Screen DC Slowdown Under Windows Vista

[Kev Peel]

Hi Folks,

The following test code works fine under Windows XP and other OSs when %LOCALDC is set to zero (draw on the screen DC), but under Vista it is very slow. It is actually to do with the new "Aero" feature, because when Aero is disabled, the drawing is as fast as normal.

I guess my question is: does anyone know of a workaround or switch to speed up the screen DC drawing when run in Vista's Aero mode? I need the whole screen DC as the actual code will need to draw outside of any windows.

I have included the %LOCALDC flag to demonstrate the speed for Vista users.

#Compile Exe
#Dim All
#Include "WIN32API.INC"
#Include "TYPES.INC"

%THICKNESS = 5          ' Line thickness (must be 1 or greater).
%STYLE = 0              ' Line style (0 solid, 1 animated).
%LOCALDC = 1            ' DC mode (0 use screen DC, 1 Use dialog DC).
Global GHDC As Dword    ' Device context.

'------------------------------------------------------------------------------
' Draws a normal or animated border rectangle to specified DC.
'------------------------------------------------------------------------------
Function DrawOutline(ByVal hDC As THANDLE, _
                     ByVal rc As RECT, _
                     ByVal nThickness As TINT, _
                     ByVal nAnimated As TINT) As TINT
  Local i As TINT
  Local hPen As THANDLE
  Local hOldPen As THANDLE
  Local hBrush As THANDLE
  Local hOldBrush As THANDLE
  Local nDrawMode As TINT
  ' Must have DC and rectangle...
  If (hDC = %NULL) Or (IsRectEmpty(rc) <> %FALSE) Then Exit Function
  If nAnimated Then
     ' Draws a Win95 style animated border...
     For i = 1 To nThickNess
         DrawFocusRect hDc, rc
         InflateRect rc, 1, 1
     Next i
  Else
     ' Draws an old fashioned border...
     ' Select GDI objects, etc,
     hPen = CreatePen(%PS_INSIDEFRAME, 0, 0)
     hOldPen = SelectObject(hDC, hPen)
     hBrush = GetStockObject(%NULL_BRUSH)
     hOldBrush = SelectObject(hDC, hBrush)
     nDrawMode = SetROP2(hDC, %R2_NOT)
     For i = 1 To nThickNess
         ' Draw rectangle
         Rectangle hDC, rc.nLeft, rc.nTop, rc.nRight, rc.nBottom
         InflateRect rc, 1, 1
     Next i
     ' Restore DC
     SetROP2 hDC, nDrawMode
     SelectObject hDC, hOldBrush
     SelectObject hDC, hOldPen
     ' Delete GDI objects
     DeleteObject hPen
  End If
  Function = %TRUE
End Function
 
CallBack Function DLGPROC
  Select Case CbMsg
         Case %WM_INITDIALOG
              ' Select DC to draw into...
              #If %LOCALDC
                  '##### Very fast on vista, but will not draw outside of window...
                  gHDC = GetDC(CbHndl)
              #Else
                  '##### All very slow on Vista...
                  'ghDC = GetDC(%NULL)
                  'ghDC = GetDC(GetDesktopWindow)
                  ghDC = CreateDC("DISPLAY", ByVal %NULL, ByVal %NULL, ByVal %NULL)
              #EndIf
             
         Case %WM_MOUSEMOVE
              Static rcOld As RECT
              Local rc As RECT
              ' MAKE NEW
              GETCURSORPOS ByVal VarPtr(RC) ' Only needs first 8 bytes (left/top).
              #If %LOCALDC
                  ScreenToClient CbHndl, ByVal VarPtr(RC) ' Only needs first 8 bytes (left/top).
              #EndIf
              RC.NRIGHT = RC.NLEFT + 100
              RC.NBOTTOM = RC.NTOP + 100
              ' NO DUPES
              If (RCOLD = RC) Then Exit Function
              ' CLEAR OLD
              DrawOutline ghDC, rcOld, %THICKNESS, %STYLE
              ' DRAW NEW
              DrawOutline ghDC, rc, %THICKNESS, %STYLE
              ' SAVE NEW
              RCOLD = RC
         Case %WM_DESTROY
              #If %LOCALDC
                  ReleaseDC CbHndl, gHDC
              #Else
                  DeleteDC gHDC
              #EndIf
  End Select
End Function

