layout: Refactor to support window decorations, add border and fullscreen backdrop

Windows are now wrapped in Tiles, which keep track of window-specific
decorations. Particularly, I implemented a black fullscreen backdrop,
which finally brings fullscreened windows smaller than the screen in
line with how the Wayland protocol says they should look—centered in a
black rectangle. I also implemented window borders, which are similar to
the focus ring, but always visible (and hence affect the layout and
sizing).

7 files changed, 454 insertions, 44 deletions

diff --git a/resources/default-config.kdl b/resources/default-config.kdl
index a028488a..f2c567f3 100644
--- a/resources/default-config.kdl
+++ b/resources/default-config.kdl
@@ -89,6 +89,17 @@ focus-ring {
     inactive-color 80 80 80 255
 }
 
+// You can also add a border. It's similar to the focus ring, but always visible.
+border {
+    // The settings are the same as for the focus ring.
+    // If you enable the border, you probably want to disable the focus ring.
+    off
+
+    width 4
+    active-color 255 200 127 255
+    inactive-color 80 80 80 255
+}
+
 cursor {
     // Change the theme and size of the cursor as well as set the
     // `XCURSOR_THEME` and `XCURSOR_SIZE` env variables.
diff --git a/src/config.rs b/src/config.rs
index b5e98adf..ff096017 100644
--- a/src/config.rs
+++ b/src/config.rs
@@ -18,6 +18,8 @@ pub struct Config {
     pub spawn_at_startup: Vec<SpawnAtStartup>,
     #[knuffel(child, default)]
     pub focus_ring: FocusRing,
+    #[knuffel(child, default = default_border())]
+    pub border: FocusRing,
     #[knuffel(child, default)]
     pub prefer_no_csd: bool,
     #[knuffel(child, default)]
@@ -190,6 +192,15 @@ impl Default for FocusRing {
     }
 }
 
+pub const fn default_border() -> FocusRing {
+    FocusRing {
+        off: true,
+        width: 4,
+        active_color: Color::new(255, 200, 127, 255),
+        inactive_color: Color::new(80, 80, 80, 255),
+    }
+}
+
 #[derive(knuffel::Decode, Debug, Default, Clone, Copy, PartialEq, Eq)]
 pub struct Color {
     #[knuffel(argument)]
@@ -203,7 +214,7 @@ pub struct Color {
 }
 
 impl Color {
-    pub fn new(r: u8, g: u8, b: u8, a: u8) -> Self {
+    pub const fn new(r: u8, g: u8, b: u8, a: u8) -> Self {
         Self { r, g, b, a }
     }
 }
@@ -590,6 +601,12 @@ mod tests {
                 inactive-color 255 200 100 0
             }
 
+            border {
+                width 3
+                active-color 0 100 200 255
+                inactive-color 255 200 100 0
+            }
+
             prefer-no-csd
 
             cursor {
@@ -680,6 +697,22 @@ mod tests {
                         a: 0,
                     },
                 },
+                border: FocusRing {
+                    off: false,
+                    width: 3,
+                    active_color: Color {
+                        r: 0,
+                        g: 100,
+                        b: 200,
+                        a: 255,
+                    },
+                    inactive_color: Color {
+                        r: 255,
+                        g: 200,
+                        b: 100,
+                        a: 0,
+                    },
+                },
                 prefer_no_csd: true,
                 cursor: Cursor {
                     xcursor_theme: String::from("breeze_cursors"),
diff --git a/src/layout/focus_ring.rs b/src/layout/focus_ring.rs
index cbcde19c..b5ead3e2 100644
--- a/src/layout/focus_ring.rs
+++ b/src/layout/focus_ring.rs
@@ -105,4 +105,12 @@ impl FocusRing {
 
         rv.into_iter()
     }
+
+    pub fn width(&self) -> i32 {
+        self.width
+    }
+
+    pub fn is_off(&self) -> bool {
+        self.is_off
+    }
 }
diff --git a/src/layout/mod.rs b/src/layout/mod.rs
index 61aaf211..8d454728 100644
--- a/src/layout/mod.rs
+++ b/src/layout/mod.rs
@@ -56,6 +56,7 @@ use crate::utils::output_size;
 
 mod focus_ring;
 mod monitor;
+mod tile;
 mod workspace;
 
 pub trait LayoutElement: PartialEq {
@@ -97,6 +98,11 @@ pub trait LayoutElement: PartialEq {
     fn set_preferred_scale_transform(&self, scale: i32, transform: Transform);
     fn output_enter(&self, output: &Output);
     fn output_leave(&self, output: &Output);
+
+    /// Whether the element is currently fullscreen.
+    ///
+    /// This will *not* switch immediately after a [`LayoutElement::request_fullscreen()`] call.
+    fn is_fullscreen(&self) -> bool;
 }
 
