Simple DLL...

[PsychoMark]

I'm writing an application in Delphi which is going to be expandable by using DLL's for plugins. The Delphi part is not a problem obviously, but I want to make sure that it is compatible with C++ DLL's too.

I don't know much about C++, so I need one of you guys to do me a favour: write a very simple DLL which takes two parameters and shows them in a MessageBox.

The first parameter will be an 'HWND' type (which should cause no problems), but the second is a PChar (that's what it's called in Delphi, it's a pointer to the first character of a string, should be C++ compatible, *char or something like that?).

I only have Borland C++ Builder installed here, so I can compile it if it's compatible...


Thanks...

[CornedBee]

Sorry, I lost my sample dlls. I just can't remember how to do them.

[PsychoMark]

I will go trough some tutorials if I can't get an answer here, but I don't want to learn C++ just for this, so if anyone has a sample though I would appreciate it a lot...

[CornedBee]

The function would look like this:

#include <windows.h>

void __stdcall ShowMB(HWND hwnd, char* str)
{
    char buffer[200]; // or more if it produces failures
    wsprintf(buffer, "Window: %d, String: %s", (int)hwnd, str);
    MessageBox(NULL, buffer, "The DLL", MB_OK);
}

and you need a .def file that has this lines:
EXPORTS
ShowMB


But I forgot the exact def file syntax.

[PsychoMark]

Thanks, that really helped me. Couldn't find the .def file thing, but the C++ Builder help had the solution:

#include <windows.h>
#pragma argsused

extern "C" __declspec(dllexport) void __stdcall test(HWND hWnd, char* pPath);

void __stdcall test(HWND hWnd, char* pPath)
{
  char buffer[200];
  wsprintf(buffer, "Window: %d\n\nPath: %s", (int)hWnd, pPath);
  MessageBox(NULL, buffer, "DLL Test", MB_OK || MB_ICONINFORMATION);
}

That works fine, although the messagebox shows OK - CANCEL instead of just ok, MB_OK should be standard API, but anyways, it works so I can safely continue coding

[parksie]

MB_OK || MB_ICONINFORMATION

|| is the logical OR operator - it returns either true or false.

Use | instead, for a bitwise OR (which combines the bit values of the two operands).

[CornedBee]

Yeah, and since MB_ICONEXCLAMATION is something > 0, it is evaluated as true which later becomes 1, which is MB_OKCANCEL.