Hi,

this code based on the GDIPlusX library should get you started.

&& prerequisites
DO system.app && initialize GDIPlusX somewhere 

&& usage example
Checkbox::SetCaption
LPARAMETERS lcText
THIS.Caption = FitTextToCheckbox(THIS, lcText, StringTrimmingEllipsisCharacter)

#DEFINE CHECKBOXWIDTHPLUSTEXTMARGINS 14

#DEFINE StringTrimmingNone    0 
#DEFINE StringTrimmingCharacter   1 
#DEFINE StringTrimmingWord    2 
#DEFINE StringTrimmingEllipsisCharacter 3 
#DEFINE StringTrimmingEllipsisWord  4 
#DEFINE StringTrimmingEllipsisPath  5 

FUNCTION FitTextToCheckbox
	LPARAMETERS loCheckBox, lcText, lnTrimMode

	LOCAL lnHeight, lnWidth
	LOCAL loFont as xfcFont
	LOCAL loBmp as xfcBitmap
	LOCAL loGfx AS xfcGraphics
	LOCAL loFormat AS xfcStringFormat
	LOCAL loSize AS xfcSize, loRect as xfcSize
	LOCAL lnCharCount
	
	m.lnCharCount = 0 
	m.lnWidth = m.loCheckBox.Width - CHECKBOXWIDTHPLUSTEXTMARGINS
	m.lnHeight = m.loCheckBox.Height
	
	WITH _SCREEN.System.Drawing		
		m.loFont = .Font.New(m.loCheckBox.Fontname, m.loCheckBox.Fontsize, 0, .GraphicsUnit.Point) && 0 = FontStyle is missing - complement ....
		m.loBmp = .Bitmap.New(1,1)
		* Retrieve the graphics object.
		m.loGfx = .Graphics.FromImage(m.loBmp)
		m.loGfx.InterpolationMode = .Drawing2D.InterpolationMode.NearestNeighbor
		m.loGfx.SmoothingMode = .Drawing2D.SmoothingMode.AntiAlias
		m.loGfx.UsePrecision = .T.
		m.loRect = .Size.New(m.lnWidth, m.lnHeight)
		m.loFormat = .StringFormat.GenericTypographic
		m.loFormat.ALIGNMENT = .Stringalignment.Near
		m.loFormat.Linealignment = .Stringalignment.Near
		m.loFormat.Trimming = lnTrimMode
		* Measure the String
		m.loGfx.MeasureString(m.lcText, m.loFont, m.loRect, m.loFormat, @m.lnCharCount)
	ENDWITH	

	IF INLIST(m.lnTrimMode, StringTrimmingEllipsisCharacter, StringTrimmingEllipsisWord) AND ;
		LEN(m.lcText) > m.lnCharCount
		RETURN SUBSTR(m.lcText, 1, m.lnCharCount) + '...'
	ELSE
		RETURN SUBSTR(m.lcText, 1, m.lnCharCount)		
	ENDIF
	
ENDFUNC

Christian