Add a new `neighboring_window` function to switch to neighboring windows in the current layout, similar to window movement in vim

Fixes #916

docs/changelog.rst

@@ -9,6 +9,9 @@ Changelog
 - Add a new ``last_used_layout`` function that can be mapped to a shortcut to
   switch to the previously used window layout (:iss:`870`)
 
+- Add a new ``neighboring_window`` function to switch to neighboring
+  windows in the current layout, similar to window movement in vim (:iss:`916`)
+
 
 0.12.1 [2018-09-08]
 ------------------------------

docs/index.rst

@@ -151,6 +151,13 @@ Focus specific window       :sc:`first_window`, :sc:`second_window` ... :sc:`ten
                             (clockwise from the top-left)
 ========================    =======================
 
+Additionally, you can define shortcuts in :file:`kitty.conf` to go to neighboring
+windows (similar to window movement in vim)::
+
+   map ctrl+left neighboring_window left
+   map ctrl+down neighboring_window bottom
+   ...
+
 
 Other keyboard shortcuts
 ----------------------------------

kitty/config.py

@@ -140,6 +140,16 @@ def clear_terminal(func, rest):
     return func, args
 
 
+@func_with_args('neighboring_window')
+def neighboring_window(func, rest):
+    rest = rest.lower()
+    rest = {'up': 'top', 'down': 'bottom'}.get(rest, rest)
+    if rest not in ('left', 'right', 'top', 'bottom'):
+        log_error('Invalid neighbor specification: {}'.format(rest))
+        rest = 'right'
+    return func, [rest]
+
+
 def parse_key_action(action):
     parts = action.split(' ', 1)
     func = parts[0]

kitty/layout.py

@@ -231,7 +231,10 @@ class Layout:  # {{{
     def neighbors(self, all_windows, active_window_idx):
         w = all_windows[active_window_idx]
         windows = process_overlaid_windows(all_windows)[1]
-        self.neighbors_for_window(w, windows)
+        ans = self.neighbors_for_window(w, windows)
+        for values in ans.values():
+            values[:] = [idx_for_id(w.id, windows) for w in values]
+        return ans
 
     def move_window(self, all_windows, active_window_idx, delta=1):
         w = all_windows[active_window_idx]
@@ -481,7 +484,7 @@ class Tall(Layout):  # {{{
         if window is windows[0]:
             return {'left': [], 'right': windows[1:], 'top': [], 'bottom': []}
         idx = windows.index(window)
-        return {'left': windows[0], 'right': [], 'top': [] if idx <= 1 else [windows[idx-1]],
+        return {'left': [windows[0]], 'right': [], 'top': [] if idx <= 1 else [windows[idx-1]],
                 'bottom': [] if window is windows[-1] else [windows[idx+1]]}
 
     def minimal_borders(self, windows, active_window, needs_borders_map):
@@ -540,7 +543,7 @@ class Fat(Tall):  # {{{
         if window is windows[0]:
             return {'left': [], 'bottom': windows[1:], 'top': [], 'right': []}
         idx = windows.index(window)
-        return {'top': windows[0], 'bottom': [], 'left': [] if idx <= 1 else [windows[idx-1]],
+        return {'top': [windows[0]], 'bottom': [], 'left': [] if idx <= 1 else [windows[idx-1]],
                 'right': [] if window is windows[-1] else [windows[idx+1]]}
 
 # }}}

kitty/tabs.py

@@ -271,6 +271,14 @@ class Tab:  # {{{
     def previous_window(self):
         self._next_window(-1)
 
+    def neighboring_window(self, which):
+        neighbors = self.current_layout.neighbors(self.windows, self.active_window_idx)
+        candidates = neighbors.get(which)
+        if candidates:
+            self.active_window_idx = self.current_layout.set_active_window(self.windows, candidates[0])
+            self.relayout_borders()
+            glfw_post_empty_event()
+
     def move_window(self, delta=1):
         self.active_window_idx = self.current_layout.move_window(self.windows, self.active_window_idx, delta)
         self.relayout()