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So, you want to drag a window without using the real title bar?
I have seen lots of people using their own code in the mouse move event to do this, and I've even done it myself.
Until I found the following code:
Declare Function ReleaseCapture Lib "user32" () As Long Declare Function PostMessage Lib "user32" Alias "PostMessageA" _ (ByVal hWnd As Long, ByVal wMsg As Long, ByVal wParam As Long, _ lParam As Any) As Long Const WM_NCLBUTTONDOWN = &HA1 Const HTCAPTION = 2
And when you want to do the dragging itself:
ReleaseCapture PostMessage Form.hWnd, WM_NCLBUTTONDOWN, HTCAPTION, ByVal 0&
This should go in the mousedown event of the control/object you want to drag the window by.
It has various advantages over home grown code:
- It's faster and rarely suffers from flickering.
- It's easier. Two lines once compared to a huge routine (or two?)
- It obeys the windows rules and settings on drawing windows while moving.
The only problems I have found with this are:
- It doesn't work when you use the right mouse button (although this may be just Windows XP)
- You cant limit it to only moving in one direction
If you want to use this to drag a control, just replace Form.hWnd with Control.hWnd. This will NOT work for dragging windowless controls like Labels or ImageBoxes but you can still drag a windowed control by them.
A small variation of this code can be used to resize forms and controls by just replacing HTCAPTION with HTBOTTOMRIGHT:
Const HTBOTTOMRIGHT = 17
ReleaseCapture PostMessage Form.hWnd, WM_NCLBUTTONDOWN, HTBOTTOMRIGHT, ByVal 0&