Dragging a Popup Window

BrentDT
Originally published in NL #143

Brent shares a demo that shows how to allow the user to drag a popup window. A popup has no titlebar, so it requires a little extra coding to make this possible.

Brent has released this code into the public domain with the following explanation.

This demo works by trapping a left-drag inside the GRAPHICBOX, then tricks the dialog window into believing you are dragging its (non-existent) title bar. The benefit of using this technique (over calling the MoveWindow API inside a similar event handler) is that this automatically takes into account the user's preference for "show window contents while dragging."

Demo

 NoMainWin 
 
 WindowWidth = 400 
 WindowHeight = 300 
 UpperLeftX = (DisplayWidth - WindowWidth) / 2 
 UpperLeftY = (DisplayHeight - WindowHeight) / 2 
 
 GraphicBox #demo.gfx, 0, 0, WindowWidth, WindowHeight 
 StyleBits #demo.gfx, 0, _WS_BORDER, 0, 0 
 
 Open "Demo" For Dialog_Popup As #demo 
 
 #demo "TrapClose demo.Close" 
 #demo.gfx "When leftButtonMove demo.gfx.leftButtonMove" 
 #demo.gfx "Down; Fill ButtonFace; BackColor ButtonFace" 
 #demo.gfx "\\\ Try dragging me around!" 
 #demo.gfx "\\ Press Alt+F4 to close." 
 #demo.gfx "Flush" 
 
 Wait 
 
 Sub demo.Close demo$ 
 Close #demo$ 
 End 
 End Sub 
 
 Sub demo.gfx.leftButtonMove demo.gfx$, X, Y 
 demo$ = Word$(demo.gfx$, 1, ".") 
 
 CallDLL #user32, "ReleaseCapture", _ 
 r As void 
 
 hWnd = HWnd(#demo$) 
 CallDLL #user32, "SendMessageA", _ 
 hWnd As ULong, _ 
 _WM_NCLBUTTONDOWN As ULong, _ 
 _HTCAPTION As Long, _ 
 0 As Long, _ 
 r As Long 
 End Sub

DraggingAPopupWindow

Dragging a Popup Window

Demo