HWND and HMODULE

They are both handles. HWND is a window handle and HMODULE is a module handle. They are used to represent, internally to the WIN32 API, a windows and a module respectively. I'm sure you've already figure this out though, so is there anything specific you don't get?

@evil: I already figure this out but, i would like to know, when shoule i use HWND and when should i use HMODULE from application perspective? and any difference between HWND and HMODULE?

am new to this kind of GUI programming!!!!!!

Regards
Sham

@evil: What do u mean, when u say, "internally to the WIN32 API, a windows and a module respectively"


Regards
Sham

@evil: WHat about HMODULE? As u said HWND points to any window kind of object, To which type of object does HMODULE point?

Regards
Sham

HMODULE represent a module... a module would be a DLL or an executable (EXE).
See the help for GetModuleHandle() and GetModuleFilename()
http://msdn.microsoft.com/en-us/library/ms683199(VS.85).aspx
http://msdn.microsoft.com/en-us/library/ms683197(VS.85).aspx

@evil: what do u mean by term module here: "  if it is working with a module it will expect a HMODULE"

module mean a function?

Regards
Sham

>> if it is working with a module it will expect a HMODULE
If the function is used to work with or manupulate a module, for example GetModuleFilename() returns the filename of a module (see my post above).

Done

Hello

We have a code where  HMODULE object is asssigned to HWND object as below:

hAPPINST=hResourceModule;

hAPPINST is of type HWND and hResourceModule is of type HMODULE

Regards
Sham
 

@evil: How can a module type handle be assigned to window type handle?

Regards
Sham

Without seeing the code and the context I can't answer that... a HWND and a HMODULE are not related types, I presume there is a cast involved in this otherwise it shouldn't compile?

#include <windows.h>
 
int main()
{
	HWND hWnd = 0;
	HMODULE hModule = hWnd;
}
 
1>------ Build started: Project: testr, Configuration: Debug Win32 ------
1>Compiling...
1>main.cpp
1>main.cpp(6) : error C2440: 'initializing' : cannot convert from 'HWND' to 'HMODULE'
1>        Types pointed to are unrelated; conversion requires reinterpret_cast, C-style cast or function-style cast
1>Build log was saved at "file:BuildLog.htm"
1>testr - 1 error(s), 0 warning(s)
========== Build: 0 succeeded, 1 failed, 0 up-to-date, 0 skipped ==========

Select allOpen in new window

@evil: Here is the code
typedef struct tagAPPINFO {
   INT      iVersion;
   INT      iFiller;

   HWND     hAppInst;
   INT      iAppType;

   HWND     hWndFrame;
   HWND     hWndMDIClient;
   HWND     hWndToolbar;
   HWND     hWndStatbar;

   UINT     uMemBlocks;
   UINT     uMemBlockSize;

   char     szAppName  [MAXOBJNAME      + 2];
   char     szFileName [FILENAME_LENGTH + 2];
   char     szHelpFile [PATHNAME_LENGTH + 2];
   char     szPathName [PATHNAME_LENGTH + 2];
   BOOL     bDeltaMode;
   char     szSysPathName[PATHNAME_LENGTH + 2];
   } APPINFO;

static HMODULE hResourceModuke;
APPINFO  appInfo;
#define hAPPINST  appInfo.hAppInst  // this is header file  

int WINAPI TNGMain (LPSTR lpszCmdLine, ULONG TNGContext, int nCmdShow, HWND hParent)
{
/* clear application information structure */
   memset  (&appInfo, '\0', sizeof (APPINFO));

   /* save instance handle in structure */
   hAPPINST = hResourceModule;
   hWndParent = hParent;

   /* set other application information in structure */
   appInfo.iVersion      = iVERSION;
   appInfo.uMemBlocks    = NUMMEMBLOCKS;
   appInfo.uMemBlockSize = MEMBLOCKSIZE;
   strncpy(appInfo.szAppName,  szAPPNAME, MAXOBJNAME);
   strcpy(appInfo.szFileName, szFILENAME);
   strcpy(appInfo.szHelpFile, sz2DHELPFILE);

   /* register window classes if this is the first instance */
   if (!RegisterClasses (hAPPINST))
      return FALSE;
.
.
.
}

Regards
Sham

Are you sure that...

#define hAPPINST  appInfo.hAppInst  // this is header file  

...isn't being conditionally precompile to be either a HWND or a HMODULE depending upon build settings? Try changing hAPPINST = hResourceModule to be appInfo.hAppInst = hResourceModule and also, put a break point on this line to confirm the type is HWND. As you an see above, the types are not compatible under normal circumstances.

am sure about it.

i wrote:

appInfo.hAppInst = hResourceModule; and compiled, it worked

Regards
Sham
 

@evil: i placed another question with subject "wndclass and registerclass", Can u please look into that?

Regards
Sham

Then, I have to be honest, I don't know. I tested this in VS2005 and the types are not compatible.

@evil: How do i know, whether, currently HWND/HMODULE pointer is pointed to some object or is NULL? can we write some debug statement?

Regards
Sham

>> How do i know, whether, currently HWND/HMODULE pointer is pointed to some object or is NULL?
Something like this maybe?

#include <windows.h>
 
int main()
{
	HWND hWnd = NULL;
	HMODULE hModule = NULL;
 
	if(NULL == hWnd) { /* it's null */ }
	if(NULL == hModule) { /* it's null */ }
 
	if(NULL != hWnd) { /* it's not null */ }
	if(NULL != hModule) { /* it's not null */ }
}

Select allOpen in new window