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

Thu Apr 11 15:57:45 UTC 2019

What you say seems irrelevant to me. Jonathan is correct.

On Thu, Apr 11, 2019, 11:34 AM Bobby de Vos <bobby_devos at sil.org> wrote:

> Paul,
>
> You don't need to convert the Google Tamil font to OpenType, Google has
> already done that at
>
>
> https://github.com/googlei18n/noto-fonts/tree/master/phaseIII_only/unhinted/otf/NotoSansTamil
>
> However, I don't think those fonts will solve your issue. The list of
> shapers that you mention are different technologies to specify the complex
> shaping (such ligatures, positioning, sub forms, half foms, etc). Indeed,
> OpenType is one such technology. SIL Graphite and Apple Advanced Typography
> (AAT) are other technologies to do this.
>
> TrueType fonts can contain OpenType shaping instructions. You do not have
> to have an OpenType font format to use OpenType shaping.
>
> TrueType fonts have quadratic Bézier curves for their glyphs. Fonts in the
> OpenType font format can use the same quadratic Bézier curves, or cubic
> Bézier curves. The OTF files I mentioned above have cubic Bézier curves.
>
> https://en.wikipedia.org/wiki/B%C3%A9zier_curve#Fonts
>
> If I have mis-understood your situation, and/or made any errors if what I
> wrote, I apologize.
>
> Bobby
> On 2019-04-10 3:25 p.m., Paul Daughetee wrote:
>
> Thanks for the quick response. I’m a licensed user of FontCreator
> Professional Edition from High-Logic and have the most recent update to
> version 11.5 installed.  The correct ligature is displayed when I type the
> tta and u Tamil characters into the test string edit box in the OpenType
> Designer dialog. In the box just below the test string the two characters
> are displayed unless I check either the _shaper or psts feature check box.
> If one of those is checked, then the correct ligature is displayed. So I
> guess Google did get the Tamil font right but I cannot seem to get HarfBuzz
> to return a single glyph id when presented with a buffer containing the tta
> and u Tamil characters. I’ve tried adding various features when calling
> hb_shape but that doesn’t seem to change anything.
>
>
>
> I noticed that when I list shapers using a call to hb_shape_list_shapers,
> the only shaper listed is “ot”. So I guess my next try will be to convert
> the Google Tamil true type font to an open type font and see if that makes
> any difference. If it does, I guess I’ll be having a “duh” moment.
>
>
>
> *From:* Cody Planteen <planteen at gmail.com> <planteen at gmail.com>
> *Sent:* April 10, 2019 12:38 PM
> *To:* Paul Daughetee <Daughetee at finaldraft.com> <Daughetee at finaldraft.com>
> *Cc:* harfbuzz at lists.freedesktop.org
> *Subject:* Re: [HarfBuzz] Question on converting UTF-8 codepoints to
> complex glyphs
>
>
>
> It's possible your font isn't doing what you think it should be. You can
> test this theory with the tool High-Logic FontCreator for Windows. I
> believe there is a free evaluation. You can open up your font, then go to
> Font -> OpenType Designer. In this dialog, you can enter your test string
> and see what glyphs come out.
>
>
>
> https://www.high-logic.com/font-editor/fontcreator
>
>
>
>
>
> On Wed, Apr 10, 2019 at 1:19 PM Paul Daughetee <Daughetee at finaldraft.com>
> wrote:
>
> 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>
> 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
> http://behdad.org/
>
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> --
> Bobby de Vos
> *bobby_devos at sil.org <bobby_devos at sil.org>*
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