The VanillaJuceAudioProcessorEditor class defined in PluginEditor.h is very simple, and little changed from what was automatically generated by the Projucer:

class VanillaJuceAudioProcessorEditor
    : public AudioProcessorEditor
    , public ChangeListener
{
public:
    VanillaJuceAudioProcessorEditor (VanillaJuceAudioProcessor&);
    ~VanillaJuceAudioProcessorEditor();
 
    void paint (Graphics&) override;
    void resized() override;
 
    virtual void changeListenerCallback(ChangeBroadcaster* source);
 
private:
    VanillaJuceAudioProcessor& processor;
    GuiTabs guiTabs;
 
    JUCE_DECLARE_NON_COPYABLE_WITH_LEAK_DETECTOR (VanillaJuceAudioProcessorEditor)
};

The editor GUI is entirely built from JUCE Component-class objects. It consists of a single GuiTabs object (the guiTabs member variable above), which itself owns and contains all the other Components. As you'll see below, all of my Gui… classes take a SynthSound* pointer as a constructor argument, and implement a void notify() member function which gets called whenever any parameter is changed. Here is the entire PluginEditor.cpp file (except for the #include lines at the top):

VanillaJuceAudioProcessorEditor::VanillaJuceAudioProcessorEditor (VanillaJuceAudioProcessor& p)
    : AudioProcessorEditor (&p)
    , processor (p)
    , guiTabs(p.getSound())
{
    setSize (600, 400);
    addAndMakeVisible(&guiTabs);
    p.addChangeListener(this);
}
 
VanillaJuceAudioProcessorEditor::~VanillaJuceAudioProcessorEditor()
{
    processor.removeChangeListener(this);
}
 
void VanillaJuceAudioProcessorEditor::paint (Graphics& g)
{
    ignoreUnused(g);
}
 
void VanillaJuceAudioProcessorEditor::resized()
{
    guiTabs.setBounds(0, 0, proportionOfWidth(1.0000f), proportionOfHeight(1.0000f));
}
 
void VanillaJuceAudioProcessorEditor::changeListenerCallback(ChangeBroadcaster* source)
{
    ignoreUnused(source);
    guiTabs.notify();
}

The constructor calls the processor's getSound() function to get a pointer to the one shared SynthSound object, which it passes to the constructor for guiTabs. It also sets the GUI window size, calls juce::Component::addAndMakeVisible() to add the tabs object as a child Component of the editor, and registers the editor as a change-listener to the processor. The destructor unregisters it.

The resized() function sets the bounds of the guiTabs object so it completely fills the editor window. As a consequence, the paint() function has nothing to do, because the tabs object will render the entire window contents.

The editor inherits from juce::ChangeListener, hence it implements changeListenerCallback(), which simply calls guiTabs.notify() (which will propagate the change notification to all of its child GUI components.)

The GuiTabs class is a container for a juce::TabbedComponent object, and three “tab” Components which are added to it:

class GuiTabs  : public Component
{
public:
    GuiTabs (SynthSound* pSynthSound);
    ~GuiTabs();
 
    void paint (Graphics& g) override;
    void resized() override;
 
    void notify();
 
private:
    ScopedPointer<TabbedComponent> tabbedComponent;
    GuiMainTab* pMainTab;
    GuiOscTab* pOscTab;
    GuiEgTab* pAmpEgTab;
 
    JUCE_DECLARE_NON_COPYABLE_WITH_LEAK_DETECTOR (GuiTabs)
};
 
GuiTabs::GuiTabs (SynthSound* pSynthSound)
{
    addAndMakeVisible (tabbedComponent = new TabbedComponent (TabbedButtonBar::TabsAtTop));
    tabbedComponent->setTabBarDepth (32);
    tabbedComponent->addTab(TRANS("Main"), Colours::lightgrey, pMainTab = new GuiMainTab(pSynthSound), true);
    tabbedComponent->addTab (TRANS("Osc"), Colours::lightgrey, pOscTab = new GuiOscTab(pSynthSound), true);
    tabbedComponent->addTab(TRANS("AmpEG"), Colours::lightgrey, pAmpEgTab = new GuiEgTab(pSynthSound), true);
    tabbedComponent->setCurrentTabIndex(0);
}
 
GuiTabs::~GuiTabs()
{
    // tabbedComponent will take care of deleting our tab objects
    tabbedComponent = nullptr;
}
 
//==============================================================================
void GuiTabs::paint (Graphics& g)
{
    g.fillAll (Colour (0xff323e44));
}
 
void GuiTabs::resized()
{
    tabbedComponent->setBounds (0, 0, proportionOfWidth (1.0000f), proportionOfHeight (1.0000f));
}
 
void GuiTabs::notify()
{
    pMainTab->notify();
    pOscTab->notify();
    pAmpEgTab->notify();
}

The constructor creates the tabbedComponent object and calls addAndMakeVisible() on it, sets the depth of the tabs bar to 32 pixels, creates the three tab objects and calls tabbedComponent→addTab, and sets the first (zeroth) tab to be the initially-selected one.