Effect of MoveWindow over ListView Control: why column headers hides away after calling the function?

Question

I have a dialog box with a listview control (lvc) in it. Because there are many editbox before lvc( 57 controls including lvc ), lvc is out of the screen. So i have to make a vertical scroll bar.

Vertical scroll bar:
Range : 0-250
every SB_PAGEDOWN, SB_PAGEUP, SB_LINEDOWN and SB_LINEUP changes scroll position by 25

#define max_scroll_range 250
#define min_scroll_range 0
#define scroll_step  max_scroll_range/10

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Project file overview

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I am providing all the files so that you could see the problem live.

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main.cpp

#include "include/basefile01.h"

/*  Declare Windows procedure  */
LRESULT CALLBACK WindowProcedure (HWND, UINT, WPARAM, LPARAM);
HINSTANCE gi ;
HWND parentHwnd;
/*  Make the class name into a global variable  */
TCHAR szClassName[ ] = _T("IGAM");

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 */
    wincl.hInstance = gi = 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 = (HICON)MAKEINTRESOURCE(APP_ICON_XL);
    wincl.hIconSm = LoadIcon (NULL, IDI_APPLICATION);
    wincl.hCursor = LoadCursor (NULL, IDC_ARROW);
    wincl.lpszMenuName = MAKEINTRESOURCE(MAIN_MENU);                 /* 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) GetStockObject( WHITE_BRUSH );

    /* 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*/
    parentHwnd = hwnd = CreateWindowEx (
           0,                   /* Extended possibilites for variation */
           szClassName,         /* Classname */
           _T("IGAM"),       /* 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_COMMAND:
        switch(LOWORD(wParam)){
        case MAIN_MENU_file_new_invoice:
                DialogBox(gi, MAKEINTRESOURCE(NEW_INVOICE_DIALOG), parentHwnd, (DLGPROC)invoice_dialog_box_message_handle);
            break;
        }
        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;
}

this file calls the DialogBox which connects it with other files.

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basefile01.cpp

#include "../include/basefile01.h"
#include <vector>
#define max_scroll_range 250
#define min_scroll_range 0
#define scroll_step  max_scroll_range/10

long iPrevVscroll = 0;

BOOL CALLBACK invoice_dialog_box_message_handle(HWND hwnd, UINT msg, WPARAM wp, LPARAM lp)
{
    static long iVscroll;
    switch(msg)
    {
    case WM_INITDIALOG:
        iVscroll = 0;
        SetScrollRange(hwnd, SB_VERT, min_scroll_range, max_scroll_range, TRUE);
        SetScrollPos(hwnd, SB_VERT, min_scroll_range, TRUE);
        create_listViews_invoice_dialog(hwnd);
        return TRUE;

    case WM_COMMAND:
        switch(LOWORD(wp))
        {
            case IDCANCEL:EndDialog(hwnd, wp); return TRUE;
        }
    break;
    /**
        there are two variables @iVscroll and @iPrevVscroll
        they are there because the every child window will be moved up
        by the between previous scroll position and the current scroll position
    */
    case WM_VSCROLL:
        switch(LOWORD(wp))
        {
            case SB_PAGEDOWN:
            case SB_LINEDOWN : iVscroll += scroll_step; break;
            case SB_PAGEUP:
            case SB_LINEUP: iVscroll -= scroll_step; break;
            case SB_THUMBTRACK: iVscroll = HIWORD(wp); break;
        };
        /// iVscroll should be in the range of min_scroll_range and max_scroll_range
        iVscroll = ( iVscroll < min_scroll_range ? min_scroll_range : ( iVscroll > max_scroll_range ? max_scroll_range : iVscroll ) );
        /// don't  move any child windows if iVscroll is at boundaries
        if(!iVscroll || iVscroll == iPrevVscroll ) return TRUE;
        SetScrollPos(hwnd, SB_VERT, iVscroll, TRUE);
        /// Enumerate to all child windows of the dialog box; this is better than calling and moving each window in a loop
        EnumChildWindows(hwnd, invoice_dialog_child_enum_scroll, (LPARAM)iVscroll);
        iPrevVscroll = iVscroll;
        /// redraw the whole dialog box client area
        InvalidateRect (hwnd, NULL, TRUE) ;
        UpdateWindow(hwnd);


