Removed unused setSVG and hash functionality from pixmapsource

[JoergAtGithub]

Instead use the getPath explicit as in key
Improved cache key string concatenation

[Swiftb0y]

Thanks for the (likely) improvement.

[Swiftb0y]

I haven't read the imagestore code too closely. Does it cache the data persistently across mixxx restarts? If thats the case, it would likely annoy people during development when they adjust and image but its not updated because the old data still lingers in the cache.

[JoergAtGithub]

This behavior is not changed. And this is one of the reasons why I clean up this code step by step. Sometimes Mixxx starts to load SVG again and the UI stucks, see #12904

[Swiftb0y]

This behavior is not changed.

Changing the cachekey from being based on the SVG content to being based on the file path does change when the cache is invalidated. Are you sure that the behavior is unchanged?

[JoergAtGithub]

Changing the cachekey from being based on the SVG content to being based on the file path does change when the cache is invalidated. Are you sure that the behavior is unchanged?

There were 2 ways to generate the key:

1. Using the the file path of the SVG
2. Hashing the SVG content

The code path that hashed the SVG content was not used (only setSVG could write m_svgSourceData and I there was no caller for this function). therefore I deleted the getKey function in this PR:

mixxx/src/skin/legacy/pixmapsource.cpp

Lines 45 to 51 in 6d23434

	QString PixmapSource::getId() const {
	if (m_svgSourceData.isEmpty()) {
	DEBUG_ASSERT(!m_path.isEmpty());
	return m_path;
	}
	return QCryptographicHash::hash(m_svgSourceData, QCryptographicHash::Sha1).toHex();
	}

Instead of getKey I use the getPath function, which is the same as the used code path of getKey:

mixxx/src/skin/legacy/pixmapsource.cpp

Lines 24 to 26 in 6d23434

	const QString& PixmapSource::getPath() const {
	return m_path;
	}

[Swiftb0y]

I see. Thank you. LGTM