QuickTime For Windows Programmers

File Selection Dialogs

When the user chooses the Open command from your File menu, you'll want to present a dialog box that allows the user to select the file to be opened. In Windows, this is normally done with the function GetOpenFileName , part of the Common Dialog Box Library. This function displays the standard Windows Open File dialog box on the screen, handles all interactions with the mouse and keyboard until the dialog is dismissed, and then returns a data structure of type OPENFILENAME identifying the file the user has selected. One of the members of this structure, lpstrFile , points to a string buffer in which to return the pathname of the file the user has selected. Ordinarily, a Windows program would simply pass this string to the appropriate Windows function, such as CreateFile , to open the designated file.

As we'll see in the next section, however, the QuickTime function OpenMovieFile instead expects to receive an analogous data structure from the Macintosh Standard File dialog package, a file-system specification record ( Listing 6 ).

Listing 6 File-system specification record



 
struct FSSpec

    {

        short    vRefNum;                   // Volume reference number

        long     parID;                     // Directory ID of parent directory

        Str255   name;                      // File name

        

    };  /* end FSSpec */

So before calling OpenMovieFile from a Windows program, you have to create a specification record to pass to it. The QTML function FSMakeFSSpec does the job:



 
OSErr

    FSMakeFSSpec

        (short              vRefNum,   // Volume reference number

         long               dirID,     // ID of parent directory

         ConstStr255Param   fileName,  // File name

         FSSpec            *spec)      // Returns a specification record

On the Macintosh, files are normally identified by giving a directory ID and a local file name within the directory. In Windows code, you set the directory ID and volume reference number to 0 and supply a full pathname instead; FSMakeFSSpec will interpret this correctly and initialize the specification record accordingly. Listing 7 shows how to use this function to mediate between the Windows common dialog box and the QTML OpenMovieFile function.

Another point to keep in mind is that the Windows GetOpenFileName function returns the file's pathname as a C-style string (terminated by a null character), whereas FSMakeFSSpec , like all QTML routines, expects it in Pascal form (preceded by a 1-byte length count).

QTML provides a pair of utility functions, c2pstr and p2cstr , for converting strings from one format to the other in place. You don't want to pass a string constant; the buffer needs to be modifiable.

Listing 7 Opening a user-selected movie file



 
OPENFILENAME   ofn;                                 // Parameters to Common Dialog Box

char           pathName[255];                       // Buffer for pathname

BOOL           confirmed;                           // Did user confirm file selection?

FSSpec         fileSpec;                            // File-system specification record

short          theFile;                             // Reference number of movie file

HWND           hwnd;                                // Handle to movie window

CGrafPtr       windowPort;                          // Window's graphics port

OSErr          errCode;                             // Result code



        ·

        ·



memset (&ofn, 0, sizeof(OPENFILENAME);              // Clear to zero

fileName[0] = `\0';                                 // No default file name



ofn.lStructSize     = sizeof(OPENFILENAME);         // Size of structure

ofn.hwndOwner       = GetActiveWindow();            // Active window owns dialog

ofn.lpstrFile       = LPSTR(pathName);              // Point to pathname buffer

ofn.nMaxFile        = 255;                          // Size of buffer

ofn.lpstrFilter     = "QuickTime Movies (*.mov;*.avi) \0 *.mov;*.avi\0";

                                                    // Filter string

ofn.nFilterIndex    = 1;                            // Index of default filter

ofn.lpstrInitialDir = NULL;                         // Use current directory



confirmed = GetOpenFileName (&ofn);                 // Let user select file



if ( confirmed )                                    // Did user confirm selection?

    {   

        c2pstr (pathName);                          // Convert to Pascal string

        FSMakeFSSpec (0, 0L, pathName, &fileSpec);  // Make specification record

        

        windowPort = GetNativeWindowPort( hwnd );   // Get window's graphics port

        SetGWorld (windowPort, nil);                // Make it the graphics world

        

        errCode = OpenMovieFile (&fileSpec, &theFile, fsRdPerm); // Open the movie file

        

    }  /* end if ( confirmed ) */