Toplevel layout abstraction

src/widgets/toplevels/mod.rs

@@ -0,0 +1,191 @@
+use cosmic::iced::{
+    advanced::{
+        layout::{self, flex::Axis},
+        mouse, renderer,
+        widget::{Operation, Tree},
+        Clipboard, Layout, Shell, Widget,
+    },
+    event::{self, Event},
+    Length, Rectangle, Size, Vector,
+};
+use std::marker::PhantomData;
+
+mod toplevel_layout;
+use toplevel_layout::{LayoutToplevel, RowColToplevelLayout, ToplevelLayout};
+
+pub fn toplevels<Msg>(children: Vec<cosmic::Element<Msg>>) -> Toplevels<Msg> {
+    Toplevels {
+        layout: RowColToplevelLayout {
+            // TODO configurable
+            spacing: 16,
+            axis: Axis::Horizontal,
+        },
+        children,
+        _msg: PhantomData,
+    }
+}
+
+pub struct Toplevels<'a, Msg> {
+    layout: RowColToplevelLayout,
+    children: Vec<cosmic::Element<'a, Msg>>,
+    _msg: PhantomData<Msg>,
+}
+
+impl<'a, Msg> Widget<Msg, cosmic::Theme, cosmic::Renderer> for Toplevels<'a, Msg> {
+    fn size(&self) -> Size<Length> {
+        self.layout.size()
+    }
+
+    fn layout(
+        &self,
+        tree: &mut Tree,
+        renderer: &cosmic::Renderer,
+        limits: &layout::Limits,
+    ) -> layout::Node {
+        // Call `.layout()` on each child with full limits to determine "preferred" sizes
+        let layout_toplevels = self
+            .children
+            .iter()
+            .zip(tree.children.iter_mut())
+            .map(|(child, tree)| {
+                let preferred_size = child.as_widget().layout(tree, renderer, limits).size();
+                LayoutToplevel {
+                    preferred_size,
+                    _phantom_data: PhantomData,
+                }
+            })
+            .collect::<Vec<_>>();
+
+        // Assign rectangles for each child using `ToplevelLayout` backend
+        let assigned_rects = self.layout.layout(limits.max(), &layout_toplevels);
+
+        let nodes = self
+            .children
+            .iter()
+            .zip(tree.children.iter_mut())
+            .zip(assigned_rects)
+            .map(|((child, tree), assigned_rect)| {
+                let child_limits = layout::Limits::new(Size::ZERO, assigned_rect.size());
+                let layout = child.as_widget().layout(tree, renderer, &child_limits);
+
+                // Center on both axes, if child didn't consume full size allocation
+                let centering_offset = Vector::new(
+                    ((assigned_rect.size().width - layout.size().width) / 2.).max(0.),
+                    ((assigned_rect.size().height - layout.size().height) / 2.).max(0.),
+                );
+
+                layout.move_to(assigned_rect.position() + centering_offset)
+            })
+            .collect();
+        layout::Node::with_children(limits.max(), nodes)
+    }
+
+    fn operate(
+        &self,
+        tree: &mut Tree,
+        layout: Layout<'_>,
+        renderer: &cosmic::Renderer,
+        operation: &mut dyn Operation<()>,
+    ) {
+        operation.container(None, layout.bounds(), &mut |operation| {
+            self.children
+                .iter()
+                .zip(&mut tree.children)
+                .zip(layout.children())
+                .for_each(|((child, state), layout)| {
+                    child
+                        .as_widget()
+                        .operate(state, layout, renderer, operation);
+                });
+        });
+    }
+
+    fn on_event(
+        &mut self,
+        tree: &mut Tree,
+        event: Event,
+        layout: Layout<'_>,
+        cursor: mouse::Cursor,
+        renderer: &cosmic::Renderer,
+        clipboard: &mut dyn Clipboard,
+        shell: &mut Shell<'_, Msg>,
+        viewport: &Rectangle,
+    ) -> event::Status {
+        self.children
+            .iter_mut()
+            .zip(&mut tree.children)
+            .zip(layout.children())
+            .map(|((child, state), layout)| {
+                child.as_widget_mut().on_event(
+                    state,
+                    event.clone(),
+                    layout,
+                    cursor,
+                    renderer,
+                    clipboard,
+                    shell,
+                    viewport,
+                )
+            })
+            .fold(event::Status::Ignored, event::Status::merge)
+    }
+
+    fn mouse_interaction(
+        &self,
+        tree: &Tree,
+        layout: Layout<'_>,
+        cursor: mouse::Cursor,
+        viewport: &Rectangle,
+        renderer: &cosmic::Renderer,
+    ) -> mouse::Interaction {
+        self.children
+            .iter()
+            .zip(&tree.children)
+            .zip(layout.children())
+            .map(|((child, state), layout)| {
+                child
+                    .as_widget()
+                    .mouse_interaction(state, layout, cursor, viewport, renderer)
+            })
+            .max()
+            .unwrap_or_default()
+    }
+
+    fn draw(
+        &self,
+        tree: &Tree,
+        renderer: &mut cosmic::Renderer,
+        theme: &cosmic::Theme,
+        style: &renderer::Style,
+        layout: Layout<'_>,
+        cursor: mouse::Cursor,
+        viewport: &Rectangle,
+    ) {
+        if let Some(viewport) = layout.bounds().intersection(viewport) {
+            for ((child, state), layout) in self
+                .children
+                .iter()
+                .zip(&tree.children)
+                .zip(layout.children())
+            {
+                child
+                    .as_widget()
+                    .draw(state, renderer, theme, style, layout, cursor, &viewport);
+            }
+        }
+    }
+
+    fn children(&self) -> Vec<Tree> {
+        self.children.iter().map(Tree::new).collect()
+    }
+
+    fn diff(&mut self, tree: &mut Tree) {
+        tree.diff_children(&mut self.children);
+    }
+}
+
+impl<'a, Msg: 'static> From<Toplevels<'a, Msg>> for cosmic::Element<'a, Msg> {
+    fn from(widget: Toplevels<'a, Msg>) -> Self {
+        cosmic::Element::new(widget)
+    }
+}

