Solved

Refreshing and Redrawing the Desktop Window

Posted on 1997-07-17
9
484 Views
Last Modified: 2013-11-20
Currently my application needs to draw directly over the entire desktop.  In doing so, I obtain its device context by calling the CWindowDC constructor.  After doing so, I am able to successfully paint directly to the desktop like I need to.  However, when I finish, I need to restore the desktop to its original state (i.e. refresh it - exactly equivalent to what happens if you click on the desktop and press the F5 key).  I have tried many ways of doing this, all without success.  Any insight would be great.  Thanks.
0
Comment
Question by:mueller
[X]
Welcome to Experts Exchange

Add your voice to the tech community where 5M+ people just like you are talking about what matters.

  • Help others & share knowledge
  • Earn cash & points
  • Learn & ask questions
  • 4
  • 4
9 Comments
 
LVL 3

Expert Comment

by:jaba
ID: 1302623
HWND hwndDT = GetDesktopWindow();
InvalidareRect(hwndDT, NULL);
UpdateWindow(hwndDT);
Thats all
0
 

Author Comment

by:mueller
ID: 1302624
Unfortunately, I went down that path prior to posting the question and came up drawing blanks.  Take the following code for example, which gets the desktop window's device context, draws a text string to it, and attempts to clean up the mess afterwards (all in the same manner as above, but as applied to MFC).

-------------------------------------------------------------------------
// get desktop window
CWnd *pWnd = GetDesktopWindow();

// get desktop window's device context
CWindowDC desktopDC( pWnd );

// write some string out to the dc
desktopDC.TextOut( 50, 50, "Hello" );

// attempt to clean up the desktop
pWnd->InvalidateRect( NULL, TRUE );

// update the window
pWnd->UpdateWindow();
-------------------------------------------------------------------------

Again, the code above does not work, and follows your example  in a similar manner (the difference being you call the Win32 API, but no big deal).  Also, when passing through the online Visual C++ 4 documentation the other day looking for info on CWnd::RedrawWindow(), I found an interesting note at the bottom of the "Remarks" section:

When the RedrawWindow member function is used to invalidate part of the desktop window, that window does not receive a WM_PAINT message. To repaint the desktop, an application should use CWnd::ValidateRgn, CWnd::InvalidateRgn, CWnd::UpdateWindow, or ::RedrawWindow.


However, when I followed the advice, I still came up drawing blanks.  If anyone has any insight, I'd be very appreciative. Thanks.
0
 
LVL 23

Expert Comment

by:chensu
ID: 1302625
Try this:

::SHChangeNotify(SHCNE_UPDATEDIR, SHCNF_FLUSH, 0, 0);
0
Independent Software Vendors: We Want Your Opinion

We value your feedback.

Take our survey and automatically be enter to win anyone of the following:
Yeti Cooler, Amazon eGift Card, and Movie eGift Card!

 
LVL 23

Expert Comment

by:chensu
ID: 1302626
Maybe the following code is better. I hope it will update the desktop.

// Get the PIDL for the Desktop.
LPITEMIDLIST pidlDesktop;  // PIDL for the Desktop
if (SUCCEEDED(::SHGetSpecialFolderLocation(pWnd->GetSafeHwnd(), CSIDL_DESKTOP, &pidlDesktop)))
{
    // Refresh the Desktop
    ::SHChangeNotify(SHCNE_UPDATEDIR, SHCNF_IDLIST, (DWORD)pidlDesktop, 0);

    // pointer to the shell's IMalloc interface.
    LPMALLOC pMalloc;

    // Get the shell's allocator.
    if (SUCCEEDED(::SHGetMalloc(&pMalloc)))
    {
        // Free the PIDL returned by SHGetSpecialFolderLocation
      pMalloc->Free(pidlDesktop);

        // Release the shell's allocator.
        pMalloc->Release();
    }
}

0
 

Author Comment

by:mueller
ID: 1302627
Unfortunately the code used to update and refresh the desktop by using the Shell API was not successful.  If anyone has any ideas, it would be great.  Thanks again.
0
 

Author Comment

by:mueller
ID: 1302628
Adjusted points to 150
0
 
LVL 23

Accepted Solution

by:
chensu earned 150 total points
ID: 1302629
The following code does it. (You can use Spy++ to find that the top desktop window is Program Manager window.)

CWnd *pWnd = CWnd::FindWindow("Progman", "Program Manager");
if (pWnd != NULL)
{
    pWnd->ShowWindow(SW_HIDE);
    pWnd->ShowWindow(SW_SHOWNA);
}

0
 

Author Comment

by:mueller
ID: 1302630
Chensu,

          Thanks for all of the help.  I did use Spy++ earlier to grab the desktop window's class name, but mine came up with
"SysListView32".  I tried the FindWindow method with that class name but always came up blank.  Again, thanks for the help.

                                                 Steve
0
 
LVL 23

Expert Comment

by:chensu
ID: 1302631
The "SysListView32" window that you got is the child of the "Program Manager" window that is the top level window. The class name "SysListView32" belongs to the List View control.
0

Featured Post

Independent Software Vendors: We Want Your Opinion

We value your feedback.

Take our survey and automatically be enter to win anyone of the following:
Yeti Cooler, Amazon eGift Card, and Movie eGift Card!

Question has a verified solution.

If you are experiencing a similar issue, please ask a related question

Suggested Solutions

Title # Comments Views Activity
iSeries FTP Exit Program 8 172
format the code in java 6 116
no14 challenge 14 77
ERP and the other system process verification 5 25
This is to be the first in a series of articles demonstrating the development of a complete windows based application using the MFC classes.  I’ll try to keep each article focused on one (or a couple) of the tasks that one may meet.   Introductio…
Introduction: The undo support, implementing a stack. Continuing from the eigth article about sudoku.   We need a mechanism to keep track of the digits entered so as to implement an undo mechanism.  This should be a ‘Last In First Out’ collec…
This video will show you how to get GIT to work in Eclipse.   It will walk you through how to install the EGit plugin in eclipse and how to checkout an existing repository.
In an interesting question (https://www.experts-exchange.com/questions/29008360/) here at Experts Exchange, a member asked how to split a single image into multiple images. The primary usage for this is to place many photographs on a flatbed scanner…

734 members asked questions and received personalized solutions in the past 7 days.

Join the community of 500,000 technology professionals and ask your questions.

Join & Ask a Question