Not Rendering graphite with nukta ring in Bloom and LibreOffice

[jayak-siva]

Dear Ones,
The graphite font TAML Thiruvalluvar is not rendering properly in Bloom and current versions LibreOffice. I have given the texts here for combinations and screenshots how it looks in Paratext (correctly rendering) and Bloom and LibreOffice.

text-combination.txt

[devosb]

I think the issue is the nukta (U+1133C GRANTHA SIGN NUKTA) is classified as Grantha script (Gran) and since the rest of the text is Tamil script (Taml), this causes the application to break the run of text at the nukta, and not pass the entire text run to the shaper. For applications that are rendering correctly, such as Paratext and (I heard) Firefox and Chrome I suspect they are reading (or maybe ICU is reading for them) ScriptExtensions.txt from the Unicode standard where the nukta is classified as having two scripts, Gran and Taml.

To test this, I would have the Bloom developers make sure they are making use of the data in ScriptExtensions.txt. If not, they should. If such a change improves the rendering, then a similar bug report can be sent to LibreOffice.