Function PBMain
  Local HDLG As Dword
  Dialog New 0, "DRAG TEST FOR VISTA", , , 400, 300, %WS_OVERLAPPEDWINDOW To HDLG
  Dialog Show Modal HDLG Call DLGPROC
End Function

[Chris Boss]

Kev,

Auro does all sorts of special stuff , so likely it is buffering all writes to DC's so it can do its stuff in the background (like alphablending). Maybe drawing to the desktop DC puts more of a burden on it.

One thing I did notice was your implimentation of getting a DC (in WM_INITDIALOG) and using it until WM_DESTROY is not a good design. It is not recommended.

The only time I get a DC , stores it handle and use it until WM_DESTROY is a memory DC. Screen DC's are quite different. Windows often uses shared DC's among windows and to use a DC the way you do is not good.

You should get the DC in your drawing code, draw with it and immediately free it.

Try this:

' test on Vista (Aero slows it down)
#COMPILE EXE
#DIM ALL
#INCLUDE "WIN32API.INC"
' #Include "TYPES.INC"
%THICKNESS = 5          ' Line thickness (must be 1 or greater).
%STYLE = 0              ' Line style (0 solid, 1 animated).
%LOCALDC = 0            ' DC mode (0 use screen DC, 1 Use dialog DC).
GLOBAL GHDC AS DWORD    ' Device context.
'------------------------------------------------------------------------------
' Draws a normal or animated border rectangle to specified DC.
'------------------------------------------------------------------------------
FUNCTION DrawOutline(BYVAL hDC AS LONG, _
                     BYVAL rc AS RECT, _
                     BYVAL nThickness AS LONG, _
                     BYVAL nAnimated AS LONG) AS LONG
  LOCAL i AS LONG
  LOCAL hPen AS LONG
  LOCAL hOldPen AS LONG
  LOCAL hBrush AS LONG
  LOCAL hOldBrush AS LONG
  LOCAL nDrawMode AS LONG
  ' Must have DC and rectangle...
  IF (hDC = %NULL) OR (IsRectEmpty(rc) <> %FALSE) THEN EXIT FUNCTION
  IF nAnimated THEN
     ' Draws a Win95 style animated border...
     FOR i = 1 TO nThickNess
         DrawFocusRect hDc, rc
         InflateRect rc, 1, 1
     NEXT i
  ELSE
     ' Draws an old fashioned border...
     ' Select GDI objects, etc,
     hPen = CreatePen(%PS_INSIDEFRAME, 0, 0)
     hOldPen = SelectObject(hDC, hPen)
     hBrush = GetStockObject(%NULL_BRUSH)
     hOldBrush = SelectObject(hDC, hBrush)
     nDrawMode = SetROP2(hDC, %R2_NOT)
     FOR i = 1 TO nThickNess
         ' Draw rectangle
         Rectangle hDC, rc.nLeft, rc.nTop, rc.nRight, rc.nBottom
         InflateRect rc, 1, 1
     NEXT i
     ' Restore DC
     SetROP2 hDC, nDrawMode
     SelectObject hDC, hOldBrush
     SelectObject hDC, hOldPen
     ' Delete GDI objects
     DeleteObject hPen
  END IF
  FUNCTION = %TRUE
END FUNCTION
CALLBACK FUNCTION DLGPROC
  SELECT CASE CBMSG
         CASE %WM_INITDIALOG
              ' Select DC to draw into...
         CASE %WM_MOUSEMOVE
              #IF %LOCALDC
                  '##### Very fast on vista, but will not draw outside of window...
                  gHDC = GetDC(CBHNDL)
              #ELSE
                  '##### All very slow on Vista...
                  'ghDC = GetDC(%NULL)
                  'ghDC = GetDC(GetDesktopWindow)
                  ghDC = CreateDC("DISPLAY", BYVAL %NULL, BYVAL %NULL, BYVAL %NULL)
              #ENDIF
              