        return TRUE;

    default :return FALSE;
    }
}

BOOL CALLBACK invoice_dialog_child_enum_scroll(HWND hwnd, LPARAM lp)
{
    long s = (long) lp;
    RECT rc;
    GetWindowRect(hwnd, &rc);
    /// the above function return the coordinates relative to the top left of the screen at which\
        i am looking at. So to convert those coordinates which are relative to\
        the dialog box the following function is used
    MapWindowPoints(HWND_DESKTOP, GetParent(hwnd), (LPPOINT)&rc, 2);
    /// move the window by the difference between @iVscroll and @iPrevVscroll
    MoveWindow(hwnd, rc.left, rc.top - ( s - iPrevVscroll ), rc.right-rc.left, rc.bottom - rc.top, TRUE);
    //SetWindowPos(hwnd, HWND_TOP,rc.left, rc.top - ( s - iPrevVscroll ), rc.right-rc.left, rc.bottom - rc.top,SWP_NOOWNERZORDER | SWP_NOSIZE);
}

BOOL create_listViews_invoice_dialog(HWND hwnd)
{
    /**
        this function creates the listview successfully
    */

    /// initializing the listview common control
    INITCOMMONCONTROLSEX icx;
    icx.dwSize = sizeof(INITCOMMONCONTROLSEX);
    icx.dwICC = ICC_LISTVIEW_CLASSES;
    InitCommonControlsEx(&icx);

    RECT LV_rect = {10,25,380,375};
    /// changing to the above coordinates to coordinates in dialog units
    MapDialogRect(hwnd, &LV_rect);
    /// creating the list view control
    HWND lv_hwnd = CreateWindow(
                                WC_LISTVIEW,
                                L"",
                                WS_CHILD | LVS_REPORT | LVS_EDITLABELS | WS_VISIBLE,
                                LV_rect.left, LV_rect.top,
                                LV_rect.right - LV_rect.left,
                                LV_rect.bottom - LV_rect.top,
                                hwnd,
                                (HMENU)nid_itd_lv,
                                (HINSTANCE)GetWindowLong(GetParent(hwnd), GWL_HINSTANCE),
                                NULL
                                );
    /// adding some extended styles and adding columns
    ListView_SetExtendedListViewStyle(lv_hwnd, LVS_EX_FLATSB | LVS_EX_FULLROWSELECT | LVS_EX_GRIDLINES | LVS_EX_LABELTIP );
    create_invoice_lv_columns(lv_hwnd);
}

BOOL create_invoice_lv_columns(HWND hwnd)
{
    LVCOLUMN lvc;
    lvc.mask = LVCF_FMT | LVCF_SUBITEM | LVCF_WIDTH | LVCF_TEXT;
    /// some variables deceleration
    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");
    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(hwnd, i, &lvc);
    }
}

basefile01.h

#define _UNICODE
#define UNICODE

#include <tchar.h>
#define _WIN32_IE 0x0700
#include <windows.h>
#include <windowsx.h>
#include <commctrl.h>

#include "main_rsc.h"

BOOL CALLBACK invoice_dialog_box_message_handle(HWND, UINT, WPARAM, LPARAM);
BOOL CALLBACK invoice_dialog_child_enum_scroll(HWND, LPARAM);
BOOL create_listViews_invoice_dialog(HWND);
BOOL create_invoice_lv_columns(HWND);

main_res.h

#define MAIN_MENU 1
    #define NEW_INVOICE_DIALOG_MENU 2
    #define NEW_INVOICE_DIALOG 3
    #define NEW_INVOICE_DIALOG_MENU_save    4
    #define NEW_INVOICE_DIALOG_MENU_help    6
    #define APP_ICON_XL 7
    #define APP_ICON_S 8

