1 files changed, 92 insertions, 0 deletions
diff --git a/Userland/Libraries/LibGUI/DisplayLink.cpp b/Userland/Libraries/LibGUI/DisplayLink.cpp
new file mode 100644
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--- /dev/null
+++ b/Userland/Libraries/LibGUI/DisplayLink.cpp
@@ -0,0 +1,92 @@
+/*
+ * 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.
+ */
+
+#include <AK/Badge.h>
+#include <AK/Function.h>
+#include <AK/HashMap.h>
+#include <LibGUI/DisplayLink.h>
+#include <LibGUI/WindowServerConnection.h>
+
+namespace GUI {
+
+class DisplayLinkCallback : public RefCounted<DisplayLinkCallback> {
+public:
+    DisplayLinkCallback(i32 link_id, Function<void(i32)> callback)
+        : m_link_id(link_id)
+        , m_callback(move(callback))
+    {
+    }
+
+    void invoke()
+    {
+        m_callback(m_link_id);
+    }
+
+private:
+    i32 m_link_id { 0 };
+    Function<void(i32)> m_callback;
+};
+
+static HashMap<i32, RefPtr<DisplayLinkCallback>>& callbacks()
+{
+    static HashMap<i32, RefPtr<DisplayLinkCallback>>* map;
+    if (!map)
+        map = new HashMap<i32, RefPtr<DisplayLinkCallback>>;
+    return *map;
+}
+
+static i32 s_next_callback_id = 1;
+
+i32 DisplayLink::register_callback(Function<void(i32)> callback)
+{
+    if (callbacks().is_empty())
+        WindowServerConnection::the().post_message(Messages::WindowServer::EnableDisplayLink());
+
+    i32 callback_id = s_next_callback_id++;
+    callbacks().set(callback_id, adopt(*new DisplayLinkCallback(callback_id, move(callback))));
+
+    return callback_id;
+}
+
+bool DisplayLink::unregister_callback(i32 callback_id)
+{
+    ASSERT(callbacks().contains(callback_id));
+    callbacks().remove(callback_id);
+
+    if (callbacks().is_empty())
+        WindowServerConnection::the().post_message(Messages::WindowServer::DisableDisplayLink());
+
+    return true;
+}
+
+void DisplayLink::notify(Badge<WindowServerConnection>)
+{
+    auto copy_of_callbacks = callbacks();
+    for (auto& it : copy_of_callbacks)
+        it.value->invoke();
+}
+
+}