The FreeType Project - Bugs: bug #57701, FT_Outline_Decompose documentation...
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bug #57701: FT_Outline_Decompose documentation isn't entirely correct.
Submitter: | bungeman <bungeman> | ||
Submitted: | Thu 30 Jan 2020 06:31:21 PM UTC | ||
Severity: | 3 - Normal | Item Group: | None |
Status: | None | Privacy: | Public |
Assigned to: | None | Open/Closed: | Open |
Planned Release: | None |
Tue 17 Mar 2020 04:52:02 PM UTC, comment #5: |
Werner LEMBERG <wl> |
Mon 16 Mar 2020 11:41:18 PM UTC, comment #4: As a note ReactOS [0] reproduces a good bit of FreeType code to walk the outline in order to avoid contours with a single point (in order to reflect GDI behavior).
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bungeman <bungeman> |
Wed 05 Feb 2020 10:30:18 PM UTC, comment #3: I suppose that OpenType CFF fonts aren't supposed to use attachment points (or at least afdko doesn't support it) [0], so speculation in the previous comment isn't really relevant. However, the fact that ps_builder_close_contour is dropping the points is still interesting.
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bungeman <bungeman> |
Wed 05 Feb 2020 10:04:06 PM UTC, comment #2: As one more data point the current implementation of ps_builder_close_contour goes out of its way to drop empty contours (a moveto followed by a moveto), so they don't even end up in the FT_Outline to begin with.
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bungeman <bungeman> |
Fri 31 Jan 2020 09:57:31 PM UTC, comment #1: In relation to FT_Stroker_ParseOutline, I noticed that when I view the Stroked.ttf in ftview outline mode (key 4) that I don't get the round caps on the degenerate two point contours. This appears to be because FT_StrokerXxxTo check if the command is degenerate and bail without clearing stoker->first_point. In the end FT_Stroker_EndSubPath is only called if !stoker->first_point.
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bungeman <bungeman> |
Thu 30 Jan 2020 06:31:21 PM UTC, original submission:
Fonts want to have lone points so that such points can be hinted and used as attachment points but there is no way to mark such points as not part of the outline. Ideally TrueType would have provided a means of marking points or contours as phantom, allowing the font designer to have these points but mark them as not part of the outline. Unfortunately, this wasn't considered at the time, and wouldn't help much now for existing fonts. As a result, the convention seems to be that lone points should be left out of a reported user level outline.
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bungeman <bungeman> |
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Corresponding source code
Thanks a lot for your very detailed analysis and thoughts (and sorry for not answering earlier).
What actions do you recommend? Maybe you even have a patch in mind?
I'm currently a bit out of FreeType business, so I would be really glad for help by volunteers...
Alexei?