ghostty/src/font/face/coretext.zig

const std = @import("std");
const assert = std.debug.assert;
const macos = @import("macos");
const harfbuzz = @import("harfbuzz");
const font = @import("../main.zig");

pub const Face = struct {
    /// Our font face
    font: *macos.text.Font,

    /// Harfbuzz font corresponding to this face.
    hb_font: harfbuzz.Font,

    /// The presentation for this font.
    presentation: font.Presentation,

    /// Initialize a CoreText-based face from another initialized font face
    /// but with a new size. This is often how CoreText fonts are initialized
    /// because the font is loaded at a default size during discovery, and then
    /// adjusted to the final size for final load.
    pub fn initFontCopy(base: *macos.text.Font, size: font.face.DesiredSize) !Face {
        // Create a copy
        const ct_font = try base.copyWithAttributes(@intToFloat(f32, size.points), null);
        errdefer ct_font.release();

        const hb_font = try harfbuzz.coretext.createFont(ct_font);
        errdefer hb_font.destroy();

        const traits = ct_font.getSymbolicTraits();

        return Face{
            .font = ct_font,
            .hb_font = hb_font,
            .presentation = if (traits.color_glyphs) .emoji else .text,
        };
    }

    pub fn deinit(self: *Face) void {
        self.font.release();
        self.hb_font.destroy();
        self.* = undefined;
    }

    /// Returns the glyph index for the given Unicode code point. If this
    /// face doesn't support this glyph, null is returned.
    pub fn glyphIndex(self: Face, cp: u32) ?u32 {
        // Turn UTF-32 into UTF-16 for CT API
        var unichars: [2]u16 = undefined;
        const pair = macos.foundation.stringGetSurrogatePairForLongCharacter(cp, &unichars);
        const len: usize = if (pair) 2 else 1;

        // Get our glyphs
        var glyphs = [2]macos.graphics.Glyph{ 0, 0 };
        if (!self.font.getGlyphsForCharacters(unichars[0..len], glyphs[0..len]))
            return null;

        // We can have pairs due to chars like emoji but we expect all of them
        // to decode down into exactly one glyph ID.
        if (pair) assert(glyphs[1] == 0);

        return @intCast(u32, glyphs[0]);
    }
};

test {
    const testing = std.testing;

    const name = try macos.foundation.String.createWithBytes("Monaco", .utf8, false);
    defer name.release();
    const desc = try macos.text.FontDescriptor.createWithNameAndSize(name, 12);
    defer desc.release();
    const ct_font = try macos.text.Font.createWithFontDescriptor(desc, 12);
    defer ct_font.release();

    var face = try Face.initFontCopy(ct_font, .{ .points = 18 });
    defer face.deinit();

    try testing.expectEqual(font.Presentation.text, face.presentation);

    // Generate all visible ASCII
    var i: u8 = 32;
    while (i < 127) : (i += 1) {
        try testing.expect(face.glyphIndex(i) != null);
        //_ = try face.renderGlyph(alloc, &atlas, ft_font.glyphIndex(i).?);
    }
}

test "emoji" {
    const testing = std.testing;

    const name = try macos.foundation.String.createWithBytes("Apple Color Emoji", .utf8, false);
    defer name.release();
    const desc = try macos.text.FontDescriptor.createWithNameAndSize(name, 12);
    defer desc.release();
    const ct_font = try macos.text.Font.createWithFontDescriptor(desc, 12);
    defer ct_font.release();

    var face = try Face.initFontCopy(ct_font, .{ .points = 18 });
    defer face.deinit();

    // Presentation
    try testing.expectEqual(font.Presentation.emoji, face.presentation);

    // Glyph index check
    try testing.expect(face.glyphIndex('🥸') != null);
}