Splits layout: Allow setting the bias of the current split using layout_action bias

Fixes #8222

docs/changelog.rst

@@ -84,6 +84,12 @@ consumption to do the same tasks.
 Detailed list of changes
 -------------------------------------
 
+0.39.1 [future]
+~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
+
+- Splits layout: Allow setting the bias of the current split using ``layout_action bias`` (:iss:`8222`)
+
+
 0.39.0 [2025-01-16]
 ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
 

docs/layouts.rst

@@ -179,6 +179,12 @@ define a few extra key bindings in :file:`kitty.conf`::
     map ctrl+up neighboring_window up
     map ctrl+down neighboring_window down
 
+    # Set the bias of the split containing the currently focused window. The
+    # currently focused window will take up the specified percent of its parent
+    # window's size.
+    map ctrl+. layout_action bias 80
+
+
 Windows can be resized using :ref:`window_resizing`. You can swap the windows
 in a split using the ``rotate`` action with an argument of ``180`` and rotate
 and swap with an argument of ``270``.

kitty/layout/splits.py

@@ -288,6 +288,10 @@ class Pair:
                 geom = window_geometry_from_layouts(xl, yl)
                 self.apply_window_geometry(self.two, geom, id_window_map, layout_object)
 
+    def set_bias(self, window_id: int, bias: int) -> None:
+        b = max(0, min(bias, 100)) / 100
+        self.bias = b if window_id == self.one else (1. - b)
+
     def modify_size_of_child(self, which: int, increment: float, is_horizontal: bool, layout_object: 'Splits') -> bool:
         if is_horizontal == self.horizontal and not self.is_redundant:
             if which == 2:
@@ -642,6 +646,15 @@ class Splits(Layout):
                         new_root.two = wg.id
                     self.pairs_root = new_root
                     return True
+        elif action_name == 'bias':
+            args = args or ('50',)
+            bias = int(args[0])
+            wg = all_windows.active_group
+            if wg is not None:
+                pair = self.pairs_root.pair_for_window(wg.id)
+                if pair is not None:
+                    pair.set_bias(wg.id, bias)
+                    return True
 
         return None