Thread: Sending WM_SETCURSOR to different windows

Let's see if I can get this answered here instead...

A little background just in case you are wondering why I am doing this:

In C#, Application.UseWaitCursor changes the cursor shape to the default hourglass shape without waiting for WM_SETCURSOR response. This means that the cursor shape doesn't last. It is set again immediately to Cursor.Current based on whatever control my mouse cursor is currently hovering.

As I understand this is by design and I'm fine with it. It only means I have to manually send WM_SETCURSOR after Application.UseWaitCursor. Without doing it, I cannot have the behavior I intend below.

.............

I need for the mouse cursor to change to an hourglass while waiting for a form to load that it's taking a few seconds to display. This form does some data processing before displaying its contents.

This is what I came up with.

Code:

static class NativeMethods
{
    [DllImport("user32.dll")]
    private static extern IntPtr SendMessage(IntPtr hWnd, int msg, IntPtr wp, IntPtr lp);

    public static void SwitchWaitCursor(IntPtr handle)
    {
        Application.UseWaitCursor = !Application.UseWaitCursor;
        SendMessage(handle, 0x20, handle, (IntPtr)1);
    }

    /*...*/
}

And I use it like this:

Code:

// When calling the slow form

NativeMethods.SwitchWaitCursor(this.Handle);
using (SlowForm diag = new SlowForm())
{
    diag.ShowDialog(this);
}


// OnShow() of the SlowForm

private void SlowForm_Shown(object sender, EventArgs e)
{
    NativeMethods.SwitchWaitCursor(this.Handle);
}

It is working exactly as expected. However, I do have one thought nagging me. Is it alright in this SendMessage usage pattern, for hWnd to refer to two different windows?