Utility to display information on all windows in z-order and their children.

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Introduction

This console program uses the GetTopWindow and GetNextWindow calls recursively to iterate through the entire tree of windows in the system. The program outputs information on these windows in a text based tree view. For each window, it shows the title, the registered class, the handle of the owner process, the coordinates, and whether or not the window is visible.

Using the code

The main work of the program is done in the PrintChildrenWindows function. This steps through the z-order, listing all windows, and recursively steps into the list of child windows for each window it visits. The output is a text tree that looks something like this:

133114 "windump - Microsoft Visual C++ - [windump.cpp]" 
                                 "Afx:400000:8:10011:0:10505" 892
|  (-4, -4)-(1028, 744)  VISIBLE
|
+-133110 "" "Afx:400000:0:10011:10:0" 892
|    (0, 723)-(1024, 740)  VISIBLE
|
+-133118 "" "Afx:400000:8" 892
| |  (0, 19)-(1024, 106)  VISIBLE
| |
| +-67628 "" "Afx:400000:b:10011:10:0" 892
| |    (367, 77)-(655, 107)  VISIBLE
| |
| +-67626 "" "Afx:400000:b:10011:10:0" 892
| |    (607, 47)-(733, 77)  VISIBLE
| |
| +-67614 "" "Afx:400000:b:10011:10:0" 892
| | |  (-1, 47)-(607, 77)  VISIBLE
| | |
| | +-67616 "" "AfxWnd42" 892
| | |    (193, 51)-(230, 73)  VISIBLE
| | |
...

The first line displays the handle, the title, the class name, and the handle of the owner process. The second line displays the coordinates (left, top)-(right, bottom), and whether or not the window is currently visible.

// recursive algorithm
// prints top level window, then tree of children windows
// calling with hwnd == NULL, level == 0 starts from top of z-order
void PrintChildrenWindows(HWND hwnd, int level)
{
    hwnd = GetTopWindow(hwnd);

    if(!hwnd)
        return;

    while(hwnd)
    {
        char levelSpace[1024];
        char nameBuffer[WINBUFF_SIZE];
        char typeBuffer[WINBUFF_SIZE];

        GetWindowText(hwnd, nameBuffer, WINBUFF_SIZE);
        RealGetWindowClassA (hwnd, typeBuffer, WINBUFF_SIZE);

        GenerateTreeString(levelSpace,    // buffer
            level,    // depth
            // are there additional siblings
            GetNextWindow(hwnd, GW_HWNDNEXT) ? true : false,
            GetTopWindow(hwnd) ? true : false,    // are there children?
            false);    // no fall through

        printf("%s%d \"%s\" \"%s\" %d\n",levelSpace, hwnd, 
          nameBuffer, typeBuffer, GetWindowThreadProcessId(hwnd, NULL));

        GenerateTreeString(levelSpace,    // buffer
            level,    // depth
            // are there more siblnigs
            GetNextWindow(hwnd, GW_HWNDNEXT) ? true : false, 
            GetTopWindow(hwnd) ? true : false, // are there chidren
            true);    // fall through

        RECT rect;
        GetWindowRect(hwnd, &rect);
        printf("%s (%d, %d)-(%d, %d)", levelSpace, 
           rect.left, rect.top, rect.right, rect.bottom);

        if(IsWindowVisible(hwnd))
            printf("  VISIBLE\n");
        else
            printf("  HIDDEN\n");

        printf("%s\n", levelSpace);

        PrintChildrenWindows(hwnd, level + 1);
        hwnd = GetNextWindow(hwnd, GW_HWNDNEXT);
    }
}

This is the recursive function which prints the window information. At the top level, hwnd is NULL. Calling GetTopWindow(NULL) gets the top window in the z-order. It then loops, calling hwnd = GetNextWindow(hwnd), to retrieve each successive window in the z-order. Also, it calls itself for each window, with hwnd equal to the window just printed. This causes the loop to process all child windows in the same way as GetTopWindow(hwnd /*!= NULL*/) gets the first child window of hwnd. If there are no child windows, GetTopWindow returns NULL, and we return, unwinding the recursion.

Points of interest

This program also contains a function called isFlagInArgs which could easily be extracted and used in other command line utilities to interpret command line arguments.