    #define MAIN_MENU_file_new_invoice  102
    #define MAIN_MENU_file_new_challan  103
    #define MAIN_MENU_file_open         104
    #define MAIN_MENU_file_export_jpeg  105
    #define MAIN_MENU_file_export_pdf   106

    #define nid_ponumber_c          107
    #define nid_ponumber_t          108
    #define nid_podate_c            109
    #define nid_podate_t            110
    #define nid_vcode_c             111
    #define nid_vcode_t             112
    #define nid_inv_no_c            113
    #define nid_inv_no_t            114
    #define nid_inv_date_t          115
    #define nid_inv_date_c          116
    #define nid_seller_gstin_c      117
    #define nid_seller_gstin_t      118
    #define nid_seller_info         119
    #define nid_seller_state_c      120
    #define nid_seller_state_t      121

    #define nid_ship_info           122
    #define nid_ship_date_c         123
    #define nid_ship_date_t         124
    #define nid_ship_add_t          125
    #define nid_ship_add_c          126
    #define nid_ship_mode_t         127
    #define nid_ship_mode_c         128
    #define nid_ship_to_t           129
    #define nid_ship_to_c           130
    #define nid_ship_gstin_t        131
    #define nid_ship_gstin_c        132
    #define nid_ship_state_t        133
    #define nid_ship_state_c        134
    #define nid_order_info          135

    #define nid_bt_info             136
    #define nid_bt_to_t             137
    #define nid_bt_to_c             138
    #define nid_bt_add_t            139
    #define nid_bt_add_c            140
    #define nid_bt_gstin_t          141
    #define nid_bt_gstin_c          142
    #define nid_bt_state_t          143
    #define nid_bt_state_c          144

    #define nid_is_bt_st_same_      145

    #define nid_tax_info            146
    #define nid_tax_rc_t            147
    #define nid_tax_rc_c            148
    #define nid_tax_cgst_t          149
    #define nid_tax_cgst_c          150
    #define nid_tax_sgst_t          151
    #define nid_tax_sgst_c          152
    #define nid_tax_igst_t          153
    #define nid_tax_igst_c          154

    #define nid_itd_info            155
    #define nid_itd_lv              156
    #define nid_itd_mat_t           157
    #define nid_itd_mat_c           158
    #define nid_itd_qty_t           159
    #define nid_itd_qty_c           160
    #define nid_itd_hsn_t           161
    #define nid_itd_hsn_c           162
    #define nid_itd_rate_t          163
    #define nid_itd_rate_c          164

main_res.rc

#include <windows.h>
#include <commctrl.h>
#include <richedit.h>
#include "../include/main_rsc.h"

///////// MENUS

MAIN_MENU MENU
{
    POPUP "File"
    {
        POPUP "New"
        {
            MENUITEM "Invoice", MAIN_MENU_file_new_invoice
            MENUITEM "Challan", MAIN_MENU_file_new_challan
        }
        MENUITEM "&open", MAIN_MENU_file_open
        POPUP "&Export"
        {
            MENUITEM "JPEG", MAIN_MENU_file_export_jpeg
            MENUITEM "PDF", MAIN_MENU_file_export_pdf
        }
    }
}

NEW_INVOICE_DIALOG_MENU MENU
{
    MENUITEM "&save", NEW_INVOICE_DIALOG_MENU_save
    MENUITEM "&help",NEW_INVOICE_DIALOG_MENU_help,HELP
}

//////////////// ICONS

APP_ICON_XL ICON "icons/icon02_256.ico"
APP_ICON_S ICON "icons/icon02_16.ico"

