Implement expand-column-to-available-width

niri-config/src/lib.rs

@@ -1593,6 +1593,7 @@ pub enum Action {
     SwitchPresetWindowHeightById(u64),
     MaximizeColumn,
     SetColumnWidth(#[knuffel(argument, str)] SizeChange),
+    ExpandColumnToAvailableWidth,
     SwitchLayout(#[knuffel(argument, str)] LayoutSwitchTarget),
     ShowHotkeyOverlay,
     MoveWorkspaceToMonitorLeft,
@@ -1794,6 +1795,7 @@ impl From<niri_ipc::Action> for Action {
             }
             niri_ipc::Action::MaximizeColumn {} => Self::MaximizeColumn,
             niri_ipc::Action::SetColumnWidth { change } => Self::SetColumnWidth(change),
+            niri_ipc::Action::ExpandColumnToAvailableWidth {} => Self::ExpandColumnToAvailableWidth,
             niri_ipc::Action::SwitchLayout { layout } => Self::SwitchLayout(layout),
             niri_ipc::Action::ShowHotkeyOverlay {} => Self::ShowHotkeyOverlay,
             niri_ipc::Action::MoveWorkspaceToMonitorLeft {} => Self::MoveWorkspaceToMonitorLeft,

niri-ipc/src/lib.rs

@@ -539,6 +539,8 @@ pub enum Action {
         #[cfg_attr(feature = "clap", arg(allow_hyphen_values = true))]
         change: SizeChange,
     },
+    /// Expand the focused column to space not taken up by other fully visible columns.
+    ExpandColumnToAvailableWidth {},
     /// Switch between keyboard layouts.
     SwitchLayout {
         /// Layout to switch to.

resources/default-config.kdl

@@ -504,6 +504,11 @@ binds {
     Mod+Ctrl+R { reset-window-height; }
     Mod+F { maximize-column; }
     Mod+Shift+F { fullscreen-window; }
+
+    // Expand the focused column to space not taken up by other fully visible columns.
+    // Makes the column "fill the rest of the space".
+    Mod+Ctrl+F { expand-column-to-available-width; }
+
     Mod+C { center-column; }
 
     // Finer width adjustments.

src/input/mod.rs

@@ -1511,6 +1511,9 @@ impl State {
                     self.niri.layout.reset_window_height(Some(&window));
                 }
             }
+            Action::ExpandColumnToAvailableWidth => {
+                self.niri.layout.expand_column_to_available_width();
+            }
             Action::ShowHotkeyOverlay => {
                 if self.niri.hotkey_overlay.show() {
                     self.niri.queue_redraw_all();

src/layout/mod.rs

@@ -2977,6 +2977,13 @@ impl<W: LayoutElement> Layout<W> {
         workspace.reset_window_height(window);
     }
 
+    pub fn expand_column_to_available_width(&mut self) {
+        let Some(monitor) = self.active_monitor() else {
+            return;
+        };
+        monitor.expand_column_to_available_width();
+    }
+
     pub fn toggle_window_floating(&mut self, window: Option<&W::Id>) {
         if let Some(InteractiveMoveState::Moving(move_)) = &mut self.interactive_move {
             if window.is_none() || window == Some(move_.tile.window().id()) {

src/layout/monitor.rs

@@ -840,6 +840,10 @@ impl<W: LayoutElement> Monitor<W> {
         self.active_workspace().set_column_width(change);
     }
 
+    pub fn expand_column_to_available_width(&mut self) {
+        self.active_workspace().expand_column_to_available_width();
+    }
+
     pub fn move_workspace_down(&mut self) {
         let mut new_idx = min(self.active_workspace_idx + 1, self.workspaces.len() - 1);
         if new_idx == self.active_workspace_idx {

src/layout/scrolling.rs

@@ -2524,6 +2524,89 @@ impl<W: LayoutElement> ScrollingSpace<W> {
         cancel_resize_for_column(&mut self.interactive_resize, col);
     }
 
