C++ Win32 Error [closed] - c++

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Closed 10 years ago.
I made a class for Win32 and I have no idea why this error happens.
This is the code:
main.cpp
using namespace std;
#include "WindowManager.h"
#define WIDTH 700
#define HEIGHT 500
#define VERSION 0.1
int WINAPI WinMain(HINSTANCE hInstance,HINSTANCE hPreviousInstance,LPSTR lpcmdline,int nCmdShow)
{
WindowManager window("TalkToMe", 100, 100, WIDTH, HEIGHT);
while(window.isWindowOpen())
{
window.PekMessage();
}
return 0;
}
WindowManager.h
#pragma once
#include <Windows.h>
class WindowManager
{
private:
MSG msg;
HWND window;
int stat;
public:
WindowManager(LPCTSTR title,int x, int y, int width, int height);
~WindowManager();
LRESULT CALLBACK WindowProcedure(HWND winhan,UINT uint_Message,WPARAM parameter1,LPARAM parameter2);
inline bool isWindowOpen() { return stat != -1; }
int getStat() { return stat; }
void PekMessage();
};
WindowManager.cpp
#include "WindowManager.h"
void WindowManager::PekMessage()
{
if(PeekMessage(&msg, window, 0, 0, PM_REMOVE))
{
TranslateMessage(&msg);
DispatchMessage(&msg);
}
}
LRESULT CALLBACK WindowManager::WindowProcedure(HWND winhan,UINT uint_Message,WPARAM parameter1,LPARAM parameter2)
{
switch(uint_Message)
{
case 16: // exit button
stat = -1;
break;
}
return DefWindowProc(winhan,uint_Message,parameter1,parameter2);
}
WindowManager::WindowManager(LPCTSTR title,int x, int y, int width, int height)
{
stat = 0;
WNDCLASSEX wnd;
wnd.cbSize = sizeof(wnd);
wnd.style = CS_HREDRAW | CS_VREDRAW;
wnd.lpfnWndProc = WindowProcedure;
wnd.cbClsExtra = 0;
wnd.cbWndExtra = 0;
wnd.hInstance = GetModuleHandle(NULL);
wnd.hIcon = NULL;
wnd.hCursor = LoadCursor(NULL,IDC_ARROW);
wnd.hbrBackground = GetSysColorBrush(NULL);
wnd.lpszClassName = "TalkToMe";
wnd.lpszMenuName = NULL;
wnd.hIconSm = LoadIcon(NULL, IDI_APPLICATION);
RegisterClassEx(&wnd);
window = CreateWindowEx(WS_EX_CONTROLPARENT, wnd.lpszClassName, title,
WS_OVERLAPPED | WS_CAPTION | WS_SYSMENU | WS_MINIMIZEBOX | WS_VISIBLE, x, y, width, height,NULL, NULL,
GetModuleHandle(NULL), NULL);
}
WindowManager::~WindowManager()
{
DestroyWindow(window);
}
This is the weird build failure:
1>------ Build started: Project: Client, Configuration: Debug Win32 ------
1> WindowManager.cpp
1>c:\users\user\documents\visual studio 2012\projects\talktome\talktome\windowmanager.cpp(31): error C3867: 'WindowManager::WindowProcedure': function call missing argument list; use '&WindowManager::WindowProcedure' to create a pointer to member
1>c:\users\user\documents\visual studio 2012\projects\talktome\talktome\windowmanager.cpp(31): error C2440: '=' : cannot convert from 'LRESULT (__stdcall WindowManager::* )(HWND,UINT,WPARAM,LPARAM)' to 'WNDPROC'
1> There is no context in which this conversion is possible
1> Generating Code...
1> Compiling...
1> Main.cpp
1> Generating Code...
========== Build: 0 succeeded, 1 failed, 0 up-to-date, 0 skipped ==========

Answer 1

This is to be expected. WindowManager::WindowManager has a hidden this argument, thus it does not respect the definition required for wnd.lpfnWndProc.
To work around this issue, you need to define a helper function as follows:
LRESULT CALLBACK HelperWindowProcedure(HWND winhan,UINT uint_Message,WPARAM parameter1,LPARAM parameter2)
{
if (uint_Message == WM_CREATE)
{
/* Retrieve "this" sent through CreateWindowEx */
WindowManager *wm = (WindowManager *)(((LPCREATESTRUCT) lParam)->lpCreateParams);
/* And store it as window-private date */
SetWindowLongPtr(winhan, GWLP_USERDATA, wm);
}
/* Retrieve WindowManager from window-private data */
WindowManager *wm = (WindowManager *)GetWindowLongPtr(winhan, GWLP_USERDATA);
/* Forward window message to WindowManager */
wm->WindowProcedure(winhan, uint_Message, parameter1, parameter2);
}
WindowManager::WindowManager()
{
...
/* use helper window procedure */
wnd.lpfnWndProc = HelperWindowProcedure;
...
/* send "this" through WM_CREATE */
window = CreateWindowEx(WS_EX_CONTROLPARENT, wnd.lpszClassName, title,
WS_OVERLAPPED | WS_CAPTION | WS_SYSMENU | WS_MINIMIZEBOX | WS_VISIBLE, x, y, width, height,NULL, NULL,
GetModuleHandle(NULL), this);
}

Answer 2

As user1202136 mentioned, C++ class methods have implicit parameter that gets passed into the function whenever it is called. It holds the pointer to the class instance (this pointer) and allows you to access the class variables. In order to resolve this issue, you can make the WindowProcedure method static and use GWL_USERDATA within the window memory to store your class instance (this pointer). Look up GetWindowLongPtr for more information. When creating the window you'll need to pass this pointer via lpParam parameter, and store it using SetWindowLongPtr when you are handling WM_CREATE message.

Answer 3

check solutions:
wnd.lpfnWndProc = (WNDPROC)WindowProcedure;
or
LRESULT WNDPROC WindowManager::WindowProcedure(HWND winhan,UINT uint_Message,WPARAM parameter1,LPARAM parameter2)