diff --git a/src/font/face/freetype.zig b/src/font/face/freetype.zig index 7d34c70f8..409b9547f 100644 --- a/src/font/face/freetype.zig +++ b/src/font/face/freetype.zig @@ -600,7 +600,6 @@ pub const Face = struct { const CalcMetricsError = error{ CopyTableError, - MissingOS2Table, }; /// Calculate the metrics associated with a face. This is not public because @@ -629,70 +628,80 @@ pub const Face = struct { const post = face.getSfntTable(.post) orelse return error.CopyTableError; // Read the 'OS/2' table out of the font data. - const os2 = face.getSfntTable(.os2) orelse return error.CopyTableError; + const maybe_os2: ?*freetype.c.TT_OS2 = os2: { + const os2 = face.getSfntTable(.os2) orelse break :os2 null; + if (os2.version == 0xFFFF) break :os2 null; + break :os2 os2; + }; // Read the 'hhea' table out of the font data. const hhea = face.getSfntTable(.hhea) orelse return error.CopyTableError; - // Some fonts don't actually have an OS/2 table, which - // we need in order to do the metrics calculations, in - // such cases FreeType sets the version to 0xFFFF - if (os2.version == 0xFFFF) return error.MissingOS2Table; - const units_per_em = head.Units_Per_EM; const px_per_em: f64 = @floatFromInt(size_metrics.y_ppem); const px_per_unit = px_per_em / @as(f64, @floatFromInt(units_per_em)); const ascent: f64, const descent: f64, const line_gap: f64 = vertical_metrics: { - const os2_ascent: f64 = @floatFromInt(os2.sTypoAscender); - const os2_descent: f64 = @floatFromInt(os2.sTypoDescender); - const os2_line_gap: f64 = @floatFromInt(os2.sTypoLineGap); + const hhea_ascent: f64 = @floatFromInt(hhea.Ascender); + const hhea_descent: f64 = @floatFromInt(hhea.Descender); + const hhea_line_gap: f64 = @floatFromInt(hhea.Line_Gap); - // If the font says to use typo metrics, trust it. - // (The USE_TYPO_METRICS bit is bit 7) - if (os2.fsSelection & (1 << 7) != 0) { + if (maybe_os2) |os2| { + const os2_ascent: f64 = @floatFromInt(os2.sTypoAscender); + const os2_descent: f64 = @floatFromInt(os2.sTypoDescender); + const os2_line_gap: f64 = @floatFromInt(os2.sTypoLineGap); + + // If the font says to use typo metrics, trust it. + // (The USE_TYPO_METRICS bit is bit 7) + if (os2.fsSelection & (1 << 7) != 0) { + break :vertical_metrics .{ + os2_ascent * px_per_unit, + os2_descent * px_per_unit, + os2_line_gap * px_per_unit, + }; + } + + // Otherwise we prefer the height metrics from 'hhea' if they + // are available, or else OS/2 sTypo* metrics, and if all else + // fails then we use OS/2 usWin* metrics. + // + // This is not "standard" behavior, but it's our best bet to + // account for fonts being... just weird. It's pretty much what + // FreeType does to get its generic ascent and descent metrics. + + if (hhea.Ascender != 0 or hhea.Descender != 0) { + break :vertical_metrics .{ + hhea_ascent * px_per_unit, + hhea_descent * px_per_unit, + hhea_line_gap * px_per_unit, + }; + } + + if (os2_ascent != 0 or os2_descent != 0) { + break :vertical_metrics .{ + os2_ascent * px_per_unit, + os2_descent * px_per_unit, + os2_line_gap * px_per_unit, + }; + } + + const win_ascent: f64 = @floatFromInt(os2.usWinAscent); + const win_descent: f64 = @floatFromInt(os2.usWinDescent); break :vertical_metrics .{ - os2_ascent * px_per_unit, - os2_descent * px_per_unit, - os2_line_gap * px_per_unit, + win_ascent * px_per_unit, + // usWinDescent is *positive* -> down unlike sTypoDescender + // and hhea.Descender, so we flip its sign to fix this. + -win_descent * px_per_unit, + 0.0, }; } - // Otherwise we prefer the height metrics from 'hhea' if they - // are available, or else OS/2 sTypo* metrics, and if all else - // fails then we use OS/2 usWin* metrics. - // - // This is not "standard" behavior, but it's our best bet to - // account for fonts being... just weird. It's pretty much what - // FreeType does to get its generic ascent and descent metrics. - - if (hhea.Ascender != 0 or hhea.Descender != 0) { - const hhea_ascent: f64 = @floatFromInt(hhea.Ascender); - const hhea_descent: f64 = @floatFromInt(hhea.Descender); - const hhea_line_gap: f64 = @floatFromInt(hhea.Line_Gap); - break :vertical_metrics .