Stretch bitmap to dialog..

[Borje Hagsten]

I was playing around with this a bit and thought I'd ask: is following
code safe? I load a bitmap in PBMAIN and store the handle globally so
it can be used for stretching the bitmap in WM_ERASEBKGND. Somehow, I
get a feeling there's something missing here, like - the global handle,
shouldn't that one also be released? No leaks as far as I can tell, so
maybe this is the way to do it.

BTW, discovered that using BeginPaint in WM_PAINT doesn't work for this
purpose. Picture becomes a mess of different sizes after a few resizing
events and not even using FillRect on hDC helps. Think Semen found some
strange things with BeginPaint a while ago too, maybe that was it?
Following works though:

'¤¤¤¤¤¤¤¤¤¤¤¤¤¤¤¤¤¤¤¤¤¤¤¤¤¤¤¤¤¤¤¤¤¤¤¤¤¤¤¤¤¤¤¤¤¤¤¤¤¤¤¤¤¤¤¤¤¤¤¤¤¤¤¤¤¤¤¤
' Declares
'¤¤¤¤¤¤¤¤¤¤¤¤¤¤¤¤¤¤¤¤¤¤¤¤¤¤¤¤¤¤¤¤¤¤¤¤¤¤¤¤¤¤¤¤¤¤¤¤¤¤¤¤¤¤¤¤¤¤¤¤¤¤¤¤¤¤¤¤
#COMPILE EXE
#INCLUDE "WIN32API.INC"
GLOBAL hBitMap AS LONG 'keep this one globally to enable rezising
DECLARE CALLBACK FUNCTION DlgProc() AS LONG
 
'¤¤¤¤¤¤¤¤¤¤¤¤¤¤¤¤¤¤¤¤¤¤¤¤¤¤¤¤¤¤¤¤¤¤¤¤¤¤¤¤¤¤¤¤¤¤¤¤¤¤¤¤¤¤¤¤¤¤¤¤¤¤¤¤¤¤¤¤
' Create dialog and controls, etc
'¤¤¤¤¤¤¤¤¤¤¤¤¤¤¤¤¤¤¤¤¤¤¤¤¤¤¤¤¤¤¤¤¤¤¤¤¤¤¤¤¤¤¤¤¤¤¤¤¤¤¤¤¤¤¤¤¤¤¤¤¤¤¤¤¤¤¤¤
FUNCTION PBMAIN () AS LONG
 LOCAL hDlg AS LONG, txt AS STRING
 
  DIALOG NEW 0, "AutoStretch test",,, 195, 50, %WS_CAPTION OR %WS_OVERLAPPEDWINDOW, 0 TO hDlg
 
  'txt = "c:\pbdll60\samples\smtp\smtp.bmp" & CHR$(0) 'change to whatever picture you have..
  'txt = "c:\windows\suback.bin" & CHR$(0) 'found this one in Win98 - heaven background..
  txt = "c:\windows\logow.sys" & CHR$(0)   'Windows shutdown screen..
  hBitMap = LoadImage(0, BYVAL STRPTR(txt), %IMAGE_BITMAP, 0, 0, %LR_LOADFROMFILE) 'load with actual size
 
  DIALOG SHOW MODAL hDlg CALL DlgProc
END FUNCTION
 
'¤¤¤¤¤¤¤¤¤¤¤¤¤¤¤¤¤¤¤¤¤¤¤¤¤¤¤¤¤¤¤¤¤¤¤¤¤¤¤¤¤¤¤¤¤¤¤¤¤¤¤¤¤¤¤¤¤¤¤¤¤¤¤¤¤¤¤¤
' Main callback
'¤¤¤¤¤¤¤¤¤¤¤¤¤¤¤¤¤¤¤¤¤¤¤¤¤¤¤¤¤¤¤¤¤¤¤¤¤¤¤¤¤¤¤¤¤¤¤¤¤¤¤¤¤¤¤¤¤¤¤¤¤¤¤¤¤¤¤¤
CALLBACK FUNCTION DlgProc() AS LONG
 
  IF CBMSG = %WM_ERASEBKGND THEN
     LOCAL hDC AS LONG, memDC AS LONG, wRect AS RECT, bm AS BITMAP
     GetClientRect CBHNDL, wRect                  'get control's size
     GetObject hBitmap, SIZEOF(bm), bm            'get bitmap properties
 
     hDC = GetDc(CBHNDL)                          'get current DC
        memDC = CreateCompatibleDC(hDC)           'create temporary DC
        SelectObject memDC, hBitmap               'select bitmap in tmpDC
 
        StretchBlt hDC, 0, 0, wRect.nright, wRect.nbottom, _
                   memDC, 0, 0, bm.bmWidth, bm.bmHeight, %SRCCOPY
 
        DeleteObject SelectObject(memDC, hBitmap) 'delete bitmap object, but keep handle
        DeleteDC memDC                            'delete temporary DC
     ReleaseDC CBHNDL, hDC
     FUNCTION = 1
  END IF
 
END FUNCTION

------------------

[Semen Matusovski]

Borje --
I approx. understood, how BeginPaint works.

