I have at last completed the compilation of a font database to examine the
issues concerning the differences in rendering text on Mac Monterey, Windows 10
and Linux Ubuntu.
Over 4600 font files have been included in the database, including the fonts
distributed with each platform, the Google fonts, STIX, KG and Janda and some
other sources. Each fontfile may have multiple style variant fonts embedded in
it so over 9200 individual fonts are included.
For each font, the ascent and descent at a range of text sizes between 8 and 25
when used on each platform is recorded, as reported by the LC measureText()
function. As previously discussed these metrics, which determine the baseline
of the text, differ markedly between platforms, so that text is rendered in
different positions in the stack, leading to alignment and clipping problems,
or simply an unprofessional-looking UI (this problem is not unique to LC).
The db also records the rendered text lengths for three sample texts at each
textsize, in order to investigate cross-platform horizontal alignment and
clipping issues.
The db also records : the fontnames for each font for each platform
(different!), the set of all alternative family names, font names (different
again!) and styles as given in the font metadata tables, the postscript name,
the number of fonts in the file, the designer's em grid size, ascent, descent
and OS/2 vertical metrics, the version and the first line o) the copyright
notice.
To summarise the conclusions of my analysis using this database:
1. Fonts which cannot be used cross-platform
There are 96 fonts in the MacOS stable which will not install on Windows,
because they lack some metadata entry. These include Helvetica, Times, Courier,
Monaco, Zapfino, Apple Symbols, Apple Chancery, LucidaGrande, Copperplate.
Apple Color Emoji. Whether a font is legal to use cross-platform is a different
question: the Apple copyright licence for New York for example restricts its
use to Apple devices.
2. Vertical alignment: No fonts are placed at the same vertical positions
across the 3 platforms. Formulae for the baseline using the ascent and descent
data are developed in the discussion paper below, and these could be used to
align text manually if exact vertical placement is required, but this is a
hack, and is not absolutely precise in some cases. What LC really needs is a
built-in fixedBaselIne property for fields similar to the fixedLineHeight
property. Until that happens, be warned that some vertical padding is needed
when designing labels and text fields for standalones to account for vertical
drift on other platforms.
3. Horizontal lengths: A number of problematic issues with LC were encountered
in this investigation which certainly slowed me down. Firstly there is a bug in
start using/stop using font file. "stop using font file" seems to leave the LC
font library in a corrupted state. On Windows, if you ask for fontNames() after
stop using but before start using another font, a standalone will crash; in the
IDE you don't get any error, but the fontNames returned may contain fonts that
were stopped earlier. There is a workaround for the crash but not the
subsequent error … because in both Windows and Mac, after stop using is called,
string widths returned by formattedWidth or measureText are randomly, about 3%
of the time, incorrect [looks like a released handle is being accessed]. These
errors could not be entirely eliminated from the db but have been mitigated so
that I have confidence in my main conclusions below. On Linux the problem
doesn’t arise because start using is not implemented on Linux; I installed the
fonts for Linux using shell commands.
A second problem arises from the way Windows names fonts combined with a
serious deficiency in LC. On Windows the font name appearing in the font menu
is in fact just the family name; the style the user wants must be suppled
separately. However LC can only supply style variations Bold, Italic and Bold
Italic. This means that literally thousands of fonts such as Arima Thin
SemiBold cannot be accessed by LC stack on Windows, which just knows about
Arima. This leaves aside the fact that fontStyles() hasn’t worked in LC for
years. A further complication is that both Mac and Windows perversely make up
their own names for the font instead of using any of the names the font
designer supplies in the metadata: on the Mac the font name usually includes
the style which is nice but occasionally it doubles the style — Arimo Italic
Italic and 88 similar cases; and Windows should use a family name but sometimes
gets it wrong!
The upshot is that effectively the fonts in my db available for cross-platform
LC stacks on Mac and Windows is limited to those with the same name on the two
platforms, or where the Mac name is " Regular”. I also disregard
about 1200 fonts in the Noto family for non-latin or regional fonts since by
and large these
