How to make a "popup" (hint, drop-down, popup) window in Winforms?

Question

How can i make, what i will call, a "popup" window" in WinForms?

Since i used my own made-up word "popup", let me give examples of this so-called "popup" window:

a tooltip window (can extend outside the boundaries of its parent form, doesn't appear in the taskbar, is not modal, and doesn't steal focus):
a popup menu window (can extend outside the boundaries of its parent form, doesn't appear in the taskbar, is not modal, and doesn't steal focus):
a drop-down window (can extend outside the boundaries of its parent form, doesn't appear in the taskbar, is not modal, and doesn't steal focus):
A main menu window (can extend outside the boundaries of its parent form, doesn't appear in the taskbar, is not modal, and doesn't steal focus):
Update A popup window not make itself the "active" window when interacted with using a mouse or keyboard (the "owner" window remains the active window):

enter image description here

The attributes that i'm looking for in this mythical "popup" are that it:

can extend outside the boundaries of its parent form (i.e. is not a child window)
doesn't appear in the taskbar (i.e. Window's heuristics of which windows should appear doesn't kick in, nor does it have WS_EX_APPWINDOW extended window style)
is not modal (i.e. doesn't disable its "owner")
doesn't steal focus
is always on-top of of it's "owner"
does not become the "active" window when interacted with (the owner remains active)

Windows applications are already managing to create such windows. How can i do it in a WinForms application?

Attempt#1

i tried the Show(onwer) + ShowWithoutActivation method:

PopupForm dd = new PopupForm ();
dd.Show(this);

with PopupForm:

public class PopupForm: Form
{
    public PopupForm()
    {
        InitilizeComponent();
    }

    private void InitilizeComponent()
    {
        this.FormBorderStyle = System.Windows.Forms.FormBorderStyle.None;
        this.WindowState = FormWindowState.Normal;
        this.ShowInTaskbar = false;
    }

    protected override bool ShowWithoutActivation
    { get { return true; } }
}

Very nearly solved the problem, but then i ~~discovered~~ was reminded of another property of "popup" windows: they do not ~~take focus from their "owner" form~~ become active when interacted with by mouse or keyboard.

you want it all to be one "popup" or severall "popup" methods? — Moonlight
@Moonlight The concepts should be identical, no matter what the contents are. Once i have a "popup form", i can put whatever contents in it i wish. — Ian Boyd
I have a hard time seeing the difference between this and yesterday's question. My answer there will work for what you are trying to do. — LarsTech
@LarsTech By asking a question about "drop-downs" i was limiting my answers to "drop-downs". i wanted a question (and answers) with wider applicibility. An answer to this question solves the "drop-down" problem - but not necessarily vice-versa. Finally, i wanted a question about "popups", so that anyone searching for "popups" will find this, and not be limited to just "dropdowns". — Ian Boyd

arx arx · Accepted Answer · 2011-12-29T15:51:28

You want an owned window. In your main form:

private void showPopup_Click(object sender, EventArgs e)
{
    PopupForm popupForm = new PopupForm();
    // Make "this" the owner of form2
    popupForm.Show(this);
}

PopupForm should look like this:

public partial class PopupForm : Form
{
    private bool _activating = false;

    public PopupForm()
    {
        InitializeComponent();
    }

    // Ensure the popup isn't activated when it is first shown
    protected override bool ShowWithoutActivation
    {
        get
        {
            return true;
        }
    }

    private const int WM_NCACTIVATE = 0x86;

    [DllImport("user32.dll", CharSet = CharSet.Auto)]
    public static extern IntPtr SendMessage(IntPtr hWnd, int msg, IntPtr wParam, IntPtr lParam);

    protected override void WndProc(ref Message m)
    {
        // The popup needs to be activated for the user to interact with it,
        // but we want to keep the owner window's appearance the same.
        if ((m.Msg == WM_NCACTIVATE) && !_activating && (m.WParam != IntPtr.Zero))
        {
            // The popup is being activated, ensure parent keeps activated appearance
            _activating = true;
            SendMessage(this.Owner.Handle, WM_NCACTIVATE, (IntPtr) 1, IntPtr.Zero);
            _activating = false;
            // Call base.WndProc here if you want the appearance of the popup to change
        }
        else
        {
            base.WndProc(ref m);
        }
    }
}

And make sure that PopupForm.ShowInTaskbar = false.

How to make a "popup" (hint, drop-down, popup) window in Winforms?

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Attempt#1

3 Answers