Below a corrected code (it seems to me works fine under Win2000)

   #Compile Exe
   #Register None
   #Dim All
   #Include "WIN32API.INC"

   $Text = "c:\pb\pbdll60\samples\tcp\smtp.bmp" 'change to whatever picture you have..
   
   CallBack Function DlgProc() As Long
      Select Case CbMsg
         Case %WM_INITDIALOG
            Dim hBitMap As Static Long
            hBitMap = LoadImage(0, $Text, %IMAGE_BITMAP, 0, 0, %LR_LOADFROMFILE)
            
         Case %WM_DESTROY
            DeleteObject hBitMap
            
         Case %WM_SIZE ' EXITSIZEMOVE ' to reduce redrawing
            InvalidateRect CbHndl, ByVal 0, 1
            
         Case %WM_ERASEBKGND
            Dim MemDC As Long, rc As RECT, bm As BITMAP
            GetClientRect CbHndl, rc
            GetObject hBitmap, SizeOf(bm), bm     ' get bitmap properties
            MemDC = CreateCompatibleDC(CbWparam)  ' create temporary DC
            SelectObject MemDC, hBitmap           'select bitmap in tmpDC
            StretchBlt CbWparam, 0, 0, rc.nRight, rc.nBottom, MemDC, 0, 0, bm.bmWidth, bm.bmHeight, %SRCCOPY
            DeleteDC MemDC                        'delete temporary DC
            Function = 1
        End Select
   End Function
   

   Function PbMain
      Dim hDlg As Long
      Dialog New 0, "AutoStretch test",,, 195, 50, %WS_CAPTION Or %WS_OVERLAPPEDWINDOW, 0 To hDlg
      Dialog Show Modal hDlg Call DlgProc
   End Function

------------------
E-MAIL: [email protected]

[Borje Hagsten]

Thanks, Semen. Yes, looks much better your way and of course - wParam
gives handle to DC directly there. But why WM_SIZE? I get same result
without. Isn't WM_ERASEBKGND always triggered at resizing? I get two
WM_ERASE.. with your code. Add "BEEP : SLEEP 100" to WM_ERASE and see..

------------------

Okay, just tested without WM_SIZE and understand. Exactly same problem
I found with BeginPaint - old picture isn't cleared. Must be something
with the bitmap handle after all, because the code I posted works
without WM_SIZE and double WM_ERASE.. Weird.



[This message has been edited by Borje Hagsten (edited May 02, 2001).]

[Borje Hagsten]

Nope, it's wParam. Try your code without WM_SIZE, but use GetDC instead.
No problems and no double calls needed. So fault is in the DC Windows
gives in message handler.

------------------

[Semen Matusovski]

Borje --
GetDC works, because it's ignores Validate/Invalidate.
Quick reconstruction (alternative)

   #Compile Exe
   #Register None
   #Dim All
   #Include "WIN32API.INC"
   $Text = "c:\pb\pbdll60\samples\tcp\smtp.bmp" 'change to whatever picture you have..
   CallBack Function DlgProc() As Long
      Select Case CbMsg
         Case %WM_INITDIALOG
            Dim hBitMap As Static Long
            hBitMap = LoadImage(0, $Text, %IMAGE_BITMAP, 0, 0, %LR_LOADFROMFILE)
         Case %WM_DESTROY
            DeleteObject hBitMap
         Case %WM_ERASEBKGND
            InvalidateRect CbHndl, ByVal 0, 0
            Function = 1
         Case %WM_PAINT
            Dim MemDC As Long, rc As RECT, bm As BITMAP, ps As PAINTSTRUCT
            BeginPaint CbHndl, ps
            GetClientRect CbHndl, rc
            GetObject hBitmap, SizeOf(bm), bm     ' get bitmap properties
            MemDC = CreateCompatibleDC(ps.hDC)  ' create temporary DC
            SelectObject MemDC, hBitmap           'select bitmap in tmpDC
            StretchBlt ps.hDC, 0, 0, rc.nRight, rc.nBottom, MemDC, 0, 0, bm.bmWidth, bm.bmHeight, %SRCCOPY
            DeleteDC MemDC                        'delete temporary DC
            EndPaint CbHndl, ps
            
        End Select
   End Function
   Function PbMain
      Dim hDlg As Long
      Dialog New 0, "AutoStretch test",,, 195, 50, %WS_CAPTION Or %WS_OVERLAPPEDWINDOW, 0 To hDlg
      Dialog Show Modal hDlg Call DlgProc
   End Function

[This message has been edited by Semen Matusovski (edited May 02, 2001).]