B4J Question BBCode and use of LaTex

    BBCodeView1.Text = "A[TextSize=12][Vertical=-8]2[/Vertical][Vertical=8]n-1[/Vertical][/TextSize]"

    Dim cv As B4XCanvas
    BBCodeView1.TextEngine = textEngine1
    Dim mathPanel As B4XView = xui.CreatePanel("")
    mathPanel.SetLayoutAnimated(0, 0, 0, 25dip, 25dip)
    BBCodeView1.Views.Put("mpan", mathPanel)
    cv.Initialize(mathPanel)
    cv.DrawText("2", 0, 10dip, xui.CreateDefaultFont(12), xui.Color_Black, "LEFT")
    cv.DrawText("n-1", 0, 25dip, xui.CreateDefaultFont(12), xui.Color_Black, "LEFT")
    Dim contents As String = _
    $"
        A[View=mpan Vertical=5/]
    "$
    BBCodeView1.Text = contents.Replace(TAB, "")

Sub Class_Globals
    Private Root As B4XView
    Private xui As XUI
    Private cvMath As B4XCanvas
    Private textEngine1 As BCTextEngine
    Private BBCodeView1 As BBCodeView
End Sub

Private Sub B4XPage_Created (Root1 As B4XView)
    Root = Root1
    Root.LoadLayout("bbc")
 
    textEngine1.Initialize(Root)
    BBCodeView1.TextEngine = textEngine1
    Dim contents As String = _
    $"
        A[Math ^2 _n-1/]    B[Math ^3 _n-2/]   ${Chr(0x03A3)}[Math ^n-1 _0/]
    "$
    BBCodeView1.Text = preprocessMath(BBCodeView1, contents)
End Sub

Private Sub preprocessMath(BBV As BBCodeView, s As String) As String
    Dim sb As StringBuilder: sb.Initialize
    s = s.Replace(TAB, "").Replace("[Math", "[math").Replace("[MATH", "[math")
    Dim v() As String = Regex.Split("\[math", s)
    If v.Length = 1 Then Return s
    sb.append(v(0))
    Dim fnt As B4XFont = xui.CreateDefaultFont(12)
    For i = 1 To v.Length - 1
        Dim t As String = v(i)
        Dim q() As String = Regex.Split("\]", t)
        Dim mathPanel As B4XView = xui.CreatePanel("")
        Dim w() As String = Regex.Split(" ", q(0).Replace("  ", " "))
        Dim superScript As String = w(1).SubString(1).Replace("/","")
        Dim subScript As String = w(2).SubString(1).Replace("/","")
        Dim rect1 As B4XRect = cvMath.MeasureText(superScript, fnt)
        Dim rect2 As B4XRect = cvMath.MeasureText(subScript, fnt)
        mathPanel.SetLayoutAnimated(0, 0, 0, 5dip + Max(rect1.Width, rect2.Width), 3 * rect1.height)
        cvMath.Initialize(mathPanel)
        cvMath.DrawText(superScript, 0, rect1.height + 1dip, xui.CreateDefaultFont(12), xui.Color_Black, "LEFT")
        cvMath.DrawText(subScript, 0, 3 * rect1.height - 1dip, xui.CreateDefaultFont(12), xui.Color_Black, "LEFT")
        sb.Append($"[View=math${i} Vertical=${rect1.height}/]"$ & q(1))
        BBV.Views.Put("math" & i, mathPanel)
    Next
'    Log(sb.toString)
    Return sb.toString
End Sub