tiny.ui.text.segment

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

1const std = @import("std");2const unicode = @import("unicode");34pub const Boundary = struct {5    byte_offset: u32,6    action: unicode.LineBreakAction,7};89const Case = struct {10    text: []const u8,11    actions: []const unicode.LineBreakAction,12};1314pub fn boundaries(15    text: []const u8,16    output: []Boundary,17) error{ OutputTooSmall, TextTooLong }![]Boundary {18    if (text.len > std.math.maxInt(u32)) return error.TextTooLong;19    std.debug.assert(std.unicode.utf8ValidateSlice(text));20    var graphemes = unicode.GraphemeIterator.init(text);21    var line: unicode.LineBreakState = .{};22    var count: usize = 0;23    while (graphemes.next()) |cluster| {24        std.debug.assert(cluster.valid_utf8);25        var cursor: usize = 0;26        var action: unicode.LineBreakAction = .prohibited;27        while (cursor < cluster.text.len) {28            const len = std.unicode.utf8ByteSequenceLength(cluster.text[cursor]) catch unreachable;29            const codepoint = std.unicode.utf8Decode(cluster.text[cursor..][0..len]) catch unreachable;30            const next = line.consume(codepoint);31            if (cursor == 0) action = next;32            cursor += len;33        }34        if (count >= output.len) return error.OutputTooSmall;35        output[count] = .{ .byte_offset = @intCast(cluster.start), .action = action };36        count += 1;37    }38    if (count >= output.len) return error.OutputTooSmall;39    output[count] = .{ .byte_offset = @intCast(text.len), .action = line.finish() };40    return output[0 .. count + 1];41}4243test "line boundaries follow selected Unicode 17 conformance cases" {44    const cases = [_]Case{45        .{ .text = "❗ ❗", .actions = &.{ .prohibited, .prohibited, .opportunity, .mandatory } },46        .{ .text = "❗\u{0308}❗", .actions = &.{ .prohibited, .prohibited, .mandatory } },47        .{48            .text = "❗\u{200b}❗",49            .actions = &.{ .prohibited, .prohibited, .opportunity, .mandatory },50        },51        .{ .text = "🇦🇦🇦🇦", .actions = &.{ .prohibited, .opportunity, .mandatory } },52        .{ .text = "a b", .actions = &.{ .prohibited, .prohibited, .opportunity, .mandatory } },53    };54    for (cases) |case| {55        var output: [16]Boundary = undefined;56        const found = try boundaries(case.text, &output);57        try std.testing.expectEqual(case.actions.len, found.len);58        for (found, case.actions) |actual, expected| {59            try std.testing.expectEqual(expected, actual.action);60        }61    }62}6364test "line boundaries never split a combining grapheme" {65    var output: [4]Boundary = undefined;66    const found = try boundaries("a\u{0308}b", &output);67    try std.testing.expectEqual(@as(usize, 3), found.len);68    try std.testing.expectEqual(@as(u32, 0), found[0].byte_offset);69    try std.testing.expectEqual(@as(u32, 3), found[1].byte_offset);70    try std.testing.expectEqual(@as(u32, 4), found[2].byte_offset);71}7273test "empty text has one mandatory end boundary" {74    var output: [1]Boundary = undefined;75    const found = try boundaries("", &output);76    try std.testing.expectEqual(@as(usize, 1), found.len);77    try std.testing.expectEqual(@as(u32, 0), found[0].byte_offset);78    try std.testing.expectEqual(unicode.LineBreakAction.mandatory, found[0].action);79}