FM 8.0.2 WinXP: Weird On-Screen Font Kerning

Question

Help! I'm experiencing a very irritating bug that didn't seem to
appear until I applied one of the FM 8 patches. I'm running FM 8.0.2
on Windows XP. I don't remember if this bug started in 8.0.1 or
8.0.2, but it didn't exist in FM 8.0.0, and it doesn't exist in FM
7.
Simply put, the spacing of the on-screen characters is wrong. Some
characters are smashed together and others have large gaps after
them. In Times New Roman 10, for example, every lowercase "m" has a
large space after it. Other font sizes, and other fonts, are also
affected. The problem doesn't seem to go away unless I use a very
large zoom-in factor (or zoom out, but then the text is illegible
anyway).
This makes it difficult for me to read and edit my own text, and it
makes it difficult to (e.g.) remove unwanted spaces.
This problem doesn't appear in printouts or PDFs, which leads me to
suspect that it was done on purpose, in order to make the on-screen
position of each character more closely follow its position on paper
when printed. If so, it seems like a misguided idea, and I would
prefer at least the option to have things back the way they were. I
am used to the idea that lines may not come as far over on the
screen as they do on the printed page.
I prefer legibility.
Can anything be done about this?
Thanks!
-- Ed

Answer 1

Ed and Chris,
I see what you observe as well and the effect is apparently most visible with low zoom levels and low font sizes. There is a trade-off between letter placement precision and low-resolution hinting rules built into fonts.
The line composer always uses the font's characters precise width data (fractional widths) to decide how many characters fit on a single line. When it comes to displaying that line on-screen there are two options:
If you have DisplayUsingPrinterMetrics=On the same precise data is used to calculate the starting point of each single character. This is very useful if you want to align certain characters to other elements on a page. Especially with mono-spaced fonts this guarantees that lines with the same amount of characters end at the same point, not only in print but also on screen.
If you have DisplayUsingPrinterMetrics=Off the display engine only uses the rounded width values returned from the hinting engine to place the characters, just ensuring they fit the line by modifying the spaces between words.
The difference between fractional widths and rounded widths gets lower if you increase font-size or zoom factor. Some character pairs are more affected in certain sizes/zooms. Also some fonts are more affected than others. The problem with monospaced fonts is that any rounding difference accumulates across the line.
From an authoring point of view fractional widths may not be the best choice, from a layout point of view they definitely are. I have to repeat that I never before heard any complaint from users where I recommended using DisplayUsingPrinterMetrics=On, maybe because most users work with higher zoom levels or rarely use a font like Times New Roman (as I guess that serif fonts might be more affected).
You have the option, and I just wanted to explain the background a little bit.
- Michael