/**
    DIALOG resource
*/

NEW_INVOICE_DIALOG 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
MENU NEW_INVOICE_DIALOG_MENU
FONT 8, "Ms Shell Dlg"
{
    GROUPBOX "Purchase Order Information", nid_order_info, 10, 10, 370, 65
    LTEXT "PO NUMBER",nid_ponumber_t,       20, 20, 50, 12
    EDITTEXT nid_ponumber_c,                70, 20, 100, 12, ES_LEFT | WS_BORDER | WS_TABSTOP | WS_GROUP | ES_AUTOHSCROLL
    LTEXT "PO DATE", nid_podate_t,          20, 40, 50, 12
    EDITTEXT nid_podate_c,                  70, 40, 100, 12, ES_LEFT | WS_BORDER | WS_TABSTOP | WS_GROUP | ES_AUTOHSCROLL
    LTEXT "Vendor Code", nid_vcode_t,       20, 60, 50, 12
    EDITTEXT nid_vcode_c,                   70, 60, 100, 12, ES_LEFT | WS_BORDER | WS_TABSTOP | WS_GROUP | ES_AUTOHSCROLL

    GROUPBOX "Seller Information", nid_seller_info, 10,80, 180, 70
    LTEXT "Invoice No.", nid_inv_no_t,   20, 90, 50, 20
    EDITTEXT nid_inv_no_c,                  70, 90, 100, 12, ES_LEFT | WS_BORDER | WS_TABSTOP | WS_GROUP | ES_AUTOHSCROLL
    LTEXT "Invoice date", nid_inv_date_t,   20, 110, 50, 12
    EDITTEXT nid_inv_date_c,                70, 110, 100, 12, ES_LEFT | WS_BORDER | WS_TABSTOP | WS_GROUP | ES_AUTOHSCROLL
    LTEXT "GSTIN", nid_seller_gstin_t,      20, 130, 50, 12
    EDITTEXT nid_seller_gstin_c,            70, 130, 100, 12, ES_LEFT | WS_BORDER | WS_TABSTOP | WS_GROUP | ES_AUTOHSCROLL

    GROUPBOX "Billed To", nid_bt_info, 10, 155, 180, 100
    LTEXT "Name", nid_bt_to_t, 20,170,50,12
    EDITTEXT nid_bt_to_c, 70, 170,100,12, ES_LEFT | WS_BORDER | WS_TABSTOP | WS_GROUP | ES_AUTOHSCROLL
    LTEXT "Address", nid_bt_add_t, 20,190,50,12
    EDITTEXT nid_bt_add_c, 70,190,100,12,  ES_LEFT | WS_BORDER | WS_TABSTOP | WS_GROUP | ES_AUTOHSCROLL
    LTEXT "GSTIN", nid_bt_gstin_t, 20, 210, 50,12
    EDITTEXT nid_bt_gstin_c, 70,210,100,12,  ES_LEFT | WS_BORDER | WS_TABSTOP | WS_GROUP | ES_AUTOHSCROLL
    LTEXT "State", nid_bt_state_t, 20, 230,50,12
    EDITTEXT nid_bt_state_c, 70,230,100,12,  ES_LEFT | WS_BORDER | WS_TABSTOP | WS_GROUP | ES_AUTOHSCROLL

