Changing the Style of Secondary Viewer Windows

MORE INFORMATION

The style of Viewer's main window can be changed using the Windows SetWindowLong() function. The prototype for SetWindowLong() is where hwnd is the handle of the secondary window, nOffset is the offset of the value to change, and nVal is the new value for the offset. Further documentation for the SetWindowLong() function can be found in the documentation for the Windows 3.1 Software Development Kit (SDK).

Perform the following two steps to get the first parameter [which will be the handle (hwnd) to your secondary window]:

1. Make sure that secondary window has the input focus. You can use the FocusWindow() Viewer command to accomplish this.
2. Use the Windows application programming interface (API) function GetParent() to extract the correct handle from the hwndContext variable. The hwndContext variable is documented on page 5-8 of the Microsoft Multimedia Viewer "Technical Reference."
   
   

   NOTE

   : hwndContext is a 32-bit value. Therefore, you will need to use the LOWORD() function to extract the 16-bit window handle. In your DLL, you should write the following function:

         HWND FAR PASCAL __export GetSecondaryHandle (DWORD hwnd)
         {
            return GetParent (LOWORD(hwnd));
         }
   						

The second parameter, nOffset, should be set to -16 (which is the value of the Windows constant GWL_STYLE) to change the window style.

The possible values for the third parameter, nVal, are combinations of the following:

   WS_CLIPSIBLINGS      0x04000000
   WS_CLIPCHILDREN      0x02000000
   WS_VISIBLE           0x10000000
   WS_DISABLED          0x08000000
   WS_MINIMIZE          0x20000000
   WS_MAXIMIZE          0x01000000
   WS_CAPTION           0x00C00000
   WS_BORDER            0x00800000
   WS_DLGFRAME          0x00400000
   WS_VSCROLL           0x00200000
   WS_HSCROLL           0x00100000
   WS_SYSMENU           0x00080000
   WS_THICKFRAME        0x00040000
   WS_MINIMIZEBOX       0x00020000
   WS_MAXIMIZEBOX       0x00010000
				

These values are combined simply by or'ing them together with the bitwise OR operator ("|"). Each call to SetWindowLong() completely replaces the previous styles for the window with the new styles specified in the nVal parameter.

By default, the main Viewer window has the styles WS_VISIBLE, WS_CLIPSIBLINGS, WS_CLIPCHILDREN, WS_CAPTION, WS_SYSMENU, WS_THICKFRAME, WS_MINIMIZEBOX, and WS_MAXIMIZEBOX (that is, nVal=0x16CF0000).

NOTE: Microsoft recommends that you always include the WS_VISIBLE, WS_CLIPSIBLINGS, and WS_CLIPCHILDREN styles in the new value. This means the value of nVal would always be at least 0x16000000.

To use SetWindowLong() and GetSecondaryHandle() from Viewer, these functions must be registered in the [CONFIG] section of the .MVP file as follows

   RegisterRoutine ("user", "SetWindowLong", "uiU")
   RegisterRoutine ("mydll", "GetSecondaryHandle()", "u=U")
				

where mydll is the name of your .DLL file.

SetWindowLong() can then be called from anywhere within the title with GetSecondaryHandle(hwndContext) as the first parameter, -16 as the second parameter, and the appropriate new style value in the third parameter.

To cause the main window frame to be redrawn immediately after the change to its style, you may need to call the Windows function SetWindowPos(), which is registered in the [CONFIG] section as follows:

   RegisterRoutine ("user", "SetWindowPos", "uuiiiiu")
				

SetWindowPos() can then be called from anywhere within the title as follows:

   SetWindowPos (GetSecondaryHandle (hwndContext), 0, 0, 0, 0, 0, 39)
				

NOTE: The SetWindowPos() call above is equivalent to the following function call using the Windows constants defined in the WINDOWS.H header file from the Windows SDK:

   SetWindowPos (hwndApp, 0, 0, 0, 0, 0,  SWP_DRAWFRAME  |
                                          SWP_NOMOVE     |
                                          SWP_NOSIZE     |
                                          SWP_NOZORDER)
				

Sample

To use a topic entry command to remove the maximize box from a secondary window called MyWindow, the SetWindowLong() call in the topic entry command code resembles the following:

   FocusWindow (MyWindow);
   SetWindowLong (GetSecondaryHandle (hwndContext), -16, 0x16CE0000);
   SetWindowPos (GetSecondaryHandle (hwndContext), 0, 0, 0, 0, 0, 39);
				

Style Reference

The following list describes the styles mentioned above:

WS_BORDER         Creates a window that has a border.

WS_CAPTION        Creates a window that has a title bar (implies the
                  WS_BORDER style). This style cannot be used with the
                  WS_DLGFRAME style.

WS_CLIPCHILDREN   Excludes the area occupied by child windows when drawing
                  within the parent window. Used when creating the parent
                  window.

WS_CLIPSIBLINGS   Clips child windows relative to each other; that is, when
                  a particular child window receives a paint message, the
                  WS_CLIPSIBLINGS style clips all other overlapped child
                  windows out of the region of the child window to be
                  updated. (If WS_CLIPSIBLINGS is not specified and child
                  windows overlap, it is possible, when drawing within the
                  client area of a child window, to draw within the client
                  area of a neighboring child window.) For use with the
                  WS_CHILD style only.

WS_DISABLED       Creates a window that is initially disabled.

WS_DLGFRAME       Creates a window with a double border but no title.

WS_HSCROLL        Creates a window that has a horizontal scroll bar.

WS_MAXIMIZE       Creates a window of maximum size.

WS_MAXIMIZEBOX    Creates a window that has a Maximize button.

WS_MINIMIZE       Creates a window that is initially minimized. For use
                  with the WS_OVERLAPPED style only.

WS_MINIMIZEBOX    Creates a window that has a Minimize button.

WS_SYSMENU        Creates a window that has a System Menu box in its title
                  bar. Used only for windows with title bars.

WS_THICKFRAME     Creates a window with a thick frame that can be used to
                  size the window.

WS_VISIBLE        Creates a window that is initially visible. This applies
                  to overlapped, child, and pop-up windows. For overlapped
                  windows, the y parameter is used as a ShowWindow()
                  function parameter.

WS_VSCROLL        Creates a window that has a vertical scroll bar.
				

NOTE: You can determine the current styles of the main Viewer window using the Spy utility that shipped with the Windows SDK. Choose Window from Spy's Window menu. Then position the cursor over the main Viewer window. Spy will display the style of the window in the last line of the Spy Window dialog box.