Usage of functions

Hello, this one is really ridiculous one. There are no problems at all with compilation but there is still a problem with functions.
I have no idea why does not the programme call my function but the code is right (I hope) if I copy the code straight to the WM_PAINT command it works normally. But if I try to call a function with the same content as before it suddenly fails to work...

Can you chceck please the code?

Code:

#include <windows.h>

LRESULT CALLBACK WndProc(HWND, UINT, WPARAM, LPARAM);

int WINAPI WinMain(HINSTANCE hInstance, HINSTANCE hPrevInstance,
                   PSTR szCmdLine, int iCmdShow)
{
    TCHAR szAppName[] = TEXT("Default window");           // Header
    HWND hWnd;
    MSG msg;
    WNDCLASSEX wc;
    
    wc.cbSize = sizeof(wc);
    wc.style = CS_HREDRAW | CS_VREDRAW;
    wc.lpfnWndProc = WndProc;
    wc.cbClsExtra = 0;
    wc.cbWndExtra = 0;
    wc.hInstance = hInstance;
    wc.hIcon = LoadIcon(NULL, IDI_APPLICATION);            // Ico
    wc.hIconSm = NULL;                                     // Ico_sm
    wc.hCursor = (HCURSOR)LoadCursor(NULL, IDC_ARROW);
    wc.hbrBackground = (HBRUSH)(COLOR_WINDOW+0);           // Background
    wc.lpszMenuName = NULL;
    wc.lpszClassName = szAppName;
    
    RegisterClassEx(&wc);
    
    hWnd = CreateWindowEx(0,szAppName,
                        szAppName,
                        WS_OVERLAPPEDWINDOW,
                        CW_USEDEFAULT,                    // Margin from left
                        CW_USEDEFAULT,                    // Margin from top
                        CW_USEDEFAULT,                    // Widht
                        CW_USEDEFAULT,                    // Height
                        NULL,
                        NULL,
                        hInstance,NULL);
    ShowWindow(hWnd, iCmdShow);
    UpdateWindow(hWnd);
    
    while(GetMessage(&msg, NULL, 0, 0))
    {
          TranslateMessage(&msg);
          DispatchMessage(&msg);
    }
    return msg.wParam;
}
void OnWM_PAINT()
{
    HWND         hWnd;
	HDC			hDC;
	PAINTSTRUCT ps;
	RECT		rect;
	GetClientRect(hWnd, &rect);
    hDC = BeginPaint(hWnd, &ps);
	DrawText(hDC, "Text text", -1, &rect, DT_SINGLELINE | DT_CENTER | DT_VCENTER);
	EndPaint(hWnd, &ps);
}
LRESULT CALLBACK WndProc(HWND hWnd, UINT message, WPARAM wParam, LPARAM lParam)
{
        switch(message)
        {
          case WM_PAINT:
	OnWM_PAINT();
	break;
          case WM_DESTROY:
          PostQuitMessage(0);
          return 0;
        }
        return DefWindowProc(hWnd, message, wParam, lParam);
}

MS VC++
Dev-C++

Thank you for support

You haven't defined rect.

because your function defines hWnd but in WndProc it's an argument. You need to use the hWnd that is passed as argument and not define one yourself.

Originally Posted by KONI

because your function defines hWnd but in WndProc it's an argument. You need to use the hWnd that is passed as argument and not define one yourself.

So I deleted the line with HWND definition, now the function is:

Code:

void OnWM_PAINT()
{
	HDC			hDC;
	PAINTSTRUCT ps;
	RECT		rect;
	GetClientRect(hWnd, &rect);
    hDC = BeginPaint(hWnd, &ps);
	DrawText(hDC, "Text text", -1, &rect, DT_SINGLELINE | DT_CENTER | DT_VCENTER);
	EndPaint(hWnd, &ps);
}

(The rest of the code was left just the same)

But there is an error in compilation:
53 c:\docume~1\gordon\desktop\window\win.cpp `hWnd' undeclared (first use this function)

And how do you think could your function possibly know about hWnd if you don't pass it as argument ?

You didn't follow instructions.

Code:

void OnWM_PAINT(HWND hWnd)
{
	HDChDC;
	PAINTSTRUCT ps;
	RECTrect;

	GetClientRect(hWnd, &rect);
	hDC = BeginPaint(hWnd, &ps);
	DrawText(hDC, "Text text", -1, &rect, DT_SINGLELINE | DT_CENTER | DT_VCENTER);
	EndPaint(hWnd, &ps);
}

Your callback function:

Code:

LRESULT CALLBACK WndProc(HWND hWnd, UINT message, WPARAM wParam, LPARAM lParam)
{
	switch(message)
	{
		case WM_PAINT:
			OnWM_PAINT(hWnd);
		break;
		case WM_DESTROY:
			PostQuitMessage(0);
		return 0;
	}
	return DefWindowProc(hWnd, message, wParam, lParam);
}

Ok cool now it works...

Thx to everybody

If you want to do the work in a separate function, you can use HANDLE_MSG

Code:

switch(message)
{
     HANDLE_MSG(hWnd, WM_PAINT, App_OnPaint);
     ...

Then your function MUST be defined with these parameters and return value:

Code:

void App_OnPaint(HWND hWnd)
{
     // This function will be called everytime you get a WM_PAINT message
}