 #[derive(Debug)]
@@ -132,6 +138,7 @@ pub struct Options {
     /// Extra padding around the working area in logical pixels.
     struts: Struts,
     focus_ring: config::FocusRing,
+    border: config::FocusRing,
     /// Column widths that `toggle_width()` switches between.
     preset_widths: Vec<ColumnWidth>,
     /// Initial width for new windows.
@@ -144,6 +151,7 @@ impl Default for Options {
             gaps: 16,
             struts: Default::default(),
             focus_ring: Default::default(),
+            border: config::default_border(),
             preset_widths: vec![
                 ColumnWidth::Proportion(1. / 3.),
                 ColumnWidth::Proportion(0.5),
@@ -180,6 +188,7 @@ impl Options {
             gaps: config.gaps.into(),
             struts: config.struts,
             focus_ring: config.focus_ring,
+            border: config.border,
             preset_widths,
             default_width,
         }
@@ -269,6 +278,13 @@ impl LayoutElement for Window {
     fn output_leave(&self, output: &Output) {
         SpaceElement::output_leave(self, output)
     }
+
+    fn is_fullscreen(&self) -> bool {
+        self.toplevel()
+            .current_state()
+            .states
+            .contains(xdg_toplevel::State::Fullscreen)
+    }
 }
 
 impl<W: LayoutElement> Layout<W> {
@@ -701,7 +717,7 @@ impl<W: LayoutElement> Layout<W> {
         }
 
         let col = &ws.columns[ws.active_column_idx];
-        Some((&col.windows[col.active_window_idx], &mon.output))
+        Some((&col.windows[col.active_window_idx].window(), &mon.output))
     }
 
     pub fn windows_for_output(&self, output: &Output) -> impl Iterator<Item = &W> + '_ {
@@ -1458,6 +1474,10 @@ mod tests {
         fn output_enter(&self, _output: &Output) {}
 
         fn output_leave(&self, _output: &Output) {}
+
+        fn is_fullscreen(&self) -> bool {
+            false
+        }
     }
 
     fn arbitrary_bbox() -> impl Strategy<Value = Rectangle<i32, Logical>> {
diff --git a/src/layout/monitor.rs b/src/layout/monitor.rs
index 8654af0e..77569a0c 100644
--- a/src/layout/monitor.rs
+++ b/src/layout/monitor.rs
@@ -345,7 +345,7 @@ impl<W: LayoutElement> Monitor<W> {
         }
 
         let column = &workspace.columns[workspace.active_column_idx];
-        Some(&column.windows[column.active_window_idx])
+        Some(column.windows[column.active_window_idx].window())
     }
 
