C# Signature:
[DllImport("gdi32.dll", CharSet = CharSet.Auto)]
static extern bool TextOut(IntPtr hdc, int nXStart, int nYStart,
string lpString, int cbString); (Please see note for CharSet in tips)
VB.NET Signature:
<DllImport("gdi32")> _
Shared Function TextOut(ByVal hdc As IntPtr, ByVal x As Integer, _
ByVal y As Integer, ByVal textstring As String, _
ByVal charCount As Integer) As Boolean
End Function
Tips & Tricks:
TextOut, unlike the Text property, have to be called every time Windows asks for a control to repaint. By using the Graphics.CopyFromScreen method one can copy the output of a Textout command and use that for repainting.
Unlike graphics.drawstring, Textout can work with fonts other than True Type, Open Type, and PostScript fonts. If you have a font that's supported by Windows but not .net you can most likely use this command to draw it.
[CharSet = CharSet.Auto] According to my experience this parameter should be used when using a LOGFONT structure and the CreateFontIndirect fuction, otherwise the selected font will not be displayed. All flags will be done (lfItalic, lfUnderline ...) but not the lfFaceName string.
Sample Code:
// Paste this at the beginning of your file if not present:
using System.Drawing;
using System.Runtime.InteropServices;
//Create a class that subclass Control and paste these methods into it.
//Then place the new control on a form.
[DllImport("gdi32.dll")]
static extern bool TextOut(IntPtr hdc, int nXStart, int nYStart,
string lpString, int cbString);
[DllImport("gdi32.dll")]
static extern bool GetTextExtentPoint(IntPtr hdc, string lpString,
int cbString, ref Size lpSize);
[DllImport("gdi32.dll")]
public static extern IntPtr SelectObject(IntPtr hdc, IntPtr hgdiobj);
[DllImport("GDI32.dll")]
public static extern bool DeleteObject(IntPtr objectHandle);
#region Font
protected override void OnKeyPress(KeyPressEventArgs e)
{
Text += e.KeyChar.ToString();
//Note, painting should not be done in the OnKeyPress method, instead:
Refresh();
//You may want to meassure the string's size for layout purposes.
using(Graphics g = base.CreateGraphics())
{
//Do the GetHdc(), GetTextExtentPoint, etc, here. Remember that you have
//to delete related objects such as fonts and call ReleaseHdc on graphics
//afterwards. If you for some reason don't want to do this you can use a
//SafeHandle (needs to be subclassed) which does this for you.
//Remember to use HandleRef when appropriate. For instance if you create
//a color that you set through SelectObject the .net garbage collector will
//happily delete the color unless you refere to it after the drawing call or
//use a HandleRef.
//In this example we used the base class font and therefore need not worry
//about the GC deleting the Font in mid drawing.
//Also keep in mind that all graphics objects _you_ create must be disposed,
//which is done through the using clause in this example. It can also be done
//by calling g.Dispose() in a finally clause (to guarantee that it's executed)
}
}
protected override void OnPaint(PaintEventArgs e)
{
IntPtr HDC = e.Graphics.GetHdc();
//We have to use SelectObject to set the font, color and other properties.
IntPtr last_font = SelectObject(HDC, Font.ToHfont());
Size MeasureSize = new Size(0, 0);
int y_pos = 0;
int x_pos = 2;
//Tasks such as these should not be done in the drawing loop as they
//slow down the drawing.
String[] lines = Text.Split(new char[] { '\n' });
try
{
//We draw out each line of text.
for(int c=0; c < lines.Length; c++)
{
String line = lines[c];
TextOut(HDC, x_pos, y_pos, line, line.Length);
//Unless you change the font, the line height never
//changes so measuring the text at each draw call is
//inefficient. Also it measure empty lines at 0 height
//so pressing multiple enters will not move the text down.
GetTextExtentPoint(HDC, line, line.Length, ref MeasureSize);
y_pos += MeasureSize.Height;
//You can use the MeasureSize.Width property to implement
//word wrapping.
}
}
finally
{
//Put here to make sure we don't get a memory leak.
DeleteObject(SelectObject(HDC, last_font));
e.Graphics.ReleaseHdc(HDC);
//Don't call dispose() on the Graphics object unless you createded it.
}
}
Vb.net Sample:
Imports System.Runtime.InteropServices
Public Class Form1
Declare Function SetTextCharacterExtra Lib "gdi32" Alias "SetTextCharacterExtra" (ByVal hDC As Integer, ByVal nCharExtra As Integer) As Integer
<DllImport("gdi32")> _
Private Shared Function TextOut(ByVal hdc As IntPtr, ByVal x As Integer, ByVal y As Integer, ByVal textstring As String, ByVal charCount As Integer) As Boolean
End Function
<DllImport("gdi32")> _
Private Shared Function SelectObject(ByVal hdc As IntPtr, ByVal hgdiobj As IntPtr) As IntPtr
End Function
<DllImport("gdi32")> _
Private Shared Function DeleteObject(ByVal objectHandle As IntPtr) As Boolean
End Function
<DllImport("gdi32")> _
Private Shared Function SetBkColor(ByVal hdc As IntPtr, ByVal crColor As Integer) As UInt32
End Function
<DllImport("gdi32")> _
Private Shared Function SetTextColor(ByVal hdc As IntPtr, ByVal crColor As Integer) As UInt32
End Function
Private Sub Button1_Click(ByVal sender As System.Object, ByVal e As System.EventArgs) Handles Button1.Click
Using G = Graphics.FromHwnd(Me.Handle)
Using myFont As New System.Drawing.Font("Arial", 20, FontStyle.Regular, GraphicsUnit.Pixel)
'Regular Way
Dim LeftEdge = 20
G.DrawString("Hello", myFont, Brushes.Red, LeftEdge, 40)
'If you want kerning
Dim Kerning As Integer = 6 'I think this is twips
Dim Hdc As IntPtr
Dim FontPtr As IntPtr
Try
'Grab the Graphic object's handle
Hdc = G.GetHdc()
'Set the current GDI font
FontPtr = SelectObject(Hdc, myFont.ToHfont())
'Set the drawing surface background color
SetBkColor(Hdc, ColorTranslator.ToWin32(Me.BackColor))
'Set the text color
SetTextColor(Hdc, ColorTranslator.ToWin32(Color.Red))
'Set the kerning
SetTextCharacterExtra(Hdc, Kerning)
Dim Text = "Hello"
'Draw the text at (20,60), Kerning will be applied so reset the left edge to half of kerning
TextOut(Hdc, LeftEdge + (Kerning \ 2), 60, Text, Text.Length)
Catch ex As Exception
Finally
'Release the font
DeleteObject(FontPtr)
'Release the handle on the graphics object
G.ReleaseHdc()
End Try
End Using
End Using
End Sub
End Class
Alternative Managed API:
Graphics.DrawString
Graphics.MeasureString
Graphics.MeasureCharacterRanges
