Multiple-Pane Splitter Bar
By Bill T.
August 12, 1999

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This bit of code will show you a very easy way to implement a vertical splitter
(as in explorer).  Using this method, the parent window handles all of the 
resizing.  The child windows are positioned so that only the space between them 
shows through.  This space (which is part of the parent) is the splitter bar.  

When you create the main window's class, you may want to change the hCursor 
member to IDC_SIZEWE or something similar so it changes when the mouse is put 
over it.  The iSeparatorPos variable holds the current x-position of the splitter
bar. 

Of course, this is not the only (or best) way to implement these splitter bars. 
For instance, this method may have difficulty with more than 2 panes, or when 
there are horiontal and vertical splitters... 

Note this is only a sample of how it might be implememnted, and is not an
actual, working implementation.


; These go into the MainWindow Procedure: 
	 mov    eax, uMsg 
	 cmp    eax, WM_MOUSEMOVE 
	 je     wmmousemove 
	 cmp    eax,WM_LBUTTONDOWN 
	 je     wmlbuttondown 
	 cmp    eax,WM_LBUTTONUP 
	 je     wmlbuttonup  
	 ... 

; mouse is moved 
wmmousemove: 
	test   wParam, MK_LBUTTON 
	jz     return 
	; left button is down, move the splitter 
	mov    eax, lParam 
	and    eax, 0000FFFFh ;LOWORD(lParam = xpos) 
	mov    iSeparatorPos, eax  
	; get the dimensions of the application window 
	invoke GetWindowRect, hWndMainApp, addr rect 
	; re-size the left pane 
	mov    eax, iSeparatorPos 
	dec    eax 
	invoke MoveWindow, hWndLeftPane, 0, 0, eax, rect.bottom, TRUE 
	; now re-size the right pane 
	mov    eax, iSeparatorPos 
	inc    eax 
	invoke MoveWindow, hWndLRightPane, eax, 0, rect.right, rect.bottom, TRUE 
	jmp    return 

; Left mouse button is pressed 
wmlbuttondown: 
	invoke SetCapture, hWnd  
	jmp    return 

; Left mouse button is released  
wmlbuttonup: 
	invoke ReleaseCapture 
	jmp    return

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Copyright (C) 1999
Bill T.  (billasm@usa.net)