     pub fn advance_animations(&mut self, current_time: Duration, is_active: bool) {
diff --git a/src/layout/tile.rs b/src/layout/tile.rs
new file mode 100644
index 00000000..2e8dcd90
--- /dev/null
+++ b/src/layout/tile.rs
@@ -0,0 +1,267 @@
+use std::cmp::max;
+use std::rc::Rc;
+use std::time::Duration;
+
+use smithay::backend::renderer::element::solid::{SolidColorBuffer, SolidColorRenderElement};
+use smithay::backend::renderer::element::utils::{Relocate, RelocateRenderElement};
+use smithay::backend::renderer::element::Kind;
+use smithay::backend::renderer::{ImportAll, Renderer};
+use smithay::utils::{Logical, Point, Scale, Size};
+
+use super::focus_ring::FocusRing;
+use super::workspace::WorkspaceRenderElement;
+use super::{LayoutElement, Options};
+
+/// Toplevel window with decorations.
+#[derive(Debug)]
+pub struct Tile<W: LayoutElement> {
+    /// The toplevel window itself.
+    window: W,
+
+    /// The border around the window.
+    border: FocusRing,
+
+    /// Whether this tile is fullscreen.
+    ///
+    /// This will update only when the `window` actually goes fullscreen, rather than right away,
+    /// to avoid black backdrop flicker before the window has had a chance to resize.
+    is_fullscreen: bool,
+
+    /// The black backdrop for fullscreen windows.
+    fullscreen_backdrop: SolidColorBuffer,
+
+    /// The size we were requested to fullscreen into.
+    fullscreen_size: Size<i32, Logical>,
+
+    /// Configurable properties of the layout.
+    options: Rc<Options>,
+}
+
+impl<W: LayoutElement> Tile<W> {
+    pub fn new(window: W, options: Rc<Options>) -> Self {
+        Self {
+            window,
+            border: FocusRing::new(options.border),
+            is_fullscreen: false, // FIXME: up-to-date fullscreen right away, but we need size.
+            fullscreen_backdrop: SolidColorBuffer::new((0, 0), [0., 0., 0., 1.]),
+            fullscreen_size: Default::default(),
+            options,
+        }
+    }
+
+    pub fn update_config(&mut self, options: Rc<Options>) {
+        self.border.update_config(options.border);
+        self.options = options;
+    }
+
+    pub fn advance_animations(&mut self, _current_time: Duration, is_active: bool) {
+        let width = self.border.width();
+        self.border.update(
+            (width, width).into(),
+            self.window.size(),
+            self.window.has_ssd(),
+        );
+        self.border.set_active(is_active);
+
+        // FIXME: remove when we can get a fullscreen size right away.
+        if self.fullscreen_size != Size::from((0, 0)) {
+            self.is_fullscreen = self.window.is_fullscreen();
+        }
+    }
+
+    pub fn window(&self) -> &W {
+        &self.window
+    }
+
+    pub fn into_window(self) -> W {
+        self.window
+    }
+
+    /// Returns `None` if the border is hidden and `Some(width)` if it should be shown.
+    fn effective_border_width(&self) -> Option<i32> {
+        if self.is_fullscreen {
+            return None;
+        }
+
+        if self.border.is_off() {
+            return None;
+        }
+
+        Some(self.border.width())
+    }
+
+    /// Returns the location of the window's visual geometry within this Tile.
+    fn window_loc(&self) -> Point<i32, Logical> {
+        let mut loc = Point::from((0, 0));
+
+        // In fullscreen, center the window in the given size.
+        if self.is_fullscreen {
+            let window_size = self.window.size();
+            let target_size = self.fullscreen_size;
+
+            // Windows aren't supposed to be larger than the fullscreen size, but in case we get
+            // one, leave it at the top-left as usual.
+            if window_size.w < target_size.w {
+                loc.x += (target_size.w - window_size.w) / 2;
+            }
+            if window_size.h < target_size.h {
+                loc.y += (target_size.h - window_size.h) / 2;
+            }
+        }
+
+        if let Some(width) = self.effective_border_width() {
+            loc += (width, width).into();
+        }
+
+        loc
+    }
+
+    pub fn tile_size(&self) -> Size<i32, Logical> {
+        let mut size = self.window.size();
+
+        if self.is_fullscreen {
+            // Normally we'd just return the fullscreen size here, but this makes things a bit
+            // nicer if a fullscreen window is bigger than the fullscreen size for some reason.
+            size.w = max(size.w, self.fullscreen_size.w);
+            size.h = max(size.h, self.fullscreen_size.h);
+            return size;
+        }
+
+        if let Some(width) = self.effective_border_width() {
+            size += (width * 2, width * 2).into();
+        }
+
+        size
+    }
+
+    pub fn window_size(&self) -> Size<i32, Logical> {
+        self.window.size()
+    }
+
+    pub fn buf_loc(&self) -> Point<i32, Logical> {
+        let mut loc = Point::from((0, 0));
+        loc += self.window_loc();
+        loc += self.window.buf_loc();
+        loc
+    }
+
+    pub fn is_in_input_region(&self, mut point: Point<f64, Logical>) -> bool {
+        point -= self.window_loc().to_f64();
+        self.window.is_in_input_region(point)
+    }
+
+    pub fn request_tile_size(&mut self, mut size: Size<i32, Logical>) {
+        // Can't go through effective_border_width() because we might be fullscreen.
+        if !self.border.is_off() {
+            let width = self.border.width();
+            size.w = max(1, size.w - width * 2);
+            size.h = max(1, size.h - width * 2);
+        }
+
+        self.window.request_size(size);
+    }
+
+    pub fn tile_width_for_window_width(&self, size: i32) -> i32 {
+        if self.border.is_off() {
+            size
+        } else {
+            size + self.border.width() * 2
+        }
+    }
+
+    pub fn tile_height_for_window_height(&self, size: i32) -> i32 {
+        if self.border.is_off() {
+            size
+        } else {
+            size + self.border.width() * 2
+        }
+    }
+
+    pub fn window_height_for_tile_height(&self, size: i32) -> i32 {
+        if self.border.is_off() {
+            size
+        } else {
+            size - self.border.width() * 2
+        }
+    }
+
+    pub fn request_fullscreen(&mut self, size: Size<i32, Logical>) {
+        self.fullscreen_backdrop.resize(size);
+        self.fullscreen_size = size;
+        self.window.request_fullscreen(size);
+    }
+
+    pub fn min_size(&self) -> Size<i32, Logical> {
+        let mut size = self.window.min_size();
+
+        if let Some(width) = self.effective_border_width() {
+            size.w = max(1, size.w);
+            size.h = max(1, size.h);
+            size += (width * 2, width * 2).into();
+        }
+
+        size
+    }
+
+    pub fn max_size(&self) -> Size<i32, Logical> {
+        let mut size = self.window.max_size();
+
+        if let Some(width) = self.effective_border_width() {
+            if size.w > 0 {
+                size.w += width * 2;
+            }
+            if size.h > 0 {
+                size.h += width * 2;
+            }
+        }
+
+        size
+    }
+
+    pub fn has_ssd(&self) -> bool {
+        self.effective_border_width().is_some() || self.window.has_ssd()
+    }
+
+    pub fn render<R: Renderer + ImportAll>(
+        &self,
+        renderer: &mut R,
+        location: Point<i32, Logical>,
+        scale: Scale<f64>,
+    ) -> Vec<WorkspaceRenderElement<R>>
+    where
+        <R as Renderer>::TextureId: 'static,
+    {
+        let mut rv = Vec::new();
+
+        let window_pos = location + self.window_loc();
+        rv.extend(self.window.render(renderer, window_pos, scale));
+
+        if self.effective_border_width().is_some() {
+            rv.extend(
+                self.border
+                    .render(scale)
+                    .map(|elem| {
+                        RelocateRenderElement::from_element(
+                            elem,
+                            location.to_physical_precise_round(scale),
+                            Relocate::Relative,
+                        )
+                    })
+                    .map(Into::into),
+            );
+        }
+
+        if self.is_fullscreen {
+            let elem = SolidColorRenderElement::from_buffer(
+                &self.fullscreen_backdrop,
+                location.to_physical_precise_round(scale),
+                scale,
+                1.,
+                Kind::Unspecified,
+            );
+            rv.push(elem.into());
+        }
+
+        rv
+    }
+}
diff --git a/src/layout/workspace.rs b/src/layout/workspace.rs
index 2187fee0..954e6ff5 100644
--- a/src/layout/workspace.rs
+++ b/src/layout/workspace.rs
@@ -4,6 +4,7 @@ use std::rc::Rc;
 use std::time::Duration;
 
