WindowServer: Load multiple scaled versions of Bitmaps and Cursors

This enables rendering of mixed-scale screen layouts with e.g. high
resolution cursors and window button icons on high-dpi screens while
using lower resolution bitmaps on regular screens.

Userland/Services/WindowServer/MultiScaleBitmaps.h

@@ -0,0 +1,32 @@
+/*
+ * Copyright (c) 2020, the SerenityOS developers.
+ *
+ * SPDX-License-Identifier: BSD-2-Clause
+ */
+
+#pragma once
+
+#include <AK/HashMap.h>
+#include <AK/RefCounted.h>
+#include <AK/RefPtr.h>
+#include <LibGfx/Bitmap.h>
+
+namespace WindowServer {
+
+class MultiScaleBitmaps : public RefCounted<MultiScaleBitmaps> {
+public:
+    static RefPtr<MultiScaleBitmaps> create(StringView const& filename, StringView const& default_filename = {});
+
+    Gfx::Bitmap const& default_bitmap() const { return bitmap(1); }
+    Gfx::Bitmap const& bitmap(int scale_factor) const;
+    Gfx::BitmapFormat format() const { return m_format; }
+
+private:
+    MultiScaleBitmaps() = default;
+    bool load(StringView const& filename, StringView const& default_filename);
+
+    HashMap<int, NonnullRefPtr<Gfx::Bitmap>> m_bitmaps;
+    Gfx::BitmapFormat m_format { Gfx::BitmapFormat::Invalid };
+};
+
+}