Check code integrity

[pfaion]

• Make sure that all code makes sense and none is superfluous.
• Make sure names are meaningful.
• Do not add new features, only get the old ones right.
• Profit.

[pfaion]

Renaming "compile" to "render" already makes much more sense. See d07cda6

[pfaion]

Todo: rename "label" in QStackedLayout somehow to represent pre-rendered images.