    CHECKBOX "Shipped to is same as Billed to", nid_is_bt_st_same_, 200, 230, 180,20

    GROUPBOX "Shipping Information", nid_ship_info, 200, 80, 180, 140
    LTEXT "Name ", nid_ship_to_t, 210, 100, 50, 12
    EDITTEXT nid_ship_to_c, 260, 100, 100, 12,ES_LEFT | WS_BORDER | WS_TABSTOP | WS_GROUP | ES_AUTOHSCROLL
    LTEXT "Address", nid_ship_add_t , 210, 120, 50,12
    EDITTEXT nid_ship_add_c, 260, 120,100,10, ES_LEFT | WS_BORDER | WS_TABSTOP | WS_GROUP | ES_AUTOHSCROLL
    LTEXT "GSTIN", nid_ship_gstin_t, 210,140,50,12
    EDITTEXT nid_ship_gstin_c, 260,140,100,12, ES_LEFT | WS_BORDER | WS_TABSTOP | WS_GROUP | ES_AUTOHSCROLL
    LTEXT "Date", nid_ship_date_t, 210,160,50,12
    EDITTEXT nid_ship_date_c, 260,160,100,12, ES_LEFT | WS_BORDER | WS_TABSTOP | WS_GROUP | ES_AUTOHSCROLL
    LTEXT "Mode", nid_ship_mode_t, 210, 180,50,12
    EDITTEXT nid_ship_mode_c, 260, 180,100,12, ES_LEFT | WS_BORDER | WS_TABSTOP | WS_GROUP | ES_AUTOHSCROLL
    LTEXT "State", nid_ship_state_t, 210,200,50,12
    EDITTEXT nid_ship_state_c, 260,200,100,12, ES_LEFT | WS_BORDER | WS_TABSTOP | WS_GROUP | ES_AUTOHSCROLL

    GROUPBOX "Taxing information", nid_tax_info, 10,270,370, 45
    CTEXT "CGST (%)", nid_tax_cgst_t, 25, 280, 100, 12
    EDITTEXT nid_tax_cgst_c, 25,295, 100, 12, ES_LEFT | WS_BORDER | WS_TABSTOP | WS_GROUP | ES_NUMBER
    CTEXT "SGST (%)", nid_tax_sgst_t, 135, 280, 100, 12
    EDITTEXT nid_tax_sgst_c, 135,295, 100, 12, ES_LEFT | WS_BORDER | WS_TABSTOP | WS_GROUP | ES_NUMBER
    CTEXT "IGST (%)", nid_tax_igst_t, 255, 280, 100, 12
    EDITTEXT nid_tax_igst_c, 255,295, 100, 12, ES_LEFT | WS_BORDER | WS_TABSTOP | WS_GROUP | ES_NUMBER

}

by the way I am using codes bock on windows vista home basics SPS2 (32 bit)

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Problem

Problem is with the MoveWindow function inside invoice_dialog_child_enum_scroll function in basefile01.cpp.

whenever WM_VSCROLL is processed and the lvc is moved up and all of its column header vanishes.

however there is no mistake or error ( as fas as I know ) in making lisview and its columns because when i change the coordinates of the lvc, so that when it is created it is on the screen which is visible to me at that time, and the moment when I click the line down/up, page down/up and thumbtrack, those column headers vanishes.

and also that if you compare the size of the lvc in both the images, first one is undesirably too small.

as mush as i could debug this project, it is MoveWindow which is making this problem and SetWindowPos is no better.

I know that this post is very long but any of your suggestion would be great!
Thanks for your time.

Answer 1

As suggested by @Barmak Shemirani and @Paul Sanders, I made whole new project but this time without extra controls and only with listview.

And i have found out that the problem was with the MoveWindow inside EnumChildWindow but I don't know why?

But Check the following link you know know why and also, i have posted the code of that project.

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

Answer 2

EnumChildWindows will go through all child windows including descendants. Meanwhile, ListView control has a child header control, that header control ends up being moved in enum procedure. You should instead move the listview control only. You can use a for loop to go through the child windows, not the descendants:

for(HWND child = GetWindow(hwnd, GW_CHILD); child; 
        child = GetWindow(child, GW_HWNDNEXT)) { }
    ...

