WM_PAINT for single control in DDT callback

[Simon Morgan]

i am drawing graphics on a static control in a ddt dialog, which has other controls
that are looked after by ddt itself. what is the correct way to process the wm_paint
message in the dialog's callback procedure?

pseudocode:

callback function mydlgproc
  
  select case cbmsg
    ...
    case %wm_paint
      control handle cbhndl, %idstatic to hstatic
      hdc=beginpaint(hstatic,lppaint)
          ....   gdi drawing commands using hdc
      endpaint hstatic,lppaint
      function=???

  end select
end function

in lance's example at:
http://www.powerbasic.com/support/pb...ead.php?t=1625

he puts function=1 to stop ddt doing its own wm_paint processing, but in that
example he has updated the whole dialog - there are no other controls.
in my case, function=1 stops ddt from drawing its own buttons.

the problem i get is that sometimes my graphics control comes out plain grey
(particularly after a screen save). this is probably because ddt has done its
screen update first and has validated the entire dialog area, leaving my beginpaint
routine no remaining unvalidated areas on which to draw. conversely, if i get
to draw first, my endpaint validates my static control, usually preventing ddt
from painting over it.

how do i get my wm_paint to run before ddt paints the remainder of the dialog?
should i use getdc in place of beginpaint?

regards, simon

[Jules Marchildon]

Simon,

You should subclass the static control and allow it to paint itself.
By doing it the above method, you will need to add some additional styles
to the Parent and child controls, like %WS_CLIPCHILDREN, %WS_CLIPSIBLINGS.
This sets some clipping regions for you when you use the above wm_paint
handler. If that doesn't work using the above method, they you will need
to refresh each control by doing a SetWindowPos with the NOMOVE flag.
I think it would be much cleaner if you subclass the static control.

HTH
Regards,
Jules

[Simon Morgan]

Thanks, Jules

I already had %WS_CLIPCHILDREN in the style of the static control used for drawing,
but adding this to the style in the DIALOG NEW statement has cured the
probem most of the time. Sometimes DDT doesn't update the remainder of the dialog
properly, presumably because my BeginPaint/EndPaint has validated the entire dialog,
so DDT and Windows think it has all been done.

I guess I have to subclass to do the job properly, as you suggest.

Regards, Simon

[Simon Morgan]

In case anyone is interested, the following (pseudo)code seems to work:

CALLBACK FUNCTION MyDlgProc
  SELECT CASE CBMSG
    ...    
    CASE %WM_PAINT
      RedrawWindow CBHNDL, BYVAL %Null, BYVAL %Null, _
        %RDW_NOINTERNALREPAINT OR %RDW_VALIDATE OR %RDW_UPDATENOW
        'redraw and validate whole dialog without generating a fresh WM_PAINT message   
      CONTROL HANDLE CBHNDL, %IDstatic TO hStatic
      hDC=GetDC (hStatic)  
         'redraw my picture control
          ....   GDI drawing commands using hDC
      ReleaseDC hStatic,hDC
      FUNCTION=%True   'tell DDT not to do its own repaint
  END SELECT
END FUNCTION

This is rather messy, so sub-classing would probably be better as Jules says.

This must be quite a common requirement (a GDI picture on a DDT dialog). Has
anyone got any better code?

Regards, Simon


P.S. The above code does not work in all circumstances. I do not recommend
using it (and neither does Lance ).


[This message has been edited by Simon Morgan (edited June 04, 2001).]