              STATIC rcOld AS RECT
              LOCAL rc AS RECT
              ' MAKE NEW
              GETCURSORPOS BYVAL VARPTR(RC) ' Only needs first 8 bytes (left/top).
              #IF %LOCALDC
                  ScreenToClient CBHNDL, BYVAL VARPTR(RC) ' Only needs first 8 bytes (left/top).
              #ENDIF
              RC.NRIGHT = RC.NLEFT + 100
              RC.NBOTTOM = RC.NTOP + 100
              ' NO DUPES
              IF (RCOLD = RC) THEN EXIT FUNCTION
              ' CLEAR OLD
              DrawOutline ghDC, rcOld, %THICKNESS, %STYLE
              ' DRAW NEW
              DrawOutline ghDC, rc, %THICKNESS, %STYLE
              ' SAVE NEW
              RCOLD = RC
              #IF %LOCALDC
                  ReleaseDC CBHNDL, gHDC
              #ELSE
                  DeleteDC gHDC
              #ENDIF
              
         CASE %WM_DESTROY
  END SELECT
END FUNCTION
FUNCTION PBMAIN
  LOCAL HDLG AS DWORD
  DIALOG NEW 0, "DRAG TEST FOR VISTA", , , 400, 300, %WS_OVERLAPPEDWINDOW TO HDLG
  DIALOG SHOW MODAL HDLG CALL DLGPROC
END FUNCTION

I don't know if this will improve the Vista performance or not, but it is the right way to draw (by using a DC and releasing it in the draw code).

[Tyrone W. Lee]

DC's

It could also be video memory use. I have a graphics engine written on a Win2K machine. It is 100% GDI, and cranks at 100FPS on 800Mhz Win2K, 512Mb Ram, ATI 7500 (32MB).

I just recently bought a WinXP machine and its twice as fast but running at only 64FPS. All of the WinXP skins use alot of memory and apear to slow down GDI drawing.

I suspect Vista is 10times worse. Its clearly a resource hog. The OS is using more of your PC than you/your apps. (in my opinion VISTA is useless)

If M$ continues this path it will only get slower/more bloated.

Tye

[Kev Peel]

Chris,

The screen DC storage does not make a difference as this is just some example code. It is Aero causing the slowdown but I do not know how to speed it up.

Tyrone,

The "dragging" action will be done directly by the user, so it doesn't matter really how much GFX % is being used. I know Vista is a hog but I need this problem solved.

Somebody must have come across it before as there is a lot of code out there that draws to the screen DC and will have this slowdown. One app that doesn't slow down (not surprisingly!) is Microsoft's Wordpad utility. Dragging the bars around in Wordpad, which draws outside of it's window, works at the normal speed. I haven't yet tested the other MFC apps that also use the docking bar control (I think Wordpad is an MFC app). I will have to do a bit more research to see how they do it.

[Chris Boss]

Kev,

Did you try the modified version of code I posted above on Vista ?

[Patrice Terrier]

Avoid using the obsolete GDI when dealing with DWM (Vista AERO)
GDIPLUS is the way to go.

And use the double buffer technic.

[Dominic Mitchell]

See the following links for the reason why GetDC(null) takes a performance hit.
http://blogs.msdn.com/greg_schechter...02/588934.aspx
http://blogs.msdn.com/nickkramer/arc...07/571162.aspx

[Kev Peel]

Hi all,

Chris,
Tried the code. Thanks but it makes no difference.

Patrice,
The code will be part of a custom control. If it was part of a main app, then I would go the GDIPlus route, but I do not want any dependencies for the new DLL (unless I could load and use GDIPlus if it's there already?).

Dominic,
Useful info. Thanks. I kinda thought that was the problem but I'm still curious about how MFC implemented the direct draw to screen as seen in Wordpad. It works really smooth.

