inset-rendering 0.12.0

//! A box that shows a native surface the host composites: Flutter's platform view render
//! object, over the `Surface` a producer feeds.
//!
//! It paints a clear rectangle at its place in paint order, so what the framework paints
//! above the surface stays and what it painted beneath is gone, and adds a [`SurfaceLayer`]
//! so the scene places the surface there. It fills what it is given: the surface's producer
//! is told the size by whoever built this widget, not by the compositor. It always needs
//! compositing, as Flutter's platform views do, so a transform or a clip above it is a layer
//! the scene places the surface under rather than a change to the canvas alone. The invariant:
//! the rectangle painted clear and the rectangle placed are the same one.

use std::sync::Arc;

use inset_embedder::{BlendMode, Offset, Paint, Size, Surface};
use inset_foundation::App;
use inset_painting::ClipContext;

use crate::box_::{BoxConstraints, RenderBox, RenderBoxData};
use crate::layer::{ErasedLayer, SurfaceLayer};
use crate::object::{RenderHandle, RenderObject, RenderObjectData};
use crate::painting_context::PaintingContext;

/// Shows a native surface in the box it is given.
pub struct RenderSurfaceView {
    render_object: RenderObjectData,
    render_box: RenderBoxData,
    surface: Arc<dyn Surface>,
}

impl RenderSurfaceView {
    pub fn new(app: &mut App, surface: Arc<dyn Surface>) -> RenderHandle<RenderSurfaceView> {
        RenderHandle::new_box(
            app,
            RenderSurfaceView {
                render_object: RenderObjectData::new(),
                render_box: RenderBoxData::new(),
                surface,
            },
        )
    }

    /// The surface shown.
    pub fn surface(self: RenderHandle<Self>, app: &App) -> &Arc<dyn Surface> {
        &self.get(app).surface
    }

    /// Shows `surface` instead, from the next paint.
    pub fn set_surface(self: RenderHandle<Self>, app: &mut App, surface: Arc<dyn Surface>) {
        if Arc::ptr_eq(&self.get(app).surface, &surface) {
            return;
        }
        self.get_mut(app).surface = surface;
        self.mark_needs_paint(app);
    }
}

impl RenderObject for RenderSurfaceView {
    crate::render_object_accessors!();

    fn always_needs_compositing(self: RenderHandle<Self>, _app: &App) -> bool {
        true
    }

    fn perform_layout(self: RenderHandle<Self>, app: &mut App) {
        let size = self.constraints(app).biggest();
        self.set_size(app, size);
    }

    /// A clear rectangle in the picture, and the surface placed over it.
    fn paint(
        self: RenderHandle<Self>,
        app: &mut App,
        context: &mut PaintingContext,
        offset: Offset,
    ) {
        let rect = offset & self.size(app);
        context.canvas().draw_rect(rect, &clearing_paint());
        let surface = Arc::clone(&self.get(app).surface);
        let layer = SurfaceLayer::new(app, surface, rect);
        context.add_layer(app, layer.as_layer());
    }
}

impl RenderBox for RenderSurfaceView {
    crate::render_box_accessors!();

    fn compute_dry_layout(
        self: RenderHandle<Self>,
        _app: &mut App,
        constraints: BoxConstraints,
    ) -> Size {
        constraints.biggest()
    }

    /// A surface takes a hit anywhere in its box, so a listener around it hears the pointer.
    fn hit_test_self(self: RenderHandle<Self>, _app: &App, _position: Offset) -> bool {
        true
    }
}

/// The paint that leaves a rectangle clear: nothing of the framework's beneath it, and what
/// is painted above it stays.
fn clearing_paint() -> Paint {
    Paint {
        blend_mode: BlendMode::Clear,
        ..Paint::default()
    }
}

#[cfg(test)]
mod tests {
    use inset_embedder::test_support::idle_surface;
    use inset_embedder::{Clip, Matrix4, Rect, SceneBuilder, SurfacePlacement, valo};
    use inset_foundation::{AppCell, Handle};

    use super::*;
    use crate::layer::{ContainerLayer, OffsetLayer};
    use crate::object::AnyRenderObject;
    use crate::pipeline_owner::PipelineOwner;

    /// Where a [`Parent`] paints its child.
    const CHILD_OFFSET: Offset = Offset::new(10.0, 5.0);

    /// A parent that lays its one child out at a fixed size and paints it as `painting` says.
    struct Parent {
        render_object: RenderObjectData,
        render_box: RenderBoxData,
        child: RenderHandle<RenderSurfaceView>,
        painting: ChildPainting,
    }

    /// How a [`Parent`] paints its child.
    #[derive(Clone, Copy)]
    enum ChildPainting {
        /// At [`CHILD_OFFSET`].
        AtOffset,
        /// At [`CHILD_OFFSET`], at half its size, clipped to the parent's top ten pixels.
        HalvedUnderAClip,
    }

    impl RenderObject for Parent {
        crate::render_object_accessors!();

