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Movie Drawing Complete Procedure with C++

Q: I'm trying to use a C++ class instance method as the Movie Drawing Complete Procedure. Is there a way to do this or is there a recommended technique? I'd like to know which Movie (my objects) have drawn a frame.

A: To assign a drawing-complete function to a Movie use the SetMovieDrawingCompleteProc call. This call takes a Movie, flags (either movieDrawingCallWhenChanged or movieDrawingCallAlways), a UPP for your callback and a RefCon. When installing the MovieDrawingCompleteProc, use a MovieDrawingCompleteUPP for a static class function, not a member function of your class. The RefCon can be used to reference the instance of your class (this).


// Example class header file
// MyClass.h
class MyClass {
public:
            MyClass() { mMovie = NULL; };
    virtual ~MyClass();

protected:
            void  InstallMovieDrawingComplete(Movie inMovie,
                                     long inFlags = movieDrawingCallAlways);
    virtual OSErr DrawingCompleteDoSomething(Movie theMovie) { return noErr; };

private:
    /*  Called when movie drawing is complete.
        typedef OSErr (*MovieDrawingCompleteProcPtr) (Movie theMovie, long refCon);
     */
    static pascal OSErr MyClassMovieDrawingCompleteProc(Movie theMovie, long refCon);
    static MovieDrawingCompleteUPP sMovieDrawingCompleteUPP;
           Movie                   mMovie;
};

// Example class implementation
// MyClass.cpp

MovieDrawingCompleteUPP MyClass::sMovieDrawingCompleteUPP = NULL;

pascal OSErr MyClass::MyClassMovieDrawingCompleteProc(Movie theMovie, long refCon)
{
    MyClass *instance = reinterpret_cast<MyClass *>(refCon);
    OSErr err = noErr;

    if (instance)
        err = instance->DrawingCompleteDoSomething(theMovie);

    return err;
}

MyClass::~MyClass()
{
    if (mMovie) ::SetMovieDrawingCompleteProc(mMovie, 0, NULL, 0L);
    if (sMovieDrawingCompleteUPP)
        ::DisposeMovieDrawingCompleteUPP(sMovieDrawingCompleteUPP);
}

/*
   inFlags: movieDrawingCallWhenChanged
                Specifies that the toolbox should call your drawing-complete
                function only when the movie has changed.
            movieDrawingCallAlways
                Specifies that the toolbox should call your drawing-complete
                function every time your application calls MoviesTask
 */
void MyClass::InstallMovieDrawingComplete(Movie inMovie, long inFlags)
{
    if (NULL == MyClass::sMovieDrawingCompleteUPP) {
        MyClass::sMovieDrawingCompleteUPP =
                 ::NewMovieDrawingCompleteUPP(MyClass::MyClassMovieDrawingCompleteProc);
    }

    if (inMovie) {
        if (mMovie) {
            // remove the callback from previous Movie
            ::SetMovieDrawingCompleteProc(mMovie, 0, NULL, 0L);
        }
        ::SetMovieDrawingCompleteProc(inMovie, inFlags,
                                      MyClass::sMovieDrawingCompleteUPP,
                                      long(this));
        mMovie = inMovie;
   }
}

Listing 1. Using a static member for a MovieDrawingCompleteProc

[Jun 18 2002]


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