A RichTextBox with added text alignment: 'Justify'.

Hi,

I should like to submit this for the vb.NET code bank.

Make a RichTextBox with added text alignment: 'Justify'.
This was designed by Passel in December 2014 in response to a request.
I have used it many time since but only today did I check to see if it was in the code bank.


Start a new project.
Add a new Class, call it: SmartBox

Paste this code in the new class.

Code:

---

Imports System.Windows.Forms
Imports System.Runtime.InteropServices

' Represents a standard RichTextBox with some minor added functionality.
' SmartBox provides methods to maintain performance while it is being updated.
' Additional formatting features have also been added.

Public Class SmartBox
    Inherits RichTextBox
    ' Maintains performance while updating.
    ' Remember to call EndUpdate when you are finished with the update.
    ' Nested calls are supported.
    ' Calling this method will prevent redrawing.
    ' It will also setup the event mask of the underlying richedit
    ' control so that no events are sent.

    Public Sub BeginUpdate()
        ' Deal with nested calls.
        updating += 1

        If updating > 1 Then
            Return
        End If

        ' Prevent the control from raising any events.
        oldEventMask = SendMessage(New HandleRef(Me, Handle), EM_SETEVENTMASK, 0, 0)

        ' Prevent the control from redrawing itself.
        SendMessage(New HandleRef(Me, Handle), WM_SETREDRAW, 0, 0)
    End Sub


    Public Sub EndUpdate()
        ' Resumes drawing and event handling.
        ' This method should be called every time a call is made
        ' made to BeginUpdate. It resets the event mask to it's
        ' original value and enables redrawing of the control.

        updating -= 1    ' Deal with nested calls.

        If updating > 0 Then
            Return
        End If
        SendMessage(New HandleRef(Me, Handle), WM_SETREDRAW, 1, 0) ' Allow the control to redraw itself.
        SendMessage(New HandleRef(Me, Handle), EM_SETEVENTMASK, 0, oldEventMask)
        ' Allow the control to raise event messages.
    End Sub

    Public Shadows Property SelectionAlignment() As TextAlign
        ' Gets or sets the alignment to apply to the current selection or insertion point.
        ' Replaces the SelectionAlignment from RichTextBox

        Get
            Dim fmt As New PARAFORMAT()
            fmt.cbSize = Marshal.SizeOf(fmt)

            ' Get the alignment.
            SendMessage(New HandleRef(Me, Handle), EM_GETPARAFORMAT, SCF_SELECTION, fmt)

            ' Default to Left align.
            If (fmt.dwMask And PFM_ALIGNMENT) = 0 Then
                Return TextAlign.Left
            End If

            Return CType(fmt.wAlignment, TextAlign)
        End Get

        Set(value As TextAlign)
            Dim fmt As New PARAFORMAT()
            fmt.cbSize = Marshal.SizeOf(fmt)
            fmt.dwMask = PFM_ALIGNMENT
            fmt.wAlignment = CShort(value)

            ' Set the alignment.
            SendMessage(New HandleRef(Me, Handle), EM_SETPARAFORMAT, SCF_SELECTION, fmt)
        End Set
    End Property

    Protected Overrides Sub OnHandleCreated(e As EventArgs)
        ' This member overrides OnHandleCreated.
        MyBase.OnHandleCreated(e)

        ' Enable support for justification.
        SendMessage(New HandleRef(Me, Handle), EM_SETTYPOGRAPHYOPTIONS, TO_ADVANCEDTYPOGRAPHY, TO_ADVANCEDTYPOGRAPHY)
    End Sub

    Private updating As Integer = 0
    Private oldEventMask As Integer = 0

    ' Constants from the Platform SDK.
    Private Const EM_SETEVENTMASK As Integer = 1073        '1073
    Private Const EM_GETPARAFORMAT As Integer = 1085        '1085
    Private Const EM_SETPARAFORMAT As Integer = 1095        '1095
    Private Const EM_SETTYPOGRAPHYOPTIONS As Integer = 1226 '1226
    Private Const WM_SETREDRAW As Integer = 11              '11
    Private Const TO_ADVANCEDTYPOGRAPHY As Integer = 1      '1
    Private Const PFM_ALIGNMENT As Integer = 8              '8
    Private Const SCF_SELECTION As Integer = 1              '1

