Thanks CornedBee, I know that and that was exactly my point, but i changed their names for a style preference. Anyways, if both the function parameter and the internal data had the same name it would be kind of hard to tell them apart dont u think?
By the way, all friend classes and other classes of this type can access its private member data.
Thx CornedBee, that anser my question :) , the how abt export a class in my previous post?
regards,
by the way, CornedBee, where should i place the "_IKDLL_INT" inside the Project Settings?
regards,
MoMad: I don't remember exactly how I wrote the class, it's been awhile.
Chris:
project->settings->C/C++->precompile-definitions (or something like that - I'm translating from german)
thx, CornedBee, I get it. it is under the 'Preprocessor Definition' :)
Is there a possible for me to create a main window + register the class, so that I can have a WndProc CALLBACK within a DLL?
regards,
I think so if you can get the instance handle. But wouldn't that take the point out of using VB?
Thx CornedBee, Im learning more about writing a DLL in various possible way.
:D here is more specific to my question, Can I write it so... As you reply in my others thread about the LoadAccelerators
Do I still need to return the msg.wParam rather than return True? But Ican't to so, 'coz the DllMain is define to return Boolean data type :(PHP Code:// DLL Main CALLBACK
BOOL APIENTRY DllMain(HANDLE hModule, DWORD dwReason, LPVOID lpReserved)
{
WNDCLASSEX wcex;
switch(dwReason)
{
case DLL_PROCESS_ATTACH:
// DLL loaded
hInst= (HINSTANCE)hModule;
MSG msg;
// Register Windows Class
wcex.cbSize = sizeof(WNDCLASSEX);
wcex.style = CS_HREDRAW | CS_VREDRAW;
wcex.lpfnWndProc = (WNDPROC)WndProc;
wcex.cbClsExtra = 0;
wcex.cbWndExtra = 0;
wcex.hInstance = hInst;
wcex.hIcon = NULL;
wcex.hCursor = NULL;
wcex.hbrBackground = (HBRUSH)(COLOR_WINDOW+1);
wcex.lpszMenuName = NULL;
wcex.lpszClassName = "MapCE";
wcex.hIconSm = NULL;
RegisterClassEx(&wcex);
// Create Map Window
hWndMap = CreateWindow("MapCE",
"MapCE",
WS_OVERLAPPED | WS_POPUP | WS_BORDER,
0,
0,
400,
400,
NULL,
NULL,
hInst,
NULL);
if (hWndMap != NULL)
{
ShowWindow(hWndMap, SW_HIDE);
UpdateWindow(hWndMap);
}
// Main message loop:
while (GetMessage(&msg, NULL, 0, 0))
{
TranslateMessage(&msg);
DispatchMessage(&msg);
}
return TRUE;
case DLL_PROCESS_DETACH:
// Dll Unload
hInst = NULL;
// Destroy the Map Window
if (hWndMap != NULL)
DestroyWindow(hWndMap);
break;
}
return TRUE;
}
with the above code, my DLL get hang at the following line..
Is this due to the inproper used of the GetMessage? or Can I change the return value of the DllMain CALLBACK function?PHP Code:// Main message loop:
while (GetMessage(&msg, NULL, 0, 0))
{
TranslateMessage(&msg);
DispatchMessage(&msg);
}
regards,
Nearly.
1) I'm not sure if DLL module handles are legal as handle for WNDCLASS(EX).
2) If hWndMap is NULL after CreateWindow, the call failed. You shouldn't simply continue.
3) The message loop is sure to make problems. It means that DllMain won't return until the program QUITS! Since DllMain will be executed at the moment the DLL is loaded. This can be either the moment you call LoadLibrary or the program start (even before WinMain). This is risky because I don't know what VB does. Most probably it won't have it's own windows displayed. So you start an application that displays a window that probably can't even end the application and then wait for the end of the application, and THEN let VB execute it's code.
There are two solutions for this:
1) Maybe VB incidently calls your WndProc too. This is possible, but I wouldn't rely on it.
