Custom Toplevels widget

Fixes centering on toplevels.

Need to use fewer hacks, and add equal scale factor.

See if Iced layout system can be improved.

src/view/mod.rs

@@ -261,12 +261,14 @@ fn toplevel_previews<'a>(
     let entries = toplevels
         .map(|t| toplevel_previews_entry(t, output))
         .collect();
-    row(entries)
+    //row(entries)
+    widget::container(crate::widgets::toplevels(entries))
+        .align_x(iced::alignment::Horizontal::Center)
         .width(width)
         .height(height)
-        .spacing(16)
+        //.spacing(16)
         .padding(12)
-        .align_items(iced::Alignment::Center)
+        //.align_items(iced::Alignment::Center)
         .into()
 }
 

src/widgets/mod.rs

@@ -17,6 +17,8 @@ mod workspace_item;
 pub use workspace_item::workspace_item;
 mod mouse_interaction_wrapper;
 pub use mouse_interaction_wrapper::mouse_interaction_wrapper;
+mod toplevels;
+pub use toplevels::toplevels;
 
 trait Foo {}
 

src/widgets/toplevels.rs

@@ -0,0 +1,221 @@
+use cosmic::iced::{
+    advanced::{
+        layout::{self, flex::Axis},
+        mouse, renderer,
+        widget::{Operation, OperationOutputWrapper, Tree},
+        Clipboard, Layout, Shell, Widget,
+    },
+    event::{self, Event},
+    Length, Point, Rectangle, Size,
+};
+use std::marker::PhantomData;
+
+// Duplicate of private methods
+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),
+        }
+    }
+}
+
+pub fn toplevels<'a, Msg>(children: Vec<cosmic::Element<'a, Msg>>) -> Toplevels<'a, Msg> {
+    Toplevels {
+        axis: Axis::Horizontal,
+        children,
+        _msg: PhantomData,
+    }
+}
+
+pub struct Toplevels<'a, Msg> {
+    axis: Axis,
+    children: Vec<cosmic::Element<'a, Msg>>,
+    _msg: PhantomData<Msg>,
+}
+
+impl<'a, Msg> Widget<Msg, cosmic::Renderer> for Toplevels<'a, Msg> {
+    fn width(&self) -> Length {
+        Length::Fill
+    }
+
+    fn height(&self) -> Length {
+        // TODO Make depend on orientation or drop that option
+        Length::Shrink
+    }
+
+    fn layout(
+        &self,
+        tree: &mut Tree,
+        renderer: &cosmic::Renderer,
+        limits: &layout::Limits,
+    ) -> layout::Node {
+        // TODO configurable
+        let spacing = 16;
+
+        // TODO scaling
+        let total_spacing = 0.max(spacing * (self.children.len() - 1)) as f32;
+        let max_main =
+            (self.axis.main(limits.max()) - total_spacing) / self.children().len() as f32;
+        let max_cross = self.axis.cross(limits.max());
+
+        // XXX sill allocating maximum main axis?
+        // - what was it doing before?
+        let mut total_main = 0.0;
+        let first = false;
+        let nodes = self
+            .children
+            .iter()
+            .zip(tree.children.iter_mut())
+            .map(|(child, tree)| {
+                if !first {
+                    total_main += spacing as f32;
+                }
+                let (max_width, max_height) = self.axis.pack(max_main, max_cross);
+                let child_limits =
+                    layout::Limits::new(Size::ZERO, Size::new(max_width, max_height));
+                let mut layout = child.layout(tree, renderer, &child_limits);
+                // Center on cross axis
+                let cross = ((max_cross - self.axis.cross(layout.size())) / 2.).max(0.);
+                let (x, y) = self.axis.pack(total_main, cross);
+                layout.move_to(Point::new(x, y));
+                total_main += self.axis.main(layout.size());
+                layout
+            })
+            .collect();
+
+        let (total_width, total_height) = self.axis.pack(total_main, max_cross);
+        let size = Size::new(total_width, total_height);
+        limits;
+        layout::Node::with_children(size, nodes)
+    }
+
+    fn operate(
+        &self,
+        tree: &mut Tree,
+        layout: Layout<'_>,
+        renderer: &cosmic::Renderer,
+        operation: &mut dyn Operation<OperationOutputWrapper<Msg>>,
+    ) {
+        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/workspace_item.rs

@@ -1,5 +1,7 @@
 // TODO rename
 // combine widgets
+// Hack: this widget defines it's width as the second child's width
+// So the width of the image will be the overall width.
 
 use cosmic::iced::{
     advanced::{
@@ -62,7 +64,10 @@ pub struct WorkspaceItem<'a, Msg> {
 
 impl<'a, Msg> Widget<Msg, cosmic::Renderer> for WorkspaceItem<'a, Msg> {
     fn width(&self) -> Length {
-        Length::Fill
+        //Length::Fill
+        // XXX doesn't work when used in standard `row` widget
+        // But fixes allocation of `dnd_source` wrapping this, within `Workspaces` row
+        Length::Shrink
     }
 
     fn height(&self) -> Length {