 use smithay::backend::renderer::element::surface::WaylandSurfaceRenderElement;
+use smithay::backend::renderer::element::utils::RelocateRenderElement;
 use smithay::backend::renderer::gles::GlesRenderer;
 use smithay::backend::renderer::ImportAll;
 use smithay::desktop::space::SpaceElement;
@@ -14,6 +15,7 @@ use smithay::render_elements;
 use smithay::utils::{Logical, Point, Rectangle, Scale, Size};
 
 use super::focus_ring::{FocusRing, FocusRingRenderElement};
+use super::tile::Tile;
 use super::{LayoutElement, Options};
 use crate::animation::Animation;
 use crate::config::{PresetWidth, SizeChange, Struts};
@@ -83,6 +85,7 @@ render_elements! {
     pub WorkspaceRenderElement<R> where R: ImportAll;
     Wayland = WaylandSurfaceRenderElement<R>,
     FocusRing = FocusRingRenderElement,
+    Border = RelocateRenderElement<FocusRingRenderElement>,
 }
 
 /// Width of a column.
@@ -121,17 +124,19 @@ pub enum WindowHeight {
 
 #[derive(Debug)]
 pub struct Column<W: LayoutElement> {
-    /// Windows in this column.
+    /// Tiles in this column.
     ///
     /// Must be non-empty.
-    pub windows: Vec<W>,
+    pub windows: Vec<Tile<W>>,
 
