Get the coordinates of a WM_NCHITTEST message?

Question

How do I get the coordinates of a WM_NCHITTEST message in C# code?
I\'d love to get the fastest way, because performance is a requirement.

Answer 1

From MSDN:

wParam
This parameter is not used.

lParam
The low-order word specifies the x-coordinate of the cursor. The coordinate is relative to the upper-left corner of the screen.
The high-order word specifies the y-coordinate of the cursor. The coordinate is relative to the upper-left corner of the screen.

So you just need to extract the low-order and high-order words from the message's lParam:

int x = lParam.ToInt32() & 0x0000FFFF;
int y = (int)((lParam.ToInt32() & 0xFFFF0000) >> 16)
Point pos = new Point(x, y);

I wouldn't worry too much about performance, since these operations are just bit level arithmetic...

Note that these coordinates are relative to the screen. If you want coordinates relative to a control (or form), you can use the PointToClient method:

Point relativePos = theControl.PointToClient(pos);