Better Vim-Style Key Bindings in Tmux

I was confused by tmux's "vi-style" key bindings in copy mode, which don't behave at all like I expected: Space starts the selection (like v in vim), Enter copies and clears the selection (like y), while Ctrl-V toggles block selection mode but doesn't start the selection.

Fortunately, tmux supports braces and conditionals in key bindings. This confused me too because there are two constructs: the %if keyword and the if-shell command.

%if conditions are only evaluated once when the config is loaded. This binding doesn't work because #{selection_present} evaluates to 0 when tmux starts:

bind-key -T copy-mode C-v {
    %if "#{selection_present}"
    display-message yes
    %else
    display-message no
    %endif
}

On the other hand, the if-shell command in this binding will be called every time Ctrl-V is pressed:

bind-key -T copy-mode C-v {
    if-shell -F "#{selection_present}" {
        display-message yes
    } {
        display-message no
    }
}

The -F flag tells tmux to evaluate the condition without calling an external shell command, as the name implies. Otherwise it would try to run 0 or 1 in the shell and fail.

In addition, if-shell commands can be nested, so we can mimic vim's behavior with the following config:

set-option -g mode-keys vi

bind-key -T copy-mode-vi v {
    if-shell -F "#{selection_present}" {
        if-shell -F "#{rectangle_toggle}" {
            send-keys -X rectangle-off
        } {
            send-keys -X clear-selection
        }
    } {
        send-keys -X begin-selection
    }
}

bind-key -T copy-mode-vi C-v {
    if-shell -F "#{selection_present}" {
        if-shell -F "#{rectangle_toggle}" {
            send-keys -X clear-selection
        } {
            send-keys -X rectangle-on
        }
    } {
        send-keys -X begin-selection
        send-keys -X rectangle-on
    }
}

bind-key -T copy-mode-vi y send-keys -X copy-selection-and-cancel