no space for new pane with main-horizontal and a few panes

Step 1: Provide a summary of your problem

I created a yaml config with five panes in layout main-horizontal (although main-vertical also breaks). When I tried to run it it failed with the following exception:

Traceback (most recent call last):
  File "/home/abraham/.local/bin/tmuxp", line 8, in <module>
    sys.exit(cli.cli())
  File "/usr/lib/python3.10/site-packages/click/core.py", line 1130, in __call__
    return self.main(*args, **kwargs)
  File "/usr/lib/python3.10/site-packages/click/core.py", line 1055, in main
    rv = self.invoke(ctx)
  File "/usr/lib/python3.10/site-packages/click/core.py", line 1657, in invoke
    return _process_result(sub_ctx.command.invoke(sub_ctx))
  File "/usr/lib/python3.10/site-packages/click/core.py", line 1404, in invoke
    return ctx.invoke(self.callback, **ctx.params)
  File "/usr/lib/python3.10/site-packages/click/core.py", line 760, in invoke
    return __callback(*args, **kwargs)
  File "/usr/lib/python3.10/site-packages/click/decorators.py", line 26, in new_func
    return f(get_current_context(), *args, **kwargs)
  File "/home/abraham/.local/lib/python3.10/site-packages/tmuxp/cli/load.py", line 573, in command_load
    load_workspace(config[-1], **tmux_options)
  File "/home/abraham/.local/lib/python3.10/site-packages/tmuxp/cli/load.py", line 418, in load_workspace
    _load_attached(builder, detached)
  File "/home/abraham/.local/lib/python3.10/site-packages/tmuxp/cli/load.py", line 159, in _load_attached
    builder.build()
  File "/home/abraham/.local/lib/python3.10/site-packages/tmuxp/workspacebuilder.py", line 268, in build
    for p, pconf in self.iter_create_panes(w, wconf):
  File "/home/abraham/.local/lib/python3.10/site-packages/tmuxp/workspacebuilder.py", line 420, in iter_create_panes
    p = w.split_window(
  File "/usr/lib/python3.10/site-packages/libtmux/window.py", line 533, in split_window
    raise exc.LibTmuxException(pane_cmd.stderr, self._info, self.panes)
libtmux.exc.LibTmuxException: (['no space for new pane'], {'session_name': 'foo', 'session_id': '$15', 'window_id': '@36', 'window_name': 'bash', 'window_width': '80', 'window_height': '24', 'window_layout': 'd96b,80x24,0,0,89', 'window_panes': '1', 'window_index': '0', 'window_flags': '*', 'window_active': '1', 'window_bell_flag': '0', 'window_activity_flag': '0', 'window_silence_flag': '0'}, [Pane(%89 Window(@36 0:bash, Session($15 foo))), Pane(%90 Window(@36 0:bash, Session($15 foo))), Pane(%91 Window(@36 0:bash, Session($15 foo))), Pane(%92 Window(@36 0:bash, Session($15 foo)))])

Step 2: Provide tmuxp details

debug-info

also my console window is 213x51

Step 3: Describe the problem:

layout is not loaded, session is partially formed but not attached, exception is thrown.

Steps to reproduce:

I created this minimal config file that reproduces the issue:

session_name: foo
windows:
- focus: 'true'
  layout: main-horizontal
  panes:
    - focus: 'true'
      shell_command:
        - echo 1
    - echo 2
    - echo 3
    - echo 4
    - echo 5

Observed Results:

A python exception

Expected Results:

A nicely built main-horizontal layout

Thoughts

Of course if I build the layout by hand it works, because I'm a human and I know that if I split the same pane over and over again, since every new pane is half the size of the previous one then soon my panes will be too small. So I resize them a little bit before splitting again, then adjust the final size.

Perhaps the algorithm for building the layout could do that. I think it is possible to know the final size of everything just from the layout, the amount of panes and the window size.

Start in tmuxp/workspacebuilder.py at build() and iter_create_panes(), where the failing window split is initiated; the traceback also points to cli/load.py. Reproduce the minimal five-pane main-horizontal configuration and investigate how pane creation handles available space. Done means the layout builds without a Python exception or partial session.