2) Write a DLL function that does advanced stuff with PeekMessage and such things. This function would need to be called repeatedly throughout your app. That would be complicated.
you posted while I was writing. This is exactly what I wanted to say: VB will hang.
so, can i remark those GetMessage function, hence, the DLL won't hang :D But... will my DLL still received those message belong to hWndMap window?
PHP Code:/*
// Main message loop:
while (GetMessage(&msg, NULL, 0, 0))
{
TranslateMessage(&msg);
DispatchMessage(&msg);
}
*/
I get a wird result :eek:, I manage to capture those WM_LBUTTONDOWN, WM_LBUTTONUP, WM_MOUSEMOVE message under the WndProc within the DLL after I remark those GetMessage API function call.
I'm appretiate if you can take a look on my enclosed sample code.
regards,
Chris.C
that's ok. It just means that internally VB has a normal message loop, that means that it captures messages for all windows of the app, and your dll created one is just one more.
so you use a c++ program... Is it just for test purposes or is it the end product?
However, as I said your message loop catches every message, including those to the MapCE window.
One word on SEH:
You used try...catch
that is c++ exception handling and is of no use in your situation. I suppose you want SEH, which uses _try..._except and _try..._finally blocks. This is an important difference! SEH is a large topic, covered in detail for exaple in "Microsoft Windows Programming for Experts", Jeffrey Richter, Microsoft Press. It costs 70-80 dollars....(1000 ÖS, where 1 $ = ~15 ÖS).... I suppose you find everything you need to know in MSDN :)
It is all the message is being capture by the DLL itself of the external application that loaded the DLL into it memory space?
yap, for instance, eMbedded VC++ will be the final platform that the reason my sample program will be in VC++. Somehow later it require to integrate to VB as well lor. so... be prepare now :) else suffer later...
I'll look into more about the SEH in MSDN and thx for your tips :) By the way, Is there ham if i continue to use the try... catch(...) to capture the all exception error messages?
regards,
Chris.C
There is a harm: it simply won't work :)
If you want to use it with VB later, you have to be aware that the mothod you use now may not work there because it may have a different message loop.
Can you rephrase your first question plz? I don't understand it...
Where did SEH come into this?
5-6 posts above in the attachement
Oh okay :) I didn't look at the attachment so when you mentioned SEH I got confused.
I don't normally use it, because any FATAL system exceptions will be caught by the normal C++ exception handling:Code:int *ptr = (int*)NULL;
try {
*ptr = 5;
} catch(...) {
cout << "Caught!" << endl;
}
I didn't know that...
that just like what i have applied in my code as below to retrieve the error message..
But... I always get the same error message as...PHP Code:LPVOID lpMsgBuf;
FormatMessage(
FORMAT_MESSAGE_ALLOCATE_BUFFER |
FORMAT_MESSAGE_FROM_SYSTEM |
FORMAT_MESSAGE_IGNORE_INSERTS,
NULL,
GetLastError(),
MAKELANGID(LANG_NEUTRAL, SUBLANG_DEFAULT), // Default language
(LPTSTR) &lpMsgBuf,
0,
NULL
);
// Display the string.
MessageBox(hWndMain, (LPCTSTR)lpMsgBuf, "RouteCE", MB_OK | MB_ICONEXCLAMATION);
// Free the buffer.
LocalFree(lpMsgBuf);
'The operation is successful completed' :( why also the same error message?
Quote:
Originally posted by parksie
Oh okay :) I didn't look at the attachment so when you mentioned SEH I got confused.
I don't normally use it, because any FATAL system exceptions will be caught by the normal C++ exception handling:Code:int *ptr = (int*)NULL;
try {
*ptr = 5;
} catch(...) {
cout << "Caught!" << endl;
}
Only Win32 API functions call SetLastError(...) so an access violation or page fault won't.
You can also call SetLastError yourself, but it isn't done by the compiler.
may i know the adv/disadv for shifting part of the code in a project into LIB (*.lib)/DLL(*.dll)? When I shoud use which?
regards,
Basically, they both allow you to reuse the same code in more than one program. A LIB is static, so it's linked directly into the program. This means that it doesn't rely on anything else for it. A DLL also has a LIB associated with it, but this is just a stub to tell it where to find the functions in the DLL.
The problem with DLLs is the usual one ;)
DLL +:
Only once in memory!
