C / C++ / MFC

Repositioning cursor in an edit box

28-Aug-03 10:23

Anonymous wrote:
I wrote a simple win32 dll (non MFC) and tried to invoke its functions using run-time Loading (LoadLibrary).

This does not indicate that two DLLS are being used. I presume this is not the case and that there are actually two DLLS, one MFC and the other non-MFC. Yes?

Are the exported functions written in C++? If so, it sounds like name-mangling is at work here.

solution!

Alexander ^M.,28-Aug-03 11:00

Alexander ^M.,

28-Aug-03 11:00

bad answer greg!!!

i assume u defined your function like this:

void __declspec( dllexport ) foo()
{
  ...
}

this causes c++ name convention when using a c++ compiler!
to get a c export(which u want), use:

extern "C" void __declspec( dllexport ) foo()
{
  ...
}

Don't try it, just do it! Wink | ;-)

Re: solution!

Anonymous28-Aug-03 11:30

Anonymous

28-Aug-03 11:30

10x

Another question: is there any way to use a class defined and exported from a dll loaded by LoadLibrary() ?
Its if you can explain what is a "name convention" it would be grate

thanks.

Re: solution!

Alexander ^M.,28-Aug-03 12:42

Alexander ^M.,

28-Aug-03 12:42

i askey myself this question many times, it is possible, the half-life engine does it, but i still dont know how...

Don't try it, just do it! Wink | ;-)

Re: solution!

Antti Keskinen29-Aug-03 9:13

Antti Keskinen

29-Aug-03 9:13

Yes there is..

In fact, I pondered over this same problem a while back. The idea was that I was supposed to use a class which is completely declared inside a DLL. I only had the header files for reference.

So, here we go, first the actual class, declared with typedef. Do this in a seperate header file:

[code]

typedef class {

public:
// Some initialization functions ?
virtual HRESULT InitModule(void);
virtual HRESULT QuitModule(void);

// A member variable perhaps ?
int iMemberVariable;

} MyExportedClassType;

// Pointer-to-function returning address-of WindowPlugin class
typedef MyExportedClassType* (*GetClass)(void);

[/code]

What ? A pointer-to-function blablabla ? What's that ?
Simple: That is the key to this whole mess: a pointer to a function. Why is it declared there ? Because the same header file is used in the loading application. Just for the sake of simplicity.

Now, when we have the actual class, let's see the DLL exporting it:

[code]

// On global level, declare an instance of the class

MyExportedClassType MyClass;

// At the DllMain, initialize the class' members

int WINAPI DllMain(HINSTANCE hInstance, DWORD dwReason, LPVOID lpVoid)
{
.... Some code here

MyClass.iMemberVariable = 10;

.... More code here

return TRUE

}

// Add an exported function, which returns the address of our class

__declspec(dllexport) MyExportedClassType* ProvideAddressOfClass(void)
{
return &MyClass;
}

[/code]

Lastly, create a module definition file

[code]

LIBRARY
EXPORTS
ProvideAddressOfClass @1

[/code]

Ok, now the DLL is ready, go compile it. Next up, the loading application:

[code]

// We must include the typedef declaration
#include "myclasstypedef.h"

HDLL hDll;

// See here: let's create a pointer-to-function which returns a class' address.. Remember, we exported this type of function from the DLL !

GetClass MyClassProvider;

// A pointer to our class type
MyExportedClassType* lpImportedClass;

// Your main function
int main(void)
{

.... Some code ?

// Load module
hDll = LoadLibrary(ModuleName[iCount]);

// Resolve address of exported function
MyClassProvider = (GetClass)GetProcAddress(hDLL, "ProvideAddress");

// Get address of class within the DLL, using the exported function
lpImportedClass = MyClassProvider();

// Let's use it !
lpImportedClass->iMemberVariable = 1;

.... Some more code

// Remember to unload the library !
UnloadLibrary(hDll);

// End application
return 0;
}

[/code]

Seems difficult ? Well, it really isn't.. To sum it all up programmer-wise:

1. Create a class using typedef
2. Create a function which returns the address of your class
3. Export this function in the DLL with __declspec AND .def file
4. Create a typedef for 'pointer-to-function' of the address-provider function

5. Load the DLL in another application
6. Get the address of the exported function
7. Use the function to get the address of the class
8. Use the class

9. NULLify pointers, unload the DLL etc clean-up work
10. Quit and get some sleep Smile | :)

I have created an example of this, an application which actually creates it's main window in a seperate DLL, and adds event handlers to this window's procedure in another DLL. You can download the entire workspace (3 projects: WinDLL, InpDLL, WinLoader) from here.

Enjoy !

-Antti

Vikram A Punathambekar28-Aug-03 8:14

Vikram A Punathambekar

28-Aug-03 8:14

[EDIT]I'm using VS6[/EDIT]
This is an obscure problem: I'm using an edit control labeled IDC_EDIT2 in a dialog-based app. To restrict the length of the content to 8, I use the following function that is called whenever the content changes:

void CFileCryptDlg::OnChangeEdit2() 
{
    char strPassword[10];
    if(GetDlgItemText(IDC_EDIT2,strPassword,10)>8)
    {
        strPassword[8]='\0';
        SetDlgItemText(IDC_EDIT2,strPassword);
    }
}

It works fine, except for one small problem: till I type the 8th character, everything's as expected. But when the 9th character is typed, the cursor moves back to the first location in the edit box. How do I retain the cursor position?

Thanks,

Vikram.

