¿Cómo puedo justificar texto en un RichTextBox?

Question

Aquí mi código, lo llamo desde un método:

private void MiMetodo( )

{

RichTextBox richTextBox = new RichTextBox(); // Crear una instancia de RichTextBox

Font font = new Font( "Microsoft Sans Serif", 12 );

int controlWidth = richTextBox.ClientSize.Width; // Ancho del RichTextBox (considerando el espacio del borde)

string textoJustificado = JustifyParagraph( RichTextBox1.Text, font, controlWidth );

RichTextBox1.Text = textoJustificado.ToString();
```}

private string JustifyParagraph(string text, Font font, int controlWidth)

{

```csharp
string[ ] lines = text.Split( new[ ] { Environment.NewLine }, StringSplitOptions.None );

StringBuilder result = new StringBuilder();

foreach ( string line in lines )

{

    string justifiedLine = Justify( line, font, controlWidth );

    result.AppendLine( justifiedLine );

}

return result.ToString().TrimEnd();
```}

private string Justify(string line, Font font, int controlWidth)

{

```csharp
string[ ] words = line.Split( ' ' );

StringBuilder justifiedLine = new StringBuilder();

int totalSpaces = controlWidth - TextRenderer.MeasureText( line, font ).Width;

int numWords = words.Length;

if ( numWords == 1 )

{

    // Si solo hay una palabra, no es necesario justificarla

    return line;

}

int spacesPerWord = totalSpaces / ( numWords - 1 );

int extraSpaces = totalSpaces % ( numWords - 1 );

for ( int i = 0; i < numWords; i++ )

{

    justifiedLine.Append( words[ i ] );

    if ( i < numWords - 1 )

    {

        int spacesToAdd = spacesPerWord + ( i < extraSpaces ? 1 : 0 );

        if ( spacesToAdd > 0 ) // Evita agregar espacios negativos

        {

            justifiedLine.Append( ' ', spacesToAdd );

        }

    }

}

return justifiedLine.ToString();
```}

Answer 1

Para lograr el justificado de una manera eficiente vas a necesitar crear un mini proyecto adjunto a tu solución en código Visual Basic (no importa que tu proyecto donde lo usaras este en C#).

1. Agrega a tu solución un nuevo proyecto Visual Basic -WindowsForm (no importa el nombre) en Visual Basic (tampoco importa si tu proyecto original lo estas trabajando en C# o en VB.NET) al compilarse son compatibles ambos códigos.
2. Agrega a dicho proyecto una clase llamada SmartBox.vb.
   1. Dentro de la clase, copia el siguiente código tal cual:

      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
      
   

3. Sobre el proyecto de VisualBasic da click derecho y selecciona la opción establecer como proyecto de inicio.
   1. Ahora ve al código del formulario y escribe solo lo siguiente (ninguna otra cosa mas):

      Public Class Form1
          Public SmartBox As SmartBox = New SmartBox
          Private Sub Form1_Load()
          End Sub
      End Class
      
   

4. Ejecuta el proyecto UNA SOLA VEZ.
5. Ahora finaliza el proyecto.
6. Revisa en el Toolbox que ahora existe un componenete llamado SmartBox:
7. Establece tu proyecto de C# como proyecto de inicio.
8. Ahora puedes arrastrar el componente SmartBox sobre tu formulario y utilizarlo para justificar utilizando la propiedad smartBox1.SelectionAlignment = WinFormsApp2.TextAlign.Justify;

public partial class Form1 : Form
{
    public Form1()
    {
        InitializeComponent();
    }
    private void button1_Click(object sender, EventArgs e)
    {
        smartBox1.SelectionAlignment = WinFormsApp2.TextAlign.Justify;
    }
}

1. 
2. Clic en el botón Justificar:
3. Listo, RichTextBox con Justificación. Basado en lo descrito por: vbforoums