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LibGfx/OpenType: Make it possible to provide an external cmap

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If this is passed in, we don't use the cmap table from the font,
but use the external lookup object instead.

This conveniently happens to create a place where we can put all the
Cmap configuration logic that was a bit spread out before.

No behavior change yet.
This commit is contained in:
Nico Weber 2024-02-16 19:50:30 -05:00 • committed by Andreas Kling
parent dd6f47e696
commit 76a439124d
2 changed files with 96 additions and 58 deletions
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140
Userland/Libraries/LibGfx/Font/OpenType/Font.cpp
View file

@ -24,6 +24,86 @@
namespace OpenType {
namespace {
class CmapCharCodeToGlyphIndex : public CharCodeToGlyphIndex {
public:
static ErrorOr<NonnullOwnPtr<CharCodeToGlyphIndex>> from_slice(Optional<ReadonlyBytes>);
virtual u32 glyph_id_for_code_point(u32 code_point) const override;
private:
explicit CmapCharCodeToGlyphIndex(Cmap cmap)
: m_cmap(cmap)
{
}
Cmap m_cmap;
};
ErrorOr<NonnullOwnPtr<CharCodeToGlyphIndex>> CmapCharCodeToGlyphIndex::from_slice(Optional<ReadonlyBytes> opt_cmap_slice)
{
if (!opt_cmap_slice.has_value())
return Error::from_string_literal("Font is missing Cmap");
auto cmap = TRY(Cmap::from_slice(opt_cmap_slice.value()));
// 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()) {
continue;
}
auto subtable = opt_subtable.value();
auto platform = subtable.platform_id();
if (!platform.has_value())
return Error::from_string_literal("Invalid Platform ID");
/* NOTE: The encoding records are sorted first by platform ID, then by encoding ID.
This means that the Windows platform will take precedence over Macintosh, which is
usually what we want here. */
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."
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."
active_cmap_index = i;
break;
}
} else if (platform.value() == Cmap::Subtable::Platform::Windows) {
if (subtable.encoding_id() == (u16)Cmap::Subtable::WindowsEncoding::UnicodeFullRepertoire) {
active_cmap_index = i;
break;
}
if (subtable.encoding_id() == (u16)Cmap::Subtable::WindowsEncoding::UnicodeBMP) {
active_cmap_index = i;
break;
}
} else if (platform.value() == Cmap::Subtable::Platform::Macintosh) {
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");
TRY(cmap.subtable(active_cmap_index.value()).value().validate_format_can_be_read());
cmap.set_active_index(active_cmap_index.value());
return adopt_nonnull_own_or_enomem(new CmapCharCodeToGlyphIndex(cmap));
}
u32 CmapCharCodeToGlyphIndex::glyph_id_for_code_point(u32 code_point) const
{
return m_cmap.glyph_id_for_code_point(code_point);
}
}
// https://learn.microsoft.com/en-us/typography/opentype/spec/otff#ttc-header
struct [[gnu::packed]] TTCHeaderV1 {
Tag ttc_tag; // Font Collection ID string: 'ttcf' (used for fonts with CFF or CFF2 outlines as well as TrueType outlines)
@ -76,7 +156,7 @@ ErrorOr<NonnullRefPtr<Font>> Font::try_load_from_resource(Core::Resource const&
return font;
}
ErrorOr<NonnullRefPtr<Font>> Font::try_load_from_externally_owned_memory(ReadonlyBytes buffer, unsigned index)
ErrorOr<NonnullRefPtr<Font>> Font::try_load_from_externally_owned_memory(ReadonlyBytes buffer, unsigned index, OwnPtr<CharCodeToGlyphIndex> external_cmap)
{
FixedMemoryStream stream { buffer };
@ -92,7 +172,7 @@ ErrorOr<NonnullRefPtr<Font>> Font::try_load_from_externally_owned_memory(Readonl
TRY(stream.seek(ttc_header_v1->table_directory_offsets + sizeof(u32) * index, SeekMode::SetPosition));
auto offset = TRY(stream.read_value<BigEndian<u32>>());
return try_load_from_offset(buffer, offset);
return try_load_from_offset(buffer, offset, move(external_cmap));
}
if (tag == Tag("OTTO"))
return Error::from_string_literal("CFF fonts not supported yet");
@ -100,11 +180,11 @@ ErrorOr<NonnullRefPtr<Font>> Font::try_load_from_externally_owned_memory(Readonl
if (tag.to_u32() != 0x00010000 && tag != Tag("true"))
return Error::from_string_literal("Not a valid font");
return try_load_from_offset(buffer, 0);
return try_load_from_offset(buffer, 0, move(external_cmap));
}
// FIXME: "loca" and "glyf" are not available for CFF fonts.
ErrorOr<NonnullRefPtr<Font>> Font::try_load_from_offset(ReadonlyBytes buffer, u32 offset)
ErrorOr<NonnullRefPtr<Font>> Font::try_load_from_offset(ReadonlyBytes buffer, u32 offset, OwnPtr<CharCodeToGlyphIndex> external_cmap)
{
FixedMemoryStream stream { buffer };
TRY(stream.seek(offset, AK::SeekMode::SetPosition));
@ -192,9 +272,7 @@ ErrorOr<NonnullRefPtr<Font>> Font::try_load_from_offset(ReadonlyBytes buffer, u3
return Error::from_string_literal("Font is missing Hmtx");
auto hmtx = TRY(Hmtx::from_slice(opt_hmtx_slice.value(), maxp.num_glyphs(), hhea.number_of_h_metrics()));
if (!opt_cmap_slice.has_value())
return Error::from_string_literal("Font is missing Cmap");
auto cmap = TRY(Cmap::from_slice(opt_cmap_slice.value()));
NonnullOwnPtr<CharCodeToGlyphIndex> cmap = external_cmap ? external_cmap.release_nonnull() : TRY(CmapCharCodeToGlyphIndex::from_slice(opt_cmap_slice.value()));
Optional<Loca> loca;
if (opt_loca_slice.has_value())
@ -221,52 +299,6 @@ ErrorOr<NonnullRefPtr<Font>> Font::try_load_from_offset(ReadonlyBytes buffer, u3
if (opt_prep_slice.has_value())
prep = Prep(opt_prep_slice.value());
// 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()) {
continue;
}
auto subtable = opt_subtable.value();
auto platform = subtable.platform_id();
if (!platform.has_value())
return Error::from_string_literal("Invalid Platform ID");
/* NOTE: The encoding records are sorted first by platform ID, then by encoding ID.
This means that the Windows platform will take precedence over Macintosh, which is
usually what we want here. */
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."
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."
active_cmap_index = i;
break;
}
} else if (platform.value() == Cmap::Subtable::Platform::Windows) {
if (subtable.encoding_id() == (u16)Cmap::Subtable::WindowsEncoding::UnicodeFullRepertoire) {
active_cmap_index = i;
break;
}
if (subtable.encoding_id() == (u16)Cmap::Subtable::WindowsEncoding::UnicodeBMP) {
active_cmap_index = i;
break;
}
} else if (platform.value() == Cmap::Subtable::Platform::Macintosh) {
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");
TRY(cmap.subtable(active_cmap_index.value()).value().validate_format_can_be_read());
cmap.set_active_index(active_cmap_index.value());
return adopt_ref(*new Font(
move(head),
move(name),
@ -644,7 +676,7 @@ void Font::populate_glyph_page(GlyphPage& glyph_page, size_t page_index) const
u32 first_code_point = page_index * GlyphPage::glyphs_per_page;
for (size_t i = 0; i < GlyphPage::glyphs_per_page; ++i) {
u32 code_point = first_code_point + i;
glyph_page.glyph_ids[i] = m_cmap.glyph_id_for_code_point(code_point);
glyph_page.glyph_ids[i] = m_cmap->glyph_id_for_code_point(code_point);
}
}
bool Font::has_color_bitmaps() const