Also use SetScrollInfo to more accurately set the scroller bar information. Example:

std::map<HWND, int> item_positions;

BOOL CALLBACK diaproc(HWND hwnd, UINT msg, WPARAM wParam, LPARAM)
{
    static HWND hlist;
    switch(msg)
    {
    case WM_INITDIALOG:
    {
        hlist = CreateWindow(WC_LISTVIEW, NULL, WS_CHILD | WS_VISIBLE | LVS_REPORT,
            10, 100, 300, 2000, hwnd, NULL, NULL, NULL);
        ListView_SetExtendedListViewStyle(hlist, LVS_EX_GRIDLINES);
        std::vector<TCHAR*> col_names = { TEXT("text1"), TEXT("text2") };
        LVCOLUMN lvc;
        lvc.mask = LVCF_FMT | LVCF_SUBITEM | LVCF_WIDTH | LVCF_TEXT;
        for(int i = 0; i < (int)col_names.size(); i++)
        {
            lvc.fmt = LVCFMT_LEFT;
            lvc.cx = 100;
            lvc.pszText = col_names[i];
            lvc.iSubItem = i;
            ListView_InsertColumn(hlist, i, &lvc);
        }

        RECT rc;
        GetClientRect(hwnd, &rc);

        //find the lowest point in dialog:
        RECT list_rect;
        GetClientRect(hlist, &list_rect);
        POINT pt = { list_rect.right, list_rect.bottom };
        ScreenToClient(hwnd, &pt);

        SCROLLINFO info = { sizeof(SCROLLINFO) };
        info.fMask = SIF_ALL;
        info.nMin = 0;
        info.nMax = pt.y + rc.bottom - 1;
        info.nPage = rc.bottom;
        info.fMask = SIF_ALL;
        SetScrollInfo(hwnd, SB_VERT, &info, TRUE);

        //save y-positions for later
        for(HWND child = GetWindow(hwnd, GW_CHILD); child;
            child = GetWindow(child, GW_HWNDNEXT))
        {
            GetWindowRect(child, &rc);
            pt = { rc.left, rc.top };
            ScreenToClient(hwnd, &pt);
            item_positions[child] = pt.y;
        }

        return FALSE;
    }

    case WM_VSCROLL:
    {
        SCROLLINFO info = { sizeof(info) };
        info.fMask = SIF_ALL;
        GetScrollInfo(hwnd, SB_VERT, &info);
        int pos = info.nPos;
        int track = HIWORD(wParam);
        switch(LOWORD(wParam))
        {
        case SB_LEFT: pos = info.nMin; break;
        case SB_RIGHT: pos = info.nMax; break;
        case SB_LINELEFT: pos--; break;
        case SB_LINERIGHT: pos++;  break;
        case SB_PAGELEFT: pos -= info.nPage; break;
        case SB_PAGERIGHT: pos += info.nPage; break;
        case SB_THUMBPOSITION: 
        case SB_THUMBTRACK: pos = track; break;
        }
        SetScrollPos(hwnd, SB_VERT, pos, FALSE);

        int count = 0;
        for(HWND child = GetWindow(hwnd, GW_CHILD); child; 
                child = GetWindow(child, GW_HWNDNEXT))
            count++;

        HDWP hdwp = BeginDeferWindowPos(count);
        for(HWND child = GetWindow(hwnd, GW_CHILD); child; 
            child = GetWindow(child, GW_HWNDNEXT))
        {
            RECT rc;
            GetWindowRect(child, &rc);
            POINT pt = { rc.left, rc.top }; 
            ScreenToClient(hwnd, &pt);

            if(item_positions.find(child) != item_positions.end())
            {
                int y = pos - item_positions[child];
                DeferWindowPos(hdwp, child, NULL, pt.x, -y, 0, 0, 
                    SWP_NOSIZE | SWP_NOACTIVATE);
            }
        }
        EndDeferWindowPos(hdwp);
        return TRUE;
    }

    case WM_COMMAND:
        if(LOWORD(wParam) == IDCANCEL) 
            EndDialog(hwnd, wParam); 
        return TRUE;

    default: return FALSE;
    }
}

int WINAPI WinMain(HINSTANCE hinst, HINSTANCE, LPSTR, int)
{
    DialogBox(hinst, MAKEINTRESOURCE(IDD_DIALOG1), 0, (DLGPROC)diaproc);
    return 0;
}