Fit the current space center text to the view width, it measures the longest line (broken up by newlines) and scales it based on that.

fitTextToWidth_SpaceCenter.py

from mojo.UI import CurrentSpaceCenter


def measureLine(pointSize, records):
    scale = pointSize / window.font.info.unitsPerEm
    sublists = []
    currentSublist = []
    lineBreakChar = "NewLineGlyph"
    for item in records:
        if item.glyph.objectName == lineBreakChar:
            if currentSublist:
                sublists.append(currentSublist)
            currentSublist = [item]
        else:
            currentSublist.append(item)
    if currentSublist:
        sublists.append(currentSublist)
    
    allLines = []
    for line in sublists:
        lineWidth = 0
        for record in line:
            gsWidth = 0
            gsWidth += record.glyph.width
            gsWidth += record.xPlacement
            gsWidth += record.xAdvance

            lineWidth += gsWidth*scale
        allLines.append(lineWidth)
        
    return allLines
    
    
debug = False

window = CurrentSpaceCenter()
view = window.glyphLineView.getNSScrollView()
frame = view.frame().size
width = frame.width

nps = ps = window.getPointSize()

m = max(measureLine(ps, window.glyphRecords))
if m > width:
    if debug: print("make smaller")
    while m > width - 50:
        
        nps -= 1
        m = max(measureLine(nps, window.glyphRecords))
else:
    if debug: print("make bigger")
    while m < width - 50:
        nps += 1
        m = max(measureLine(nps, window.glyphRecords))

window.setPointSize(nps)