From 1a7cde9e3e61826cc863848d697079b8927aada0 Mon Sep 17 00:00:00 2001
From: Mitchell Hashimoto <mitchell.hashimoto@gmail.com>
Date: Mon, 27 May 2024 20:23:10 -0700
Subject: [PATCH] font/coretext: can read font tables

---
 pkg/macos/foundation/base.zig | 17 +++++++++++++++++
 pkg/macos/foundation/data.zig |  6 +++++-
 pkg/macos/text/font.zig       | 18 ++++++++++++++++++
 src/font/face/coretext.zig    | 32 ++++++++++++++++++++++++++++++++
 4 files changed, 72 insertions(+), 1 deletion(-)

diff --git a/pkg/macos/foundation/base.zig b/pkg/macos/foundation/base.zig
index bfd436115..24673ea2f 100644
--- a/pkg/macos/foundation/base.zig
+++ b/pkg/macos/foundation/base.zig
@@ -16,3 +16,20 @@ pub const Range = extern struct {
         return @bitCast(c.CFRangeMake(@intCast(loc), @intCast(len)));
     }
 };
+
+pub const FourCharCode = packed struct(u32) {
+    d: u8,
+    c: u8,
+    b: u8,
+    a: u8,
+
+    pub fn init(v: *const [4]u8) FourCharCode {
+        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: FourCharCode) [4]u8 {
+        return .{ self.a, self.b, self.c, self.d };
+    }
+};
diff --git a/pkg/macos/foundation/data.zig b/pkg/macos/foundation/data.zig
index 7c9b7d6cb..cbac0db54 100644
--- a/pkg/macos/foundation/data.zig
+++ b/pkg/macos/foundation/data.zig
@@ -20,9 +20,13 @@ pub const Data = opaque {
         foundation.CFRelease(self);
     }
 
-    pub fn getPointer(self: *Data) *const anyopaque {
+    pub fn getPointer(self: *Data) [*]const u8 {
         return @ptrCast(c.CFDataGetBytePtr(@ptrCast(self)));
     }
+
+    pub fn getLength(self: *Data) usize {
+        return @intCast(c.CFDataGetLength(@ptrCast(self)));
+    }
 };
 
 test {
diff --git a/pkg/macos/text/font.zig b/pkg/macos/text/font.zig
index f4db72d6c..10f8c23ca 100644
--- a/pkg/macos/text/font.zig
+++ b/pkg/macos/text/font.zig
@@ -67,6 +67,14 @@ pub const Font = opaque {
         return @ptrCast(@constCast(c.CTFontCopyDefaultCascadeListForLanguages(@ptrCast(self), null)));
     }
 
+    pub fn copyTable(self: *Font, tag: FontTableTag) ?*foundation.Data {
+        return @constCast(@ptrCast(c.CTFontCopyTable(
+            @ptrCast(self),
+            @intFromEnum(tag),
+            c.kCTFontTableOptionNoOptions,
+        )));
+    }
+
     pub fn getGlyphCount(self: *Font) usize {
         return @intCast(c.CTFontGetGlyphCount(@ptrCast(self)));
     }
@@ -195,6 +203,16 @@ pub const FontOrientation = enum(c_uint) {
     vertical = c.kCTFontOrientationVertical,
 };
 
+pub const FontTableTag = enum(u32) {
+    svg = c.kCTFontTableSVG,
+    _,
+
+    pub fn init(v: *const [4]u8) FontTableTag {
+        const raw: u32 = @bitCast(foundation.FourCharCode.init(v));
+        return @enumFromInt(raw);
+    }
+};
+
 test {
     const testing = std.testing;
 
diff --git a/src/font/face/coretext.zig b/src/font/face/coretext.zig
index 72c0a6d9e..fdc063b1c 100644
--- a/src/font/face/coretext.zig
+++ b/src/font/face/coretext.zig
@@ -570,6 +570,21 @@ pub const Face = struct {
 
         return result;
     }
+
+    /// Copy the font table data for the given tag.
+    pub fn copyTable(self: Face, alloc: Allocator, tag: *const [4]u8) !?[]u8 {
+        const data = self.font.copyTable(macos.text.FontTableTag.init(tag)) orelse
+            return null;
+        defer data.release();
+
+        const buf = try alloc.alloc(u8, data.getLength());
+        errdefer alloc.free(buf);
+
+        const ptr = data.getPointer();
+        @memcpy(buf, ptr[0..buf.len]);
+
+        return buf;
+    }
 };
 
 test {
@@ -727,3 +742,20 @@ test "mixed color/non-color font treated as text" {
 
     try testing.expect(face.presentation == .text);
 }
+
+test "svg font table" {
+    const testing = std.testing;
+    const alloc = testing.allocator;
+    const testFont = @import("../test.zig").fontJuliaMono;
+
+    var lib = try font.Library.init();
+    defer lib.deinit();
+
+    var face = try Face.init(lib, testFont, .{ .size = .{ .points = 12 } });
+    defer face.deinit();
+
+    const table = (try face.copyTable(alloc, "SVG ")).?;
+    defer alloc.free(table);
+
+    try testing.expect(table.len > 0);
+}