tiny.filigree.font.metrics

1const std = @import("std");2const binary = @import("binary.zig");3const directory = @import("directory.zig");4const model = @import("model.zig");56const FontError = model.FontError;7const Table = binary.Table;8const readI16 = binary.readI16;9const readU16 = binary.readU16;1011pub const VerticalMetrics = struct {12    table: ?Table,13    count: u16,14};1516pub const Vorg = struct {17    table: Table,18    default_y: i16,19    record_count: u16,2021    pub fn init(data: []const u8, vorg_table: Table) FontError!Vorg {22        if (vorg_table.len < 8) return error.InvalidFont;23        const major = try readU16(data, vorg_table.offset);24        const minor = try readU16(data, vorg_table.offset + 2);25        if (major != 1 or minor != 0) return error.InvalidFont;26        const record_count = try readU16(data, vorg_table.offset + 6);27        if (@as(u64, record_count) * 4 > @as(u64, vorg_table.len - 8)) return error.InvalidFont;28        const result = Vorg{29            .table = vorg_table,30            .default_y = try readI16(data, vorg_table.offset + 4),31            .record_count = record_count,32        };33        var previous: ?u16 = null;34        for (0..record_count) |record_index| {35            const glyph_id = try readU16(data, result.recordOffset(record_index));36            if (previous) |previous_glyph| {37                if (glyph_id <= previous_glyph) return error.InvalidFont;38            }39            previous = glyph_id;40        }41        return result;42    }4344    pub fn originY(self: Vorg, data: []const u8, glyph_id: u32) FontError!i16 {45        if (glyph_id > std.math.maxInt(u16)) return self.default_y;46        const wanted: u16 = @intCast(glyph_id);47        var left: usize = 0;48        var right: usize = self.record_count;49        while (left < right) {50            const mid = left + (right - left) / 2;51            const offset = self.recordOffset(mid);52            const current = try readU16(data, offset);53            if (wanted < current) {54                right = mid;55            } else if (wanted > current) {56                left = mid + 1;57            } else {58                return try readI16(data, offset + 2);59            }60        }61        return self.default_y;62    }6364    fn recordOffset(self: Vorg, record_index: usize) usize {65        return self.table.offset + 8 + record_index * 4;66    }67};6869pub const HorizontalMetrics = struct {70    ascender: i16,71    descender: i16,72    line_gap: i16,73};7475pub fn verticalMetrics(data: []const u8, directory_offset: usize, num_glyphs: u16) VerticalMetrics {76    const vhea = directory.optionalAt(data, directory_offset, "vhea") orelse return .{ .table = null, .count = 0 };77    const vmtx = directory.optionalAt(data, directory_offset, "vmtx") orelse return .{ .table = null, .count = 0 };78    if (vhea.len < 36) return .{ .table = null, .count = 0 };79    const count = readU16(data, vhea.offset + 34) catch return .{ .table = null, .count = 0 };80    if (count == 0 or count > num_glyphs) return .{ .table = null, .count = 0 };81    if (@as(usize, count) > vmtx.len / 4) return .{ .table = null, .count = 0 };82    return .{ .table = vmtx, .count = count };83}8485pub fn horizontalTypoMetrics(data: []const u8, directory_offset: usize) ?HorizontalMetrics {86    const os2 = directory.optionalAt(data, directory_offset, "OS/2") orelse return null;87    if (os2.len < 74) return null;88    return .{89        .ascender = readI16(data, os2.offset + 68) catch return null,90        .descender = readI16(data, os2.offset + 70) catch return null,91        .line_gap = readI16(data, os2.offset + 72) catch return null,92    };93}

1pub const metrics = @import("metrics.zig");