German Schriftgröße in Label anpassen

Sub SetTextSize(lbl As Label, txt As String)
    Private cvs As Canvas
    Private bmp As Bitmap

    Private dt As Float
    Private limit = 0.5 As Float
    Private h, w As Int

    bmp.InitializeMutable(2dip, 2dip)
    cvs.Initialize2(bmp)
    lbl.Text = txt
    lbl.TextSize = 300
    dt = lbl.TextSize
    h = stu.MeasureMultilineTextHeight(lbl, txt)
'    h = cvs.MeasureStringHeight(txt, lbl.Typeface, lbl.TextSize) 'gibt falsche Werte
    w = cvs.MeasureStringWidth(txt, lbl.Typeface, lbl.TextSize)
    Do While dt > limit Or h > lbl.Height Or w > lbl.Width
        dt = dt / 2
'        h = cvs.MeasureStringHeight(txt, lbl.Typeface, lbl.TextSize)
        h = stu.MeasureMultilineTextHeight(lbl, txt)
        w = cvs.MeasureStringWidth(txt, lbl.Typeface, lbl.TextSize)
        Log(h & " / " & w & " / " & lbl.TextSize)
        
        If h > lbl.Height Or w > lbl.Width Then
            lbl.TextSize = lbl.TextSize - dt
        Else
            lbl.TextSize = lbl.TextSize + dt
        End If
    Loop
    
End Sub