Regression: DropShadows render incorrectly for Paths on macOS

[pflugshaupt]

The GPU-based DropShadows for paths do not draw correctly on macOS using JUCE 8.0.6.

I am trying to migrate from drawForRectangle() because it is now slowish on D2D.

drawForRectangle stayed the same since before the J8 shadow optimizations as it is a gradient based ‘trick’.

I made this code to compare it against drawForPath:

void MainComponent::paint (juce::Graphics& g)
{
    g.fillAll (juce::Colours::grey);

	juce::DropShadow ds(juce::Colours::black.withAlpha(0.7f), 10, {1, 2});

    // Top (clipped)
	juce::Path p3;
	p3.addRectangle(juce::Rectangle<int>{0, -11, getWidth(), 10});
	ds.drawForPath(g, p3);

    // Left
	ds.drawForRectangle(g, {80, 80, 40, 40});

    // Middle
	juce::Path p;
	p.addRectangle(juce::Rectangle<int>(160, 80, 40, 40));
	ds.drawForPath(g, p);

    // Right
	juce::Path p2;
	p2.addEllipse(juce::Rectangle<float>(240, 80, 40, 40));
	ds.drawForPath(g, p2);
}

This is result on macOS (tested on multiple macOS versions):

Same code on Windows 11 using the D2D renderer:

The Windows version is the way it should render IMHO - macOS is bugged and it makes my UI look very bad, the shadow all have hard borders now .

The macOS drawing result looks like something is wrong with the alpha channel. Maybe there is some mismatch or premultiplied alpha and non-premultiplied alpha going on?

[pflugshaupt]

I found out this has been working correctly in 8.0.5 and is a regression from recent changes, so I did a git bisect and found the commit that broke the DropShadow for Path rendering:

ImagePixelData: Update signatures of functions providing whole-image effects

@reuk, I think the changes to CoreGraphicsContext need another look.

[pflugshaupt]

This is how my example app looks before and after the commit.
Before:

After:

Code:
ShadowIssues.zip (4.6 KB)

[pflugshaupt]

Hmm… besides no longer rendering correctly I also see a massive performance problem with applyFilterInArea<>. My plugin is no longer able to hold 60fps rendering with about 10 small DropShadows visible.

And yes, this is of course with a release build. Somehow these changes seem to have imported similar issues to macOS as we’ve been seeing with D2D on Windows.

[pflugshaupt]

This thread was no longer accessible for some reason and now has been somehow resurrected.

I already started another one where the discussion continues:

[Bug] DropShadow draws incorrect shadows for Paths on macOS

Curious… I spent hours researching a problem in Juce develop 8.0.6 today and now the thread with my findings seems gone. Luckily, I don’t mind posting again. The previous thread has been made private for some reason… Why would that happen? https://forum.juce.com/t/dropshadow-renders-incorrectly-for-paths-on-macos/65109 To sum it up. Since this commit: DropShadow renders incorrect shadows on macOS for Paths and is very slow. I wrote some test code: void MainComponent::paint (juce::Graphics&…