feature: Allow switching between containers

etc/sway/modes/default.conf

@@ -79,6 +79,10 @@ $bindsym Mod1+Tab exec env RUST_BACKTRACE=1 swayr switch-to-urgent-or-lru-window
 ## Navigation // Switch to the last recently used workspace ##
 $bindsym $mod+Tab workspace back_and_forth
 
+## Navigation // Switching between containers in the workspace // $mod + [] ##
+$bindsym $mod+bracketright nop top_next
+$bindsym $mod+bracketleft nop top_prev
+
 #
 # Workspaces:
 #

usr/lib/systemd/user/switch-top-level.service

@@ -0,0 +1,10 @@
+[Unit]
+Requires=graphical-session.target
+
+[Service]
+ExecStart=/usr/share/sway/scripts/switch-top-level.py
+Restart=on-failure
+RestartSec=1
+
+[Install]
+WantedBy=graphical-session.target

usr/share/sway/scripts/switch-top-level.py

@@ -0,0 +1,98 @@
+#!/usr/bin/env python3
+import i3ipc
+#
+# This script requires i3ipc-python package (install it from a system package manager
+# or pip).
+#
+# The scripts allows you to define two new bindings:
+#    bindsym $mod+bracketright nop top_next
+#    bindsym $mod+bracketleft nop top_prev
+#
+# The purpose of it is to switch between top-level containers (windows) in a workspace.
+# One possible usecase is having a workspace with two (or more on large displays)
+# columns of tabs: one on left and one on right. In such setup, "move left" and
+# "move right" will only switch tabs inside the column.
+#
+# You can add a systemd user service to run this script on startup:
+#
+# ~> cat .config/systemd/user/switch-top-level.service
+# [Install]
+# WantedBy=graphical-session.target
+
+# [Service]
+# ExecStart=path/to/switch-top-level.py
+# Restart=on-failure
+# RestartSec=1
+
+# [Unit]
+# Requires=graphical-session.target
+
+
+class TopLevelSwitcher:
+    def __init__(self):
+        self.top_to_selected = {} # top i3ipc.Con -> selected container id
+        self.con_to_top = {} # container id -> top i3ipc.Con
+        self.prev = None # previously focused container id
+
+        self.i3 = i3ipc.Connection()
+        self.i3.on('window::focus', self.on_window_focus)
+        self.i3.on(i3ipc.Event.BINDING, self.on_binding)
+
+        self.update_top_level()
+        self.i3.main()
+
+    def top_level(self, node):
+        if len(node.nodes) == 1:
+            return self.top_level(node.nodes[0])
+        return node.nodes
+
+    def update_top_level(self):
+        tree = self.i3.get_tree()
+        for ws in tree.workspaces():
+            for con in self.top_level(ws):
+                self.update_top_level_rec(con, con.id)
+
+    def update_top_level_rec(self, con: i3ipc.Con, top: i3ipc.Con):
+        self.con_to_top[con.id] = top
+        for child in con.nodes:
+            self.update_top_level_rec(child, top)
+
+        if len(con.nodes) == 0 and top not in self.top_to_selected:
+            self.top_to_selected[top] = con.id
+
+    def save_prev(self):
+        if not self.prev:
+            return
+        prev_top = self.con_to_top.get(self.prev)
+        if not prev_top:
+            return
+        self.top_to_selected[prev_top] = self.prev
+
+
+    def on_window_focus(self, _i3, event):
+        self.update_top_level()
+        self.save_prev()
+        self.prev = event.container.id
+
+    def on_top(self, _i3, _event, diff: int):
+        root = self.i3.get_tree()
+        if not self.prev:
+            return
+        top = self.con_to_top[self.prev]
+        ws = [top.id for top in self.top_level(root.find_focused().workspace())]
+
+        top_idx = ws.index(top)
+        top_idx = (top_idx + diff + len(ws)) % len(ws)
+        next_top = ws[top_idx]
+        next_window = self.top_to_selected.get(next_top)
+        self.i3.command('[con_id=%s] focus' % next_window)
+
+    def on_binding(self, i3, event):
+        if event.binding.command.startswith('nop top_next'):
+            self.on_top(i3, event, 1)
+        elif event.binding.command.startswith('nop top_prev'):
+            self.on_top(i3, event, -1)
+
+
+if __name__ == '__main__':
+    TopLevelSwitcher()