font/coretext: support synthetic bold

1 files changed, 29 insertions, 3 deletions

diff --git a/src/font/Collection.zig b/src/font/Collection.zig
index 256c6b73e..01237a107 100644
--- a/src/font/Collection.zig
+++ b/src/font/Collection.zig
@@ -273,9 +273,15 @@ pub fn completeStyles(self: *Collection, alloc: Allocator) CompleteError!void {
 
     // If we don't have bold, use the regular font.
     const bold_list = self.faces.getPtr(.bold);
-    if (bold_list.count() == 0) {
-        log.warn("bold style not available, using regular font", .{});
-        try bold_list.append(alloc, .{ .alias = regular_entry });
+    if (bold_list.count() == 0) bold: {
+        const synthetic = self.syntheticBold(regular_entry) catch |err| {
+            log.warn("failed to create synthetic bold, bold style will not be available err={}", .{err});
+            try bold_list.append(alloc, .{ .alias = regular_entry });
+            break :bold;
+        };
+
+        log.info("synthetic bold face created", .{});
+        try bold_list.append(alloc, .{ .loaded = synthetic });
     }
 
     // If we don't have bold italic, use the regular italic font.
@@ -305,6 +311,26 @@ pub fn completeStyles(self: *Collection, alloc: Allocator) CompleteError!void {
 }
 
 // Create an synthetic italic font face from the given entry and return it.
+fn syntheticBold(self: *Collection, entry: *Entry) !Face {
+    // Not all font backends support synthetic bold.
+    if (comptime !@hasDecl(Face, "syntheticBold")) return error.SyntheticBoldUnavailable;
+
+    // We require loading options to create a synthetic bold face.
+    const opts = self.load_options orelse return error.DeferredLoadingUnavailable;
+
+    // Try to bold it.
+    const regular = try self.getFaceFromEntry(entry);
+    const face = try regular.syntheticBold(opts.faceOptions());
+
+    var buf: [256]u8 = undefined;
+    if (face.name(&buf)) |name| {
+        log.info("font synthetic bold created family={s}", .{name});
+    } else |_| {}
+
+    return face;
+}
+
+// Create an synthetic italic font face from the given entry and return it.
 fn syntheticItalic(self: *Collection, entry: *Entry) !Face {
     // Not all font backends support synthetic italicization.
     if (comptime !@hasDecl(Face, "syntheticItalic")) return error.SyntheticItalicUnavailable;