C# Signature:

[DllImport("gdi32.dll")]
static extern bool GetTextExtentPoint32(IntPtr hdc, string lpString,
   int cbString, out SIZE lpSize);
static extern bool GetTextExtentPoint(IntPtr hdc, string lpString,
   int cbString, ref Size lpSize);

User-Defined Types:

None.

None. (None needed)

Notes:

None.

Notes (From MSDN):

The GetTextExtentPoint function uses the currently selected font to compute the dimensions of the string. GetTextExtentPoint computes the width and height, in logical units, without considering any clipping.

Because some devices kern characters, the sum of the extents of the characters in a string does not always equal to the extent of the string.

The GetTextExtentPoint function is identical to the GetTextExtentPoint32 function.

Tips & Tricks:

If you need to treat unicode text, you'll need to set the CharSet option to Unicode or Auto (which is default on WindowsNT)

[DllImport("gdi32.dll", CharSet=CharSet.Unicode)]
static extern bool GetTextExtentPoint32(IntPtr hdc, string lpString, int cbString, out SIZE lpSize);

Notes (From Author/Editor Gabriel Sharp)

If you use TextOut, you will need to save the screen to a back buffer or else this output will disappear. You can either use a backbuffer directly or through the Graphics.CopyFromScreen method. Advanced users might also try the BitBlt Api call, which can sometimes, under certain conditions, be faster.

Sample Code:

// the GDI class contains static "gdi32.dll" calls
public Size getExtent(string text, Graphics graphics, Font font)
{
    Size sz = Size.Empty;
    IntPtr hdc = graphics.GetHdc();
    IntPtr oldfnt = GDI.SelectObject(hdc, font.ToHfont());

    GDI.GetTextExtentPoint32(hdc, text, text.Length,out sz);

    // reset old font
    GDI.DeleteObject(GDI.SelectObject(hdc, oldfnt));
    graphics.ReleaseHdc(hdc);
    return sz;
}

Tips & Tricks:

This API is useful for TextOut preparation or post comparison. These API's are most useful when working with fonts other than

(but not restricted to) True Type, Open Type, and PostScript fonts. The most common being raster (pixel) fonts which are not supported

by the .NET framework. TextOut and it's helpers tend to be a bit faster because they are unmanaged and work well with .NET's existing

[Graphics.GetHdc()] method. Any graphics / bitmap pair you create will already have a default font, and you can start using TextOut and the above function right away without having to pre-init all the stuff that goes with it (Fonts, Brushes, etc). Good luck!

Alternative Managed API:

If you are using GDI+ with a Graphics object you can make use of the following code sample:

Sample Code:

    // Paste this at the beginning of your file if not present:

    using System.Windows.Forms; // for TextRenderer

using System.Drawing;

using System.Runtime.InteropServices;

    Size size=TextRenderer.MeasureText(g, str, f, new Size(), TextFormatFlags.NoPadding);
    // Paste This Inside a New Form's Code After InitializeComponent() {}

Since .NET padding has been added to font's height and width. So you need to make use of the format flag TextFormatFlags.NoPadding to get the real size of the text.

    [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);

Variables:

    g - is the Graphics object you want to draw on
    str - the string that should be measured
    f - the font you want to use
    new Size() - just a dummy parameter
    int x = 0;
    int y = 0;

For more information see

http://msdn.microsoft.com/de-de/library/system.windows.forms.textrenderer(VS.80).aspx

    protected override void OnKeyPress(KeyPressEventArgs e)
    {
        IntPtr HDC = CreateGraphics().GetHdc();
        Size MeasureSize = new Size(0, 0);
        String strOut =  e.KeyChar.ToString();
        int strLen =  e.KeyChar.ToString().Length;

       TextOut(HDC, x,y, strOut,strLen);

Good luck and have fun (Julian Taupe)

        GetTextExtentPoint(HDC, strOut, strLen, ref MeasureSize);

        x += MeasureSize.Width;

        if ((x+MeasureSize.Width) > ClientRectangle.Width)
        {
        y += MeasureSize.Height;
        x = 0;
        }

    }

Alternative Managed API:

Graphics.DrawString
Graphics.MeasureString
Graphics.MeasureCharacterRanges

Full Documentation: GetTextExtentPoint on MSDN

Original API Call in C++

BOOL GetTextExtentPoint32(
   HDC hdc,
   LPCTSTR lpString,
   int cbString,
   LPSIZE lpSize);

Library: gdi32.dll

Header: wingdi.h

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