[Bug]: Incorrect radial gradient (CoreGraphics)

[alexrodi]

juce::ColourGradient with isRadial set to true doesn't blend RGB components correctly when using CoreGraphics.

Code

void MainComponent::paint (juce::Graphics& g)
{
    g.fillAll(juce::Colours::black);
    
    
    g.setGradientFill({
        juce::Colours::white, {0.0f, 0.0f},
        juce::Colours::red.withAlpha(0.0f), {0.0f, (float)getHeight()}
        , false
    });
    g.fillRect(getLocalBounds().removeFromLeft(getWidth() / 2));
    
    
    g.setGradientFill({
        juce::Colours::white, {(float)getWidth()*0.5f, 0.0f},
        juce::Colours::red.withAlpha(0.0f), {(float)getWidth()*0.5f, (float)getHeight()}
        , true
    });
    g.fillRect(getLocalBounds().removeFromRight(getWidth() / 2));
}

Result

Apparently, radial gradients only mix alpha values when one of the colour stops is transparent.

Expected behaviour

All components of the colour stops should mix and the transparent colour should be visible in the interpolation. (In the provided example code, the gradients should be seamless)

Observations

• Software renderer works as expected.
• The very first frame of the window is actually correct, only to get immediately redrawn as shown.

---

Version

JUCE v8.0.8

Operating systems

macOS Sonoma 14.5 (23F79)

Architectures

Arm64/aarch64

Testing on the develop branch

I have tested against the develop branch

Code of Conduct

• [x] I agree to follow the Code of Conduct