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hb-view doesn't render anything with this font #2675

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olivierberten opened this issue Sep 9, 2020 · 13 comments
Closed

hb-view doesn't render anything with this font #2675

olivierberten opened this issue Sep 9, 2020 · 13 comments
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@behdad

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@olivierberten
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it seems to work anywhere else (hb-shape included) but hb-view renders an empty image
SN Kh SONY Moul.ttf.zip
source
@khaledhosny
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khaledhosny commented Sep 10, 2020 •
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The font has COLR table that seems to be breaking something, if I drop that table things get fixed.

I though the table is bogus, but it seems that hb-view will not show anything for glyphs not covered by COLR, not just in this font which makes no sense. I wonder where is this breaking, pango-view seems fine, so I guess it is not Cairo or FreeType.

@behdad
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behdad commented Sep 10, 2020

Is definitely Cairo or FreeType issue since hb-view by itself doesn't do any magic. It might be that FT_HAS_COLOR is broken for this font.

What happens if you pass --background=01?

@behdad
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behdad commented Sep 10, 2020

When reporting bugs please also specify sample text to reproduce the bug. Thanks.

@behdad
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behdad commented Sep 10, 2020

What happens if you pass --background=01?

Doesn't do anything.

I can reproduce. Will look into later.

@khaledhosny
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khaledhosny commented Sep 10, 2020 •
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The issue happens with other fonts too, for glyphs not covered by COLR table (e.g. a م in Amiri Quran Colored).

@behdad
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behdad commented Sep 10, 2020

So, the color glyphs work?

@khaledhosny
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Yes.

@behdad behdad self-assigned this Sep 20, 2020
@simoncozens
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Removing the 0 && from this line

harfbuzz/util/view-cairo.cc

Line 123 in ea4476d

if (0 && cairo_surface_get_type (cairo_get_target (cr)) == CAIRO_SURFACE_TYPE_IMAGE) {

makes it display. That might not be the fix because I presume it's if'd out for a reason. But it should be a good place to start looking.

@behdad
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behdad commented Dec 22, 2020

makes it display. That might not be the fix because I presume it's if'd out for a reason. But it should be a good place to start looking.

Basically what that suggests is that it's a bug in cairo's color-glyph processing. Which is what I knew anyway since we don't do any of that.

@matthiasclasen
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Here is what I see with that font:

Screenshot from 2021-07-31 08-37-08

It is not that nothing is there, it is that you get white-on-white text.

@matthiasclasen
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Fixed here: https://gitlab.freedesktop.org/cairo/cairo/-/merge_requests/224

@behdad
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behdad commented Aug 1, 2021

Thanks Matthias.

@behdad behdad closed this as completed Aug 1, 2021
jollaitbot pushed a commit to sailfishos-mirror/cairo that referenced this issue Aug 14, 2021
Fix compositing non-color glyphs in one case
4e859dd 
The intention here is: "if show_text_glyphs is unsupported,
try show_gyphs". We need to make sure to set the status to
unsupported before checking it, otherwise we end up looking
at the status that was set by composite_color_glyphs if
show_text_glyphs is NULL.

This showed up in harfbuzz/harfbuzz#2675
@khaledhosny khaledhosny mentioned this issue Feb 8, 2022
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@behdad
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behdad commented Feb 11, 2022

Related https://gitlab.freedesktop.org/cairo/cairo/-/issues/533

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@khaledhosny @simoncozens @behdad @olivierberten @matthiasclasen