    ' It makes no difference if we use PARAFORMAT or
    ' PARAFORMAT2 here, so I have opted for PARAFORMAT2.
    <StructLayout(LayoutKind.Sequential)> _
    Private Structure PARAFORMAT
        Public cbSize As Integer
        Public dwMask As UInteger
        Public wNumbering As Short
        Public wReserved As Short
        Public dxStartIndent As Integer
        Public dxRightIndent As Integer
        Public dxOffset As Integer
        Public wAlignment As Short
        Public cTabCount As Short
        <MarshalAs(UnmanagedType.ByValArray, SizeConst:=32)> _
        Public rgxTabs As Integer()

        ' PARAFORMAT2 from here onwards.
        Public dySpaceBefore As Integer
        Public dySpaceAfter As Integer
        Public dyLineSpacing As Integer
        Public sStyle As Short
        Public bLineSpacingRule As Byte
        Public bOutlineLevel As Byte
        Public wShadingWeight As Short
        Public wShadingStyle As Short
        Public wNumberingStart As Short
        Public wNumberingStyle As Short
        Public wNumberingTab As Short
        Public wBorderSpace As Short
        Public wBorderWidth As Short
        Public wBorders As Short
    End Structure

    <DllImport("user32", CharSet:=CharSet.Auto)> _
    Private Shared Function SendMessage(hWnd As HandleRef, msg As Integer, wParam As Integer, lParam As Integer) As Integer
    End Function

    <DllImport("user32", CharSet:=CharSet.Auto)> _
    Private Shared Function SendMessage(hWnd As HandleRef, msg As Integer, wParam As Integer, ByRef lp As PARAFORMAT) As Integer
    End Function
End Class

Public Enum TextAlign
    ' Specifies how text in a SmartBox is horizontally aligned.

    Left = 1 ' The text is aligned to the left.
    Right = 2 ' The text is aligned to the right.
    Center = 3 ' The text is aligned in the center.
    Justify = 4 ' The text is justified.
End Enum

---

________________________________________________________________________________________________

Make only Form1: Private Sub Form1_Load. DO NOT write any code in it.
Declare the SmartBox thus:

Code:

---

Public Class Form1

Public SmartBox As SmartBox = New SmartBox

 Private Sub Form1_Load.

End Sub
End Class

---

Now run the project (and stop it)

A control called SmartBox will now be in the ToolBox for this project, you will be able to use the new control in this or any other form.
Use this control as any other TextBox or RichTextBox with the added advantage of being able to justify large amounts of text.


Poppa

There have been occaisions when I've wanted to place a heading or cautionary note in the center of a long text, in a user guide for instance, at first I'd just make two or more SmartBoxes with a Center aligned TextBox between them. That's ok, but you have to juggle the positions and sizes carefully or put the different boxes in a TableLayoutPanel to make a neat presentation, but then, things don't always work as expected when different resolution screens display the same layout. TableLayoutPanels don't always resolve the problem.

Subheadings are straight forward enough, justified text are basically left aligned when the text line is shorter than the control width, but for centralised text I now use this little Function...

Code:

---

    Public Function Gap(ByVal msg As String, ctrl As Control) As Int32
        Dim num, spc As Int32
        num = 0 : spc = 0
        msg += "."                  'Ensure at least two characters.
        While spc < ctrl.Width
            msg = msg.Insert(1, " ") ' Insert a space into the string.
            num += 1                ' Count the added spaces.
            Using gr As Graphics = ctrl.CreateGraphics
                spc = CInt(gr.MeasureString(msg, ctrl.Font).Width) ' Measure the new string.
            End Using
        End While
        ' We only need half the number of spaces to centralise the original text.
        num \= 2 : If num < 1 then num = 1 ' In case the string is too long anyway.
        Return num
    End Function

---

... Like this example from a game:

Code:

---

     
        Dim midBit, txt as String   
        txt  = "By default the game allows a player to 'Drag' the cursor from square to "
        txt += "square by keeping the mouse button down whilst moving." & vbCrLf
        txt += "On the  'Hall Of Fame'  page you will find a control to disable this feature. "
        txt += "With 'No Drag' selected, should you realise BEFORE you've released the "
        txt += "Left button, that you had meant to use the Right button you can correct "
        txt += "the error with a Right Click or by sliding into another square.  Changing the "
        txt += "state of this control will Not affect your current game." & vbCrLf & vbCrLf
        midBit = "The mines are set totally at random for every game, therefore there's no "
        midBit += "guarantee that this game can be solved by logic alone."
        txt += Space(Gap(midBit, SmartBox1)) & midBit & vbCrLf & vbCrLf
        midBit = "Clear all the field and find all the mines to win the game."
        txt += Space(Gap(midBit, SmartBox1)) & midBit
        SmartBox1.Text = txt

---

Poppa