private void ShowDropDown()
{
var rect = RectangleToScreen(ClientRectangle);
var location = new Point(rect.X, rect.Y + Height);
_dropDownControl.Size = new Size(rect.Width, _checkedListBox.Items.Count * _checkedListBox.ItemHeight + ScreenHelpers.ScaleByCurrentDPI(5));
_dropDownControl.Show(location);
_dropDownClosing = true;
_dropDownControl.Focus();
}
///<summary></summary>
///<param name="keepMenuOpen">An open to keep the drop down menu open if the main window is no longer the active window.</param>
public ToolStripDropDownAttacher(ToolStripDropDown menu, Control c, bool keepMenuOpen = true)
{
Menu = menu;
Control = c;
KeepMenuOpen = keepMenuOpen;
menu.AutoClose = false;
menu.Click += delegate {
isFocusing = true;
menu.Focus();
IntPtr h = GetTopWindow(c.Handle);
// after the main window is minimized and restored, clicking on
// clock will deactivate the main window title bar unless this is called:
SendMessage(h, WM_NCACTIVATE, (IntPtr)1, (IntPtr)0);
isFocusing = false;
};
menu.Closing += (o, e) => {
if (isClosing)
{
e.Cancel = false;
}
};
menu.KeyDown += (o, e) => {
if (e.KeyCode == Keys.Escape && !menu.AutoClose)
{
CloseMenu(ToolStripDropDownCloseReason.Keyboard);
e.Handled = true;
//e.SuppressKeyPress = true;
}
};
menu.GotFocus += delegate {
// click on the control, then tab to focus on the drop down
// then minimize the main window, then restore the main window
// tabbing into the drop down deactivates the main window
var tl = GetTopWindow(c.Handle);
SendMessage(tl, WM_NCACTIVATE, (IntPtr)1, (IntPtr)0);
};
menu.LostFocus += delegate {
// if another window is clicked, then two issues occur:
// 1) The top level window doesn't deactivate, so two windows on the
// desktop both appear active.
// 2) When the focus returns to this program's main window, clicking
// on thedrop down shows this window's caption as deactivated.
if (!c.Focused && !isFocusing && !isClosing)
{
if (KeepMenuOpen)
{
IntPtr fg = GetForegroundWindow();
IntPtr tl = GetTopWindow(c.Handle);
bool b = fg == tl;
if (!b)
{
SendMessage(tl, WM_NCACTIVATE, (IntPtr)0, (IntPtr)0);
return;
}
}
CloseMenu(ToolStripDropDownCloseReason.CloseCalled);
}
};
c.MouseDown += delegate {
ShowMenu();
};
/*
* Removing this help preventing menu showing on Tab or windows focus change
* by: Awais Ahmad Alvi
*
* c.GotFocus += delegate {
* if (!menu.Visible && !isClosing)
* ShowMenu();
* };
*
*/
c.LostFocus += delegate {
// if the focus was transferred to another window, then keep
// the drop down open. Otherwise if the focus was transfered to
// another control in the same window then close the menu
bool b = true;
if (KeepMenuOpen)
{
IntPtr fg = GetForegroundWindow();
IntPtr tl = GetTopWindow(c.Handle);
b = tl == fg;
}
if (!menu.Focused && b)
{
CloseMenu(ToolStripDropDownCloseReason.CloseCalled);
}
};
c.KeyDown += (o, e) => {
if (e.KeyData == Keys.Escape)
{
e.Handled = true;
e.SuppressKeyPress = true; // stops the beep
if (menu.Visible)
{
CloseMenu(ToolStripDropDownCloseReason.Keyboard);
}
}
};
c.EnabledChanged += delegate {
menu.Enabled = c.Enabled;
};
Application.AddMessageFilter(this);
}
