font/coretext: ability to set variation axes

pkg/macos/text/font.zig

@@ -39,6 +39,14 @@ pub const Font = opaque {
         c.CFRelease(self);
     }
 
+    pub fn retain(self: *Font) void {
+        _ = c.CFRetain(self);
+    }
+
+    pub fn copyDescriptor(self: *Font) *text.FontDescriptor {
+        return @ptrCast(@constCast(c.CTFontCopyFontDescriptor(@ptrCast(self))));
+    }
+
     pub fn getGlyphsForCharacters(self: *Font, chars: []const u16, glyphs: []graphics.Glyph) bool {
         assert(chars.len == glyphs.len);
         return c.CTFontGetGlyphsForCharacters(

pkg/macos/text/font_descriptor.zig

@@ -31,6 +31,21 @@ pub const FontDescriptor = opaque {
         ) orelse Allocator.Error.OutOfMemory;
     }
 
+    pub fn createCopyWithVariation(
+        original: *FontDescriptor,
+        id: *foundation.Number,
+        value: f64,
+    ) Allocator.Error!*FontDescriptor {
+        return @as(
+            ?*FontDescriptor,
+            @ptrCast(@constCast(c.CTFontDescriptorCreateCopyWithVariation(
+                @ptrCast(original),
+                @ptrCast(id),
+                value,
+            ))),
+        ) orelse Allocator.Error.OutOfMemory;
+    }
+
     pub fn release(self: *FontDescriptor) void {
         c.CFRelease(self);
     }

src/font/discovery.zig

@@ -5,6 +5,7 @@ const fontconfig = @import("fontconfig");
 const macos = @import("macos");
 const options = @import("main.zig").options;
 const DeferredFace = @import("main.zig").DeferredFace;
+const Variation = @import("main.zig").face.Variation;
 
 const log = std.log.scoped(.discovery);
 
@@ -43,6 +44,11 @@ pub const Descriptor = struct {
     bold: bool = false,
     italic: bool = false,
 
+    /// Variation axes to apply to the font. This also impacts searching
+    /// for fonts since fonts with the ability to set these variations
+    /// will be preferred, but not guaranteed.
+    variations: []const Variation = &.{},
+
     /// Convert to Fontconfig pattern to use for lookup. The pattern does
     /// not have defaults filled/substituted (Fontconfig thing) so callers
     /// must still do this.
@@ -149,7 +155,21 @@ pub const Descriptor = struct {
             );
         }
 
-        return try macos.text.FontDescriptor.createWithAttributes(@ptrCast(attrs));
+        // Build our descriptor from attrs
+        var desc = try macos.text.FontDescriptor.createWithAttributes(@ptrCast(attrs));
+        errdefer desc.release();
+
+        // Variations are built by copying the descriptor. I don't know a way
+        // to set it on attrs directly.
+        for (self.variations) |v| {
+            const id = try macos.foundation.Number.create(.int, @ptrCast(&v.id));
+            defer id.release();
+            const next = try desc.createCopyWithVariation(id, v.value);
+            desc.release();
+            desc = next;
+        }
+
+        return desc;
     }
 };
 

src/font/face.zig

@@ -1,3 +1,4 @@
+const std = @import("std");
 const builtin = @import("builtin");
 const options = @import("main.zig").options;
 const freetype = @import("face/freetype.zig");
@@ -36,6 +37,31 @@ pub const DesiredSize = struct {
     }
 };
 
+/// A font variation setting. The best documentation for this I know of
+/// is actually the CSS font-variation-settings property on MDN:
+/// https://developer.mozilla.org/en-US/docs/Web/CSS/font-variation-settings
+pub const Variation = struct {
+    id: Id,
+    value: f64,
+
+    pub const Id = packed struct(u32) {
+        d: u8,
+        c: u8,
+        b: u8,
+        a: u8,
+
+        pub fn init(v: *const [4]u8) Id {
+            return .{ .a = v[0], .b = v[1], .c = v[2], .d = v[3] };
+        }
+
+        /// Converts the ID to a string. The return value is only valid
+        /// for the lifetime of the self pointer.
+        pub fn str(self: Id) [4]u8 {
+            return .{ self.a, self.b, self.c, self.d };
+        }
+    };
+};
+
 /// Metrics associated with the font that are useful for renderers to know.
 pub const Metrics = struct {
     /// Recommended cell width and height for a monospace grid using this font.
@@ -77,3 +103,17 @@ pub const Foo = if (options.backend == .coretext) coretext.Face else void;
 test {
     @import("std").testing.refAllDecls(@This());
 }
+
+test "Variation.Id: wght should be 2003265652" {
+    const testing = std.testing;
+    const id = Variation.Id.init("wght");
+    try testing.expectEqual(@as(u32, 2003265652), @as(u32, @bitCast(id)));
+    try testing.expectEqualStrings("wght", &(id.str()));
+}
+
+test "Variation.Id: slnt should be 1936486004" {
+    const testing = std.testing;
+    const id: Variation.Id = .{ .a = 's', .b = 'l', .c = 'n', .d = 't' };
+    try testing.expectEqual(@as(u32, 1936486004), @as(u32, @bitCast(id)));
+    try testing.expectEqualStrings("slnt", &(id.str()));
+}

src/font/face/coretext.zig

@@ -64,11 +64,33 @@ pub const Face = struct {
         const ct_font = try base.copyWithAttributes(@floatFromInt(size.pixels()), null, null);
         errdefer ct_font.release();
 
