Effect of MoveWindow in EnumChildWindows over listview inside the Dialog Box: Why ListView Header is not correctly scrolling

Question

I have a listview control (lvc) and it is inside a DialogBox(dbx) and that dbx also has a vertical scroll bar.

Whenever the scrollbar is scrolled EnumChildWindows is called to enumerate all the child window of the dbx. The callback function contains a MoveWindow function that would move that lvc. lvc is scrolling fine but not its column headers, they are not moving with the list view.

If i comment out the MoveWindow function inside the callback function then nothing changes. ( Off-course lvc won't move! ) that means EnumChildWindow has got no problem, but MoveWindow inside the callback function is causing problem and i am sure about this because calling MoveWindow function from outside the callback function works correctly ( because in this example there is only one control, i.e. lvc, so i don't need to enumerate all the child window ).

here is the Code:

main.cpp

#if defined(UNICODE) && !defined(_UNICODE)
    #define _UNICODE
#elif defined(_UNICODE) && !defined(UNICODE)
    #define UNICODE
#endif

#include <tchar.h>
#define _WIN32_IE 0x0700
#include <windows.h>
#include <windowsx.h>
#include <commctrl.h>
#include <vector>
#include "res.h"
#define btn 0
#include <iostream>

/*  Declare Windows procedure  */
LRESULT CALLBACK WindowProcedure (HWND, UINT, WPARAM, LPARAM);
BOOL CALLBACK diaproc(HWND hwmd, UINT msg, WPARAM wp, LPARAM lp);
BOOL CALLBACK edc(HWND hwmd,LPARAM lp);
HINSTANCE gi;
int iPrevVscroll=0;
/*  Make the class name into a global variable  */
TCHAR szClassName[ ] = _T("CodeBlocksWindowsApp");

int WINAPI WinMain (HINSTANCE hThisInstance,
                     HINSTANCE hPrevInstance,
                     LPSTR lpszArgument,
                     int nCmdShow)
{
    HWND hwnd;               /* This is the handle for our window */
    MSG messages;            /* Here messages to the application are saved */
    WNDCLASSEX wincl;        /* Data structure for the windowclass */

    /* The Window structure */
    gi = wincl.hInstance = hThisInstance;
    wincl.lpszClassName = szClassName;
    wincl.lpfnWndProc = WindowProcedure;      /* This function is called by windows */
    wincl.style = CS_DBLCLKS ;                 /* Catch double-clicks */
    wincl.cbSize = sizeof (WNDCLASSEX);

    /* Use default icon and mouse-pointer */
    wincl.hIcon = LoadIcon (NULL, IDI_APPLICATION);
    wincl.hIconSm = LoadIcon (NULL, IDI_APPLICATION);
    wincl.hCursor = LoadCursor (NULL, IDC_ARROW);
    wincl.lpszMenuName = NULL;                 /* No menu */
    wincl.cbClsExtra = 0;                      /* No extra bytes after the window class */
    wincl.cbWndExtra = 0;                      /* structure or the window instance */
    /* Use Windows's default colour as the background of the window */
    wincl.hbrBackground = (HBRUSH) COLOR_BACKGROUND;

    /* Register the window class, and if it fails quit the program */
    if (!RegisterClassEx (&wincl))
        return 0;

    /* The class is registered, let's create the program*/
    hwnd = CreateWindowEx (
           0,                   /* Extended possibilites for variation */
           szClassName,         /* Classname */
           _T("Code::Blocks Template Windows App"),       /* Title Text */
           WS_OVERLAPPEDWINDOW, /* default window */
           CW_USEDEFAULT,       /* Windows decides the position */
           CW_USEDEFAULT,       /* where the window ends up on the screen */
           544,                 /* The programs width */
           375,                 /* and height in pixels */
           HWND_DESKTOP,        /* The window is a child-window to desktop */
           NULL,                /* No menu */
           hThisInstance,       /* Program Instance handler */
           NULL                 /* No Window Creation data */
           );

