Need understanding of the code

[topten]

Hello
I am walking through a win32 api tutorial. I dont understand some thing
I have .rc file where I have

//Microsoft Developer Studio generated resource script.
//
#include "Resource.h"

#define APSTUDIO_READONLY_SYMBOLS
/////////////////////////////////////////////////////////////////////////////
//
// Generated from the TEXTINCLUDE 2 resource.
//
#include "Windows.h"

/////////////////////////////////////////////////////////////////////////////
#undef APSTUDIO_READONLY_SYMBOLS

/////////////////////////////////////////////////////////////////////////////
// English (U.S.) resources

#if !defined(AFX_RESOURCE_DLL) || defined(AFX_TARG_ENU)
#ifdef _WIN32
LANGUAGE LANG_ENGLISH, SUBLANG_ENGLISH_US
#pragma code_page(1252)
#endif //_WIN32

/////////////////////////////////////////////////////////////////////////////
//
// Dialog
//

IDD_ERRORSHOW DIALOGEX 0, 0, 182, 42
STYLE DS_SETFOREGROUND | DS_3DLOOK | DS_CENTER | WS_MINIMIZEBOX | WS_VISIBLE |
WS_CAPTION | WS_SYSMENU
CAPTION "Error Show2"
FONT 8, "MS Sans Serif"
BEGIN
LTEXT "Error:", IDC_STATIC, 4, 4, 19, 8
EDITTEXT IDC_ERRORCODE, 24, 2, 24, 14, ES_AUTOHSCROLL | ES_NUMBER
DEFPUSHBUTTON "Look up", IDOK, 56, 2, 36, 14
CONTROL "&On top", IDC_ALWAYSONTOP, "Button", BS_AUTOCHECKBOX |
WS_TABSTOP, 104, 4, 38, 10
EDITTEXT IDC_ERRORTEXT, 4, 20, 176, 20, ES_MULTILINE | ES_AUTOVSCROLL |
ES_READONLY | NOT WS_BORDER | WS_VSCROLL,
WS_EX_CLIENTEDGE
END


/////////////////////////////////////////////////////////////////////////////
//
// DESIGNINFO
//

#ifdef APSTUDIO_INVOKED
GUIDELINES DESIGNINFO DISCARDABLE
BEGIN
IDD_ERRORSHOW, DIALOG
BEGIN
LEFTMARGIN, 7
RIGHTMARGIN, 175
TOPMARGIN, 7
BOTTOMMARGIN, 35
END
END
#endif // APSTUDIO_INVOKED


#ifdef APSTUDIO_INVOKED
/////////////////////////////////////////////////////////////////////////////
//
// TEXTINCLUDE
//

1 TEXTINCLUDE DISCARDABLE
BEGIN
"Resource.h\0"
END

2 TEXTINCLUDE DISCARDABLE
BEGIN
"#include ""Windows.h""\r\n"
"\0"
END

3 TEXTINCLUDE DISCARDABLE
BEGIN
"\r\n"
"\0"
END

#endif // APSTUDIO_INVOKED


/////////////////////////////////////////////////////////////////////////////
//
// Icon
//

// Icon with lowest ID value placed first to ensure application icon
// remains consistent on all systems.
IDI_ERRORSHOW ICON DISCARDABLE "ErrorShow.ico"
#endif // English (U.S.) resources
/////////////////////////////////////////////////////////////////////////////



#ifndef APSTUDIO_INVOKED
/////////////////////////////////////////////////////////////////////////////
//
// Generated from the TEXTINCLUDE 3 resource.
//


/////////////////////////////////////////////////////////////////////////////
#endif // not APSTUDIO_INVOKED


And I have a cpp file where I have

/******************************************************************************


#include "CmnHdr.h" /* See Appendix A. */
#include <Windowsx.h>
#include <tchar.h>
#include "Resource.h"


///////////////////////////////////////////////////////////////////////////////


#define ESM_POKECODEANDLOOKUP (WM_USER + 100)
const TCHAR g_szAppName[] = TEXT("Error Show2");


///////////////////////////////////////////////////////////////////////////////


BOOL Dlg_OnInitDialog(HWND hwnd, HWND hwndFocus, LPARAM lParam) {

chSETDLGICONS(hwnd, IDI_ERRORSHOW);

// Don't accept error codes more than 5 digits long
Edit_LimitText(GetDlgItem(hwnd, IDC_ERRORCODE), 5);

// Look up the command-line passed error number
SendMessage(hwnd, ESM_POKECODEANDLOOKUP, lParam, 0);
return(TRUE);
}


