رنگ کنترل رسمی ( Custom Control) در SubClaasing

ساب کلاس کردن کنترل ترسیمی  ( تنها یک کنترل ) 

Type  cz As SIZE

cx As Long ' Width

cy As Long  ' Height

End Type 

Type CustCtrl

'Foreground text colour

crForeGnd As Long 

'Background text colour

crBackGnd As Long 

'The font

hFont As Long 

'The control's window handle

hwnd As Long 

End Type 

Painting the control

Whenever windows wants us to update the contents of our window (the client area), a WM_PAINT message will be sent. So, whenever the WM_PAINT message is received, we need to call our control’s painting routine.

case WM_PAINT

 CustCtrl_OnPaint ccp,wParam, lParam

(CustCtrl_OnPaint(ccp As CustCtrl,wParam,lParam

Dim  hdc As Long

Dim ps As PAINTSTRUCTHANDLE

Dim hOldFont As Long

Dim szText As String*200

Dim rc As RECT

Get a device context for this window'

(hdc=BeginPaint(ccp.hwnd,ps

Set the font we are going to use'

(hOldFont=SelectObject(hdc,ccp.hFont

Set the text colours'

SetTextColor hdc,ccp.crForeGnd

SetBkColor  hdc,ccp.crBackGnd

Find the text to draw'

(GetWindowText ccp.hwnd,szText, Len(szText

Work out where to draw'

GetClientRect ccp.hwnd,rc

computes the width and height of the '

.specified string of text'

GetTextExtentPoint32 hdc,szText, len(szText),sz

Center the text'

x=(rc.right-sz.cx)/2

y=(rc.bottom-sz.cy)/2

Draw the text'

ETO_OPAQUE'

The current background color should be used to fill'

the rectangle'

ExtTextOut hdc,x,y,ETO_OPAQUE,rc,szText,len(szText),0

Restore the old font when we have finished'

SelectObject hdc,hOldFont

Release the device context'

EndPaint ccp.hwnd,ps

return 0

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The GWL_USERDATA area

Every window in the system has a 32bit integer which can be set to any value. This 4 byte storage area is enough to store a pointer to a structure. We set this integer using SetWindowLong, and retrieve the integer using GetWindowLong. Using this technique, our function will look like this:

(GetCustCtrl(hwnd
return=GetWindowLong(hwnd,GWL_USERDATA

(SetCustCtrl(ByVal hwnd As Long,ByRef ccp As CustCtrl

SetWindowLong hwnd,GWL_USERDATA,ccp

This method is usually used when subclassing a control

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Memory allocated by HeapAlloc is not movable. The address returned by HeapAlloc is valid until the memory block is freed or reallocated; the memory 

.block does not need to be locked

To free a block of memory allocated byHeapAlloc, use 

.the HeapFree function

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Our custom control will change colour whenever the user clicks the mouse on it. Therefore the next message handler will be for the 

.WM_LBUTTONDOWNmessage

case WM_LBUTTONDOWN

CustCtrl_OnLButtonDown ccp, wParam, lParam


CustCtrl_OnLButtonDown(ByRef ccp As 

(CustCtrl,wParam,lParam
(col=RGB(rnd()*256,rnd()*256,rnd()*256 

Change the foreground colour'
ccp.crForeGnd=col
Use the inverse of the foreground colour'

(ccp.crBackGnd=((col) And &Hffffff
Now redraw the control'
InvalidateRect ccp.hwnd,0,0
UpdateWindow ccp.hwnd
return 0

WM_MOUSEACTIVATE=&H21

'Activates the window, and does not discard the mouse'

.message
MA_ACTIVATE =1

case WM_MOUSEACTIVATE
    SetFocus hwnd
    return MA_ACTIVATE