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WindowsCE.[Essential Windows CE Application Programming].Jon Wiley & Son.zip

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<B>Essential Windows CE Application Programming</B>
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<I>(Publisher: John Wiley & Sons, Inc.)</I>
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Author(s): Robert Burdick
<BR>
ISBN: 0471327476
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Publication Date: 03/01/99
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<P>When the options window draws the buttons in response to the various WM_DRAWITEM messages it is sent, it uses the control identifier of the button sending the WM_DRAWITEM message to determine which set of images to use from the button image bitmap.
</P>
<!-- CODE //-->
<PRE>
  #define BMP_WIDTH  48
  LRESULT CALLBACK OptionsWndProc(
    HWND hwnd,
    UINT message,
    WPARAM wParam,
    LPARAM lParam)
  &#123;
    HDC hdc;
    UINT nID;
    RECT rc;
    switch(message)
    &#123;
    //Other message handlers
    //&#133;
    case WM_DRAWITEM:
    LPDRAWITEMSTRUCT lpdis;
    int xBmp, xBmpPressed;
    nID = (UINT)wParam;
    lpdis = (LPDRAWITEMSTRUCT)lParam;
    rc = lpdis-&gt;rcItem;
    hdc = lpdis-&gt;hDC;
    xBmp = 0;
    xBmpPressed = BMP_WIDTH;
    switch(nID)
    &#123;
     case IDC_DEPOSIT:
      xBmp &#43;= 2*BMP_WIDTH;
      xBmpPressed &#43;= 2*BMP_WIDTH;
      break;
     case IDC_WITHDRAW:
      xBmp &#43;= 4*BMP_WIDTH;
      xBmpPressed &#43;= 4*BMP_WIDTH;
      break;
     default:
      break;
    &#125;  //End of switch(nID) block
</PRE>
<!-- END CODE //-->
<P>The WM_DRAWITEM handler first extracts the information it needs to draw the button bitmaps such as the device context of the button and the button&#146;s bounding rectangle. Next, it initializes the two offset variables, <I>xBmp</I> and <I>xBmpPressed</I>, to the x pixel offsets of the first unpressed and pressed button images.</P>
<P>The <I>nID</I> switch statement then adjusts these values to correspond to the left edge of the appropriate button bitmaps depending on which button sent the WM_DRAWITEM message.</P>
<P>For example, if the WM_DRAWITEM message was sent by the IDC_DEPOSIT button, <I>xBmp</I> and <I>xBmpPressed</I> are set to the values 96 and 120, respectively. These values correspond to the leftmost pixels of the images to be used to draw the pressed and unpressed states of the IDC_DEPOSIT button.</P>
<P>Finally, the WM_DRAWITEM handler checks the <I>itemState</I> of the button, and displays the proper image with a call to <I>BitBlt</I>:</P>
<!-- CODE //-->
<PRE>
   /* If the button is pressed&#133; */
  if (lpdis-&gt;itemState &#38; ODS_SELECTED)
  &#123;
    BitBlt(hdc, rc.left,rc.top,
    (rc.right-rc.left),
    (rc.bottom-rc.top),
    hdcButtons,
    xBmpPressed,0,SRCCOPY);
  &#125;
  /* If the button is not pressed&#133; */
  else
  &#123;
    BitBlt(hdc, rc.left,rc.top,
    (rc.right-rc.left),
    (rc.bottom-rc.top),
    hdcButtons,
    xBmp,0,SRCCOPY);
  &#125;
  return (TRUE);
</PRE>
<!-- END CODE //-->
<H3><A NAME="Heading8"></A><FONT COLOR="#000077">Concluding Remarks</FONT></H3>
<P>In this chapter, you have been introduced to some of the more common techniques for programming custom Windows CE user interfaces. But owner draw controls and offscreen bitmaps are but a few of the many ways that you can create user interfaces for your applications that are different from the Windows CE standard.
</P>
<P>The next chapter expands on the owner draw concept with the more general subject of the Windows CE custom draw service. The custom draw service, like owner draw controls, allows you to dramatically influence the look and feel of various Windows CE controls&#151;but with much more flexibility.</P><P><BR></P>
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