Graphics.DrawString() method throws GDI+ exception when the string length is too long

user_7574796 0
Viewed 281

The below code block which throws

System.Runtime.InteropServices.ExternalException: 'A generic error occurred in GDI+.

exception when the string passed to draw is too long.

public partial class Form1 : Form
{
    string longString;
    public Form1()
    {
        InitializeComponent();

        for (int i = 0; i < 40000; i++)
            longString += "s";
    }


    protected override void OnPaint(PaintEventArgs e)
    {
        base.OnPaint(e);
        e.Graphics.DrawString(longString, new Font("Segeo UI", 11, FontStyle.Regular), new SolidBrush(Color.Black), new RectangleF(0, 0, 100, 30),
            new StringFormat()
            {
                LineAlignment = StringAlignment.Center,
                Alignment = StringAlignment.Center,
                Trimming= StringTrimming.None,
                FormatFlags = StringFormatFlags.DirectionRightToLeft
            });
    }
}

How to resolve this exception when drawing long string with the specified format?

drawstring winforms
1 Answers

I have experienced the same problem. It is not related to the font you are using, the graphics objects being leaked or the StringFormatFlags. It is caused by the length of your string. The exception condition is being triggered by unmanaged code, propagates to the .NET Framework, and ends up in your application. It occurs in both

Graphics.DrawString(...)

and

Graphics.MeasureString(...).

There are a number of other posts on the web related to this issue. None offer a solution. They suggest that the problem occurs when string length exceeds about 40,000 characters. I can confirm that this problem occurs in my code for a string length just over 44,000 characters.

The solution? In my case I added code to detect "long" strings and truncate them, with appropriate notification to the user. It would seem that this is a Microsoft bug. It may predate .NET and exist in earlier MS native code, or in the COM wrapper MS uses to interop between .NET and their native code.

user_49935290
Related