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Transparent label bkgrd on gradient dialog

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  • Transparent label bkgrd on gradient dialog

    I'm using some gradient code to paint my dialog background in the WM_PAINT event. I'm using the code below to color the labels
              SELECT CASE GetDlgCtrlID(CBLPARAM) 
                CASE 500 TO 1500
                  SetBkMode CBWPARAM, %Transparent
                  SelectObject CBWPARAM, hFontCap 
                  FUNCTION = GetStockObject(%NULL_BRUSH)
    When my dialog comes up the background is gradient from rgb(202,214,255) down to white but the label background is rgb(202,214,255). If I click a button, the label background turns to the shade of the gradient at that position on the screen which is the way I want it to start out.

    I would like the label background to be transparent, showing the shade behind it from initialization. I would also like to try making the label background itself a gradient but will probably have to subclass the control to do that.

    Bob Mechler

  • #2
    Doing a Dialog Redraw hdlg just before my first textbox got focus did the trick but I'd like somewhere in the dialog call back to be the place where it's called.

    Bob Mechler


    • #3
      Have you considered PTFC?


      • #4
        Use the WS_EX_TRANSPARENT extended window style with the label controls, so they repaint after the dialog does and only the text.

        If you change the text of the labels dynamically after being created, you will have to invalidate their client areas too, to make sure the background redraws correctly.
        Chris Boss
        Computer Workshop
        Developer of "EZGUI"


        • #5
          If GetStockObject (%NULL_BRUSH) returns zero (I would not be surprised were that so) I think DDT has a little problem.

          Try using a different stock object, eg GetStockObject (%WHITE_BRUSH). If that results in a white background, then your problem is as suggested.

          If that doesn't solve the problem, at least you will know what it isn't.

          If that is the problem, you may have to go to full owner-draw or eschew DDT-style for SDK-style for this screen.
          Michael Mattias
          Tal Systems (retired)
          Port Washington WI USA
          [email protected]


          • #6
            After I do a DIALOG SHOW MODELESS, I add all my controls to hdlg. Labels act like their is no gradient and even though I now use the %WS_EX_TRANSPARENT property when adding LABELS, it still uses the Dialog color initially set, even though I use a %NULL_BRUSH in the callback. If I specifically cause the entire window to be come Invalid, then the labels are drawn with a transparent background.

            If I use the coordinates of the label and translate them to pixels and use the textout function with setbkmode hdc,%transparent, selectobject hdc,hFontCap instead, it draws right the first time.

            Is there a way to erase text drawn by textout. The only way I've found is to textout the same text but in the background color of the dialog. With a gradient situation I'm not sure how to do that since it is a different color depending on where the textout text was placed. (GetBkColor?) with DC of the dialog client area?

            I'll post code later today of what happens with the two methods. I wasted a lot of hours yesterday trying to get this working without having to invalidate the entire dialog client area to have the lables redraw and honor the WS_EX_TRANSPARENT style. Textout worked the first time with those attributes set.

            BOB MECHLER


            • #7
              >Is there a way to erase text drawn by textout

              I have cheated on this by doing a FillRect with the background color before TextOut or DrawText....

              I think I posted an example of this somewhere, let me look...yes, I did...

              Listview with Multiple Checkbox Columns Demo 2-20-05

              The FillRect() is even in bold! (I had to add that later after some sharp-eyed user noted that I needed to do 'something' about the old text not going away).

              Don't know how that will work with your gradient.

              Maybe it's just as simple as invalidating the rect (with the erase background flag set) where you want to draw the text and forcing a repaint. But that will no doubt have a 'flicker' unless your paint routine is set up to only paint the invalid portion of the screen. (code not shown).

              Last edited by Michael Mattias; 3 Feb 2008, 09:27 AM.
              Michael Mattias
              Tal Systems (retired)
              Port Washington WI USA
              [email protected]


              • #8
                The following code works fine and I also know now why mine doesn't.
                As long as the CONTROL SET COLOR statements and labels are added prior to the DIALOG SHOW whether MODAL or MODELESS, they work fine. My code does the DIALOG SHOW MODELESS first and add my labels and other controls after that. If the following code had the CONTROLS ADDED after a DIALOG SHOW MODELESS and BEFORE it encountered the DO/LOOP they won't work without Invalidating the Rect.

