Terminal Palettes

September 3, 2017

For some recent work, I was switching between OmniFocus and OmniPlan code often. To keep my source directories straight in my head, I tweaked the colors of the two Terminal tabs to use the apps’ branding fonts: purple text for OmniFocus; yellow text for OmniPlan. I mentioned this hack in an engineering meeting and Ken promptly dropped the nerd snipe: “Does it switch automatically?”

It didn’t then. Now it does.

With a three part solution — AppleScript, shell script, and a zsh hook — my Terminal palette now updates whenever I switch between source directories. Yours can too.

ZSH Hook

I added the following code to my .zshrc file:

if [[ "$TERM_PROGRAM" == "Apple_Terminal" ]] && [[ -z "$INSIDE_EMACS" ]]; then

    update_terminal_cwd() {
        # Identify the directory using a "file:" scheme URL, including
        # the host name to disambiguate local vs. remote paths.

        # Percent-encode the pathname.
        # http://superuser.com/questions/313650/resume-zsh-terminal-os-x-lion/328148#328148
        local URL_PATH=''
        {
            # Use LANG=C to process text byte-by-byte.
            local i ch hexch LANG=C
            for ((i = 1; i <= ${#PWD}; ++i)); do
                ch="$PWD[i]"
                if [[ "$ch" =~ [/._~A-Za-z0-9-] ]]; then
                    URL_PATH+="$ch"
                else
                    hexch=$(printf "%02X" "'$ch")
                    URL_PATH+="%$hexch"
                fi
            done
        }

        local PWD_URL="file://$HOST$URL_PATH"
        #echo "$PWD_URL"        # testing
		print -Pn "\]0;%n@%m: %~\" # get the tab title right: http://www.tldp.org/HOWTO/Xterm-Title-4.html#ss4.1
		printf '\]7;%s\' "$PWD_URL" # get path restore right
		~/bin/terminalPalette.sh "$PWD_URL" # update colors
    }

    # Register the function so it is called whenever the working
    # directory changes.
    autoload add-zsh-hook
    add-zsh-hook chpwd update_terminal_cwd

    # Tell the terminal about the initial directory.
    update_terminal_cwd
fi

This code first declares a local function, update_terminal_cwd(), then hooks the shell directory change command to run the function. Finally it calls the function so that a new terminal window will trigger the code as well.

Inside the function, we percent-encode the current working directory. Then we set the tab title, save the working directory so it restores on the next launch of Terminal, and finally call the terminalPalette.sh script to update the color palette.

Shell Script

The terminalPalette.sh script lives in the bin subdirectory of my home directory.

The script starts with a fairly standard preamble like so:

#!/bin/zsh

func usage() {
        echo "Usage:"
        echo "${0} (<file url>|<settings name>)"
}

PROFILE=${1}

if [[ -z ${PROFILE} ]] ; then
        usage
        exit 1
fi

The script takes a single argument. That argument can either be a file URL, like

terminalPalette.sh file://localhost/Users/curt/bin

or the name of a Terminal.app profile, like

terminalPalette.sh "Man Page"

The preamble just checks for any single argument and reports the correct usage if the argument is missing.

Next, we bridge the shell argument into AppleScript so we can drive Terminal.app:

osascript - `tty` ${PROFILE} <<SCRIPT

Invoked with - as the first argument, osascript will run a script passed in on standard input, feeding the subsequent arguments to the embedded script. Here we pass the current tty — we’ll see why shortly — and the original argument. Then we begin a here doc with the <<SCRIPT incantation. Until the end of the here doc, we’re coding in AppleScript:

on run argv
	set theTTY to item 1 of argv
	set settingsNameOrPath to item 2 of argv
	if settingsNameOrPath starts with "file://" then
		set settingsName to my settingsNameForPath(settingsNameOrPath)
	else
		set settingsName to settingsNameOrPath
	end if
	
	if settingsName is missing value then return
	
	tell application "Terminal"
		set desiredSettings to first settings set whose name is settingsName
		if desiredSettings is missing value then return
		repeat with matchingTab in my tabForTTY(theTTY)
			set current settings of matchingTab to desiredSettings
		end repeat
	end tell
end run

The run handler extracts the tty and the original script’s argument into theTTY and settingsNameOrPath respectively. Then it detects what sort of argument was passed to the original script and converts that to a Terminal app settings name. (In grand AppleScript tradition, the UI for Terminal.app calls its color palettes “Profiles” but the AppleScript dictionary calls them “Settings”.) If the argument was a file URL, we call a handler settingsNameForPath — see below — to get the settings name. Otherwise we use it directly.

Then we drive the Terminal app to look up the desired settings, find the tab that is rendering the current tty, and change the settings of that tab to the desired ones.

Now we just need to define a couple of helpers.

on settingsNameForPath(thePath)
	if thePath ends with "SourceDirs" then return "Man Page"
	if thePath contains "SourceDirs/OmniFocus" then return "OmniFocus"
	if thePath contains "SourceDirs/OmniCurt" then return "OmniCurt"
	if thePath contains "SourceDirs/OmniPlan" then return "OmniPlan"
	if thePath contains "SourceDirs/curtclifton.net" then return "curtclifton.net"
	if thePath contains "SourceDirs" then return "Ocean"
	return missing value
end settingsNameForPath

The settingsNameForPath handler maps from the path argument to custom palette names. If you’re setting up this script for your own use, you’ll want to tweak this handler and your Terminal profiles. I added some app and project specific profiles, like OmniFocus and curtclifton.net. So far I’ve just been tweaking the handler as I add more profiles, though someday it would be nice to make this do a bit more parsing to avoid the repetitive if statements.

on tabForTTY(theTTY)
	tell application "Terminal"
		repeat with aWindow in every window
			repeat with aTab in every tab of aWindow
				set currentTTY to tty of aTab
				if currentTTY is theTTY then
					return {aTab}
				end if
			end repeat
		end repeat
		return {}
	end tell
end tabForTTY

This last handler iterates through every Terminal tab looking for the one rendering the script’s tty. This might become too slow with a lot of tabs open, but so far it’s been fine with my usual four or five tabs at once.

Finally, we end the here doc and the script:

SCRIPT

This was a fun bit of hackery. I hope you enjoyed it too. You can download the terminalPalette.sh script in its entirety here.

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Terminal Palettes

ZSH Hook

Shell Script