License.
// You may obtain a copy of the License at
//
//     http://www.apache.org/licenses/LICENSE-2.0
//
// Unless required by applicable law or agreed to in writing, software
// distributed under the License is distributed on an "AS IS" BASIS,
// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
// See the License for the specific language governing permissions and
// limitations under the License.

//! A widget that sizes its child to the child's maximum intrinsic width.

use crate::widget::Axis;
use crate::{
    BoxConstraints, Data, Env, Event, EventCtx, LayoutCtx, LifeCycle, LifeCycleCtx, PaintCtx, Size,
    UpdateCtx, Widget,
};

/// A widget that sizes its child to the child's maximum intrinsic width.
///
/// This widget is useful, for example, when unlimited width is available and you would like a child
/// that would otherwise attempt to expand infinitely to instead size itself to a more reasonable
/// width.
///
/// The constraints that this widget passes to its child will adhere to the parent's
/// constraints, so if the constraints are not large enough to satisfy the child's maximum intrinsic
/// width, then the child will get less width than it otherwise would. Likewise, if the minimum
/// width constraint is larger than the child's maximum intrinsic width, the child will be given
/// more width than it otherwise would.
pub struct IntrinsicWidth<T> {
    child: Box<dyn Widget<T>>,
}

impl<T: Data> IntrinsicWidth<T> {
    /// Wrap the given `child` in this widget.
    pub fn new(child: impl Widget<T> + 'static) -> Self {
        Self {
            child: Box::new(child),
        }
    }
}

impl<T: Data> Widget<T> for IntrinsicWidth<T> {
    fn event(&mut self, ctx: &mut EventCtx, event: &Event, data: &mut T, env: &Env) {
        self.child.event(ctx, event, data, env);
    }

    fn lifecycle(&mut self, ctx: &mut LifeCycleCtx, event: &LifeCycle, data: &T, env: &Env) {
        self.child.lifecycle(ctx, event, data, env);
    }

    fn update(&mut self, ctx: &mut UpdateCtx, old_data: &T, data: &T, env: &Env) {
        self.child.update(ctx, old_data, data, env);
    }

    fn layout(&mut self, ctx: &mut LayoutCtx, bc: &BoxConstraints, data: &T, env: &Env) -> Size {
        let iw = self
            .child
            .compute_max_intrinsic(Axis::Horizontal, ctx, bc, data, env);
        let new_bc = bc.shrink_max_width_to(iw);

        self.child.layout(ctx, &new_bc, data, env)
    }

    fn paint(&mut self, ctx: &mut PaintCtx, data: &T, env: &Env) {
        self.child.paint(ctx, data, env);
    }

    fn compute_max_intrinsic(
        &mut self,
        axis: Axis,
        ctx: &mut LayoutCtx,
        bc: &BoxConstraints,
        data: &T,
        env: &Env,
    ) -> f64 {
        match axis {
            Axis::Horizontal => self.child.compute_max_intrinsic(axis, ctx, bc, data, env),
            Axis::Vertical => {
                if !bc.is_width_bounded() {
                    let w = self
                        .child
                        .compute_max_intrinsic(Axis::Horizontal, ctx, bc, data, env);
                    let new_bc = bc.shrink_max_width_to(w);
                    self.child
                        .compute_max_intrinsic(axis, ctx, &new_bc, data, env)
                } else {
                    self.child.compute_max_intrinsic(axis, ctx, bc, data, env)
                }
            }
        }
    }
}