3rdpartylibs/fastreports.wpf/FastReport/Utils/DrawUtils.Win32.cs

using System;
using System.Drawing;
using System.Runtime.InteropServices;
using System.Windows.Forms;

namespace FastReport.Utils
{
    partial class DrawUtils
    {
        [DllImport("user32.dll")]
        static extern IntPtr SendMessage(IntPtr hWnd, int msg, IntPtr wParam, DrawingOptions drawingOptions);

        const int WM_PRINT = 0x317;

        [Flags]
        enum DrawingOptions
        {
            PRF_CHECKVISIBLE = 0x01,
            PRF_NONCLIENT = 0x02,
            PRF_CLIENT = 0x04,
            PRF_ERASEBKGND = 0x08,
            PRF_CHILDREN = 0x10,
            PRF_OWNED = 0x20
        }

        private static void FloodFill(Bitmap bmp, int x, int y, Color color, Color replacementColor)
        {
            if (x < 0 || y < 0 || x >= bmp.Width || y >= bmp.Height || bmp.GetPixel(x, y) != color)
                return;
            bmp.SetPixel(x, y, replacementColor);
            FloodFill(bmp, x - 1, y, color, replacementColor);
            FloodFill(bmp, x + 1, y, color, replacementColor);
            FloodFill(bmp, x, y - 1, color, replacementColor);
            FloodFill(bmp, x, y + 1, color, replacementColor);
        }

        /// <summary>
        /// Draws control to a bitmap.
        /// </summary>
        /// <param name="control">Control to draw.</param>
        /// <param name="children">Determines whether to draw control's children or not.</param>
        /// <returns>The bitmap.</returns>
        public static Bitmap DrawToBitmap(Control control, bool children)
        {
            Bitmap bitmap = new Bitmap(control.Width, control.Height);
            using (Graphics gr = Graphics.FromImage(bitmap))
            {
                IntPtr hdc = gr.GetHdc();
                DrawingOptions options = DrawingOptions.PRF_ERASEBKGND | DrawingOptions.PRF_CLIENT | DrawingOptions.PRF_NONCLIENT;
                if (children)
                    options |= DrawingOptions.PRF_CHILDREN;
                SendMessage(control.Handle, WM_PRINT, hdc, options);
                gr.ReleaseHdc(hdc);
            }
            
            if (control is Form)
            {
                // form has round edges which are filled black (DrawToBitmap issue/bug).
                FloodFill(bitmap, 0, 0, Color.FromArgb(0, 0, 0), Color.White);
                FloodFill(bitmap, bitmap.Width - 1, 0, Color.FromArgb(0, 0, 0), Color.White);
            }

            return bitmap;
        }
    }
}