Fix for randomly not loaded CoverArt in Spinnies

[JoergAtGithub]

Im not sure if this fix is the appropriated solution, but it fixes the issue #11131 for me.
The problem is, that the requestor of cached CoverArt is not always WSpinnyBase - it can also be WCoverArt.

[daschuer]

Every widget is running it's own request, because of size constrains.
There must be a race-codition that the cover is not requested of the responds is lost.
Is WSpinnyBase::slotTrackCoverArtUpdated always called?

[JoergAtGithub]

I set a breakpoint in WSpinnyBase::slotTrackCoverArtUpdated() and it's was never called.

[ronso0]

I agree with daschuer, now the spinny will receive signals meant for other widgets, so it will receive more unneeded updates.

@JoergAtGithub You found out #11131 (comment)

The following function is executed three times, when a track is loaded into a deck. The first two times pixmap is alway NULL and it returns early. The third call differs in failure case, when the Coverart is not loaded, pixmap is NULL as well.

mixxx/src/widget/wspinnybase.cpp

Lines 377 to 386 in 4a51c39

	QPixmap WSpinnyBase::scaleToSize(const QPixmap& pixmap) const {
	if (pixmap.isNull()) {
	return QPixmap();
	}
	QPixmap scaled = pixmap.scaled(size() * devicePixelRatioF(),
	Qt::KeepAspectRatio,
	Qt::SmoothTransformation);
	scaled.setDevicePixelRatio(devicePixelRatioF());
	return scaled;
	}

I wonder why it's called 3 times in the first place.

[ronso0]

Closing this one since the bug seems to by fixed en passant by #11840

[JoergAtGithub]

Unfortunately this bug is not fixed by #11840

[ronso0]

Sorry, I confused it with the slip indicator bug.

[JoergAtGithub]

Closing this PR - I agree, that this is not the correct fix for this bug.