Something with callbacks and object instance and such...
From: Robert Diamond (aorevolt_at_hotmail.com)
Date: 03/26/04
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Date: Fri, 26 Mar 2004 10:02:22 GMT
Ok... I write uber cool oop code to get my app started with objects all
over the place and tweak a few things and it works... Then in my makeshift
main objects WndProc I try to read or write to a protected var and it
crashes the app "An Access Violation (Segmentation Fault) raised in your
program." (from the dev-c++ debuger). Change the var to public and it
crashes... remove that code and try to set-up a timer (timers are callback
functions that get run after a timeout) in the same way i set-up the
makeshift WndProc. The timer (which is basically a duplicate of my WndProc)
can read/write to private/protected/public vars :) ... but why not WndProc?
Anyways, If you managed to read all this and think you can help out... here
is some code snipets:
/******* Main.cpp *******/
// The object that does all the work
MainObj *mainObj= NULL;
LRESULT CALLBACK MainWndProc(HWND hWnd, UINT uMsg, WPARAM wParam, LPARAM
lParam) {
return (*mainObj).WndProc(hWnd, uMsg, wParam, lParam);
}
VOID CALLBACK WndProcDuplicateTimer(HWND hWnd, UINT uMsg, UINT_PTR idEvent,
DWORD dwTime) {
(*mainObj).WndProcDuplicateTimer(hWnd, uMsg, idEvent, dwTime);
}
...
int WINAPI WinMain(...) {
...
// Create our base object that is basically a oop replacement for
winmain and such (constructor sets up window and callback and timer and
such)
if ((mainObj = new MainObj()) == NULL) error = true;
if (!error) {
// Loop That Runs While we don't have a WM_QUIT
while (GetMessage(&msg, NULL, 0, 0)) {
TranslateMessage(&msg); // Translate The Message
DispatchMessage(&msg); // Dispatch The Message (this get's sent
to MainWndProc, which then sends it to the (*mainObj).WndProc)
}
}
// If our Main Object still exists, delete it (destructor handles app
cleanup)
if (glMain != NULL)
delete glMain;
return error;
}
/*********** MainObj.cpp ************/
class MainObj {
public:
MainObj();
LRESULT /*NOT Callback... it's not a function pointer, just a
regular function*/ WndProc(HWND hWndHdl, UINT uMsg, WPARAM wParam, LPARAM
lParam);
void WndProcDuplicateTimer(HWND hWndHdl, UINT uMsg, UINT_PTR
idEvent, DWORD dwTime);
~GlMain();
protected:
...
bool active;
...
};
in WndProc and WndProcDuplicateTimer if put a simple single line "if
(active) active = true;" in WndProc I get Segmentation failure and in
WndProcDuplicateTimer I get no error. BTW MainObj::WinProc has stuff to
handle WM_QUIT can do stuff like "if (HIWORD(wParam)) return 0;" and calls
DefWindowProc if it get's to that... I think the reason things are failing
is because the callback function in Main.cpp is calling the
MainObj::WndProc. I tried to setup MainObj::WndProc as the callback, but
keeped getting "Can't convert ...(MainObj::*)WndProc... to ...(*)WndProc..."
so I came up with this solution. Something to note... I don't virtual,
inline, etc. any of the functions (at least not until I knw thier working).
Thanks in advance, and I know this may be a tuff one, but any help will help
alot, i'm completely lost ;(
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