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User 665828-Aug-03 8:41

User 6658

28-Aug-03 8:41

Why don't you just do SendMessage(wndOfYourEdit, EM_EXLIMITTEXT, 8, 0);?
This will limit the edit control to accept max. 8 chars. Smile | :)

regards

modified 12-Sep-18 21:01pm.

Vikram A Punathambekar28-Aug-03 8:59

Vikram A Punathambekar

28-Aug-03 8:59

I tried what David said below and it works. Smile | :)

On a purely academic note, how come neither

::SendMessage(((CEdit *)GetDlgItem(IDC_EDIT2))->m_hWnd, EM_EXLIMITTEXT, 8, 0);

nor

GetDlgItem(IDC_EDIT2)->SendMessage(EM_EXLIMITTEXT, 8, 0);

works when called from the dialog's InitInstance() function? Confused | :confused:

They don't restrict the number of characters at all.

Cheers,

Vikram.

David Crow28-Aug-03 9:11

28-Aug-03 9:11

Probably because a dialog does not have such a method. Are you talking about OnInitDialog()? Either way, the EM_EXLIMITTEXT message is for rich edit controls.

User 665828-Aug-03 9:31

User 6658

28-Aug-03 9:31

Is your edit control already created in InitInstance()? I'd prefer OnInitDialog().

modified 12-Sep-18 21:01pm.

David Crow28-Aug-03 8:45

28-Aug-03 8:45

Why not just use SetLimitText(8)?

COleSafeArray::PutElement

Vikram A Punathambekar28-Aug-03 9:04

Vikram A Punathambekar

28-Aug-03 9:04

Works!

Thanks a zillion ! Rose | [Rose]

Regards,

Vikram.

act_x28-Aug-03 6:27

act_x

28-Aug-03 6:27

COleSafeArray::PutElement

Does this function append to the array ?

Re: COleSafeArray::PutElement

Steve S29-Aug-03 2:18

Steve S

29-Aug-03 2:18

Nope. I can say this caregorically, since it's a wrapper around the SafeArrayPutElement function, and that doesn't.

Use the source, Luke

Steve S

Creating CRichEditCtrl Version 2.0/3.0

Larry J. Siddens28-Aug-03 6:03

28-Aug-03 6:03

This should be a simple question, but how do you create a CRichEditCtrl for version 2.0/3.0 using either Create or CreateEx?

Larry J. Siddens
Cornerstone Communications

TAME THE DOCUMENT MONSTER
www.unifier.biz

David Crow28-Aug-03 7:02

28-Aug-03 7:02

What specifically is not working for you? If the control's parent is a dialog, add a control variable to the dialog's .H file, and then in the dialog's OnInitDialog() method, add:

AfxInitRichEdit();<br />
richedit.Create(...);

Steve S28-Aug-03 7:08

Steve S

28-Aug-03 7:08

Might be that they're wanting specifically to create a richedit with Word-style paragraph formatting (left, centre, right, align). The default MFC way means that an old style rich edit is created all the time. In some cases, the way I've done this is in OnInitDialog to get the old one's attributes, trash it and recreate the control in place, before calling the default OnInitDialog in case that maps a control.

There are two Windows class names, "RichEdit" which is v1.0 and RICHEDIT_CLASS which expands at compile time to produce the appropriate name for v2 or later.

Steve S

Larry J. Siddens28-Aug-03 7:41

28-Aug-03 7:41

The AfxInitRichEdit() loads the RICHED32.DLL with is version 1.0. I want to load 2.0/3.0

Thanks

Larry J. Siddens
Cornerstone Communications

TAME THE DOCUMENT MONSTER
www.unifier.biz

David Crow28-Aug-03 8:00

28-Aug-03 8:00

My bad. When I saw richedit32, I just assumed v3.2, not 1.0. You have to go to richedit20 in order to get v3.0. D'Oh! | :doh:

Are we confused yet? Confused | :confused:

So, the moral to your story is that the CRichEditCtrl class does not support the Rich Edit v2.0 control. In order to use Rich Edit 2.0 in an MFC application, call LoadLibrary() to load the Riched20.dll and access its functionality through the Win32 API. Hmmm

Larry J. Siddens28-Aug-03 8:06

28-Aug-03 8:06

So you use the LoadLibrary to load the riched20.dll and use the handle to set the fonts, formating, . . . Correct?

Can you place a small example. I have not called items from the library.

Thanks

Larry J. Siddens
Cornerstone Communications

TAME THE DOCUMENT MONSTER
www.unifier.biz

David Crow28-Aug-03 8:41

28-Aug-03 8:41

HMODULE hLibrary = LoadLibrary("riched20.dll");<br />
<br />
m_richedit = CreateWindowEx(0, RICHEDIT_CLASS, "", WS_CHILD | WS_VISIBLE | ES_MULTILINE, 5, 50, 100, 100, GetSafeHwnd(), NULL, NULL, NULL);<br />
<br />
::SendMessage(m_richedit, WM_PASTE, 0, 0);

Larry J. Siddens28-Aug-03 8:44

28-Aug-03 8:44

You are loading the library to check if the riched20.dll is there correct? Now I have one more question. Have you been able to print that area correctly? If so, how? I'm trying to do that. The problem is that we don't know what the output device will be at the time of creation. Interesting twist huh?

Thanks again.

Larry J. Siddens
Cornerstone Communications

TAME THE DOCUMENT MONSTER
www.unifier.biz

David Crow28-Aug-03 8:56