As a side note, the GDI might be 'obsolete' but I believe Microsoft have made a big mistake by causing these incompatibilities. They should, at the very least, have provided a workaround for this crappy VISTA slowdown.

[Patrice Terrier]

(unless I could load and use GDIPlus if it's there already?).

IF VISTA() = %TRUE THEN
UseGDIPLUS
ELSE
UseGDI
END IF

I posted several examples on Jose Roca's forum related to the use of VISTA DWM (Device Window Manager), and I showed how to write on the composited GLASS section.

Once you know how to use it, you will see all the benefit of using DWM.

As an example, download the Crystal demo there:
http://www.jose.it-berater.org/smffo...p?topic=1372.0
and see how fast it could be with VISTA while in AERO GLASS mode.

[Dominic Mitchell]

but I'm still curious about how MFC implemented the direct draw to screen as seen in Wordpad.

Microsofts' Wordpad? Which command accesses this feature?

[Kev Peel]

Move the toolbars in Wordpad. The rectangle draws on the screen.

Since I have VS 2005, I looked at MFC's C++ source (dockcont.cpp) it uses LockWindowUpdate and GetDCEx (DCX_WINDOW, DCX_CACHE, DCX_LOCKWINDOWUPDATE flags) with the desktop window but it doesn't seem to have any effect. Strange.

I'm missing something, or the "CWnd" object MFC uses is doing more "behind the scenes"

[Dominic Mitchell]

OK. I also do the same in Phoenix with the docking container.
I will have to test on Vista to see if I have the same problem.
In my case, if there is a problem I can move the full docking window when it is being dragged, and draw a rectangle iff the container is over or near the target area of the host window(GetDC(hWndHost)).

[Chris Boss]

Kev,

Dominics post above (to msdn blogs) answers the question.

Drawing within a window is fine, but attempting to draw on the screen DC, when Aero is running is problematic. XORing requires bytes from video memory to be read when drawing and it appears that Aero doesn't like this.

There is a video manager of sorts in Aero which buffers all windows so drawing on a window DC, you are never drawing on the screen DC. Aero buffers the draws and then it takes care of putting the image on the screen. This allows all the alphablending tricks it does.

By attempting to draw on the screen (or desktop), you are trying to work around the video manager and obviously it does not like it.

Drawing on a window DC is fine though.

So the question is, how to get around this quirk of Aero ?

Don't draw on the screen directly (ie. GetDC(NULL)).

You can create a custom window class for the rectangular image you are trying to move around. This window can use a region to define the visible area, so the rest is transparent. When the window is resized, simply generate a new window region to match.

I have used this technique successfully with my drag handle control. It has 8 drag handles (one each on the four corners and four sides). When the control is resized, the control creates a new region on the fly and then redraws itself.

Using this technique you only draw on an actual window DC. The region is what allows it to appear transparent. By keeping it at the top of the zorder, it will stay above all other windows.

[Dominic Mitchell]

You can create a custom window class for the rectangular image you are trying to move around.
This window can use a region to define the visible area, so the rest is transparent. When the
window is resized, simply generate a new window region to match.

I use the same technique to allow floating windows to dock in Pheonix when the "No Background"
option is set. The "No Background" option allows the user to see other applications underneath
Phoenix. As Chris points out, it works very well, and resizing a rectangular hole is very fast.

[Kev Peel]

Thanks, but I have managed to get it working without using an additional window. Basically, you lock the desktop window and get it's DC, then draw onto it using XOR regions and PatBlt. I was using the API's DrawFocusRect() and Rectangle() functions, with a NULL brush - this method was very slow.

I found out how Microsoft did it by looking at the functions in MFC's dockcont.cpp. I implemented their method and it now works fine with any size line width and no speed penalty under Vista.

[Dominic Mitchell]

I was using the API's DrawFocusRect() and Rectangle() functions, with a NULL brush

In my case I use a path and FillPath, so I am probably OK.

[Kev Peel]

Finally got around to posting my solution

http://www.powerbasic.com/support/pbforums/showthread.php?p=292336