using System; using System.Windows.Forms; namespace WeifenLuo.WinFormsUI.Docking { // Inspired by Chris Sano's article: // http://msdn.microsoft.com/smartclient/default.aspx?pull=/library/en-us/dnwinforms/html/colorpicker.asp // In Sano's article, the DragForm needs to meet the following criteria: // (1) it was not to show up in the task bar; // ShowInTaskBar = false // (2) it needed to be the top-most window; // TopMost = true (not necessary here) // (3) its icon could not show up in the ALT+TAB window if the user pressed ALT+TAB during a drag-and-drop; // FormBorderStyle = FormBorderStyle.None; // Create with WS_EX_TOOLWINDOW window style. // Compares with the solution in the artile by setting FormBorderStyle as FixedToolWindow, // and then clip the window caption and border, this way is much simplier. // (4) it was not to steal focus from the application when displayed. // User Win32 ShowWindow API with SW_SHOWNOACTIVATE // In addition, this form should only for display and therefore should act as transparent, otherwise // WindowFromPoint will return this form, instead of the control beneath. Need BOTH of the following to // achieve this (don't know why, spent hours to try it out :( ): // 1. Enabled = false; // 2. WM_NCHITTEST returns HTTRANSPARENT internal class DragForm : Form { public DragForm() { FormBorderStyle = FormBorderStyle.None; ShowInTaskbar = false; SetStyle(ControlStyles.Selectable, false); Enabled = false; } protected override CreateParams CreateParams { get { CreateParams createParams = base.CreateParams; createParams.ExStyle |= (int)Win32.WindowExStyles.WS_EX_TOOLWINDOW; return createParams; } } protected override void WndProc(ref Message m) { if (m.Msg == (int)Win32.Msgs.WM_NCHITTEST) { m.Result = (IntPtr)Win32.HitTest.HTTRANSPARENT; return; } base.WndProc (ref m); } public virtual void Show(bool bActivate) { if (bActivate) Show(); else NativeMethods.ShowWindow(Handle, (int)Win32.ShowWindowStyles.SW_SHOWNOACTIVATE); } } }