src/widgets/toplevels/toplevel_layout/mod.rs

@@ -0,0 +1,35 @@
+// TODO: More generic widget in libcosmic? Improve iced layout system?
+// - preferred_size concept
+
+use cosmic::iced::{Length, Rectangle, Size};
+use std::marker::PhantomData;
+
+mod row_col_toplevel_layout;
+mod utils;
+pub(crate) use row_col_toplevel_layout::RowColToplevelLayout;
+
+pub(crate) struct LayoutToplevel<'a> {
+    //toplevel: &'a crate::Toplevel,
+    /// Preferred size of the child widget, if it fill the parent container
+    pub preferred_size: Size,
+    pub _phantom_data: PhantomData<&'a crate::Toplevel>,
+}
+
+/// An implementor of this trait defines a layout for the [`Toplevels`] widget
+/// as a pure function, without dealing with all the details of the iced layout
+/// system.
+pub(crate) trait ToplevelLayout {
+    /// [`Size`] the container widget should request
+    fn size(&self) -> Size<Length>;
+    /// Decide size and location of each widget
+    ///
+    /// - `max_limit` is the total size available for all children
+    /// - For each entry in `toplevels`, this should yield one `Rectangle`
+    ///
+    /// If a child doesn't use it's entire rectangle, it will be centered in that space.
+    fn layout(
+        &self,
+        max_limit: Size,
+        toplevels: &[LayoutToplevel<'_>],
+    ) -> impl Iterator<Item = Rectangle>;
+}

src/widgets/toplevels/toplevel_layout/row_col_toplevel_layout.rs

@@ -0,0 +1,51 @@
+use cosmic::iced::{advanced::layout::flex::Axis, Length, Point, Rectangle, Size};
+
+use super::{utils::AxisExt, LayoutToplevel, ToplevelLayout};
+
+pub(crate) struct RowColToplevelLayout {
+    pub axis: Axis,
+    pub spacing: u32,
+}
+
+impl ToplevelLayout for RowColToplevelLayout {
+    fn size(&self) -> Size<Length> {
+        Size {
+            width: Length::Fill,
+            // TODO Make depend on orientation or drop that option
+            height: Length::Shrink,
+        }
+    }
+
+    fn layout(
+        &self,
+        max_limit: Size,
+        toplevels: &[LayoutToplevel<'_>],
+    ) -> impl Iterator<Item = Rectangle> {
+        // Get total requested main axis length if widget could have all the space
+        let total_spacing = self.spacing as usize * (toplevels.len().saturating_sub(1)).max(0);
+        let requested_main_total: f32 = toplevels
+            .iter()
+            .map(|t| self.axis.main(t.preferred_size))
+            .sum::<f32>()
+            + total_spacing as f32;
+        let scale_factor = (self.axis.main(max_limit) / requested_main_total).min(1.0);
+        let max_cross = self.axis.cross(max_limit);
+
+        let mut total_main = 0.0;
+        let mut first = true;
+        toplevels.iter().map(move |child| {
+            let requested_main = self.axis.main(child.preferred_size);
+            if !first {
+                total_main += self.spacing as f32;
+            }
+            first = false;
+
+            let max_main = requested_main * scale_factor;
+
+            let (width, height) = self.axis.pack(max_main, max_cross);
+            let (x, y) = self.axis.pack(total_main, 0.0);
+            total_main += max_main;
+            Rectangle::new(Point::new(x, y), Size::new(width, height))
+        })
+    }
+}

src/widgets/toplevels/toplevel_layout/utils.rs

@@ -0,0 +1,31 @@
+use cosmic::iced::{advanced::layout::flex::Axis, Size};
+
+// Duplicate of private methods
+pub(super) trait AxisExt {
+    fn main(&self, size: Size) -> f32;
+    fn cross(&self, size: Size) -> f32;
+    fn pack(&self, main: f32, cross: f32) -> (f32, f32);
+}
+
+impl AxisExt for Axis {
+    fn main(&self, size: Size) -> f32 {
+        match self {
+            Axis::Horizontal => size.width,
+            Axis::Vertical => size.height,
+        }
+    }
+
+    fn cross(&self, size: Size) -> f32 {
+        match self {
+            Axis::Horizontal => size.height,
+            Axis::Vertical => size.width,
+        }
+    }
+
+    fn pack(&self, main: f32, cross: f32) -> (f32, f32) {
+        match self {
+            Axis::Horizontal => (main, cross),
+            Axis::Vertical => (cross, main),
+        }
+    }
+}