+    pub fn expand_column_to_available_width(&mut self) {
+        if self.columns.is_empty() {
+            return;
+        }
+
+        let col = &mut self.columns[self.active_column_idx];
+        if col.is_fullscreen || col.is_full_width {
+            return;
+        }
+
+        if self.is_centering_focused_column() {
+            // Always-centered mode is different since the active window position cannot be
+            // controlled (it's always at the center). I guess you could come up with different
+            // logic here that computes the width in such a way so as to leave nearby columns fully
+            // on screen while taking into account that the active column will remain centered
+            // after resizing. But I'm not sure it's that useful? So let's do the simple thing.
+            let col = &mut self.columns[self.active_column_idx];
+            col.set_column_width(SizeChange::SetProportion(1.), None, true);
+            cancel_resize_for_column(&mut self.interactive_resize, col);
+            return;
+        }
+
+        // Consider the end of an ongoing animation because that's what compute to fit does too.
+        let view_x = self.target_view_pos();
+        let working_x = self.working_area.loc.x;
+        let working_w = self.working_area.size.w;
+
+        // Count all columns that are fully visible inside the working area.
+        let mut width_taken = 0.;
+        let mut leftmost_col_x = None;
+        let mut active_col_x = None;
+
+        let gap = self.options.gaps;
+        let col_xs = self.column_xs(self.data.iter().copied());
+        for (idx, col_x) in col_xs.take(self.columns.len()).enumerate() {
+            if col_x < view_x + working_x + gap {
+                // Column goes off-screen to the left.
+                continue;
+            }
+
+            leftmost_col_x.get_or_insert(col_x);
+
+            let width = self.data[idx].width;
+            if view_x + working_x + working_w < col_x + width + gap {
+                // Column goes off-screen to the right. We can stop here.
+                break;
+            }
+
+            if idx == self.active_column_idx {
+                active_col_x = Some(col_x);
+            }
+
+            width_taken += width + gap;
+        }
+
+        if active_col_x.is_none() {
+            // The active column wasn't fully on screen, so we can't meaningfully do anything.
+            return;
+        }
+
+        let available_width = working_w - gap - width_taken;
+        if available_width <= 0. {
+            // Nowhere to expand.
+            return;
+        }
+
+        let active_width = self.data[self.active_column_idx].width;
+
+        let col = &mut self.columns[self.active_column_idx];
+        col.width = ColumnWidth::Fixed(active_width + available_width);
+        col.preset_width_idx = None;
+        col.is_full_width = false;
+        col.update_tile_sizes(true);
+
+        cancel_resize_for_column(&mut self.interactive_resize, col);
+
+        // Put the leftmost window into the view.
+        let new_view_x = leftmost_col_x.unwrap() - gap - working_x;
+        self.animate_view_offset(self.active_column_idx, new_view_x - active_col_x.unwrap());
+        // Just in case.
+        self.animate_view_offset_to_column(None, self.active_column_idx, None);
+    }
+
     pub fn set_fullscreen(&mut self, window: &W::Id, is_fullscreen: bool) -> bool {
         let (mut col_idx, tile_idx) = self
             .columns

src/layout/tests.rs

@@ -496,6 +496,7 @@ enum Op {
         #[proptest(strategy = "proptest::option::of(1..=5usize)")]
         id: Option<usize>,
     },
+    ExpandColumnToAvailableWidth,
     ToggleWindowFloating {
         #[proptest(strategy = "proptest::option::of(1..=5usize)")]
         id: Option<usize>,
@@ -1133,6 +1134,7 @@ impl Op {
                 let id = id.filter(|id| layout.has_window(id));
                 layout.reset_window_height(id.as_ref());
             }
+            Op::ExpandColumnToAvailableWidth => layout.expand_column_to_available_width(),
             Op::ToggleWindowFloating { id } => {
                 let id = id.filter(|id| layout.has_window(id));
                 layout.toggle_window_floating(id.as_ref());

src/layout/workspace.rs

@@ -1128,6 +1128,13 @@ impl<W: LayoutElement> Workspace<W> {
         }
     }
 
+    pub fn expand_column_to_available_width(&mut self) {
+        if self.floating_is_active.get() {
+            return;
+        }
+        self.scrolling.expand_column_to_available_width();
+    }
+
     pub fn set_fullscreen(&mut self, window: &W::Id, is_fullscreen: bool) {
         let mut unfullscreen_to_floating = false;
         if self.floating.has_window(window) {