Auto-size function doesn't work on linked text boxes with Data Merge

Hi @JacquesCapeTown (and @Eugene Tyson) here's one idea. I've written a script that just expands the width of any text frame marked with the script label "expandFrame" until the first paragraph fits. It won't always work, but it should work whenever the datamerge is expecting a single line paragraph. If you find a bug, let me know.

- Mark

/**
 * Expands width of text frames having label "expandFrame" in
 * an attempt to fit first paragraph of text frame in one line.
 * Notes:
 * - Label can contain other text as well as "expandFrame"
 * - Does not expand frame height
 * - Does not expand wider than the page width
 * @author m1b
 * @discussion https://community.adobe.com/t5/indesign-discussions/auto-size-function-doesn-t-work-on-linked-text-boxes-with-data-merge/m-p/13950905
 */
function main() {

    if (app.documents.length > 0)
        expandFrames(app.activeDocument, /\bexpandFrame\b/i);

};
app.doScript(main, ScriptLanguage.JAVASCRIPT, undefined, UndoModes.ENTIRE_SCRIPT, 'Expand Labelled Frames');


/**
 * Expand width of all text frames
 * in `doc` with matching label, in
 * attempt to fit first paragraph.
 * @author m1b
 * @version 2023-07-25
 * @param {Document} doc - an Indesign Document.
 * @param {RegExp} matcher - the regex to test each frame's label.
 */
function expandFrames(doc, matcher) {

    app.scriptPreferences.measurementUnit = MeasurementUnits.POINTS;

    var autoSizeRefToAnchorPoint = {
        1651467109: AnchorPoint.BOTTOM_CENTER_ANCHOR,
        1651469413: AnchorPoint.BOTTOM_LEFT_ANCHOR,
        1651470953: AnchorPoint.BOTTOM_RIGHT_ANCHOR,
        1668183154: AnchorPoint.CENTER_ANCHOR,
        1818583909: AnchorPoint.LEFT_CENTER_ANCHOR,
        1919509349: AnchorPoint.RIGHT_CENTER_ANCHOR,
        1953456997: AnchorPoint.TOP_CENTER_ANCHOR,
        1953459301: AnchorPoint.TOP_LEFT_ANCHOR,
        1953460841: AnchorPoint.TOP_RIGHT_ANCHOR,
    };

    var frames = doc.textFrames,
        inc = 1,
        frame,
        label,
        width,
        maxWidth,
        paragraph,
        end;

    for (var i = frames.length - 1; i >= 0; i--) {

        frame = frames[i];
        label = frame.label;
        width = (frame.geometricBounds[3] - frame.geometricBounds[1]);

        if (
            !label
            || !matcher.test(label)
        )
            continue;

        anchor = autoSizeRefToAnchorPoint[Number(frame.textFramePreferences.autoSizingReferencePoint)];
        paragraph = frame.paragraphs.firstItem();
        end = paragraph.characters.lastItem();

        // maxWidth is for reality testing
        if (frame.parentPage.isValid)
            maxWidth = frame.parentPage.bounds[3] - frame.parentPage.bounds[1];
        else
            maxWidth = doc.pages.firstItem().bounds[3] - doc.pages.firstItem().bounds[1];

        while (
            frame.id !== end.parentTextFrames[0].id
            && (width += inc) <= maxWidth
        )
            // expand the frame by a bit
            frame.resize(CoordinateSpaces.PARENT_COORDINATES, anchor, ResizeMethods.ADDING_CURRENT_DIMENSIONS_TO, [inc, 0]);

    }

};

And that holds true with your examples. The top unthreaded frames adjust, the threaded frames only adjust the last frame.

Do they need to be threaded?

~Barb

Hi Jacques:

In my experience, it doesn't work that way. If two frames aren't linked, both will adjust to fit the content.

If two (or more) frames are linked, only the last box will adjust even though the property is enabled for both, because the overflowing text in frame 1 just flows to the next box in the series.

~Barb

Having a hard time digitising the workflow in my brain - can you provide images or a sample doc? 

Sorry - my 3D engine seems to be down