///////////////////////////////////////////////////////////////////////////////


void Dlg_OnCommand(HWND hwnd, int id, HWND hwndCtl, UINT codeNotify) {

switch (id) {

case IDCANCEL:
EndDialog(hwnd, id);
break;

case IDC_ALWAYSONTOP:
SetWindowPos(hwnd, IsDlgButtonChecked(hwnd, IDC_ALWAYSONTOP)
? HWND_TOPMOST : HWND_NOTOPMOST, 0, 0, 0, 0, SWP_NOMOVE | SWP_NOSIZE);
break;

case IDC_ERRORCODE:
EnableWindow(GetDlgItem(hwnd, IDOK), Edit_GetTextLength(hwndCtl) > 0);
break;

case IDOK:
// Get the error code
DWORD dwError = GetDlgItemInt(hwnd, IDC_ERRORCODE, NULL, FALSE);

HLOCAL hlocal = NULL; // Buffer that gets the error message string

// Use the default system locale since we look for Windows messages.
// Note: this MAKELANGID combination has 0 as value
DWORD systemLocale = MAKELANGID(LANG_NEUTRAL, SUBLANG_NEUTRAL);

// Get the error code's textual description
BOOL fOk = FormatMessage(
FORMAT_MESSAGE_FROM_SYSTEM | FORMAT_MESSAGE_IGNORE_INSERTS |
FORMAT_MESSAGE_ALLOCATE_BUFFER,
NULL, dwError, systemLocale,
(PTSTR)&hlocal, 0, NULL);

if (!fOk) {
// Is it a network-related error?
HMODULE hDll = LoadLibraryEx(TEXT("netmsg.dll"), NULL,
DONT_RESOLVE_DLL_REFERENCES);

if (hDll != NULL) {
fOk = FormatMessage(
FORMAT_MESSAGE_FROM_HMODULE | FORMAT_MESSAGE_IGNORE_INSERTS |
FORMAT_MESSAGE_ALLOCATE_BUFFER,
hDll, dwError, systemLocale,
(PTSTR)&hlocal, 0, NULL);
FreeLibrary(hDll);
}
}

if (fOk && (hlocal != NULL)) {
SetDlgItemText(hwnd, IDC_ERRORTEXT, (PCTSTR)LocalLock(hlocal));
LocalFree(hlocal);
}
else {
SetDlgItemText(hwnd, IDC_ERRORTEXT,
TEXT("No text found for this error number."));
}

break;
}
}


///////////////////////////////////////////////////////////////////////////////


INT_PTR WINAPI Dlg_Proc(HWND hwnd, UINT uMsg, WPARAM wParam, LPARAM lParam) {

switch (uMsg) {
chHANDLE_DLGMSG(hwnd, WM_INITDIALOG, Dlg_OnInitDialog);
chHANDLE_DLGMSG(hwnd, WM_COMMAND, Dlg_OnCommand);

case ESM_POKECODEANDLOOKUP:
SetDlgItemInt(hwnd, IDC_ERRORCODE, (UINT)wParam, FALSE);
FORWARD_WM_COMMAND(hwnd, IDOK, GetDlgItem(hwnd, IDOK), BN_CLICKED,
PostMessage);
SetForegroundWindow(hwnd);
break;
}

return(FALSE);
}


///////////////////////////////////////////////////////////////////////////////


int WINAPI _tWinMain(HINSTANCE hinstExe, HINSTANCE, PTSTR pszCmdLine, int) {

HWND hwnd = FindWindow(TEXT("#32770"), TEXT("Error Show2"));
if (IsWindow(hwnd)) {
// An instance is already running, activate it and send it the new #
SendMessage(hwnd, ESM_POKECODEANDLOOKUP, _ttoi(pszCmdLine), 0);
}
else {
DialogBoxParam(hinstExe, MAKEINTRESOURCE(IDD_ERRORSHOW),
NULL, Dlg_Proc, _ttoi(pszCmdLine));
}
return(0);
}


//////////////////////////////// End of File //////////////////////////////////


The question is How the gui and dialogue in cpp file formed by rc file?
How are they related to each other.
Could I have everything in one file, say cpp file?
Just please help me understand

[kbw]

How are they related to each other.

The .rc file is compiled by a "resource compiler", you get a .res file. It's linked with the.obj file to create the executable.

The program can create the dialog box defined in the resource file by using IDD_ERRORSHOW. It then has handlers for the things that happen when it's poked.

Could I have everything in one file, say cpp file?

You can't have everything in one file. Well, you can (because nothing's impossible), but you shouldn't. It's normal for applications to be built this way in Windows.

Just please help me understand

What is it you don't understand?

[topten]

Great thanx for your comments

What I dont understand is: How did .rc file appear in the project? Did it appear automatically after the programmer created the gui in the vs constructor? Or the programmer created this file?

Thanx in advance!

[kbw]

A Visual Studio wizard will create it. There's also a resource.h that is included by the .rc and .c/.cpp file where the constants are defined, like IDD_ERRORSHOW and any elements used by the dialog box. IDOK and IDCANCEL have always been used by every dialog box, so are defined thru using windows.h.