Gsoc2016 Keyboard Classes Overview

Controller

Abstract class representing a controller. For each controller type there's a subclass: HidController, MidiController... Jordi will need to create a KeyboardController subclass.

ControllerDebug

This class is used to provide the controllerDebug(String s) macro. This macro prints controller debug messages. It is only needed to include the header file in each file where you want to use this macro. There's nothing that needs to be instantiated.

ControllerPreset

Abstract class representing a controller preset. For each controller type there's a subclass: HidControllerPreset, MidiControllerPreset... Jordi will need to create a KeyboardControllerPreset subclass.

ControllerPresetFileHandler

Handles loading and saving of Controller presets.

ControllerPresetVisitor

Controller::setPreset(const Controller& preset) needs to know the dynamic type of preset, because a controller should only handle its corresponding preset types (e.g. a MidiController should only handle instances of MidiControllerPreset).

To achieve this, the Visitor pattern is used.

Suppose preset is a MidiControllerPreset. First Controller::setPreset(const Controller& preset) calls the preset.accept(ControllerVisitor* visitor), which calls visitor.visit(this). But since preset is of type MidiControllerPreset, the method that is called is Controller::visit(MidiControllerPreset* preset), thus controller now knows the type of preset.

Providing a fallback Controller::visit(ControllerPreset* preset) saves us from implementing a visit method for each subclass of ControllerPreset.

ControllerEngine

It manages the loading and execution of a script. Controller class holds a ControllerEngine instance.

ControllerEnumerator

Abstract class that looks for available controllers. For each controller type there's a subclass: HidEnumerator, MidiEnumerator... Jordi will need to create a KeyboardEnumerator subclass.

For example if a user has two MIDI controllers connected to the computer, MidiEnumerator::queryDevices() returns a list with two instances of MidiController.

Here is were Jordi will have to figure out if two keyboards connected to the same computer can be used as two controllers or the OS presents them as a single one.

ControllerManager class holds a list of ControllerEnumerator instances.

ControllerManager

Manages creation/enumeration/deletion of hardware controllers. When a class wants to access a controller or query the available ones, it asks ControllerManager. There's only one instance of ControllerManager that is created in MixxxMainWindow (mixxx.cpp) and gets its slotSetUpDevices method called, at Mixxx start.