Prevent zooming out of tmux pane

There were issues (e.g. christoomey#56) and pull requests (christoomey#65 and christoomey#104) to improve this
behavior, but they were mainly rejected because it breaks other use cases.

This PR adds an option that can be enabled to have the current behavior
(`let g:tmux_navigator_move_out_of_zoomed_tmux = 1`) by default, but it also
recognizes when the user tries to get out of the zoomed pane twice, and
then allows for it.

plugin/tmux_navigator.vim

@@ -79,6 +79,27 @@ function! s:TmuxAwareNavigate(direction)
       endtry
     endif
     let args = 'select-pane -t ' . shellescape($TMUX_PANE) . ' -' . tr(a:direction, 'phjkl', 'lLDUR')
+
+    " Handle delay for moving out of zoomed tmux pane.
+    " This wraps the tmux args conditionally.
+    let timeout = get(g:, 'tmux_navigator_zoomed_tmux_delay', 0.5)
+    if timeout != 0
+      let msg = 'Tmux is zoomed, not moving out.'
+      let curtime = reltimefloat(reltime())
+      if (a:direction != s:tried_moving_out_of_zoomed_tmux[0]
+            \ || curtime > (s:tried_moving_out_of_zoomed_tmux[1] + timeout))
+        " 0 to zoom out always
+        " -1 can be used to never zoom out.
+        let msg .= printf(' Trigger it again in %.1f seconds to zoom out.',
+              \ timeout)
+        let msg .= ' See the help for g:tmux_navigator_zoomed_tmux_delay.'
+        let s:tried_moving_out_of_zoomed_tmux = [a:direction, curtime]
+        let args = "if -F '#{window_zoomed_flag}' 'display \"".msg."\"'"
+              \ ." '".args."'"
+      else
+        let s:tried_moving_out_of_zoomed_tmux = ['', 0]
+      endif
+    endif
     silent call s:TmuxCommand(args)
     if s:NeedsVitalityRedraw()
       redraw!
@@ -88,6 +109,7 @@ function! s:TmuxAwareNavigate(direction)
     let s:tmux_is_last_pane = 0
   endif
 endfunction
+let s:tried_moving_out_of_zoomed_tmux = ['', 0]
 
 function! s:VimNavigate(direction)
   try