MobileRead Forums - View Single Post

GeoffR · 09-11-2015, 01:55 AM

There are a lot of things I don't understand about how fonts work, I hope someone else who has worked out these problems with another languages might be able to share some insights that might apply to Vietnamese too.

The fonts needed to display languages that are not supported by the interface, such as Arabic and Hebrew, are not loaded when the device first boots, only later when opening a book or when opening the font menu in an ePub book. Once that has happened, the glyphs that were missing from the boot fonts can be substituted with glyphs from the newly loaded fonts. I thought the same would apply to all languages, but perhaps that is not the case.

There is a problem with text that appears in italics in the interface (such as book titles) because it seems the mechanism for substituting slyphs from other fonts can't substitute a normal glyph if there is no italic version available, and I guess some languages don't use italics.

Some things to check:

* Have you sideloaded a font with all the Vietnamese glyphs you neeed? Fonts embedded in the book won't be available for use by the rest of the system.

* Have you opened the font menu in the book? That might be necessary to make the other fonts avaialble to the system when reading ePubs, although for KePubs it seems to be enough just to open the book.

It could be that the firmware only checks the built-in fonts and not sideloaded fonts when looking for the glyphs that it needs to substitute for missing glyphs. If that is the case then there might not be any solution to your problem, because I don't think anyone has worked out how to modify or replace the built-in fonts, which are all encrypted.

Here is a post that shows the Latin Extended Additional glyphs available in the Kobo Nickel font, which I think is the only built-in font that has any of those glyphs. If you have sideloaded a font with all the glyphs but are still missing the same glyphs that are missing in Kobo Nickel, then that probably indicates that only the built-in fonts are being used to substitute missing glyphs.

There is a list of 11 'priviledged' fonts: Amasis, Avenir Next Medium, Caecilia, Delima, Felbridge, Georgia, Gill Sans, Kobo Nickel, Malabar, Rockwell, Times New Roman. The ones in bold are not supplied with the current firmware, but were in earlier firmware versions. They are still treated as priviledged in that the advanced font menu will work (without any patches needed) if you have a sideloaded font with one of those names. It might be worth trying to rename a font with all the Vietnamese glyphs you need to one of those names and see if that causes it to be considered as a source of substitute glyphs.

Edit: From discussion in the Summary of modified fonts thread it appears that the interface and KePub reader are selecting fonts based on their PANOSE information. So something else to consider is the possibility that substitutes for missing glyphs might only be sourced from fonts with a compatible PANOSE profile.

09-11-2015, 01:55 AM	#4
GeoffR Wizard Posts: 3,821 Karma: 19162882 Join Date: Nov 2012 Location: Te Riu-a-Māui Device: Kobo Glo	There are a lot of things I don't understand about how fonts work, I hope someone else who has worked out these problems with another languages might be able to share some insights that might apply to Vietnamese too. The fonts needed to display languages that are not supported by the interface, such as Arabic and Hebrew, are not loaded when the device first boots, only later when opening a book or when opening the font menu in an ePub book. Once that has happened, the glyphs that were missing from the boot fonts can be substituted with glyphs from the newly loaded fonts. I thought the same would apply to all languages, but perhaps that is not the case. There is a problem with text that appears in italics in the interface (such as book titles) because it seems the mechanism for substituting slyphs from other fonts can't substitute a normal glyph if there is no italic version available, and I guess some languages don't use italics. Some things to check: * Have you sideloaded a font with all the Vietnamese glyphs you neeed? Fonts embedded in the book won't be available for use by the rest of the system. * Have you opened the font menu in the book? That might be necessary to make the other fonts avaialble to the system when reading ePubs, although for KePubs it seems to be enough just to open the book. It could be that the firmware only checks the built-in fonts and not sideloaded fonts when looking for the glyphs that it needs to substitute for missing glyphs. If that is the case then there might not be any solution to your problem, because I don't think anyone has worked out how to modify or replace the built-in fonts, which are all encrypted. Here is a post that shows the Latin Extended Additional glyphs available in the Kobo Nickel font, which I think is the only built-in font that has any of those glyphs. If you have sideloaded a font with all the glyphs but are still missing the same glyphs that are missing in Kobo Nickel, then that probably indicates that only the built-in fonts are being used to substitute missing glyphs. There is a list of 11 'priviledged' fonts: Amasis, Avenir Next Medium, Caecilia, Delima, Felbridge, Georgia, Gill Sans, Kobo Nickel, Malabar, Rockwell, Times New Roman. The ones in bold are not supplied with the current firmware, but were in earlier firmware versions. They are still treated as priviledged in that the advanced font menu will work (without any patches needed) if you have a sideloaded font with one of those names. It might be worth trying to rename a font with all the Vietnamese glyphs you need to one of those names and see if that causes it to be considered as a source of substitute glyphs. Edit: From discussion in the Summary of modified fonts thread it appears that the interface and KePub reader are selecting fonts based on their PANOSE information. So something else to consider is the possibility that substitutes for missing glyphs might only be sourced from fonts with a compatible PANOSE profile. Last edited by GeoffR; 09-11-2015 at 02:14 AM. Reason: ... PANOSE ...