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LibGfx/OpenType: Error on fonts without a supported subtable

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This would've saved me some debugging on #23103.

We now return an error instead of a font that draws squares for all
characters. That seems preferable since it makes these cases easy to
find. This fires for three files in my 1000-file PDF test set, so it's
not exceedingly common (...but I wasn't aware that three files were
rendering boxes for this reason, and now I am and can just make them
work in the future).
This commit is contained in:
Nico Weber 2024-02-07 20:22:50 -05:00 • committed by Sam Atkins
parent b177e0dd66
commit be8b5b794f
1 changed files with 9 additions and 5 deletions
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14
Userland/Libraries/LibGfx/Font/OpenType/Font.cpp
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@ -223,6 +223,7 @@ ErrorOr<NonnullRefPtr<Font>> Font::try_load_from_offset(ReadonlyBytes buffer, u3
// Select cmap table. FIXME: Do this better. Right now, just looks for platform "Windows"
// and corresponding encoding "Unicode full repertoire", or failing that, "Unicode BMP"
Optional<u32> active_cmap_index;
for (u32 i = 0; i < cmap.num_subtables(); i++) {
auto opt_subtable = cmap.subtable(i);
if (!opt_subtable.has_value()) {
@ -239,28 +240,31 @@ ErrorOr<NonnullRefPtr<Font>> Font::try_load_from_offset(ReadonlyBytes buffer, u3
if (platform.value() == Cmap::Subtable::Platform::Unicode) {
if (subtable.encoding_id() == (u16)Cmap::Subtable::UnicodeEncoding::Unicode2_0_FullRepertoire) {
// "Encoding ID 3 should be used in conjunction with 'cmap' subtable formats 4 or 6."
cmap.set_active_index(i);
active_cmap_index = i;
break;
}
if (subtable.encoding_id() == (u16)Cmap::Subtable::UnicodeEncoding::Unicode2_0_BMP_Only) {
// "Encoding ID 4 should be used in conjunction with subtable formats 10 or 12."
cmap.set_active_index(i);
active_cmap_index = i;
break;
}
} else if (platform.value() == Cmap::Subtable::Platform::Windows) {
if (subtable.encoding_id() == (u16)Cmap::Subtable::WindowsEncoding::UnicodeFullRepertoire) {
cmap.set_active_index(i);
active_cmap_index = i;
break;
}
if (subtable.encoding_id() == (u16)Cmap::Subtable::WindowsEncoding::UnicodeBMP) {
cmap.set_active_index(i);
active_cmap_index = i;
break;
}
} else if (platform.value() == Cmap::Subtable::Platform::Macintosh) {
cmap.set_active_index(i);
active_cmap_index = i;
// Intentionally no `break` so that Windows (value 3) wins over Macintosh (value 1).
}
}
if (!active_cmap_index.has_value())
return Error::from_string_literal("No suitable cmap subtable found");
cmap.set_active_index(active_cmap_index.value());
return adopt_ref(*new Font(
move(head),