Trouble drawing theme elements transparently

Trouble drawing theme elements transparently

• soader

  Control windows don't support alpha transparency. You need to either use graphical components, all drawn on a single control, or use windows with alpha transparency -- they cannot be child windows.
  
  Regards,
  Frank Hileman

  check out VG.net: http://www.vgdotnet.com
  Animated vector graphics system
  Integrated Visual Studio .NET graphics editor
  

  
  
  

• ToddNR

  Bitmap output = new Bitmap(closeButton.Width, closeButton.Height, System.Drawing.Imaging.PixelFormat.Format32bppArgb);
              Graphics fx = Graphics.FromImage(output);
             
  
              IntPtr hTheme = OpenThemeData (Handle, "Window");
             
              if (hTheme == IntPtr.Zero)
              {
                  fx.Dispose();
                  return drawLegacyCloseButton (state);
              }
  
              Rectangle rClose = new Rectangle(0, 0, closeButton.Width, closeButton.Height);
              RECT reClose = rClose;
              RECT reClip = reClose; // should fx.VisibleClipBounds be used here
             
              fx.Clear(Color.Transparent);
              IntPtr hDC = fx.GetHdc();
              if (IsThemeBackgroundPartiallyTransparent(hTheme, WP_CLOSEBUTTON, state) != 0)
              {
                  DrawThemeParentBackground(this.Handle, hDC, ref reClose);
              }
              DrawThemeBackground (hTheme, hDC, WP_CLOSEBUTTON, state, ref reClose, ref reClip);
              fx.ReleaseHdc (hDC);
              fx.DrawImage(output,rClose);
              CloseThemeData (hTheme);
              fx.Dispose();
  
              output.Save("close" + state.ToString() + ".png");
  
              return output;
  
  

• David Christie

  In this case maybe you are not drawing child controls, so my last post may be irrelevent. Have you looked at IsThemeBackgroundPartiallyTransparent
  

  
  
  

• 大頭仔

  This works perfectly for me.
  What are you doing with the output Bitmap
  

• ETSUGeek

   

  if (IsThemeBackgroundPartiallyTransparent(_hTheme, BP_PUSHBUTTON, _iStateId))   {     DrawThemeParentBackground(_hwnd, hdcPaint, prcPaint);   }   DrawThemeBackground(_hTheme,                     hdcPaint,                     BP_PUSHBUTTON,                     _iStateId,                     &rcClient,                     prcPaint);

  
  That is the MSDN sample. If IsThemeBackgroundPartiallyTransparent returns false, there is no alpha blending -- that is the correct behavior.
  
  

• Mike for VB

  Yes, I've tried that, but it didn't help. See, I'm not drawing to a control, I'm drawing to a bitmap - it seems that this should be pretty simple in that case, right
  
  

• HumanPixel

  I don't see any code clearing your bitmap to transparent alpha.
  

  fx.Clear(Color.Transparent);

  
  
  

• DaveDeath

  I think that explains why the button looks so oogly as well You may need your own close button if you want something better.
  
  

• OwenSmith

  No ideas why this wouldn't draw the element transparently
  
  

• Yesb2k

  When I use that code, I still get the same result - all the alpha-blended bits are drawn onto gray, and only the fully-transparent bits are transparent. And I set a breakpoint - IsThemeBackgroundPartiallyTransparent is returning true.
  
  This is weird because the code I took this from (which did all its drawing itself, in WmPaint), does not have this problem - it is able to draw the same button nicely alpha-blended. The only difference is that I draw to a Bitmap.
  
  

• Dan Wahlin

  Still works perfectly for me although I did change the code very slightly.

  Rectangle and RECT are not interchangeable.

  struct RECT
  {
   public int Left, Top, Right, Bottom;
   public RECT(int l, int t, int r, int b)
   {
    Left = l;
    Top = t;
    Right = r;
    Bottom = b;
   }
   public RECT(Rectangle r)
   {
    Left = r.Left;
    Top = r.Top;
    Right = r.Right;
    Bottom = r.Bottom;
   }
   public Rectangle ToRectangle()
   {
    return Rectangle.FromLTRB(Left, Top, Right, Bottom);
   }
  }
  
  Rectangle rClose = new Rectangle(0, 0, closeButton.Width, closeButton.Height);
  RECT reClose = new RECT(rClose);
  

  Although Format32bppArgb does work for me, the format should really be Format32bppPArgb.

  
  

• xyzt

  Well, I was assigning it to a PictureBox (I'm trying to fake a themed close button). I also called Save on it so I could check it out as a PNG, but the image is non-transparent there too.
  
  A clarification - the image I get is index-transparent, but not alpha transparent. There are little bits that are transparent, but none of the pixels on the edge are half-transparent.  
  
  

• JohnVP

  I just tried that out (Yeah, I forgot about this thread and gave up) and it still doesn't work...
  
  
• Trouble drawing theme elements transparently