Is it possible to map one key to two commands, doing 2nd command only if first fails

Question

I want to map the tab key to <c-w>w to switch windows when there is more than one window open. But if there is only one window but multiple tabs, I want it to detect that there is only one window and to switch tabs instead by mapping to gt. Note both commands are in the same mode.

Is this possible? I am asking this one key to map to two different choices and the key only performs the second choice when the first one fails.

Answer 1

You can do it using an expression-mapping like this:

nnoremap <expr><silent> <tab> winnr('$')>1 ? "\<c-w>w" : 'gt'

this makes the mapping basically check, if there are several windows open (winnr('$') is greater than 1) and in that case returns CTRLW else, it returns gt

Note: the double quotation marks are necessary, to make Vim correctly parse the key code <c-w>.

In case there exists only one tabpage, you need to add 2 checks, something like this:

nnoremap <expr><silent> <tab> winnr('$')>1 ? "\<c-w>w" : (tabpagenr('$')>1 ? 'gt' : ":bn\<cr>")