14
Userland/Libraries/LibGfx/Font/OpenType/Font.h
View file

@ -20,12 +20,18 @@
namespace OpenType {
class CharCodeToGlyphIndex {
public:
virtual ~CharCodeToGlyphIndex() = default;
virtual u32 glyph_id_for_code_point(u32) const = 0;
};
class Font : public Gfx::VectorFont {
AK_MAKE_NONCOPYABLE(Font);
public:
static ErrorOr<NonnullRefPtr<Font>> try_load_from_resource(Core::Resource const&, unsigned index = 0);
static ErrorOr<NonnullRefPtr<Font>> try_load_from_externally_owned_memory(ReadonlyBytes bytes, unsigned index = 0);
static ErrorOr<NonnullRefPtr<Font>> try_load_from_externally_owned_memory(ReadonlyBytes bytes, unsigned index = 0, OwnPtr<CharCodeToGlyphIndex> external_cmap = {});
virtual Gfx::ScaledFontMetrics metrics(float x_scale, float y_scale) const override;
virtual Gfx::ScaledGlyphMetrics glyph_metrics(u32 glyph_id, float x_scale, float y_scale, float point_width, float point_height) const override;
@ -68,7 +74,7 @@ private:
EmbeddedBitmapData embedded_bitmap_data_for_glyph(u32 glyph_id) const;
static ErrorOr<NonnullRefPtr<Font>> try_load_from_offset(ReadonlyBytes, unsigned index = 0);
static ErrorOr<NonnullRefPtr<Font>> try_load_from_offset(ReadonlyBytes, unsigned index, OwnPtr<CharCodeToGlyphIndex> external_cmap);
Font(
Head&& head,
@ -76,7 +82,7 @@ private:
Hhea&& hhea,
Maxp&& maxp,
Hmtx&& hmtx,
Cmap&& cmap,
NonnullOwnPtr<CharCodeToGlyphIndex> cmap,
Optional<Loca>&& loca,
Optional<Glyf>&& glyf,
Optional<OS2> os2,
@ -114,7 +120,7 @@ private:
Hmtx m_hmtx;
Optional<Loca> m_loca;
Optional<Glyf> m_glyf;
Cmap m_cmap;
NonnullOwnPtr<CharCodeToGlyphIndex> m_cmap;
Optional<OS2> m_os2;
Optional<Kern> m_kern;
Optional<Fpgm> m_fpgm;