c# - System.ArgumentException: 'targetBounds'

Question

I am trying to print a panel and it's child controls inside of it. But when I run the program, it is throwing an error:

System.ArgumentException: 'targetBounds'

in line ctl.DrawToBitmap(bitmap, bounds);

Here is the code I used from this answer

private void BtnPrint_Click(object sender, EventArgs e)
    {
        Print(this.pnlID);
    }


    public void Print(Panel pnl)
    {
        PrinterSettings ps = new PrinterSettings();
        //pnlID = pnl;
        //GetPrintArea(pnl);
        prntprvw.Document = printdoc;
        printdoc.PrintPage += new PrintPageEventHandler(printdoc_printpage);
        prntprvw.ShowDialog();

    }

    public void printdoc_printpage(Object sender, PrintPageEventArgs e)
    {
        var bitmap = ScrollableControlToBitmap(this.pnlID, false);
        Rectangle pagearea = e.PageBounds;
        e.Graphics.DrawImage(bitmap, new Rectangle( 0, 0, pnlID.Width, pnlID.Height));
    }


    public Bitmap ScrollableControlToBitmap(ScrollableControl canvas, bool includeHidden)
    {
        canvas.AutoScrollPosition = new Point(0, 0);
        if (includeHidden)
        {
            canvas.SuspendLayout();
            foreach (Control child in canvas.Controls)
            {
                child.Visible = true;
            }
            canvas.ResumeLayout(true);
        }

        Size containerSize = canvas.PreferredSize;
        var bitmap = new Bitmap(containerSize.Width, containerSize.Height, PixelFormat.Format32bppArgb);
        bitmap.SetResolution(this.DeviceDpi, this.DeviceDpi);

        var graphics = Graphics.FromImage(bitmap);
        graphics.Clear(canvas.BackColor);
        var rtfPrinter = new RichEditPrinter(graphics);

        try
        {
            DrawNestedControls(canvas, canvas, new Rectangle(Point.Empty, containerSize), bitmap, rtfPrinter);
            return bitmap;
        }
        finally
        {
            rtfPrinter.Dispose();
            graphics.Dispose();
        }
    }

    private void DrawNestedControls(Control outerContainer, Control parent, Rectangle parentBounds, Bitmap bitmap, RichEditPrinter rtfPrinter)
    {
        for (int i = parent.Controls.Count - 1; i >= 0; i--)
        {
            var ctl = parent.Controls[i];
            var clipBounds = (parent == outerContainer)
                           ? ctl.Bounds
                           : Rectangle.Intersect(new Rectangle(Point.Empty, parentBounds.Size), ctl.Bounds);

            if (ctl.Visible)
            {
                var bounds = outerContainer.RectangleToClient(parent.RectangleToScreen(clipBounds));

                if (ctl is RichTextBox rtb)
                {
                    rtfPrinter.DrawRtf(rtb.Rtf, parentBounds, clipBounds);
                }
                else
                {
                    ctl.DrawToBitmap(bitmap, bounds);
                }
            }
            if (ctl.HasChildren)
            {
                DrawNestedControls(outerContainer, ctl, clipBounds, bitmap, rtfPrinter);
            }
        }
    }


    public class RichEditPrinter : IDisposable
    {
        Graphics dc = null;
        RTBPrinter rtb = null;

        public RichEditPrinter(Graphics graphics)
        {
            this.dc = graphics;
            this.rtb = new RTBPrinter() { ScrollBars = RichTextBoxScrollBars.None };
        }

        public void DrawRtf(string rtf, Rectangle canvas, Rectangle layoutArea)
        {
            rtb.Rtf = rtf;
            rtb.Draw(dc, canvas, layoutArea);
            rtb.Clear();
        }
        public void Dispose() => this.rtb.Dispose();

        private class RTBPrinter : RichTextBox
        {
            //Code converted from code found here: http://support.microsoft.com/kb/812425/en-us
            public void Draw(Graphics g, Rectangle hdcArea, Rectangle layoutArea)
            {
                IntPtr hdc = g.GetHdc();
                var canvasAreaTwips = new RECT().ToInches(hdcArea);
                var layoutAreaTwips = new RECT().ToInches(layoutArea);

                FORMATRANGE fmtRange = new FORMATRANGE()
                {
                    chrg = new CHARRANGE() { cpMax = -1, cpMin = 0 },
                    hdc = hdc,
                    hdcTarget = hdc,
                    rc = layoutAreaTwips,
                    rcPage = canvasAreaTwips
                };

                IntPtr lParam = Marshal.AllocCoTaskMem(Marshal.SizeOf(fmtRange));
                Marshal.StructureToPtr(fmtRange, lParam, false);

                SendMessage(this.Handle, EM_FORMATRANGE, (IntPtr)1, lParam);
                Marshal.FreeCoTaskMem(lParam);
                g.ReleaseHdc(hdc);
            }

            [DllImport("User32.dll", CharSet = CharSet.Auto, SetLastError = true)]
            internal static extern int SendMessage(IntPtr hWnd, int uMsg, IntPtr wParam, IntPtr lParam);

            internal const int WM_USER = 0x0400;
            // https://docs.microsoft.com/en-us/windows/win32/controls/em-formatrange
            internal const int EM_FORMATRANGE = WM_USER + 57;

            [StructLayout(LayoutKind.Sequential)]
            internal struct RECT
            {
                public int Left;
                public int Top;
                public int Right;
                public int Bottom;

                public Rectangle ToRectangle() => Rectangle.FromLTRB(Left, Top, Right, Bottom);
                public RECT ToInches(Rectangle rectangle)
                {
                    float inch = 14.9f;
                    return new RECT()
                    {
                        Left = (int)(rectangle.Left * inch),
                        Top = (int)(rectangle.Top * inch),
                        Right = (int)(rectangle.Right * inch),
                        Bottom = (int)(rectangle.Bottom * inch)
                    };
                }
            }

            // https://docs.microsoft.com/en-us/windows/win32/api/richedit/ns-richedit-formatrange?
            [StructLayout(LayoutKind.Sequential)]
            internal struct FORMATRANGE
            {
                public IntPtr hdcTarget;    // A HDC for the target device to format for
                public IntPtr hdc;          // A HDC for the device to render to, if EM_FORMATRANGE is being used to send the output to a device
                public RECT rc;             // The area within the rcPage rectangle to render to. Units are measured in twips.
                public RECT rcPage;         // The entire area of a page on the rendering device. Units are measured in twips.
                public CHARRANGE chrg;      // The range of characters to format (see CHARRANGE)
            }

            [StructLayout(LayoutKind.Sequential)]
            internal struct CHARRANGE
            {
                public int cpMin;           // First character of range (0 for start of doc)
                public int cpMax;           // Last character of range (-1 for end of doc)
            }
        }
    }

How can I fix the error?

Answer 1

Adding the if (ctl.Width < 1 || ctl.Height < 1) continue; fixed the problem.