Can be updated, recompiled and replaced wtihout having to recompile the application (as ling as the front-end remains the same, the entry points would probably change so this is more a theoretical advantage)
Can be used in more languages (how to use libs in VB or pascal?)
LIB +:
Called faster
Easier to write :)
Included in exe, so shipping is just one file.
There may be more, but that's what comes to mind...
:) thx both Parksie & CornedBee. I get the different now.
:D after long period and I finally found the way to return a string from a VC++ dll to VB application and just woulkd like to share with your guy. :) I also enclose the sample code here...
PHP Code:// DLL External Callback Function Definition
typedef void (CALLBACK* ExSockProc)(UINT msg, long lParam, BSTR bstrBuffer);
// Callback function declaration
ExSockProc MyExSockProc;
BSTR bstr;
// Allocate BSTR buffer
bstr = SysAllocStringLen(NULL, lstrlen(lpszMessage));
// convert from char to BSTR
MultiByteToWideChar(CP_ACP,
0,
(LPSTR)lpszMessage,
strlen(lpszMessage),
LPWSTR(bstr),
lstrlen(lpszMessage));
// Send the error message back to external program
if (MyExSockProc != NULL)
MyExSockProc(SOCKET_SENDCOMPLETE, lstrlen(lpszMessage), bstr);
// Release the used memory
SysFreeString(bstr);
It's been a long time...
Just one more thing: when you know you're dealing with a UNICODE string, you shouldn't use lstrlen but rather lstrlenW or wcslen, because lstrlen will be either lstrlenA or lstrlenW depending on compiler settings.
ic, but the lpszMessage is a char array. Should I proceed to use lstrlenW?
no, wait, I misunderstood your code. It's ok.
Chris,
Great to see you finally got it working. Now I want to ask you a few questions:
- How would you pass a UDT to a VC program, modify the value, and then show it in VB?
- Declare a callback function from vb?? how to use a "function" as the callback and not a "sub"??
I had more, but forgot. But most importantly, this is what killed me:
VB Code:
I just want to know why Functions cant be used as callbacks (or event) as opposed to subs. also, why cant you "modify" the value of a VB UDT?
Regards,
MoMad
Hi Momad, the callback function need not must be a Function, it can be a Sub as well. Since the AddressOf function is just passing the memory location of the respective function/sub into the dll. So that, any need the dll can execute the original function/sub as below:
VB Code:
As for the UDT, I'll back to you later :)
Just remember that the callback must be in the main module of your project. And watch out. If any parameter except strings is not explicitely declared as ByVal, you need to use &var in C to pass it.
So your function must be called like:
else you see VB going down with an access violation and this may kill your entire progress if you didn't save.Code:int DllFunc(VBCB pCallback)
{
int i = 4, j = 7;
pCallback(/*string*/, &i, j);
}
Juz include one more function in the sample code:
and in VB will be like...PHP Code:typedef struct tagUSERDATA
{
long Param1;
long Param2;
LPSTR lpszParam3;
} USERDATA, FAR * LPUSERDATA;
extern "C" __declspec(dllexport) void FillUDT(LPUSERDATA UserData)
{
// Fillup the pass in UserData structure
UserData->Param1 = 100;
UserData->Param2 = 201;
sprintf(UserData->lpszParam3, "This is the data return from VC++ DLL through structure.");
}
VB Code:
regards,
thanks, ill look at this later, i lost my connection this weekend.
Chris, I need some help here :rolleyes:
http://www.vbforums.com/showthread.p...hreadid=281510
Whoa, that is SOME old thread you revived...
Hi Gtarawneh,
Yup, it was really a old thread, and you can passing data between 2 application by sending the WM_COPYDATA. With this message, you can passing your own structure.
All you need is to locate the recepient winow handle by FindWindow or FindWindowEx, Also you need to subclass the VB application main window procedure.
Do let me know if you need any sample :)
regards,
Oops! Sorry guys :rolleyes:
Anyway, Chris I think you misunderstood! I am looking for a way to pass my structure into a C++ DLL (Precisely an ATL Com DLL), just the same as you, except that you were using API! Not from one C++ application into another VB application :)