feat(wm): add opt to keep focused column centered on scrolling layout

This commit adds a new option under layout_options.scrolling -
"center_focused_column", which defaults to false. When

set to true, and when the number of scrolling columns is an odd number
>=3, komorebi will, if there are enough windows being managed on the
workspace, and if the focused window is not too close to either the
beginning or the end of the workspace ring, keep the focused window in a
centered position in the layout

komorebi/src/core/arrangement.rs

@@ -78,6 +78,13 @@ impl Arrangement for DefaultLayout {
                     // treat >= column_count as scrolling
                     len => {
                         let visible_columns = area.right / column_width;
+                        let keep_centered = layout_options
+                            .and_then(|o| {
+                                o.scrolling
+                                    .map(|s| s.center_focused_column.unwrap_or_default())
+                            })
+                            .unwrap_or(false);
+
                         let first_visible: isize = if focused_idx == 0 {
                             // if focused idx is 0, we are at the beginning of the scrolling strip
                             0
@@ -95,6 +102,16 @@ impl Arrangement for DefaultLayout {
 
                             let focused_idx = focused_idx as isize;
 
+                            // if center_focused_column is enabled, and we have an odd number of visible columns,
+                            // center the focused window column
+                            if keep_centered && visible_columns % 2 == 1 {
+                                let center_offset = visible_columns as isize / 2;
+                                (focused_idx - center_offset).max(0).min(
+                                    (len as isize)
+                                        .saturating_sub(visible_columns as isize)
+                                        .max(0),
+                                )
+                            } else {
                                 if focused_idx < previous_first_visible {
                                     // focused window is off the left edge, we need to scroll left
                                     focused_idx
@@ -113,6 +130,7 @@ impl Arrangement for DefaultLayout {
                                         .saturating_sub(visible_columns as isize)
                                         .max(0),
                                 )
+                            }
                         };
 
                         for i in 0..len {

komorebi/src/core/default_layout.rs

@@ -37,6 +37,8 @@ pub struct LayoutOptions {
 pub struct ScrollingLayoutOptions {
     /// Desired number of visible columns (default: 3)
     pub columns: usize,
+    /// With an odd number of visible columns, keep the focused window column centered
+    pub center_focused_column: Option<bool>,
 }
 
 impl DefaultLayout {

komorebi/src/process_command.rs

@@ -921,6 +921,7 @@ impl WindowManager {
                     None => LayoutOptions {
                         scrolling: Some(ScrollingLayoutOptions {
                             columns: count.into(),
+                            center_focused_column: Default::default(),
                         }),
                     },
                 };

schema.json

@@ -1814,6 +1814,10 @@
                         "columns"
                       ],
                       "properties": {
+                        "center_focused_column": {
+                          "description": "With an odd number of visible columns, keep the focused window column centered",
+                          "type": "boolean"
+                        },
                         "columns": {
                           "description": "Desired number of visible columns (default: 3)",
                           "type": "integer",