SEEing LaTeX 12: Setting the Environment

Last time, I reworked the shell script and AppleScript that invokes LaTeX compilation from within SubEthaEdit. In some sense, it was pointless: instead of having a fixed method for compilation defined in a shell script, I now run a flexible shell script within an environment fixed by the AppleScript. The relevant portion of the AppleScript is the prependEnvironment handler:

to prependEnvironment onto scriptString
    "export SEE_LATEX_COMPILER='latexmk -pdf -quiet \"$FILE\"'; export SEE_LATEX_PRODUCT_TYPE=pdf; export SEE_LATEX_VIEWER='/Applications/Skim.app/Contents/SharedSupport/displayline \"$LINE\" \"$PRODUCT\" \"$FILE\"';" & scriptString
end prependEnvironment

The handler abstracts away the details of how the environment is constructed from the rest of the AppleScript. We can thus just focus on the internals of the handler, without worrying about how the rest of the AppleScript will be affected. Put another way, we'll replace the string defining the environment by a function call that returns the string.

The approach I'll take will be to store the environment settings in a property list file, read them into lists representing variables and values, and format the list contents appropriately. This is pretty easy, thanks to the property list suite in System Events. I'll encapsulate reading the environment into a handler of its own:

to readEnvironment out of plist
    readListPair out of plist
    environmentString from result
end readEnvironment

The plist parameter is the path to the property list file containing our environment.

With readEnvironment, the prependEnvironment handler is pretty straightforward. We just define the path to the environment file and let readEnvironment do the work. All that remains is to decide where to store the environment settings. The Preferences folder seems like a natural choice, so let's use a file called de.codingmonkeys.SubEthaEdit.LaTeX_environment.plist, which is similar to how the LaTeX mode settings are treated in TextMate. The handler becomes:

to prependEnvironment onto scriptString
    set envFilePath to (path to preferences from user domain as string) & "de.codingmonkeys.SubEthaEdit.LaTeX_environment.plist"
    (readEnvironment out of envFilePath) & scriptString
end prependEnvironment

To be clear, it is not necessary to have the plist file present at all, since we defined our shell script to use default values when no environment variables are set. We'll handle the case of an absent environment file below.

We now need to provide readListPair and environmentString handlers. The former draws on the property list suite of System Events, returning two lists of equal length. The first list contains the environment variable names, while the second contains the corresponding values. The handler is complicated a bit by checking whether the plist exists, but has a single get at its core:

to readListPair out of plist
    tell application "System Events"
        if exists file plist then
            tell property list file plist
                get {name, value} of every property list item
            end tell
        else
            {{}, {}}
        end if
    end tell
end readPlist

To format the list contents into an appropriate string, we define the environmentString handler:

on environmentString from keyValueListPair
    set {plistKeys, plistValues} to keyValueListPair
    set accumulator to {}
    set oldTIDs to text item delimiters of AppleScript
    set text item delimiters of AppleScript to ""
    repeat with i from 1 to number of items in plistKeys
        set tokens to {"export ", item i of plistKeys, "=", item i of plistValues, ";"}
        copy (tokens as string) to the end of the accumulator
    end repeat
    set AppleScript's text item delimiters to space
    set envString to accumulator as string
    set AppleScript's text item delimiters to oldTIDs
    envString
end environmentString

This is a straightforward, ugly function that just iterates through the lists, formatting the contents. Each variable-value pair is turned into a shell-style export statement and accumulated in a list. The accumulated export statements are then joined together into one big string that defines the environment.

To test all of this out, it is easier to just call the base prependEnvironment handler, instead of working through a SEE mode. I used prependEnvironment onto "buildScript", and ran it with the environment plist both present and absent. It works as expected, so could be simply dropped into the LaTeX mode bundle. However, I prefer to make another, relatively minor change that requires an extra parameter for the prependEnvironment handler. Specifically, I will pass in the active mode from SubEthaEdit:

to prependEnvironment for seeMode onto scriptString
    set envFilePath to (path to preferences from user domain as string) & "de.codingmonkeys.SubEthaEdit." & (name of seeMode) & "_environment.plist"
    (readEnvironment out of envFilePath) & scriptString
end prependEnvironment

Later extensions could make use of more properties of the mode, so I passed in the entire mode, instead of just the name. The advantage of passing the mode as a parameter is that all of the stuff I've shown in this post can be used without change for other scripts and for other modes. It will only be necessary to change the line defining the string holding the shell script and to make appropriate redefinitions of the seescriptsettings handler.

Next time, I'll take a look at how to easily access and make changes to the environment.

For completeness, here's the entire AppleScript:

tell application "SubEthaEdit"
    if exists path of front document then
        if modified of front document then
            try
                save front document
            end try
        end if
        set filePath to path of front document
        set lineNumber to startLineNumber of selection of front document
        set activeMode to mode of front document
        set modeResources to resource path of activeMode
    else
        error "You have to save the document first"
    end if
end tell

set buildScript to prependEnvironment for activeMode onto (join of {quotedForm for (modeResources & "/Scripts/shell/buildlatex.sh"), quotedForm for filePath, lineNumber} by space)

do shell script buildScript

on seescriptsettings()
    return {displayName:"Typeset and View PDF", shortDisplayName:"Typeset", keyboardShortcut:"@b", toolbarIcon:"ToolbarIconBuildAndRun", inDefaultToolbar:"yes", toolbarTooltip:"Typeset and view the current document", inContextMenu:"no"}
end seescriptsettings

on join of tokenList by delimiter
    set oldTIDs to text item delimiters of AppleScript
    set text item delimiters of AppleScript to delimiter
    set joinedString to tokenList as string
    set text item delimiters of AppleScript to oldTIDs
    return joinedString
end join

on quotedForm for baseString  
    quote & baseString & quote
end quotedForm

to prependEnvironment for seeMode onto scriptString
    set envFilePath to (path to preferences from user domain as string) & "de.codingmonkeys.SubEthaEdit." & (name of seeMode) & "_environment.plist"
    (readEnvironment out of envFilePath) & scriptString
end prependEnvironment

to readEnvironment out of plist
    readListPair out of plist
    environmentString from result
end readEnvironment

to readListPair out of plist
    tell application "System Events"
        if exists file plist then
            tell property list file plist
                get {name, value} of every property list item
            end tell
        else
            {{}, {}}
        end if
    end tell
end readPlist

on environmentString from keyValueListPair
    set {plistKeys, plistValues} to keyValueListPair
    set accumulator to {}
    set oldTIDs to text item delimiters of AppleScript
    set text item delimiters of AppleScript to ""
    repeat with i from 1 to number of items in plistKeys
        set tokens to {"export ", item i of plistKeys, "=", item i of plistValues, ";"}
        copy (tokens as string) to the end of the accumulator
    end repeat
    set AppleScript's text item delimiters to space
    set envString to accumulator as string
    set AppleScript's text item delimiters to oldTIDs
    envString
end environmentString