{ - hhea_ascent * px_per_unit, - hhea_descent * px_per_unit, - hhea_line_gap * px_per_unit, - }; - } - - if (os2_ascent != 0 or os2_descent != 0) { - break :vertical_metrics .{ - os2_ascent * px_per_unit, - os2_descent * px_per_unit, - os2_line_gap * px_per_unit, - }; - } - - const win_ascent: f64 = @floatFromInt(os2.usWinAscent); - const win_descent: f64 = @floatFromInt(os2.usWinDescent); + // If our font has no OS/2 table, then we just + // blindly use the metrics from the hhea table. break :vertical_metrics .{ - win_ascent * px_per_unit, - // usWinDescent is *positive* -> down unlike sTypoDescender - // and hhea.Descender, so we flip its sign to fix this. - -win_descent * px_per_unit, - 0.0, + hhea_ascent * px_per_unit, + hhea_descent * px_per_unit, + hhea_line_gap * px_per_unit, }; }; @@ -714,17 +723,25 @@ pub const Face = struct { @as(f64, @floatFromInt(post.underlineThickness)) * px_per_unit; // Similar logic to the underline above. - const has_broken_strikethrough = os2.yStrikeoutSize == 0; + const strikethrough_position, const strikethrough_thickness = st: { + if (maybe_os2) |os2| { + const has_broken_strikethrough = os2.yStrikeoutSize == 0; - const strikethrough_position = if (has_broken_strikethrough and os2.yStrikeoutPosition == 0) - null - else - @as(f64, @floatFromInt(os2.yStrikeoutPosition)) * px_per_unit; + const pos: ?f64 = if (has_broken_strikethrough and os2.yStrikeoutPosition == 0) + null + else + @as(f64, @floatFromInt(os2.yStrikeoutPosition)) * px_per_unit; - const strikethrough_thickness = if (has_broken_strikethrough) - null - else - @as(f64, @floatFromInt(os2.yStrikeoutSize)) * px_per_unit; + const thick: ?f64 = if (has_broken_strikethrough) + null + else + @as(f64, @floatFromInt(os2.yStrikeoutSize)) * px_per_unit; + + break :st .{ pos, thick }; + } + + break :st .{ null, null }; + }; // Cell width is calculated by calculating the widest width of the // visible ASCII characters. Usually 'M' is widest but we just take @@ -754,37 +771,33 @@ pub const Face = struct { break :cell_width max; }; - // The OS/2 table does not include sCapHeight or sxHeight in version 1. - const has_os2_height_metrics = os2.version >= 2; - - // We use the cap height specified by the font if it's - // available, otherwise we try to measure the `H` glyph. - const cap_height: ?f64 = cap_height: { - if (has_os2_height_metrics) { - break :cap_height @as(f64, @floatFromInt(os2.sCapHeight)) * px_per_unit; + // We use the cap and ex heights specified by the font if they're + // available, otherwise we try to measure the `H` and `x` glyphs. + const cap_height: ?f64, const ex_height: ?f64 = heights: { + if (maybe_os2) |os2| { + break :heights .{ + @as(f64, @floatFromInt(os2.sCapHeight)) * px_per_unit, + @as(f64, @floatFromInt(os2.sxHeight)) * px_per_unit, + }; } - if (face.getCharIndex('H')) |glyph_index| { - if (face.loadGlyph(glyph_index, .{ .render = true })) { - break :cap_height f26dot6ToF64(face.handle.*.glyph.*.metrics.height); - } else |_| {} - } - - break :cap_height null; - }; - - // We use the ex height specified by the font if it's - // available, otherwise we try to measure the `x` glyph. - const ex_height: ?f64 = ex_height: { - if (has_os2_height_metrics) { - break :ex_height @as(f64, @floatFromInt(os2.sxHeight)) * px_per_unit; - } - if (face.getCharIndex('x')) |glyph_index| { - if (face.loadGlyph(glyph_index, .{ .render = true })) { - break :ex_height f26dot6ToF64(face.handle.*.glyph.*.metrics.height); - } else |_| {} - } - - break :ex_height null; + break :heights .{ + cap: { + if (face.getCharIndex('H')) |glyph_index| { + if (face.loadGlyph(glyph_index, .{ .render = true })) { + break :cap f26dot6ToF64(face.handle.*.glyph.*.metrics.height); + } else |_| {} + } + break :cap null; + }, + ex: { + if (face.getCharIndex('x')) |glyph_index| { + if (face.loadGlyph(glyph_index, .{ .render = true })) { + break :ex f26dot6ToF64(face.handle.*.glyph.*.metrics.height); + } else |_| {} + } + break :ex null; + }, + }; }; var result = font.face.Metrics.calc(.{