Qt 4.8: Path Class Reference

Qt Reference Documentation

- Qt 4.8
- ALL VERSIONS

- A
- A
- A
- Print

# Path Class Reference

(Phonon::Path)

The Path class describes connections between media nodes. More...

     #include <Phonon/Path>

This class was introduced in Qt 4.4.

- List of all members, including inherited members

## Public Functions

| Path ()
| Path ( const Path & path )
| ~Path ()
bool | disconnect ()
QList<Effect *> | effects () const
Effect * | insertEffect ( const EffectDescription & desc, Effect * insertBefore = 0 )
bool | insertEffect ( Effect * effect, Effect * insertBefore = 0 )
bool | isValid () const
bool | reconnect ( MediaNode * source, MediaNode * sink )
bool | removeEffect ( Effect * effect )
MediaNode * | sink () const
MediaNode * | source () const
bool | operator!= ( const Path & p ) const
Path & | operator= ( const Path & p )
bool | operator== ( const Path & p ) const

## Related Non-Members

Path | createPath ( MediaNode * source, MediaNode * sink )

## Detailed Description

The Path class describes connections between media nodes.

In a media graph, MediaNodes are connected by Paths. The multimedia travels in streams over these paths.

You create a path between two media nodes using the static Phonon::createPath() function, which takes two nodes as arguments. The first argument will send the media stream to the second. Please refer to the class description of the individual media nodes and the Phonon overview to see which nodes can be connected to each other.

Paths are also used to insert audio Effects between two media nodes. The effect will then alter the stream on the path. Notice that Effects also are media nodes, but that insertEffect() - instead of Phonon::createPath() - is used to insert them into the media graph.

The following code example shows how to create a path between two media nodes and insert an effect on that path.

     MediaObject *media = new MediaObject;
     AudioOutput *output = new AudioOutput(Phonon::MusicCategory);
     Path path = Phonon::createPath(media, output);
     Q_ASSERT(path.isValid()); // for this simple case the path should always be
                               //valid - there are unit tests to ensure it
     // insert an effect
     QList<EffectDescription> effectList = BackendCapabilities::availableAudioEffects();
     if (!effectList.isEmpty()) {
         Effect *effect = path.insertEffect(effectList.first());
     }

See also Phonon::MediaNode, Phonon::MediaObject, Phonon::AudioOutput, Phonon::VideoWidget, and Phonon Module.

## Member Function Documentation

### Path::Path ()

Creates an invalid path.

You can still make it a valid path by calling reconnect. It is recommended to use the Phonon::createPath() function to create paths.

See also Phonon::createPath() and isValid().

### Path::Path ( const Path & path )

Constructs a copy of the other path specified.

This constructor is fast thanks to explicit sharing.

### Path::~Path ()

Destroys this reference to the Path. If the path was valid the connection is not broken as both the source and the sink MediaNodes still keep a reference to the Path.

See also disconnect().

### bool Path::disconnect ()

Tries to disconnect the path from the MediaNodes it is connected to, returning true if successful or false if unsuccessful.

If successful, the path is invalidated: isValid() will returns false.

### QList<Effect *> Path::effects () const

Returns a list of Effect objects that are currently used as effects. The order in the list determines the order the signal is sent through the effects.

Returns A list with all current effects.

See also insertEffect() and removeEffect().

### Effect * Path::insertEffect ( const EffectDescription & desc, Effect * insertBefore = 0 )

Creates and inserts an effect into the path.

You may insert effects of the same class as often as you like, but if you insert the same object, the call will fail.

desc is the EffectDescription object for the effect to be inserted.

If you already inserted an effect you can tell with insertBefore in which order the data gets processed. If this is `0` the effect is appended at the end of the processing list. If the effect has not been inserted before the method will do nothing and return `false`.

Returns a pointer to the effect object if it could be inserted at the specified position. If `0` is returned, the effect was not inserted.

Below is a code example for inserting an effect into a path:

         QList<Phonon::EffectDescription> effectDescriptions =
                 Phonon::BackendCapabilities::availableAudioEffects();
         Phonon::EffectDescription effectDescription = effectDescriptions.at(4);

         Phonon::Path path = Phonon::createPath(mediaObject, audioOutput);

         Phonon::Effect *effect = new Phonon::Effect(effectDescription);
         path.insertEffect(effect);

See also removeEffect() and effects().

### bool Path::insertEffect ( Effect * effect, Effect * insertBefore = 0 )

Inserts the given effect into the path before the effect specified by insertBefore and returns true if successful; otherwise returns false.

If insertBefore is zero, the effect is appended to the processing list.

You may insert effects of the same class as often as you like, but if you insert the same object, the call will fail.

effect will be inserted right before insertBefore. If insertBefore is `0`, the effect is appended at the end of the processing list. If the effect has not been inserted before the method will do nothing and return `false`.

Returns whether the effect could be inserted at the specified position. If `false` is returned the effect was not inserted.

See also removeEffect() and effects().

### bool Path::isValid () const

A path is considered valid if it is connected to two media nodes, in which case this function returns true. If it is connected to one or no media nodes, it is consider invalid, and this function will then return false.

### bool Path::reconnect ( MediaNode * source, MediaNode * sink )

Changes the media nodes the path is connected to by connecting the path to the source and sink nodes specified. Returns true if successful; otherwise returns false.

If unsuccessful, the path remains connected to the same nodes as before.

See also Phonon::createPath() and Phonon Overview.

### bool Path::removeEffect ( Effect * effect )

Removes the given effect from the path and returns true; otherwise returns false.

Removes an effect from the path.

If the effect is deleted while it is still connected, the effect will be removed automatically.

See also insertEffect() and effects().

### MediaNode * Path::sink () const

Returns the sink MediaNode used by the path.

### MediaNode * Path::source () const

Returns the source MediaNode used by the path.

### bool Path::operator!= ( const Path & p ) const

Returns true if this Path is not equal to p; otherwise returns false.

### Path & Path::operator= ( const Path & p )

Assigns p to this Path and returns a reference to this Path.

This operation is fast thanks to explicit sharing.

### bool Path::operator== ( const Path & p ) const

Returns true if this Path is equal to p; otherwise returns false;

## Related Non-Members

### Path Phonon::createPath ( MediaNode * source, MediaNode * sink )

Creates a new Path connecting the two MediaNodes source and sink.

The implementation will automatically select the right format and media type. E.g. connecting a MediaObject and AudioOutput will create a Path object connecting the audio. This might be represented as PCM or perhaps even AC3 depending on the AudioOutput object.

source The MediaNode to connect an output from sink The MediaNode to connect to.