TYPO3 Core

Example:

top: calc(100% + 5px);

is compressed to

top:calc(100%+5px);

The latter on is invalid and thus ignored by browsers. From here :

Note: The + and - operators must always be surrounded by whitespace.
The operand of calc(50% -8px) for instance will be parsed as a percentage
followed by a negative length, an invalid expression, while the operand
of calc(50% - 8px) is a percentage followed by a minus sign and a length.
Even further, calc(8px + -50%) is treated as a length followed by a plus
sign and a negative percentage. The * and / operators do not require
whitespace, but adding it for consistency is allowed, and recommended.