                That makes me wonder if I should create all the controls my screen will ever use and then hide them prior to the DIALOG SHOW MODELESS STATMENT.

                #DIM NONE
                #INCLUDE "WIN32API.INC"
                'Code for SetColor and PaintBg from an example by Chris Boss
                FUNCTION SetColor (BYVAL tCOLOR AS BYTE) AS WORD
                    ' the windows api GradientFill routine wants r/g/b colors to be
                    ' 16 bit words with the 8 bit color values left shifted 8 bits.
                    ' this takes care of that.
                    LOCAL clr AS WORD
                    clr = tCOLOR
                    SHIFT LEFT clr, 8
                    FUNCTION = clr
                END FUNCTION
                SUB PaintBg(BYVAL hDialog AS LONG, BYVAL r AS LONG, BYVAL g AS LONG, BYVAL b AS LONG)
                     ' this is to paint the background of the dialog
                     ' it's all straight out of the MSDN help file.  We can change the values
                     ' if we like.
                     LOCAL ps AS PAINTSTRUCT
                     LOCAL rc AS Rect
                     LOCAL hDc AS DWORD
                     LOCAL Xin&
                     LOCAL Yin&
                     DIM vert(1) AS TRIVERTEX
                     DIM gRect AS GRADIENT_RECT
                     hDC = BeginPaint(hDialog, ps)
                       ' Tile the background
                     GetClientRect hdialog, rc
                     Xin = rc.nRight - rc.nLeft
                     Yin = rc.nBottom - rc.nTop
                     Xin = rc.nRight - rc.nLeft
                     Yin = rc.nBottom - rc.nTop
                     vert(0).x      = 0
                     vert(0).y      = 0
                     vert(0).Red    = SetColor(r)
                     vert(0).Green  = SetColor(g)
                     vert(0).Blue   = SetColor(b)
                     vert(0).Alpha  = &h0000
                     vert(1).x      = xin
                     vert(1).y      = yin
                     vert(1).Red    = SetColor(255)
                     vert(1).Green  = SetColor(255)
                     vert(1).Blue   = SetColor(255)
                     vert(1).Alpha  = &h0000
                     gRect.UpperLeft  = 0
                     gRect.LowerRight = 1
                     GradientFill hDc, vert(0), 2, gRect, 1, %GRADIENT_FILL_RECT_v
                     EndPaint hDialog, ps
                END SUB                                 
                CALLBACK FUNCTION hdlgproc
                  SELECT CASE CBMSG
                    CASE %WM_PAINT
                      CALL PaintBg(CBHNDL,0,0,0)
                  END SELECT
                END FUNCTION
                FUNCTION PBMAIN
                  DIALOG NEW 0,"Transparent label background test",,,200,300,%WS_SYSMENU TO hdlg&
                  DIALOG FONT "Arial",10
                  CONTROL ADD LABEL, hdlg&,1001,"Test Label",10,100,60,15
                  CONTROL ADD LABEL, hdlg&,1002,"Test Label",10,115,60,15
                  CONTROL ADD LABEL, hdlg&,1003,"Test Label",10,130,60,15
                  CONTROL ADD LABEL, hdlg&,1004,"Test Label",10,145,60,15
                  CONTROL ADD LABEL, hdlg&,1005,"Test Label",10,160,60,15
                  CONTROL SET COLOR hdlg&,1001,%BLACK,-2&
                  CONTROL SET COLOR hdlg&,1002,%BLACK,-2&
                  CONTROL SET COLOR hdlg&,1003,%BLACK,-2&
                  CONTROL SET COLOR hdlg&,1004,%BLACK,-2&
                  CONTROL SET COLOR hdlg&,1005,%BLACK,-2&
                  DIALOG SHOW MODAL hdlg& CALL hdlgproc
                END FUNCTION