Modify mouse crosshairs code to be on top of form?

Question

On a blank winform code can be added to show lines that intersect (crosshairs) at the mouse pointer. The problem is that the lines don't show (or are partially hidden) by controls on the form (ie listview, splitcontainer, buttons).

How would I modify the code below to show on-top (bring to front...) of all the controls present on the form?

int lastX = 0;
int lastY = 0;
private void Form1_MouseMove(object sender, MouseEventArgs e)
{
Region r = new Region();
r.Union(new Rectangle(0, lastY, this.Width, 1));
r.Union(new Rectangle(lastX, 0, 1, this.Height));
this.Invalidate(r);
this.Update();
Graphics g = Graphics.FromHwnd(this.Handle);

g.DrawLine(Pens.Chocolate, 0, e.Y, this.Width, e.Y);
g.DrawLine(Pens.Chocolate, e.X, 0, e.X, this.Height);
lastX = e.X;
lastY = e.Y;
}

private void Form1_MouseLeave(object sender, EventArgs e)
{
this.Invalidate();
}

Answer 1

Hi, Please just try first sending to back(Control.SendToBack()) the controls on the form (ie listview, splitcontainer, buttons). Put this at the FormLoad event. I have experimented the same nightmare with a Windows MDI application. Hope that helps,

Answer 2

Enumerate through the desired controls and call the .BringToFront(); function on them.

listBox1.BringToFront();

Answer 3

According to the documentation, the region object should be in world co-ordinates, you're passing in client co-ordinates. Use Control.PointToScreen to map the rectangles' top left coordinate to world space.

I'd also be tempted to defer the drawing to the OnPaint method.

Answer 4

You need a transparent window that's on top of all the other controls. The only way to get one is by overlapping the form with another form, made transparent with its TranparencyKey property. You'll find sample code for this in my answer in this thread.