Created attachment 154676 [details]
Screenshot illustrating bug
Please see the attachment showing the sequence दे॒वेभ्य॑ः. This is created by latest LibreOffice 6.3.2 on Kubuntu Bionic LTS. (I do not use Windows so did not test this there.)
It is observed that there is a dotted circle before the visarga but there should not be.
The same is observed with other common Devanagari fonts like Noto Sans Devanagari and Lohit Devanagari. This needs to be fixed.
Indic visarga characters are always spacing and placed to the right of the syllable. Vedic tone markers whether spacing or non-spacing will always be input before visarga because they apply to the vowel before the visarga.
So the expected sequence is:
syllable + zero or more tone markers + visarga
and so sequences like the example above where the visarga is placed after such a tone marker should not cause a dotted circle due to cluster breakup.
The file http://www.unicode.org/Public/UNIDATA/IndicSyllabicCategory.txt does an excellent job of listing the visarga characters and the tone markers under the sections:
Please provide a sample document (simple text runs in several of the fonts that support the combining glyphs).
Created attachment 154697 [details]
Font supporting relevant characters
Created attachment 154698 [details]
Script to produce random test samples
Hello. There was some problem in auto-detecting and manually setting the content type of the font to font/ttf. Don't know why. So have set to application/octet-stream.
Anyway, I am not aware of any one publicly available font that supports all relevant characters since Vedic is a rare use case. I have uploaded the OFL Lohit Devanagari locally modified by myself adding the extra required characters.
I have also uploaded a Python script to produce test case sequences. Hope this would be sufficient.
Note that currently the script only produces test cases for Devanagari as I only have a Vedic-supporting font for that script, but you can see that it can be easily toggled to printing randomly other scripts also.
Confirmed on a Windows 10 Home 64-bit en-US with
Version: 126.96.36.199 (x64)
Build ID: 98b30e735bda24bc04ab42594c85f7fd8be07b9c
CPU threads: 4; OS: Windows 10.0; UI render: GL; VCL: win;
Locale: en-US (en_US); UI-Language: en-US
with Devanagari (0x0900-0x097f) coverage in Microsoft provided Nimala UI, and installed Code 2000, and Adobe Devanagari.
Only picking up the first in a sequence of combining glyphs.
Happens with both default GDI rendering, and with OpenGL rendering.
Are multiple combining glyphs for CTL handled in HarfBuzz?
I can reproduce with hb-view utility from HarfBuzz, so it is a HarfBuzz issue. Please report on https://github.com/harfbuzz/harfbuzz/issues
Reported upstream as https://github.com/harfbuzz/harfbuzz/issues/2017.