Where exactly in the Android OS is text renderred?

Let me first state what I am trying to achieve:

To create a patch for the Android OS to enable it to display Arabic/Hebrew correctly. Both of these languages are Right-to-Left (RTL) and their script involves connected letters/glyphs (unlike Latin alphabets which have discrete letters).


The Arabic word for "car" is:


The discrete letters look like this:

س ي ا ر ة

As you can see, each letter connects to each other letter in different ways depending on what precedes it & what follows it. Ok, enough with the language lessons :) My question is:

What binary/class in android do I need to hijack to enable this functionality?

Another way to put it is; if you wanted every instance "x" to be displayed as "y", system-wide, what binary/class would you need to meddle with?

The source code is browsable at GitHub: http://github.com/android/

I think it might be somewhere under the C/C++ platform_system_core, or thier custom JVM platfom_dalvik.

Just to be clear, the font is not an issue since you can drop Arabic/Hebrew fonts as fall-back fonts and they would display, albeit in discrete form.

Your help would be much appreciated :)

Asked by: Sarah201 | Posted: 24-01-2022

Answer 1

see external/skia in a checked-out source tree. that's the skia graphics library, and that's ultimately responsible for font rendering.

Answered by: Julian493 | Posted: 25-02-2022

Answer 2

Remember that the problem is more complicated than modifying the underlying graphics engine.

If you apply reshaping in Skia, you might run into problems if lines' widths change (happens when لا replaces ل followed by ا). This is because reshaping arabic might change the sequence of letters as well and Skia, as I see, tries to act passively regarding contents of text. It simply outputs the letters to the the display device as-are.

Now the worse problem is actually in Android itself. Arabic/Hebrew requires BiDi repositioning of text, which is very dumb in Android and can't handle very basic issues.

More bad news? Android's font, Droid, doesn't contain Arabic or Hebrew glyphs. Unless we root the device and replace it with another font, squares are displayed instead of arabic letters :)

The whole platform is still far from being able to cope with any RTL language, especially Arabic.

As you see, a correct modification for RTL languages isn't only in Skia ....

Answered by: Darcy120 | Posted: 25-02-2022

Answer 3

See if this helps:


Answered by: Ned102 | Posted: 25-02-2022

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