    /* Make the window visible on the screen */
    ShowWindow (hwnd, nCmdShow);

    /* Run the message loop. It will run until GetMessage() returns 0 */
    while (GetMessage (&messages, NULL, 0, 0))
    {
        /* Translate virtual-key messages into character messages */
        TranslateMessage(&messages);
        /* Send message to WindowProcedure */
        DispatchMessage(&messages);
    }

    /* The program return-value is 0 - The value that PostQuitMessage() gave */
    return messages.wParam;
}


/*  This function is called by the Windows function DispatchMessage()  */

LRESULT CALLBACK WindowProcedure (HWND hwnd, UINT message, WPARAM wParam, LPARAM lParam)
{
    switch (message)                  /* handle the messages */
    {
    case WM_CREATE:
        CreateWindow(WC_BUTTON, "CLICK", WS_CHILD | BS_DEFPUSHBUTTON | WS_VISIBLE, 10, 10, 80, 30, hwnd, (HMENU)btn, gi, NULL  );

    break;
    case WM_COMMAND:{
        if( LOWORD(wParam) == btn && HIWORD(wParam) == BN_CLICKED ) DialogBox(gi, MAKEINTRESOURCE(dia), hwnd,(DLGPROC)diaproc);
        DWORD err = GetLastError();
        std::cout<<err<<std::endl<<dia;
    }
    break;
        case WM_DESTROY:
            PostQuitMessage (0);       /* send a WM_QUIT to the message queue */
            break;
        default:                      /* for messages that we don't deal with */
            return DefWindowProc (hwnd, message, wParam, lParam);
    }

    return 0;
}

BOOL CALLBACK diaproc(HWND hwnd, UINT msg, WPARAM wParam, LPARAM lp)
{

    static HWND lv_hwnd;
    static int sci;
    switch(msg)
    {
    case WM_INITDIALOG:
        {

            INITCOMMONCONTROLSEX is;
            is.dwSize = sizeof(INITCOMMONCONTROLSEX);
            is.dwICC = ICC_LISTVIEW_CLASSES;
            InitCommonControlsEx(&is);

            int col_fmt[5] = { LVCFMT_CENTER, LVCFMT_LEFT, LVCFMT_CENTER, LVCFMT_CENTER, LVCFMT_CENTER };
            int col_wid[5] = { 30, 90, 50, 30, 70 };
            std::vector<TCHAR*> col_nam(5);
            col_nam[0] = _T("S.No"); col_nam[1] = _T("Description"); col_nam[2] = _T("HSN"); col_nam[3] = _T("QTY"); col_nam[4] = _T("Rate");

            lv_hwnd = CreateWindow(
                                        WC_LISTVIEW,
                                        _T(""),
                                        WS_CHILD | LVS_REPORT | LVS_EDITLABELS | WS_VISIBLE,
                                        10, 0, 300, 200,
                                        hwnd,
                                        NULL,
                                        (HINSTANCE)GetWindowLong(hwnd, GWL_HINSTANCE),
                                        NULL
                                        );
            ListView_SetExtendedListViewStyle(lv_hwnd, LVS_EX_FLATSB | LVS_EX_FULLROWSELECT | LVS_EX_GRIDLINES | LVS_EX_LABELTIP );
            LVCOLUMN lvc;
            lvc.mask = LVCF_FMT | LVCF_SUBITEM | LVCF_WIDTH | LVCF_TEXT;
            for(int i =0; i < 5; i++)
            {
                lvc.fmt = col_fmt[i];
                lvc.cx = col_wid[i];
                lvc.pszText = col_nam[i];
                lvc.iSubItem =  i;
                ListView_InsertColumn(lv_hwnd, i, &lvc);
            }

