First implementation of Event system

Signed-off-by: Francis Bouvier <francis@lightpanda.io>

src/dom/event_target.zig

@@ -1,3 +1,10 @@
+const std = @import("std");
+
+const jsruntime = @import("jsruntime");
+const Callback = jsruntime.Callback;
+const Case = jsruntime.test_utils.Case;
+const checkCases = jsruntime.test_utils.checkCases;
+
 const parser = @import("../netsurf.zig");
 
 const DOMException = @import("exceptions.zig").DOMException;
@@ -6,4 +13,55 @@ pub const EventTarget = struct {
     pub const Self = parser.EventTarget;
     pub const Exception = DOMException;
     pub const mem_guarantied = true;
+
+    // JS funcs
+    // --------
+
+    const js_handler = struct {
+        fn handle(event: ?*parser.Event, data: ?*anyopaque) callconv(.C) void {
+            const ptr: *align(@alignOf(*Callback)) anyopaque = @alignCast(data.?);
+            const func = @as(*Callback, @ptrCast(ptr));
+            func.call(.{event}) catch unreachable;
+            // NOTE: we can not call func.deinit here
+            // b/c the handler can be called several times
+            // as the event goes through the ancestors
+            // TODO: check the event phase to call func.deinit and free func
+        }
+    }.handle;
+
+    pub fn _addEventListener(
+        self: *parser.EventTarget,
+        alloc: std.mem.Allocator,
+        eventType: []const u8,
+        cbk: Callback,
+    ) !void {
+        // TODO: when can we free this allocation?
+        const cbk_ptr = try alloc.create(Callback);
+        cbk_ptr.* = cbk;
+        const func = @as(*anyopaque, @ptrCast(cbk_ptr));
+        try parser.eventTargetAddEventListener(self, eventType, func, js_handler);
+    }
+
+    pub fn _dispatchEvent(self: *parser.EventTarget, event: *parser.Event) !bool {
+        return try parser.eventTargetDispatchEvent(self, event);
+    }
+
+    pub fn deinit(_: *parser.EventTarget, _: std.mem.Allocator) void {}
 };
+
+// Tests
+// -----
+
+pub fn testExecFn(
+    _: std.mem.Allocator,
+    js_env: *jsruntime.Env,
+) anyerror!void {
+    var basic = [_]Case{
+        .{ .src = "let event = new Event('myEvent')", .ex = "undefined" },
+        .{ .src = "let content = document.getElementById('content')", .ex = "undefined" },
+        .{ .src = "var nb = 0; content.addEventListener('myEvent', function(event) {nb ++;})", .ex = "undefined" },
+        .{ .src = "content.dispatchEvent(event)", .ex = "true" },
+        .{ .src = "nb", .ex = "2" }, // 2 because the callback is called twice
+    };
+    try checkCases(js_env, &basic);
+}