attempt at fixing #309 layout issues with tmux 2.6

even after setting -x and -y with new-session, select-layout won't take
effect. However, it is necessary in 2.6 to get pane creation in detached
mode to work.

the only way found for tmux select-layout to take effect and prior
behavior to have viewed the window you are running "select-layout"
for in the client.

a solution has been devised to connect the client to the session, then
run select-layout on each window in the session. However, it's still not
enough to load the session, it seems the window must be selected by the client
at least once for the select-layout to take effect.

so a hook against the session is created for the session that selects each
window, runs select layout at the -t target for the window id. and after
that, the hook is neatly unset when that's finished.

Author: tony

tmuxp/cli.py

@@ -14,7 +14,7 @@
 import click
 import kaptan
 from click.exceptions import FileError
-from libtmux.common import has_minimum_version, which
+from libtmux.common import has_minimum_version, which, has_gte_version
 from libtmux.exc import TmuxCommandNotFound
 from libtmux.server import Server
 
@@ -278,7 +278,48 @@ def reattach(session):
                 sys.exit('Session created in detached state.')
 
         if not detached:
+
+            if has_gte_version('2.6'):
+                # tmuxp issue: https://github.com/tony/tmuxp/issues/309
+                # tmux issue: https://github.com/tmux/tmux/issues/1106
+                #
+                # tmux now requires that the window be viewed with the client
+                # before select-layout adjustments can be meaningful
+                #
+                # To handle this, let's create a temporary hook for this
+                # session to iterage and run select-layout on all windows
+                # after client attaches.
+                cmd = [
+                    'set-hook',
+                    '-t', builder.session.id,
+                    'client-attached'
+                ]
+                hook_cmd = []
+                for window in builder.session.windows:
+                    # unfortunately, select-layout won't work unless
+                    # we've literally selected the window at least once
+                    # with the client
+                    hook_cmd.append('selectw -t {}'.format(window.id))
+                    hook_cmd.append('selectl -t {}'.format(window.id))
+                    hook_cmd.append('selectw -p'.format(window.id))
+
+                # unset the hook immediately after executing
+                hook_cmd.append(
+                    'set-hook -u -t {target_session} client-attached'.format(
+                        target_session=builder.session.id
+                    )
+                )
+
+                # join the hook's commands with semicolons
+                hook_cmd = '{}'.format('; '.join(hook_cmd))
+
+                # append the hook command
+                cmd.append(hook_cmd)
+
+                # create the hook
+                builder.session.cmd(*cmd)
             builder.session.attach_session()
+
     except exc.TmuxpException as e:
         import traceback