     /// Heights of the windows.
     ///
     /// Must have the same number of elements as `windows`.
+    ///
+    /// These heights are window heights, so they exclude tile decorations, if any.
     heights: Vec<WindowHeight>,
 
-    /// Index of the currently active window.
+    /// Index of the currently active tile.
     pub active_window_idx: usize,
 
     /// Desired width of this column.
@@ -231,11 +236,20 @@ impl<W: LayoutElement> Workspace<W> {
 
         let view_pos = self.view_pos();
 
+        for (col_idx, col) in self.columns.iter_mut().enumerate() {
+            for (win_idx, tile) in col.windows.iter_mut().enumerate() {
+                let is_active = is_active
+                    && col_idx == self.active_column_idx
+                    && win_idx == col.active_window_idx;
+                tile.advance_animations(current_time, is_active);
+            }
+        }
+
         // This shall one day become a proper animation.
         if !self.columns.is_empty() {
             let col = &self.columns[self.active_column_idx];
             let active_win = &col.windows[col.active_window_idx];
-            let size = active_win.size();
+            let size = active_win.tile_size();
             let has_ssd = active_win.has_ssd();
 
             let win_pos = Point::from((
@@ -264,7 +278,10 @@ impl<W: LayoutElement> Workspace<W> {
     }
 
     pub fn windows(&self) -> impl Iterator<Item = &W> + '_ {
-        self.columns.iter().flat_map(|col| col.windows.iter())
+        self.columns
+            .iter()
+            .flat_map(|col| col.windows.iter())
+            .map(Tile::window)
     }
 
     pub fn set_output(&mut self, output: Option<Output>) {
@@ -315,20 +332,33 @@ impl<W: LayoutElement> Workspace<W> {
     }
 
     fn toplevel_bounds(&self) -> Size<i32, Logical> {
+        let mut border = 0;
+        if !self.options.border.off {
+            border = self.options.border.width as i32 * 2;
+        }
+
         Size::from((
-            max(self.working_area.size.w - self.options.gaps * 2, 1),
-            max(self.working_area.size.h - self.options.gaps * 2, 1),
+            max(self.working_area.size.w - self.options.gaps * 2 - border, 1),
+            max(self.working_area.size.h - self.options.gaps * 2 - border, 1),
         ))
     }
 
     pub fn configure_new_window(&self, window: &Window) {
         let width = if let Some(width) = self.options.default_width {
-            max(1, width.resolve(&self.options, self.working_area.size.w))
+            let mut width = width.resolve(&self.options, self.working_area.size.w);
+            if !self.options.border.off {
+                width -= self.options.border.width as i32 * 2;
+            }
+            max(1, width)
         } else {
             0
         };
 
-        let height = self.working_area.size.h - self.options.gaps * 2;
+        let mut height = self.working_area.size.h - self.options.gaps * 2;
+        if !self.options.border.off {
+            height -= self.options.border.width as i32 * 2;
+        }
+
         let size = Size::from((width, max(height, 1)));
 
         let bounds = self.toplevel_bounds();
@@ -478,7 +508,7 @@ impl<W: LayoutElement> Workspace<W> {
 
     pub fn remove_window_by_idx(&mut self, column_idx: usize, window_idx: usize) -> W {
         let column = &mut self.columns[column_idx];
-        let window = column.windows.remove(window_idx);
+        let window = column.windows.remove(window_idx).into_window();
         column.heights.remove(window_idx);
 
         if let Some(output) = &self.output {
@@ -746,20 +776,20 @@ impl<W: LayoutElement> Workspace<W> {
             col.window_y(col.active_window_idx),
         ));
         if active_win.is_in_input_region(pos - win_pos.to_f64()) {
-            return Some((active_win, win_pos + active_win.buf_loc()));
+            return Some((active_win.window(), win_pos + active_win.buf_loc()));
         }
 
         let mut x = -view_pos;
         for col in &self.columns {
             for (win, y) in zip(&col.windows, col.window_ys()) {
-                if win == active_win {
+                if win.window() == active_win.window() {
                     // Already handled it above.
                     continue;
                 }
 
                 let win_pos = Point::from((x, y));
                 if win.is_in_input_region(pos - win_pos.to_f64()) {
-                    return Some((win, win_pos + win.buf_loc()));
+                    return Some((win.window(), win_pos + win.buf_loc()));
                 }
             }
 
