LibCore: Add Core::Timer::create_single_shot()

This is just a convenience function for creating single-shot timers.

Libraries/LibCore/Timer.h

@@ -32,8 +32,16 @@
 namespace Core {
 
 class Timer final : public Object {
-    C_OBJECT(Timer)
+    C_OBJECT(Timer);
+
 public:
+    static NonnullRefPtr<Timer> create_single_shot(int interval, Function<void()>&& timeout_handler, Object* parent = nullptr)
+    {
+        auto timer = adopt(*new Timer(interval, move(timeout_handler), parent));
+        timer->set_single_shot(true);
+        return timer;
+    }
+
     virtual ~Timer() override;
 
     void start();

Libraries/LibWeb/DOM/Document.cpp

@@ -62,12 +62,9 @@ Document::Document()
     , m_style_resolver(make<StyleResolver>(*this))
     , m_window(Window::create_with_document(*this))
 {
-    m_style_update_timer = Core::Timer::construct();
-    m_style_update_timer->set_single_shot(true);
-    m_style_update_timer->set_interval(0);
-    m_style_update_timer->on_timeout = [this] {
+    m_style_update_timer = Core::Timer::create_single_shot(0, [this] {
         update_style();
-    };
+    });
 }
 
 Document::~Document()

Servers/DHCPClient/DHCPv4Client.cpp

@@ -165,14 +165,14 @@ void DHCPv4Client::handle_ack(const DHCPv4Packet& packet, const ParsedDHCPv4Opti
     auto new_ip = packet.yiaddr();
     auto lease_time = convert_between_host_and_network(options.get<u32>(DHCPOption::IPAddressLeaseTime).value_or(transaction->offered_lease_time));
     // set a timer for the duration of the lease, we shall renew if needed
-    Core::Timer::construct(
-        lease_time * 1000, [this, transaction, interface = InterfaceDescriptor { interface }, new_ip] {
+    Core::Timer::create_single_shot(
+        lease_time * 1000,
+        [this, transaction, interface = InterfaceDescriptor { interface }, new_ip] {
             transaction->accepted_offer = false;
             transaction->has_ip = false;
             dhcp_discover(interface, new_ip);
         },
-        this)
-        ->set_single_shot(true);
+        this);
     set_params(transaction->interface, new_ip, options.get<IPv4Address>(DHCPOption::SubnetMask).value(), options.get_many<IPv4Address>(DHCPOption::Router, 1).first());
 }
 
@@ -189,12 +189,12 @@ void DHCPv4Client::handle_nak(const DHCPv4Packet& packet, const ParsedDHCPv4Opti
     transaction->accepted_offer = false;
     transaction->has_ip = false;
     auto& iface = transaction->interface;
-    Core::Timer::construct(
-        10000, [this, iface = InterfaceDescriptor { iface }] {
+    Core::Timer::create_single_shot(
+        10000,
+        [this, iface = InterfaceDescriptor { iface }] {
             dhcp_discover(iface);
         },
-        this)
-        ->set_single_shot(true);
+        this);
 }
 
 void DHCPv4Client::process_incoming(const DHCPv4Packet& packet)

Servers/WindowServer/Compositor.cpp

@@ -62,30 +62,23 @@ WallpaperMode mode_to_enum(const String& name)
 
 Compositor::Compositor()
 {
-    m_compose_timer = add<Core::Timer>();
-    m_immediate_compose_timer = add<Core::Timer>();
+    m_compose_timer = Core::Timer::create_single_shot(
+        1000 / 60,
+        [this] {
+            notify_display_links();
+            compose();
+        },
+        this);
+
+    m_immediate_compose_timer = Core::Timer::create_single_shot(
+        0,
+        [this] {
+            compose();
+        },
+        this);
 
     m_screen_can_set_buffer = Screen::the().can_set_buffer();
-
     init_bitmaps();
-
-    m_compose_timer->on_timeout = [&]() {
-        notify_display_links();
-#if defined(COMPOSITOR_DEBUG)
-        dbgprintf("Compositor: delayed frame callback: %d rects\n", m_dirty_rects.size());
-#endif
-        compose();
-    };
-    m_compose_timer->set_single_shot(true);
-    m_compose_timer->set_interval(1000 / 60);
-    m_immediate_compose_timer->on_timeout = [this]() {
-#if defined(COMPOSITOR_DEBUG)
-        dbgprintf("Compositor: immediate frame callback: %d rects\n", m_dirty_rects.size());
-#endif
-        compose();
-    };
-    m_immediate_compose_timer->set_single_shot(true);
-    m_immediate_compose_timer->set_interval(0);
 }
 
 void Compositor::init_bitmaps()