While examining my bug #6458, I found that FOP has problems handling non-integer
font-sizes (non-integral point sizes).

The summary of my source browsing and debugging is this:
- FOP accepts non-integral point sizes
- FOP hands non-integral point sizes over to formatters (e.g. PDF)
- Character widths of the default fonts (I checked with Helvetica) are
  calculated as if they had the next lower integral font size. This may
  be so either because the metrics file generator is broken or because
  of a bug in FOP - I did not check this).
- The PDF renderer DOES handle non-integral font sizes correctly. Because
  the renderer partially performs his own calculations, the result
  will - depending on the circumstances - either look good (but measure wrong)
  or totally broken. One effect that can happen is described in #6458.
- I rated this bug as major, because this bug can be very difficult
  to diagnose for uses - lots of wasted time.
The current workaround is not to use non-integral font sizes.

- As a consequence, at least FOP should round font sizes in formatting
  objects down to the next lower integral point size.