So I've been trying to learn about opentype features you can add.
(
https://www.microsoft.com/typography/otspec/features_ae.htm)Most of fonts I looked through have their own kerning and metric #s but in opentype feature, I also see "kern" but not a full list of kerning adjustment I see from metric/kerning window in FL.
example:
feature kern { # Kerning
# DEFAULT
lookup kern1 {
pos space Alphatonos -50;
pos space Omicrontonos -12;
So why are there two different places dealing with kerning and why is this one not a 100% same as ones I see in FL's kerning window.
Comments
liga" option, is that possible?
The OpenType spec makes recommendations to app developers [not rules] for each registered feature about whether it should be implemented by default and how the UI should handle it. In some cases, the app makers follow these and in some cases not. Over time, certain conventional behaviors have solidified, like Standard Ligatures being on by default (which happens also to be the recommendation).
Font makers work with the constraints of what is or is not implemented in the anticipated end-use environment(s). In the case of OpenType Layout features, we provide, but we cannot dictate.
If you have ligatures that you don’t want enabled by default, then you are best off not putting them in a feature that most environments enable by default. Like Ray said.
So, do you recommending adjusting kerning on both?
If you do your kerning in FontLab, the data is stored internally and can be included in the generated fonts either as an old style kern table, a kern feature (using "update kern feature"), or both.
Note that the old style kern table is more limited in size and is "flat". It's just a simple list of character pairs and kerning offsets. As I recall the limit is around 5000 pairs.
The kern feature allows you to kern classes of characters. This both reduces the amount of data needed and in effect allows many more pairs to be included by an order of magnitude.
If you "flatten" class kerning, you can easily exceed the limits of the old style kern table. For this reason, if you include both types of kerning in your font, it's likely that the old style kern table will need to be limited to a subset of pairs. FontLab offers to do this for you if it happens.
On a funny side note, if you expand the class-based kerning in FontLab Studio 5 and limit the number of pairs to exactly 10920, FontLab will generate a font with empty kerning table.
No known application looks beyond the first kern subtable, and fonts with more than two kern subtables are flagged as defective in recent Mac OS X versions.