[Sony Cross-Device General] IgorEisberg:
Yes, once you flash this ZIP it will replace stuff in system partition, but after that no other changes are made to the system partition by the app itself. iFont, however, physically replaces fonts in order to install them, which means my selector takes priority as soon as you select a font pack. There shouldn't be any crashes, if that's what you ask.

The even better thing is that the font selector uses only the characters that are avaiable in the fonts pack, and for the missing characters it falls back to Roboto. Installing fonts with iFonts does not, they will fall back to some ugly fallback font instead.

It will work on an odexed ROM up to the point you wipe the dalvik-cache. Once you wiped the dalvik-cache, you'll be stuck in a bootloop (signature checking will fail, thus has to be patched). This is actually true for any other modified/third-party APK that you attempt to flash on an odex ROM

Unlike what iFont made you believe, a font in Android is not a single TTF file, it has variants like Light, Bold, Italic, BoldItalic, etc. And these variants have to be mapped to the corresponding font families they should replace. You can decompile one of my font packs to see how a font pack actually works. The key file is the "/res/xml/fonts.xml".

Here's how this XML file should look like (I setup the Biko font to only replace Sans Serif, Sans Serif Condensed, SST and SST Condensed fonts, but you can actually replace even more less-used fonts):

<?xml version="1.0" encoding="utf-8"?>
<familyset>
<family name="sans-serif">
<font weight="100" style="normal">Biko-Light.ttf</font>
<font weight="100" style="italic">Biko-LightItalic.ttf</font>
<font weight="300" style="normal">Biko-Light.ttf</font>
<font weight="300" style="italic">Biko-LightItalic.ttf</font>
<font weight="400" style="normal">Biko-Regular.ttf</font>
<font weight="400" style="italic">Biko-Italic.ttf</font>
<font weight="500" style="normal">Biko-Regular.ttf</font>
<font weight="500" style="italic">Biko-Italic.ttf</font>
<font weight="900" style="normal">Biko-Black.ttf</font>
<font weight="900" style="italic">Biko-BlackItalic.ttf</font>
<font weight="700" style="normal">Biko-Bold.ttf</font>
<font weight="700" style="italic">Biko-BoldItalic.ttf</font>
</family>
<family name="sans-serif-condensed">
<font weight="300" style="normal">Biko-Light.ttf</font>
<font weight="300" style="italic">Biko-LightItalic.ttf</font>
<font weight="400" style="normal">Biko-Regular.ttf</font>
<font weight="400" style="italic">Biko-Italic.ttf</font>
<font weight="700" style="normal">Biko-Bold.ttf</font>
<font weight="700" style="italic">Biko-BoldItalic.ttf</font>
</family>
<family name="x-sst">
<font weight="100" style="normal">Biko-Light.ttf</font>
<font weight="100" style="italic">Biko-LightItalic.ttf</font>
<font weight="300" style="normal">Biko-Light.ttf</font>
<font weight="300" style="italic">Biko-LightItalic.ttf</font>
<font weight="400" style="normal">Biko-Regular.ttf</font>
<font weight="700" style="normal">Biko-Bold.ttf</font>
<font weight="500" style="normal">Biko-Regular.ttf</font>
<font weight="500" style="italic">Biko-Italic.ttf</font>
<font weight="900" style="normal">Biko-Bold.ttf</font>
<font weight="900" style="italic">Biko-BoldItalic.ttf</font>
</family>
<family name="x-sst-condensed">
<font weight="400" style="normal">Biko-Regular.ttf</font>
<font weight="700" style="normal">Biko-Bold.ttf</font>
</family>
</familyset>