LibWeb: Implement performance.now()

This patch introduces the HighResolutionTime namespace which is home to
the Performance object (exposed via window.performance)

performance.now() is currently the only function, and it returns the
number of milliseconds since the window object was constructed. :^)

1 files changed, 57 insertions, 0 deletions

diff --git a/Libraries/LibWeb/HighResolutionTime/Performance.h b/Libraries/LibWeb/HighResolutionTime/Performance.h
new file mode 100644
index 0000000000..588652400d
--- /dev/null
+++ b/Libraries/LibWeb/HighResolutionTime/Performance.h
@@ -0,0 +1,57 @@
+/*
+ * Copyright (c) 2020, Andreas Kling <kling@serenityos.org>
+ * All rights reserved.
+ *
+ * Redistribution and use in source and binary forms, with or without
+ * modification, are permitted provided that the following conditions are met:
+ *
+ * 1. Redistributions of source code must retain the above copyright notice, this
+ *    list of conditions and the following disclaimer.
+ *
+ * 2. Redistributions in binary form must reproduce the above copyright notice,
+ *    this list of conditions and the following disclaimer in the documentation
+ *    and/or other materials provided with the distribution.
+ *
+ * THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS "AS IS"
+ * AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
+ * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE
+ * DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT HOLDER OR CONTRIBUTORS BE LIABLE
+ * FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
+ * DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR
+ * SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER
+ * CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY,
+ * OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE
+ * OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
+ */
+
+#pragma once
+
+#include <LibCore/ElapsedTimer.h>
+#include <LibWeb/Bindings/Wrappable.h>
+#include <LibWeb/DOM/EventTarget.h>
+
+namespace Web::HighResolutionTime {
+
+class Performance final
+    : public DOM::EventTarget
+    , public Bindings::Wrappable {
+public:
+    using WrapperType = Bindings::PerformanceWrapper;
+
+    explicit Performance(DOM::Window&);
+    ~Performance();
+
+    double now() const { return m_timer.elapsed(); }
+
+    virtual void ref_event_target() override;
+    virtual void unref_event_target() override;
+
+    virtual void dispatch_event(NonnullRefPtr<DOM::Event>) override;
+    virtual Bindings::EventTargetWrapper* create_wrapper(JS::GlobalObject&) override;
+
+private:
+    DOM::Window& m_window;
+    Core::ElapsedTimer m_timer;
+};
+
+}