            SetScrollRange(hwnd, SB_VERT, 0, 225, TRUE);
            SetScrollPos(hwnd, SB_VERT, 0, TRUE);
        } return FALSE;

        case WM_VSCROLL:
        {
            RECT rc; GetWindowRect(lv_hwnd, &rc);
            POINT pt1 = {rc.left, rc.top}; ScreenToClient(hwnd, &pt1);
            POINT pt2 = {rc.right, rc.bottom}; ScreenToClient(hwnd, &pt2);
            std::cout<<"rc.top : "<< rc.top<<"\nrc.bottom: "<< rc.bottom <<"\nrc.right : "<<rc.right<<"\nrc.left : "<<rc.left<<"\n\n";
            std::cout<<"pt1.y : "<< pt1.y<<"\npt2.y: "<< pt2.y<<"\npt2.x : "<<pt2.x<<"\npt1.x : "<<pt1.x<<"\n\n\n";

            switch(LOWORD(wParam))
            {
            case SB_PAGEDOWN:
            case SB_LINEDOWN:
                sci += 10; break;
            case SB_PAGEUP:
            case SB_LINEUP:
                sci -= 10; break;
            case SB_THUMBTRACK:
                sci = HIWORD(wParam); break;
            };
            sci = sci < 0 ? 0 : sci > 225 ? 225 : sci;
            SetScrollPos(hwnd, SB_VERT, sci, FALSE);
            //MoveWindow(lv_hwnd, pt1.x, pt1.y - sci + iPrevVscroll, pt2.x - pt1.x, pt2.y - pt1.y, TRUE);
            EnumChildWindows(hwnd, edc, (LPARAM)sci);
        }; return TRUE;
            case WM_COMMAND:
                if(LOWORD(wParam) == IDCANCEL) EndDialog(hwnd, wParam); return TRUE;

        default: return FALSE;
    }
}

BOOL CALLBACK edc(HWND hwnd, LPARAM lp)
{
    long s = (long) lp;

    RECT rc; GetWindowRect(hwnd, &rc);
    POINT pt1 = {rc.left, rc.top}; ScreenToClient(hwnd, &pt1);
    POINT pt2 = {rc.right, rc.bottom}; ScreenToClient(hwnd, &pt2);
    MoveWindow(hwnd, pt1.x, pt1.y + s - iPrevVscroll, pt2.x - pt1.x, pt2.y - pt1.y, TRUE);

}

res.h

#define lv 1
#define dia 2

res.rc

#include <windows.h>
#include <commctrl.h>
#include <richedit.h>
#include "res.h"

dia DIALOGEX 0,0,500,300
CAPTION "New Invoice"
STYLE DS_3DLOOK | DS_CENTER | DS_MODALFRAME | DS_SHELLFONT | WS_CAPTION | WS_VISIBLE | WS_POPUP | WS_SYSMENU | WS_THICKFRAME | WS_VSCROLL

FONT 8, "Ms Shell Dlg"
{

}

in main.cpp you find the MoveWindow and other related functions at the bottom.

The following Images are useful.

also that the logic of scrolling in both MoveWindow is different, again, for the purpose of illustration.

Initially i was working on a project with many controls when i encountered this problem. I analysed this separately and found out what i have written above. Although I bypassed this problem through adopting a different method to scroll down all the controls(the one which do not includes calling MoveWindow from inside EnumChildWindows ), but i am curious to know the reason and the solution of this problem.

Thank you for your time on this long post. Any suggestions or improvement would also be amazing!

Answer 1

From the remarks section of EnumChildWindows() reference:

If a child window has created child windows of its own, EnumChildWindows enumerates those windows as well.

So what you are doing here is scrolling the listview control and then also scroll the header control separately. The result is that the header control moves relative to the listview control as seen in your 2nd screenshot.

Instead you should only move immediate children of the dialog box, because grand children will move automatically with their parents.

Possible solutions:

• Check parent/child relationship in the EnumChildWindows() callback (e. g. by calling GetParent() on the child and compare it with your dialog handle).
• Instead of calling EnumChildWindows() and MoveWindow(), call ScrollWindowEx() with SW_SCROLLCHILDREN. This is the easiest way of implementing scrolling, so I would prefer this solution.