ListBox alpha ignored

General JUCE discussion
1

Hi everyone,

I’m having trouble getting the alpha of ListBoxes to work properly.
It looks like the alpha is ignored or not handled correctly.
Here is some example code with a slider that changes the alpha of the main component, I expect that it should change the alpha of the listbox, but for some reason it doesn’t.

Hopefully someone can tell me what’s wrong in my code… or is it a bug?

// A component with children at different levels to test nested alpha
struct NestedRects : juce::Component
{
    NestedRects(int numNested)
    {
        if (numNested > 0)
        {
            nested_ = std::make_unique<NestedRects>(numNested - 1);
            addAndMakeVisible(*nested_);
        }
    }
    
    void paint(juce::Graphics& g) override
    {
        g.fillAll(colour_);
    }
    
    void resized() override
    {
        if (nested_)
        {
            nested_->setBounds(getLocalBounds().reduced(20));
        }
    }
    
    juce::Colour colour_ = juce::Colour::fromRGB(juce::Random().nextInt(255),
                                                 juce::Random().nextInt(255),
                                                 juce::Random().nextInt(255));
    std::unique_ptr<NestedRects> nested_;
};

class MainComponent  : public juce::Component
{
public:
    //==============================================================================
    MainComponent()
    {
        addAndMakeVisible(listBox_);
        listBox_.updateContent();
        
        addAndMakeVisible(nestedRects_);
        
        addAndMakeVisible(alphaSlider_);
        alphaSlider_.setRange(0.0, 1.0);
        alphaSlider_.onValueChange = [&]
        {
            setAlpha(alphaSlider_.getValue());
        };
        
        setSize (600, 400);
    }
    
    ~MainComponent() override {}

    //==============================================================================
    void paint (juce::Graphics& g) override
    {
        g.fillAll (getLookAndFeel().findColour (juce::ResizableWindow::backgroundColourId));
    }
    
    void resized() override
    {
        listBox_.setBounds(10, 10, 100, 400);
        nestedRects_.setBounds(150, 75, 300, 300);
        alphaSlider_.setBounds(150, 10, 200, 40);
    }

private:
    //==============================================================================
    struct : juce::ListBoxModel
    {
        int getNumRows() override
        {
            return 10;
        }
        
        void paintListBoxItem (int rowNumber, juce::Graphics &g, int width, int height, bool rowIsSelected) override
        {
            g.fillAll(juce::Colours::white);
            g.setColour(juce::Colours::black);
            g.drawText("Item " + juce::String(rowNumber), 0, 0, width, height, juce::Justification::centredLeft);
        }
    } model_;
    
    juce::ListBox listBox_ {"", &model_};
    
    NestedRects nestedRects_ { 4 };
    
    juce::Slider alphaSlider_;

    JUCE_DECLARE_NON_COPYABLE_WITH_LEAK_DETECTOR (MainComponent)
};

Thank you all,
Jelle