From bf07659dd57ccd45b3a027da42caacf6f1a8a0b1 Mon Sep 17 00:00:00 2001
From: Pierre Tachoire <pierre@lightpanda.io>
Date: Wed, 11 Mar 2026 22:16:35 +0100
Subject: [PATCH] FontFaceSet is now an EventTarget

Dispatch loading and loaddone events on load() call
---
 src/browser/tests/css/font_face_set.html | 22 ++++++++++++++++
 src/browser/webapi/EventTarget.zig       |  3 +++
 src/browser/webapi/css/FontFaceSet.zig   | 32 ++++++++++++++++++++----
 3 files changed, 52 insertions(+), 5 deletions(-)

diff --git a/src/browser/tests/css/font_face_set.html b/src/browser/tests/css/font_face_set.html
index a860669e..c0248a74 100644
--- a/src/browser/tests/css/font_face_set.html
+++ b/src/browser/tests/css/font_face_set.html
@@ -56,3 +56,25 @@
     testing.expectEqual('FontFaceSet', document.fonts.constructor.name);
 }
 </script>
+
+<script id="document_fonts_addEventListener">
+{
+    let loading = false;
+    document.fonts.addEventListener('loading', function() {
+        loading = true;
+    });
+
+    let loadingdone = false;
+    document.fonts.addEventListener('loadingdone', function() {
+        loadingdone = true;
+    });
+
+    document.fonts.load("italic bold 16px Roboto");
+
+    testing.eventually(() => {
+      testing.expectEqual(true, loading);
+      testing.expectEqual(true, loadingdone);
+    });
+    testing.expectEqual(true, true);
+}
+</script>
diff --git a/src/browser/webapi/EventTarget.zig b/src/browser/webapi/EventTarget.zig
index 715c209a..cfdf0872 100644
--- a/src/browser/webapi/EventTarget.zig
+++ b/src/browser/webapi/EventTarget.zig
@@ -44,6 +44,7 @@ pub const Type = union(enum) {
     screen_orientation: *@import("Screen.zig").Orientation,
     visual_viewport: *@import("VisualViewport.zig"),
     file_reader: *@import("FileReader.zig"),
+    font_face_set: *@import("css/FontFaceSet.zig"),
 };
 
 pub fn init(page: *Page) !*EventTarget {
@@ -139,6 +140,7 @@ pub fn format(self: *EventTarget, writer: *std.Io.Writer) !void {
         .screen_orientation => writer.writeAll("<ScreenOrientation>"),
         .visual_viewport => writer.writeAll("<VisualViewport>"),
         .file_reader => writer.writeAll("<FileReader>"),
+        .font_face_set => writer.writeAll("<FontFaceSet>"),
     };
 }
 
@@ -157,6 +159,7 @@ pub fn toString(self: *EventTarget) []const u8 {
         .screen_orientation => return "[object ScreenOrientation]",
         .visual_viewport => return "[object VisualViewport]",
         .file_reader => return "[object FileReader]",
+        .font_face_set => return "[object FontFaceSet]",
     };
 }
 
diff --git a/src/browser/webapi/css/FontFaceSet.zig b/src/browser/webapi/css/FontFaceSet.zig
index 2a4a000d..36c89570 100644
--- a/src/browser/webapi/css/FontFaceSet.zig
+++ b/src/browser/webapi/css/FontFaceSet.zig
@@ -21,28 +21,34 @@ const js = @import("../../js/js.zig");
 const Page = @import("../../Page.zig");
 const Session = @import("../../Session.zig");
 const FontFace = @import("FontFace.zig");
+const EventTarget = @import("../EventTarget.zig");
+const Event = @import("../Event.zig");
 
 const Allocator = std.mem.Allocator;
 
 const FontFaceSet = @This();
 
+_proto: *EventTarget,
 _arena: Allocator,
 
 pub fn init(page: *Page) !*FontFaceSet {
     const arena = try page.getArena(.{ .debug = "FontFaceSet" });
     errdefer page.releaseArena(arena);
 
-    const self = try arena.create(FontFaceSet);
-    self.* = .{
+    return page._factory.eventTargetWithAllocator(arena, FontFaceSet{
+        ._proto = undefined,
         ._arena = arena,
-    };
-    return self;
+    });
 }
 
 pub fn deinit(self: *FontFaceSet, _: bool, session: *Session) void {
     session.releaseArena(self._arena);
 }
 
+pub fn asEventTarget(self: *FontFaceSet) *EventTarget {
+    return self._proto;
+}
+
 // FontFaceSet.ready - returns an already-resolved Promise.
 // In a headless browser there is no font loading, so fonts are always ready.
 pub fn getReady(_: *FontFaceSet, page: *Page) !js.Promise {
@@ -56,8 +62,24 @@ pub fn check(_: *const FontFaceSet, font: []const u8) bool {
 }
 
 // load(font, text?) - resolves immediately with an empty array.
-pub fn load(_: *FontFaceSet, font: []const u8, page: *Page) !js.Promise {
+pub fn load(self: *FontFaceSet, font: []const u8, page: *Page) !js.Promise {
+    // TODO parse font to check if the font has been added before dispatching
+    // events.
     _ = font;
+
+    // Dispatch loading event
+    const target = self.asEventTarget();
+    if (page._event_manager.hasDirectListeners(target, "loading", null)) {
+        const event = try Event.initTrusted(comptime .wrap("loading"), .{}, page);
+        try page._event_manager.dispatchDirect(target, event, null, .{ .context = "load font face set" });
+    }
+
+    // Dispatch loadingdone event
+    if (page._event_manager.hasDirectListeners(target, "loadingdone", null)) {
+        const event = try Event.initTrusted(comptime .wrap("loadingdone"), .{}, page);
+        try page._event_manager.dispatchDirect(target, event, null, .{ .context = "load font face set" });
+    }
+
     return page.js.local.?.resolvePromise({});
 }