[HarfBuzz] Question on converting UTF-8 codepoints to complex glyphs

[Paul Daughetee]

Let me give you a little more info. I just recently built and installed vcpkg and used it to install HarfBuzz on Windows 10. It installed version 2.3.1-3 of the static libraries for Window x86. I linked my app to the HarfBuzz library and its dependencies. I added code to my app to capture single words that I could send to be processed by HarfBuzz as they were typed by the user. I installed Google’s NotoSansTamil true type font after verifying that it properly defined substitutions for the ligature that is formed by the Tamil consonant “tta” when paired with a vowel such as “u” or “I”. After processing a UTF-8 string containing the consonant and the vowel “tta” and “u” [0xE0, 0xAE, 0x9F, 0xE0, 0xAE, 0x89], the hb_glyph_info_t object I get back has tow glyph indices, the same indices as the “tta” and “u” (17, 10) rather than the index for the “ttauvowelsign” (116) ligature I expected. My code is virtually identical to the examples found in the HarfBuzz wiki and to several examples found in git. Any help here would be greatly appreciated.

From: Behdad Esfahbod <behdad at behdad.org>
Sent: April 8, 2019 1:47 PM
To: Paul Daughetee <Daughetee at finaldraft.com>
Cc: harfbuzz at lists.freedesktop.org
Subject: Re: [HarfBuzz] Question on converting UTF-8 codepoints to complex glyphs

On Mon, Apr 8, 2019 at 4:12 PM Paul Daughetee <Daughetee at finaldraft.com<mailto:Daughetee at finaldraft.com>> wrote:
I’m new to HarfBuzz and attempting to use it for converting a UTF-8 string that contains one or more sets of codepoints that should combine to form single complex glyphs to the correct string of glyphs. I’ve followed numerous examples and they all lead me to the point where I use hb_buffer_get_glyph_infos to get what I thought would be a hb_glyph_info object that contains the codepoints for the glyphs I seek. So my first question is as follows. Is that what I should be getting? I ask because I’m not getting what I would expect to get.

Yes.


I can’t even successfully get a complex glyph to represent the combination of the letter A and the grave accent. So if I’m just confused as to how or what HarfBuzz does, please help me find a better path. Thanks!

What do you get?  A + grave-accent only forms one glyph if the font was designed so.  It may very well be represented by two glyphs.

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behdad
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