@@ -815,7 +845,7 @@ impl<W: LayoutElement> Workspace<W> {
             // This wasn't the only window in its column; extract it into a separate column.
             let target_window_was_focused =
                 self.active_column_idx == col_idx && col.active_window_idx == win_idx;
-            let window = col.windows.remove(win_idx);
+            let window = col.windows.remove(win_idx).into_window();
             col.heights.remove(win_idx);
             col.active_window_idx = min(col.active_window_idx, col.windows.len() - 1);
             col.update_window_sizes();
@@ -872,7 +902,8 @@ impl Workspace<Window> {
         let bounds = self.toplevel_bounds();
 
         for (col_idx, col) in self.columns.iter().enumerate() {
-            for (win_idx, win) in col.windows.iter().enumerate() {
+            for (win_idx, tile) in col.windows.iter().enumerate() {
+                let win = tile.window();
                 let active = self.active_column_idx == col_idx && col.active_window_idx == win_idx;
                 win.set_activated(active);
 
@@ -922,7 +953,7 @@ impl Workspace<Window> {
         let mut x = -view_pos;
         for col in &self.columns {
             for (win, y) in zip(&col.windows, col.window_ys()) {
-                if win == active_win {
+                if win.window() == active_win.window() {
                     // Already handled it above.
                     continue;
                 }
@@ -989,6 +1020,16 @@ impl<W: LayoutElement> Column<W> {
             update_sizes = true;
         }
 
+        if self.options.border.off != options.border.off
+            || self.options.border.width != options.border.width
+        {
+            update_sizes = true;
+        }
+
+        for tile in &mut self.windows {
+            tile.update_config(options.clone());
+        }
+
         self.options = options;
 
         if update_sizes {
@@ -1003,11 +1044,17 @@ impl<W: LayoutElement> Column<W> {
     }
 
     pub fn contains(&self, window: &W) -> bool {
-        self.windows.iter().any(|win| win == window)
+        self.windows
+            .iter()
+            .map(Tile::window)
+            .any(|win| win == window)
     }
 
     pub fn position(&self, window: &W) -> Option<usize> {
-        self.windows.iter().position(|win| win == window)
+        self.windows
+            .iter()
+            .map(Tile::window)
+            .position(|win| win == window)
     }
 
     fn activate_window(&mut self, window: &W) {
@@ -1016,8 +1063,9 @@ impl<W: LayoutElement> Column<W> {
     }
 
     fn add_window(&mut self, window: W) {
+        let tile = Tile::new(window, self.options.clone());
         self.is_fullscreen = false;
-        self.windows.push(window);
+        self.windows.push(tile);
         self.heights.push(WindowHeight::Auto);
         self.update_window_sizes();
     }
@@ -1028,8 +1076,8 @@ impl<W: LayoutElement> Column<W> {
             return;
         }
 
-        let min_size: Vec<_> = self.windows.iter().map(LayoutElement::min_size).collect();
-        let max_size: Vec<_> = self.windows.iter().map(LayoutElement::max_size).collect();
+        let min_size: Vec<_> = self.windows.iter().map(Tile::min_size).collect();
+        let max_size: Vec<_> = self.windows.iter().map(Tile::max_size).collect();
 
         // Compute the column width.
         let min_width = min_size
@@ -1067,8 +1115,15 @@ impl<W: LayoutElement> Column<W> {
         let width = width.resolve(&self.options, self.working_area.size.w);
         let width = max(min(width, max_width), min_width);
 
-        // Compute the window heights.
-        let mut heights = self.heights.clone();
+        // Compute the window heights. Start by converting window heights to tile heights.
+        let mut heights = zip(&self.windows, &self.heights)
+            .map(|(tile, height)| match *height {
+                WindowHeight::Auto => WindowHeight::Auto,
+                WindowHeight::Fixed(height) => {
+                    WindowHeight::Fixed(tile.tile_height_for_window_height(height))
+                }
+            })
+            .collect::<Vec<_>>();
         let mut height_left = self.working_area.size.h - self.options.gaps;
         let mut auto_windows_left = self.windows.len();
 
@@ -1162,18 +1217,22 @@ impl<W: LayoutElement> Column<W> {
             assert_eq!(auto_windows_left, 0);
         }
 
