Amadeusz Wieczorek Amadeusz Wieczorek - 2 months ago 22
C# Question

Activate a form and process button click at the same time?

I'm using Windows Forms in C#.

I have a main form with a couple of toolbars that contain toolStripButtons. After working with another form that contains data, the main form loses focus and clicking on a toolStripButton does not trigger OnClick event: the first click activates the main form, and only the second click actually pushes the button. I need the user to click a button only once to trigger a Click event, any ideas on how to do that? Thanks.

Notes:


  • I was using MDI and there were no problems clicking on the parent's form buttons. But now the paramount is to have forms freely floating across multiple displays.

  • The worker forms have the main form as the Owner property, this way they stay on top of the main form.

  • When I click on the button of an inactive form, none of MouseHover, MouseEnter, MouseDown nor MouseUp fires. It's just main form's Activate event that fires.

  • There is a treeView (inside a tabControl, inside a splitContainer, inside a panel), on the main form. Its items are selected upon a first mouse click, even if the main form is inactive. I guess not all controls are equal!


Answer

What you need to do is create a class that inherits ToolStrip and handles the WndProc. This is one way to do it. There are others.

private class MyToolStrip : ToolStrip
{
    private const uint WM_LBUTTONDOWN = 0x201;
    private const uint WM_LBUTTONUP   = 0x202;

    private static bool down = false;

    protected override void WndProc(ref Message m)
    {
        if (m.Msg == WM_LBUTTONUP && !down)
        {
            m.Msg = (int)WM_LBUTTONDOWN;
            base.WndProc(ref m);
            m.Msg = (int)WM_LBUTTONUP;
        }

        if (m.Msg == WM_LBUTTONDOWN) down = true;
        if (m.Msg == WM_LBUTTONUP)   down = false;
        base.WndProc(ref m);
    }
}

I've also seen this solution:

protected override void WndProc(ref Message m)
{
    // WM_MOUSEACTIVATE = 0x21
    if (m.Msg == WM_MOUSEACTIVATE && this.CanFocus && !this.Focused)
        this.Focus();
    base.WndProc(ref m);
}

I ran into this at the last place I worked, I think the solution I came up with worked more like the latter, but I don't have access to the exact code I used.