B4J Question JavaFX resizing problem with library.

#Region Project Attributes 
    #MainFormWidth: 600
    #MainFormHeight: 200
#End Region

Sub Process_Globals
    Private fx As JFX
    Private MainForm As Form
    Dim ABox As HBox
    Dim Btn1 As Button
    Dim Btn2 As Button
    Dim Btn3 As Button
    Dim txt1 As TextField
    Dim PN1 As Pane
    Dim I As Image
    Dim JO As JavaObject
End Sub

Sub AppStart (Form1 As Form, Args() As String)
    MainForm = Form1
    MainForm.Show
    Btn1.Initialize("Btn_1")
    Btn2.Initialize("Btn_2")
    Btn3.Initialize("Btn_3")
    txt1.Initialize("txt_1")
    PN1.Initialize("PN1")
    ABox.Initialize("Hbox")
    ABox.setPadding(10,10,10,10)
    ABox.Spacing = 10
    ABox.FillHeight = True
    ABox.PrefWidth = 300
    txt1.PrefWidth = 50
   

    Btn1.Text = "Press Me"
    ABox.AddNode(Btn1)
    ABox.AddNode(Btn2)
    ABox.AddNode(Btn3)
    ABox.AddNode(txt1)
    ABox.setHgrow(txt1,"SOMETIMES")

    ABox.MinWidth =200
    MainForm.RootPane.AddNode(ABox,10,10,400,40)
    Log(ABox.MinWidth)

   
    MainForm.RootPane.AddNode(PN1,12,100,400,40)
    CSSUtils.SetBackgroundColor(ABox,fx.Colors.DarkGray)
    CSSUtils.SetBackgroundColor(PN1,fx.Colors.DarkGray)
   
   
   
   
End Sub

'Return true to allow the default exceptions handler to handle the uncaught exception.
Sub Application_Error (Error As Exception, StackTrace As String) As Boolean
    Return True
End Sub

Sub Btn_1_MouseClicked (EventData As MouseEvent)
    Dim FN As String = Rnd(1,1000000) & ".png"
    I = MainForm.RootPane.Snapshot
    Dim Out As OutputStream = File.OpenOutput("C:\_2",FN,False)
    I.WriteToStream(Out)
    Out.Close
    Log("Hbox Min Width: " & ABox.MinWidth)
    Log("HBox Width: " & ABox.Width)
    Log("MainForm Width: " & MainForm.Width)
    Log("RootPane Widht:" &MainForm.RootPane.Width)
   
   
End Sub

Hbox Min Width: 200
HBox Width: 400
MainForm Width: 343
RootPane Widht:343