Codebase overview

Audacity 4's codebase consists of 3 main parts: Audacity 3 code invoked through a wrapper, Audacity 4 code, and the Muse Framework.

Audacity 3 code in the main au3/ folder is unused; it's merely kept to make copypasting bits into the active src/ somewhat more easy. Active Audacity 3 code may be found in some subdirectories of src/.

Muse Framework code is not part of the Audacity repo, and can be found here (or eventually here). It provides elements common to Audacity and MuseScore Studio, most notably low-level functionality, buttons and graphics, the preferences system, and things like that. At the time of writing, active development of the framework happens in the musescore/musescore repo, with updates to the framework repo being extracted from there - though this will change soon, probably.

Architectural information on the Muse Framework can be found at the framework's Github wiki.

Audacity 4-specific code can be found in src/. On a high level, it is structured as follows:

Contents of src/

• app/ contains the base of the program, including default configurations and theme configuration.

• appshell/ contains various dialogs and pages, such as the preferences.

• au3audio/ contains the PortAudio-based audio engine found in Audacity 3. It is scheduled for replacement with a new engine.

• au3wrap/ contains the wrapper for old Audacity 3 code. You'll find au3/ subdirectories in various other places, this is what makes it run within Audacity 4.

• context/ contains the different contexts actions can exist in.

• effects/ contains effects and plugin implementations.

• importexport/ contains importing and exporting code.

• playback/ contains everything needed for playback, including device configuration and meters.

• project/ contains code related to the project itself, so anything that loads/writes to/modifies AUP3 files.

• projectscene/ contains all of the stuff needed to show what a project contais - clips, tracks, etc.

• record/ contains everything needed for recording.

• trackedit/ contains everything related to editing and modifying audio clips and tracks.

Internal structure

The directories in src/ contain subdirectories with some separation of concerns:

• internal/ contains the internal calculations, generally only relevant within the directory its in.

• qml/ contains QML files - ie layouts for various components.

• tests/ contains unit tests. New code should have at least 80% unit test coverage.

• types/ contains custom types and data structures needed in that area.

• view/ contains the things data which should be displayed by the QML above.

Note: In addition to this separation of concerns, Audacity also uses the Model-View-Controller model.