System.Windows.Forms.XplatUIX11.DefWndProc C# (CSharp) Method

		internal override IntPtr DefWndProc(ref Message msg) {
			switch ((Msg)msg.Msg) {
				
				case Msg.WM_IME_COMPOSITION:
					string s = Keyboard.GetCompositionString ();
					foreach (char c in s)
						SendMessage (msg.HWnd, Msg.WM_IME_CHAR, (IntPtr) c, msg.LParam);
					return IntPtr.Zero;

				case Msg.WM_IME_CHAR:
					// On Windows API it sends two WM_CHAR messages for each byte, but
					// I wonder if it is worthy to emulate it (also no idea how to 
					// reconstruct those bytes into chars).
					SendMessage (msg.HWnd, Msg.WM_CHAR, msg.WParam, msg.LParam);
					return IntPtr.Zero;

				case Msg.WM_PAINT: {
					Hwnd hwnd;

					hwnd = Hwnd.GetObjectFromWindow(msg.HWnd);
					if (hwnd != null) {
						hwnd.expose_pending = false;
					}

					return IntPtr.Zero;
				}

				case Msg.WM_NCPAINT: {
					Hwnd hwnd;

					hwnd = Hwnd.GetObjectFromWindow(msg.HWnd);
					if (hwnd != null) {
						hwnd.nc_expose_pending = false;
					}

					return IntPtr.Zero;
				}

				case Msg.WM_NCCALCSIZE: {
					Hwnd hwnd;

					if (msg.WParam == (IntPtr)1) {
						hwnd = Hwnd.GetObjectFromWindow (msg.HWnd);
						
						XplatUIWin32.NCCALCSIZE_PARAMS ncp;
						ncp = (XplatUIWin32.NCCALCSIZE_PARAMS)Marshal.PtrToStructure (msg.LParam, typeof (XplatUIWin32.NCCALCSIZE_PARAMS));

						// Add all the stuff X is supposed to draw.
						Control ctrl = Control.FromHandle (hwnd.Handle);
						
						if (ctrl != null) {
							Hwnd.Borders rect = Hwnd.GetBorders (ctrl.GetCreateParams (), null);
							
							ncp.rgrc1.top += rect.top;
							ncp.rgrc1.bottom -= rect.bottom;
							ncp.rgrc1.left += rect.left;
							ncp.rgrc1.right -= rect.right;
							
							Marshal.StructureToPtr (ncp, msg.LParam, true);
						}
					}

					return IntPtr.Zero;
				}

				case Msg.WM_CONTEXTMENU: {
					Hwnd hwnd;

					hwnd = Hwnd.GetObjectFromWindow(msg.HWnd);

					if ((hwnd != null) && (hwnd.parent != null)) {
						SendMessage(hwnd.parent.client_window, Msg.WM_CONTEXTMENU, msg.WParam, msg.LParam);
					}
					return IntPtr.Zero;
				}

				case Msg.WM_MOUSEWHEEL: {
					Hwnd hwnd;

					hwnd = Hwnd.GetObjectFromWindow(msg.HWnd);

					if ((hwnd != null) && (hwnd.parent != null)) {
						SendMessage(hwnd.parent.client_window, Msg.WM_MOUSEWHEEL, msg.WParam, msg.LParam);
						if (msg.Result == IntPtr.Zero) {
							return IntPtr.Zero;
						}
					}
					return IntPtr.Zero;
				}

				case Msg.WM_SETCURSOR: {
					Hwnd	hwnd;

					hwnd = Hwnd.GetObjectFromWindow(msg.HWnd);
					if (hwnd == null)
						break; // not sure how this happens, but it does

					// Pass to parent window first
					while ((hwnd.parent != null) && (msg.Result == IntPtr.Zero)) {
						hwnd = hwnd.parent;
						msg.Result = NativeWindow.WndProc(hwnd.Handle, Msg.WM_SETCURSOR, msg.HWnd, msg.LParam);
					}

					if (msg.Result == IntPtr.Zero) {
						IntPtr handle;

						switch((HitTest)(msg.LParam.ToInt32() & 0xffff)) {
							case HitTest.HTBOTTOM:		handle = Cursors.SizeNS.handle; break;
							case HitTest.HTBORDER:		handle = Cursors.SizeNS.handle; break;
							case HitTest.HTBOTTOMLEFT:	handle = Cursors.SizeNESW.handle; break;
							case HitTest.HTBOTTOMRIGHT:	handle = Cursors.SizeNWSE.handle; break;
							case HitTest.HTERROR:		if ((msg.LParam.ToInt32() >> 16) == (int)Msg.WM_LBUTTONDOWN) {
												AudibleAlert(AlertType.Default);
											}
											handle = Cursors.Default.handle;
											break;

							case HitTest.HTHELP:		handle = Cursors.Help.handle; break;
							case HitTest.HTLEFT:		handle = Cursors.SizeWE.handle; break;
							case HitTest.HTRIGHT:		handle = Cursors.SizeWE.handle; break;
							case HitTest.HTTOP:		handle = Cursors.SizeNS.handle; break;
							case HitTest.HTTOPLEFT:		handle = Cursors.SizeNWSE.handle; break;
							case HitTest.HTTOPRIGHT:	handle = Cursors.SizeNESW.handle; break;

							#if SameAsDefault
							case HitTest.HTGROWBOX:
							case HitTest.HTSIZE:
							case HitTest.HTZOOM:
							case HitTest.HTVSCROLL:
							case HitTest.HTSYSMENU:
							case HitTest.HTREDUCE:
							case HitTest.HTNOWHERE:
							case HitTest.HTMAXBUTTON:
							case HitTest.HTMINBUTTON:
							case HitTest.HTMENU:
							case HitTest.HSCROLL:
							case HitTest.HTBOTTOM:
							case HitTest.HTCAPTION:
							case HitTest.HTCLIENT:
							case HitTest.HTCLOSE:
							#endif
							default: handle = Cursors.Default.handle; break;
						}
						SetCursor(msg.HWnd, handle);
					}
					return (IntPtr)1;
				}
			}
			return IntPtr.Zero;
		}