+        return try initFont(ct_font);
+    }
+
+    /// Initialize a face with a CTFont. This will take ownership over
+    /// the CTFont. This does NOT copy or retain the CTFont.
+    pub fn initFont(ct_font: *macos.text.Font) !Face {
         var hb_font = try harfbuzz.coretext.createFont(ct_font);
         errdefer hb_font.destroy();
 
         const traits = ct_font.getSymbolicTraits();
 
+        // Get variation axes
+        // if (ct_font.copyAttribute(.variation_axes)) |axes| {
+        //     defer axes.release();
+        //     const len = axes.getCount();
+        //     for (0..len) |i| {
+        //         const dict = axes.getValueAtIndex(macos.foundation.Dictionary, i);
+        //         const Key = macos.text.FontVariationAxisKey;
+        //         const name_ = dict.getValue(Key.name.Value(), Key.name.key());
+        //         if (name_) |name_val| {
+        //             var buf: [1024]u8 = undefined;
+        //             const namestr = name_val.cstring(&buf, .utf8) orelse "";
+        //             log.warn("AXES: {s}", .{namestr});
+        //         }
+        //     }
+        // }
+
         var result: Face = .{
             .font = ct_font,
             .hb_font = hb_font,
@@ -89,8 +111,8 @@ pub const Face = struct {
     /// matrix applied to italicize it.
     pub fn italicize(self: *const Face) !Face {
         const ct_font = try self.font.copyWithAttributes(0.0, &italic_skew, null);
-        defer ct_font.release();
-        return try initFontCopy(ct_font, .{ .points = 0 });
+        errdefer ct_font.release();
+        return try initFont(ct_font);
     }
 
     /// Returns the font name. If allocation is required, buf will be used,
@@ -115,6 +137,31 @@ pub const Face = struct {
         self.* = face;
     }
 
+    /// Set the variation axes for this font. This will modify this font
+    /// in-place.
+    pub fn setVariations(
+        self: *Face,
+        vs: []const font.face.Variation,
+    ) !void {
+        // Create a new font descriptor with all the variations set.
+        var desc = self.font.copyDescriptor();
+        defer desc.release();
+        for (vs) |v| {
+            const id = try macos.foundation.Number.create(.int, @ptrCast(&v.id));
+            defer id.release();
+            const next = try desc.createCopyWithVariation(id, v.value);
+            desc.release();
+            desc = next;
+        }
+
+        // Initialize a font based on these attributes.
+        const ct_font = try self.font.copyWithAttributes(0, null, desc);
+        errdefer ct_font.release();
+        const face = try initFont(ct_font);
+        self.deinit();
+        self.* = face;
+    }
+
     /// 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 {
@@ -492,3 +539,55 @@ test "in-memory" {
         _ = try face.renderGlyph(alloc, &atlas, face.glyphIndex(i).?, .{});
     }
 }
+
+test "variable" {
+    const testing = std.testing;
+    const alloc = testing.allocator;
+    const testFont = @import("../test.zig").fontVariable;
+
+    var atlas = try font.Atlas.init(alloc, 512, .greyscale);
+    defer atlas.deinit(alloc);
+
+    var lib = try font.Library.init();
+    defer lib.deinit();
+
+    var face = try Face.init(lib, testFont, .{ .points = 12 });
+    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, face.glyphIndex(i).?, .{});
+    }
+}
+
+test "variable set variation" {
+    const testing = std.testing;
+    const alloc = testing.allocator;
+    const testFont = @import("../test.zig").fontVariable;
+
+    var atlas = try font.Atlas.init(alloc, 512, .greyscale);
+    defer atlas.deinit(alloc);
+
+    var lib = try font.Library.init();
+    defer lib.deinit();
+
+    var face = try Face.init(lib, testFont, .{ .points = 12 });
+    defer face.deinit();
+
+    try testing.expectEqual(font.Presentation.text, face.presentation);
+
+    try face.setVariations(&.{
+        .{ .id = font.face.Variation.Id.init("wght"), .value = 400 },
+    });
+
+    // 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, face.glyphIndex(i).?, .{});
+    }
+}

src/font/test.zig

@@ -2,3 +2,4 @@ pub const fontRegular = @embedFile("res/Inconsolata-Regular.ttf");
 pub const fontBold = @embedFile("res/Inconsolata-Bold.ttf");
 pub const fontEmoji = @embedFile("res/NotoColorEmoji.ttf");
 pub const fontEmojiText = @embedFile("res/NotoEmoji-Regular.ttf");
+pub const fontVariable = @embedFile("res/Lilex-VF.ttf");