
=pod

=head1 NAME

SDL::Mixer::Music - functions for music

=head1 CATEGORY

Mixer

=head1 METHODS

=head2 load_MUS

 my $music = SDL::Mixer::Music::load_MUS( $file );

C<load_MUS> loads a music file into a C<SDL::Mixer::MixMusic> structure. This can be passed to L<play_music|SDL::Mixer::Music/"play_music">.

=head2 hook_music

 SDL::Mixer::Music::hook_music( $callback, $position );
 
This sets up a custom music player function, so you can pass your own audio stream data into the SDL::Mixer.
The function will be called with C<position> passed into the first parameter when the C<callback> is called.
The audio stream buffer has to be filled with length bytes of music (2nd parameter).
The music player will then be called automatically when the mixer needs it. Music playing will start as soon as this is called. 
All the music playing and stopping functions have no effect on music after this. Pause and resume will work. 
Using a custom music player and the internal music player is not possible, the custom music player takes priority. 

To stop the custom music player call C<hook_music()> without arguments.

B<Note>: NEVER call C<SDL::Mixer> functions, nor L<SDL::Audio::lock|SDL::Audio/"lock">, from a callback function.

B<Note>: At program termination also call C<SDL::Mixer::Music::hook_music()> to stop this callback.

Example:

 sub callback
 {
     my $position = shift; # position (first time its 0, on each call $length is added)
     my $length   = shift; # length of bytes we have to put in stream
     my @stream   = '';
 
     printf("position=%8d, stream length=%6d\n", $position, $length);
 
     for(my $i = 0; $i < $length; $i++)
     {
         push(@stream, (($i + $position) & 0xFF));
     }
 
     return @stream;
 }
 
 SDL::Mixer::Music::hook_music( 'main::callback', 0 );

=head2 hook_music_finished

 SDL::Mixer::Music::hook_music_finished( 'main::callback' );

This callback is called when music called by e.g. L<SDL::Mixer::Music::play_music|SDL::Mixer::Music/"play_music"> or 
L<SDL::Mixer::Music::fade_in_music|SDL::Mixer::Music/"fade_in_music"> stops naturally. 
This happens when the music is over or is fading out.

B<Note>: If you play music via L<SDL::Mixer::Music::hook_music|SDL::Mixer::Music/"hook_music">, this callback will never be called.

Example:

 my $music_is_playing = 0;
 my @music            = qw(first.mp3 next.mp3 other.mp3 last.mp3);
 sub callback
 {
     $music_is_playing = 0;
 }
 
 SDL::Mixer::Music::hook_music_finished( 'main::callback' );
 
 foreach my $this_song ( @music )
 {
     SDL::Mixer::Music::play_music( $this_song, 0 );
     $music_is_playing = 1;
 
     SDL::delay( 100 ) while( $music_is_playing );
 }
 
 SDL::Mixer::Music::hook_music_finished(); # cleanup

=head2 get_music_hook_data

 my $position = SDL::Mixer::Music::get_music_hook_data();

Returns the C<position> (first) parameter that will be passed to L<SDL::Mixer::Music::hook_music|SDL::Mixer::Music/"hook_music">'s callback.

=head2 play_music

 my $play_music = SDL::Mixer::Music::play_music( $mix_music, $loops );

C<play_music> plays a given C<SDL::Mixer::MixMusic>.
Passing -1 to C<$loops> will loop the music infinitely. 

Example:

 my $music = SDL::Mixer::Music::load_MUS( 'music.mp3' );
 
 unless(SDL::Mixer::Music::play_music($sample_music, -1))
 {
     print("Something went wrong!\n");
 }

=head2 fade_in_music

 my $music = SDL::Mixer::Music::fade_in_music( $mix_music, $loops, $ms );

Same as L<SDL::Mixer::Music::play_music|SDL::Mixer::Music/"play_music"> but you can specify the fade-in time by C<$ms>.

=head2 fade_out_music

 my $fading_music = SDL::Mixer::Music::fade_out_music( $ms );

C<fade_out_music> fades out the music with a duration specified in C<ms> in milliseconds.

Returns the the number of channels that will be faded out.

=head2 fading_music

 my $fading_music = SDL::Mixer::Music::fading_music();

Returns one of the following:

=over 4

=item *

MIX_NO_FADING

=item *

MIX_FADING_OUT

=item *

MIX_FADING_IN

=back

=head2 volume_music

 my $volume_before = SDL::Mixer::Music::volume_music( $new_volume );

C<volume_music> set the volume in C<$new_volume> and returns the volume that was set before.
Passing C<-1> as argument causes only to return the current volume.

Volume is between C<0> (silence) and C<MIX_MAX_VOLUME = 128>.

Example:

 # set the music volume to 1/2 maximum, and then check it
 printf( "volume was    : %d\n", SDL::Mixer::Music::volume_music( MIX_MAX_VOLUME / 2 ) );
 printf( "volume is now : %d\n", SDL::Mixer::Music::volume_music( -1 ) );

=head2 halt_music

 SDL::Mixer::Music::halt_music();

Halts the music.

=head2 pause_music

 SDL::Mixer::Music::pause_music();

Pauses the music.

=head2 resume_music

 SDL::Mixer::Music::resume_music();

Resumes the music.

=head2 rewind_music

 SDL::Mixer::Music::rewind_music();

Rewinds the music.

=head2 set_music_position

 SDL::Mixer::Music::set_music_position( $position );

Set the position of the currently playing music. The position takes different meanings for different music sources. It only works on the 
music sources listed below.

=over 4

=item MOD

The double is cast to Uint16 and used for a pattern number in the module.
Passing zero is similar to rewinding the song. 

=item OGG

Jumps to position seconds from the beginning of the song. 

=item MP3

Jumps to position seconds from the current position in the stream.
So you may want to call L<SDL::Mixer::Music::rewind_music|SDL::Mixer::Music/"rewind_music"> before this.
Does not go in reverse... negative values do nothing. 

=back

Returns: C<0> on success, or C<-1> if the codec doesn't support this function. 

=head2 paused_music

 my $paused = SDL::Mixer::Music::paused_music();

Returns C<1> if the music is paused, otherwise C<0>.

=head2 playing_music

 my $playing_music = SDL::Mixer::Music::playing_music();

Returns C<1> if the music is playing sound, otherwise C<0>. It does'nt check if the music is paused.

=head1 AUTHORS

See L<SDL/AUTHORS>.

=cut
