asked on

vc++ unicode messagebox char issue

i need to pass path information from one event to another, but the char that i use for that gets 'garbled' in the process

i.e. for the code below, the first Messagebox shows me a file path as i need, whereas the second messagebox shows a lot of weird characters. ...

whats going on, is this to do with the fact that my project is compiled in unicode?

char *currentSongPath;
 
LRESULT CALLBACK WinampWndProc(HWND hwnd, UINT umsg, WPARAM wParam, LPARAM lParam) {
	int ret = CallWindowProc(proc,hwnd,umsg,wParam,lParam);
 
	if (umsg == WM_WA_IPC && lParam == IPC_PLAYING_FILE) { 
		// File Path and Name about to be played right now
 
		currentSongPath = (char*)wParam;
		MessageBoxA(NULL,currentSongPath,"This outputs a file path as it should", MB_OK);
	}
 
	if (umsg == WM_WA_IPC && lParam == IPC_GET_NEXT_PLITEM) {
		// res will be millisecond into play when next is played or if song finishes
		
		MessageBoxA(NULL, currentSongPath,"This same line outputs a garbled thing", MB_OK);
}
 
	return ret;
}

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jkr

No, but in the 2nd case, you are using an uninitialized pointer variable, it is only being assigned a value in the 1st 'if' body. Try

char *currentSongPath;
 
LRESULT CALLBACK WinampWndProc(HWND hwnd, UINT umsg, WPARAM wParam, LPARAM lParam) {
        int ret = CallWindowProc(proc,hwnd,umsg,wParam,lParam);
 
        if (umsg == WM_WA_IPC && lParam == IPC_PLAYING_FILE) { 
                // File Path and Name about to be played right now
 
                currentSongPath = (char*)wParam;
                MessageBoxA(NULL,currentSongPath,"This outputs a file path as it should", MB_OK);
        }
 
        if (umsg == WM_WA_IPC && lParam == IPC_GET_NEXT_PLITEM) {
                // res will be millisecond into play when next is played or if song finishes
                
                currentSongPath = (char*)wParam; // assign here, too
                MessageBoxA(NULL, currentSongPath,"This same line should be OK now", MB_OK);
}
 
        return ret;
}

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KristjanLaane

ASKER

this does not work as wParam holds completely different values for the differnet events.

and the event where lParam == IPC_PLAYING_FILE always occurs before the event where lParam == IPC_GET_NEXT_PLITEM, so currentSongPath shoudl be initialised anyway when the event lParam == IPC_GET_NEXT_PLITEM is raised

and im not sure this is an initialisation problem, i think the garbage might be to do with character encoding ...

jkr

>>and im not sure this is an initialisation problem

It pretty certainly is, look at your code:

char *currentSongPath;
 
LRESULT CALLBACK WinampWndProc(HWND hwnd, UINT umsg, WPARAM wParam, LPARAM lParam) {
        int ret = CallWindowProc(proc,hwnd,umsg,wParam,lParam);
 
        if (umsg == WM_WA_IPC && lParam == IPC_PLAYING_FILE) { 
                // File Path and Name about to be played right now
 
                currentSongPath = (char*)wParam;
                MessageBoxA(NULL,currentSongPath,"This outputs a file path as it should", MB_OK);
        }
 
        if (umsg == WM_WA_IPC && lParam == IPC_GET_NEXT_PLITEM) {
                // res will be millisecond into play when next is played or if song finishes
                
                //
                // here, 'currentSongPath' is not assigned a value
                // and the last value from a previous call is no 
                // longer valid. You need to initialize this variable
                // somehow or you'l get 'garbage'
                //
                MessageBoxA(NULL, currentSongPath,"This same line outputs a garbled thing", MB_OK);
}
 
        return ret;
}

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xtravagan

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KristjanLaane

ASKER

i got this error message when i tried to compile
Error 6 error C2664: 'strncpy' : cannot convert parameter 2 from 'size_t' to 'const char *' e:\Code\SoundCutPrototype\SoundCut4Winamp\main.cpp 86 gen_blah

then realised the 8th line had a syntax error, and when i fixed it to below, it works ! thanks !!!

strncpy(currentSongPath, (char*)wParam, sizeof(currentSongPath) - 1);

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