        /// The root of a painted tree owns the root layer.
        fn is_repaint_boundary(self: RenderHandle<Self>, _app: &App) -> bool {
            true
        }

        fn perform_layout(self: RenderHandle<Self>, app: &mut App) {
            let child = self.get(app).child;
            child.layout(app, BoxConstraints::tight(Size::new(30.0, 20.0)), false);
            self.set_size(app, Size::new(100.0, 100.0));
        }

        fn visit_children(
            self: RenderHandle<Self>,
            app: &App,
            visitor: &mut dyn FnMut(AnyRenderObject),
        ) {
            visitor(self.get(app).child.as_object());
        }

        fn paint(
            self: RenderHandle<Self>,
            app: &mut App,
            context: &mut PaintingContext,
            offset: Offset,
        ) {
            let child = self.get(app).child.as_object();
            match self.get(app).painting {
                ChildPainting::AtOffset => context.paint_child(app, child, offset + CHILD_OFFSET),
                ChildPainting::HalvedUnderAClip => {
                    let needs_compositing = self.as_object().needs_compositing(app);
                    context.push_clip_rect(
                        app,
                        needs_compositing,
                        offset,
                        Rect::from_ltwh(0.0, 0.0, 100.0, 10.0),
                        |app, context, offset| {
                            context.push_transform(
                                app,
                                needs_compositing,
                                offset + CHILD_OFFSET,
                                Matrix4::scale(0.5, 0.5),
                                |app, context, offset| context.paint_child(app, child, offset),
                                None,
                            );
                        },
                        Clip::HardEdge,
                        None,
                    );
                }
            }
        }
    }

    impl RenderBox for Parent {
        crate::render_box_accessors!();
    }

    /// Lays out and paints a view of `surface` under a parent that paints it as `painting`
    /// says, and answers the scene.
    fn scene_of_one_frame(
        app: &mut App,
        surface: Arc<dyn Surface>,
        painting: ChildPainting,
    ) -> (inset_embedder::Scene, Handle<PipelineOwner>) {
        let owner = PipelineOwner::new(app, None, None);
        let child = RenderSurfaceView::new(app, surface);
        let parent = RenderHandle::new_box(
            app,
            Parent {
                render_object: RenderObjectData::new(),
                render_box: RenderBoxData::new(),
                child,
                painting,
            },
        );
        parent.adopt_child(app, child.as_object());
        owner.set_root_node(app, Some(parent.as_object()));
        parent.schedule_initial_layout(app);
        let root = OffsetLayer::new(app, Offset::ZERO);
        root.as_layer().attach(app, parent.as_object().id());
        parent
            .as_object()
            .schedule_initial_paint(app, root.as_container_layer());
        owner.flush_layout(app);
        owner.flush_compositing_bits(app);
        owner.flush_paint(app);
        let scene = root
            .as_container_layer()
            .build_scene(app, SceneBuilder::new());
        (scene, owner)
    }

    #[test]
    fn the_rectangle_painted_clear_is_the_rectangle_placed() {
        let cell = AppCell::new();
        let mut app = cell.borrow_mut();
        let surface = idle_surface();
        let (scene, _owner) =
            scene_of_one_frame(&mut app, Arc::clone(&surface), ChildPainting::AtOffset);
        let placed = Rect::from_ltwh(10.0, 5.0, 30.0, 20.0);
        assert_eq!(
            scene.surfaces,
            [SurfacePlacement {
                surface,
                rect: placed,
                scale: 1.0,
                clip: placed,
            }]
        );
        let ops = inset_embedder::flattened_ops(&scene.picture);
        let holes: Vec<valo::Rect> = ops
            .iter()
            .filter_map(|op| match op {
                valo::Op::DrawRect { rect, paint, .. } if paint.blend_mode == BlendMode::Clear => {
                    Some(*rect)
                }
                _ => None,
            })
            .collect();
        assert_eq!(holes, [valo::Rect::from(placed)], "{ops:?}");
    }

    /// A transform and a clip above a surface are layers of their own, as they are above
    /// Flutter's platform views, so the scene places the surface under both.
    #[test]
    fn a_surface_is_placed_under_the_transform_and_the_clip_above_it() {
        let cell = AppCell::new();
        let mut app = cell.borrow_mut();
        let surface = idle_surface();
        let (scene, _owner) = scene_of_one_frame(
            &mut app,
            Arc::clone(&surface),
            ChildPainting::HalvedUnderAClip,
        );
        assert_eq!(
            scene.surfaces,
            [SurfacePlacement {
                surface,
                rect: Rect::from_ltwh(10.0, 5.0, 15.0, 10.0),
                scale: 0.5,
                clip: Rect::from_ltrb(10.0, 5.0, 25.0, 10.0),
            }]
        );
    }
}