Tags: background, current, desktop, fileand, image, microsoft, msdn, software, text, visual, wallpaper, write

how to write text to desktop wallpaper

On Microsoft » Microsoft Visual C#

9,548 words with 7 Comments; publish: Sun, 23 Dec 2007 08:23:00 GMT; (30062.50, « »)

Hi,

Does anybody know how to write some text to the desktop background.

Currently, I can write some text to the current wallpaper image file

and then use SystemParametersInfo to display the new image...but that

doesn't seem to be a good way to do so because the text format will be

changed according to the setting of the screen resolution and the

position property (center, stretch, tile).

Is there any way to output the text directly to the desktop without touching the background image?

Thanks.

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  • 7 Comments

    • Hi,

      You need to get the handle from the desktop. You need to call the unmanaged method "GetDesktopWindow". Check the following example:

      [DllImport("user32.dll")]

      static extern IntPtr GetDesktopWindow();

      [DllImport("user32.dll")]

      static extern IntPtr GetDCEx(IntPtr hwnd, IntPtr hrgn, uint flags);

      IntPtr hdc = GetDCEx(GetDesktopWindow(), IntPtr.Zero, 1027);

      using(Graphics g = Graphics.FromHdc(hdc))

      {

      g.FillEllipse(Brushes.Red, 0, 0, 400, 400); // Or draw a string or whatever you want

      }

      Hope you find the post useful,

      Best regards

      #1; Thu, 30 Aug 2007 17:34:00 GMT

    • Hi,

      You need to get the handle from the desktop. You need to call the unmanaged method "GetDesktopWindow". Check the following example:

      [DllImport("user32.dll")]

      static extern IntPtr GetDesktopWindow();

      [DllImport("user32.dll")]

      static extern IntPtr GetDCEx(IntPtr hwnd, IntPtr hrgn, uint flags);

      IntPtr hdc = GetDCEx(GetDesktopWindow(), IntPtr.Zero, 1027);

      using(Graphics g = Graphics.FromHdc(hdc))

      {

      g.FillEllipse(Brushes.Red, 0, 0, 400, 400); // Or draw a string or whatever you want

      }

      Hope you find the post useful,

      Best regards

      That method won't be persistent, for example; if another window is maximized the results of the draw operation will be erased.
      #2; Thu, 30 Aug 2007 17:35:00 GMT
    • You may also want to consider creating a form that just has the text, with every other part transparent. There is a way to make sure that the window stays underneath other windows. I'm not sure what it is, but desktop widget programs can do it, so it is possible.
      #3; Thu, 30 Aug 2007 17:36:00 GMT

    • Hi Peter,

      Thanks for the point, I thought it was obvious that eveytime that you paint something on windows you will need to re paint once the region is invalidated.

      As for the desktop you don't have the OnPaint event as you will have on a .net component you need to peek the message. You can do this intercepting the message WM_PAINT using the PeekMessage function.

      BOOL PeekMessage(

      LPMSG lpMsg, // Pointer to the message

      HWND hWnd, // Send the desktop handle

      UINT wMsgFilterMin, // here use WM_PAINT

      UINT wMsgFilterMax, // Same one as we are peeking only one message

      UINT wRemoveMsg // send PM_NOREMOVE

      );

      Hope this helps, thanks for the point Peter.

      Cheers

      #4; Thu, 30 Aug 2007 17:37:00 GMT
    • Thanks for the point, I thought it was obvious that eveytime that you paint something on windows you will need to re paint once the region is invalidated.

      As for the desktop you don't have the OnPaint event as you will have on a .net component you need to peek the message. You can do this intercepting the message WM_PAINT using the PeekMessage function.

      BOOL PeekMessage(

      LPMSG lpMsg, // Pointer to the message

      HWND hWnd, // Send the desktop handle

      UINT wMsgFilterMin, // here use WM_PAINT

      UINT wMsgFilterMax, // Same one as we are peeking only one message

      UINT wRemoveMsg // send PM_NOREMOVE

      );

      You're suggesting that he write an application to intercept all windows messages for the Desktop and provide additional processing for some. This suggestion is downright scary. First of all, the question was simply regarding writing to the desktop wallpaper, otherwise modifying a bitmap. Second, PeekMessage is considered bad form and a serious design flaw. You might want to check out the PeekMessage entry in The n Habits of Highly Defective Windows Applications. As well, Raymond Chen has one of many other comments about the consequense of using PeekMessage incorrectly: http://blogs.msdn.com/oldnewthing/archive/2005/02/09/369804.aspx which details how much more complicated it is than simply calling PeekMessage

      #5; Thu, 30 Aug 2007 17:38:00 GMT

    • Hi,

      It is true, reading the first post again he wants to write text on an image file (my fault ). Thanks for the links, I will have a look.

      Cheers

      #6; Thu, 30 Aug 2007 17:39:00 GMT
    • Hi,

      Thank all for your suggestions !!!

      I think making a transparent form is a good idea. I actually played

      around with it yesterday and it worked very well. Also, if the form

      uses a web browser to display text, you will have more controls on the

      text format. And yes, making a window stay underneath the others

      is quite possible

      #7; Thu, 30 Aug 2007 17:40:00 GMT