-        for (win, h) in zip(&self.windows, heights) {
+        for (tile, h) in zip(&mut self.windows, heights) {
             let WindowHeight::Fixed(height) = h else {
                 unreachable!()
             };
 
             let size = Size::from((width, height));
-            win.request_size(size);
+            tile.request_tile_size(size);
         }
     }
 
     fn width(&self) -> i32 {
-        self.windows.iter().map(|win| win.size().w).max().unwrap()
+        self.windows
+            .iter()
+            .map(|win| win.tile_size().w)
+            .max()
+            .unwrap()
     }
 
     fn focus_up(&mut self) {
@@ -1265,7 +1324,13 @@ impl<W: LayoutElement> Column<W> {
         const MAX_F: f64 = 10000.;
 
         let width = match (current, change) {
-            (_, SizeChange::SetFixed(fixed)) => ColumnWidth::Fixed(fixed.clamp(1, MAX_PX)),
+            (_, SizeChange::SetFixed(fixed)) => {
+                // As a special case, setting a fixed column width will compute it in such a way
+                // that the active window gets that width. This is the intention behind the ability
+                // to set a fixed size.
+                let tile = &self.windows[self.active_window_idx];
+                ColumnWidth::Fixed(tile.tile_width_for_window_width(fixed).clamp(1, MAX_PX))
+            }
             (_, SizeChange::SetProportion(proportion)) => {
                 ColumnWidth::Proportion((proportion / 100.).clamp(0., MAX_F))
             }
@@ -1291,45 +1356,51 @@ impl<W: LayoutElement> Column<W> {
 
     fn set_window_height(&mut self, change: SizeChange) {
         let current = self.heights[self.active_window_idx];
-        let current_px = match current {
-            WindowHeight::Auto => self.windows[self.active_window_idx].size().h,
+        let tile = &self.windows[self.active_window_idx];
+        let current_window_px = match current {
+            WindowHeight::Auto => tile.window_size().h,
             WindowHeight::Fixed(height) => height,
         };
-        let current_prop = (current_px + self.options.gaps) as f64
+        let current_tile_px = tile.tile_height_for_window_height(current_window_px);
+        let current_prop = (current_tile_px + self.options.gaps) as f64
             / (self.working_area.size.h - self.options.gaps) as f64;
 
         // FIXME: fix overflows then remove limits.
         const MAX_PX: i32 = 100000;
 
-        let mut height = match change {
+        let mut window_height = match change {
             SizeChange::SetFixed(fixed) => fixed,
             SizeChange::SetProportion(proportion) => {
-                ((self.working_area.size.h - self.options.gaps) as f64 * proportion
+                let tile_height = ((self.working_area.size.h - self.options.gaps) as f64
+                    * proportion
                     - self.options.gaps as f64)
-                    .round() as i32
+                    .round() as i32;
+                tile.window_height_for_tile_height(tile_height)
             }
-            SizeChange::AdjustFixed(delta) => current_px.saturating_add(delta),
+            SizeChange::AdjustFixed(delta) => current_window_px.saturating_add(delta),
             SizeChange::AdjustProportion(delta) => {
                 let proportion = current_prop + delta / 100.;
-                ((self.working_area.size.h - self.options.gaps) as f64 * proportion
+                let tile_height = ((self.working_area.size.h - self.options.gaps) as f64
+                    * proportion
                     - self.options.gaps as f64)
-                    .round() as i32
+                    .round() as i32;
+                tile.window_height_for_tile_height(tile_height)
             }
         };
 
         // Clamp it against the window height constraints.
-        let win = &self.windows[self.active_window_idx];
+        let win = &self.windows[self.active_window_idx].window();
         let min_h = win.min_size().h;
         let max_h = win.max_size().h;
 
         if max_h > 0 {
-            height = height.min(max_h);
+            window_height = window_height.min(max_h);
         }
         if min_h > 0 {
-            height = height.max(min_h);
+            window_height = window_height.max(min_h);
         }
 
-        self.heights[self.active_window_idx] = WindowHeight::Fixed(height.clamp(1, MAX_PX));
+        self.heights[self.active_window_idx] = WindowHeight::Fixed(window_height.clamp(1, MAX_PX));
         self.update_window_sizes();
     }
 
@@ -1352,7 +1423,7 @@ impl<W: LayoutElement> Column<W> {
 
         self.windows.iter().map(move |win| {
             let pos = y;
-            y += win.size().h + self.options.gaps;
+            y += win.tile_size().h + self.options.gaps;
             pos
         })
     }