Libraries: Create top level directory for libraries.

Things were getting a little crowded in the project root, so this patch
moves the Lib*/ directories into Libraries/.

Libraries/LibGUI/GModel.h

@@ -0,0 +1,108 @@
+#pragma once
+
+#include <AK/AKString.h>
+#include <AK/Badge.h>
+#include <AK/Function.h>
+#include <AK/HashTable.h>
+#include <AK/RefCounted.h>
+#include <LibGUI/GModelIndex.h>
+#include <LibGUI/GVariant.h>
+#include <SharedGraphics/TextAlignment.h>
+
+class Font;
+class GAbstractView;
+
+enum class GSortOrder {
+    None,
+    Ascending,
+    Descending
+};
+
+class GModelNotification {
+public:
+    enum Type {
+        Invalid = 0,
+        ModelUpdated,
+    };
+
+    explicit GModelNotification(Type type, const GModelIndex& index = GModelIndex())
+        : m_type(type)
+        , m_index(index)
+    {
+    }
+
+    Type type() const { return m_type; }
+    GModelIndex index() const { return m_index; }
+
+private:
+    Type m_type { Invalid };
+    GModelIndex m_index;
+};
+
+class GModel : public RefCounted<GModel> {
+public:
+    struct ColumnMetadata {
+        int preferred_width { 0 };
+        TextAlignment text_alignment { TextAlignment::CenterLeft };
+        const Font* font { nullptr };
+    };
+
+    enum class Role {
+        Display,
+        Sort,
+        Custom,
+        ForegroundColor,
+        BackgroundColor,
+        Icon
+    };
+
+    virtual ~GModel();
+
+    virtual int row_count(const GModelIndex& = GModelIndex()) const = 0;
+    virtual int column_count(const GModelIndex& = GModelIndex()) const = 0;
+    virtual String row_name(int) const { return {}; }
+    virtual String column_name(int) const { return {}; }
+    virtual ColumnMetadata column_metadata(int) const { return {}; }
+    virtual GVariant data(const GModelIndex&, Role = Role::Display) const = 0;
+    virtual void update() = 0;
+    virtual GModelIndex parent_index(const GModelIndex&) const { return {}; }
+    virtual GModelIndex index(int row, int column = 0, const GModelIndex& = GModelIndex()) const { return create_index(row, column); }
+    virtual GModelIndex sibling(int row, int column, const GModelIndex& parent) const;
+    virtual bool is_editable(const GModelIndex&) const { return false; }
+    virtual void set_data(const GModelIndex&, const GVariant&) {}
+
+    bool is_valid(const GModelIndex& index) const
+    {
+        return index.row() >= 0 && index.row() < row_count() && index.column() >= 0 && index.column() < column_count();
+    }
+
+    void set_selected_index(const GModelIndex&);
+    GModelIndex selected_index() const { return m_selected_index; }
+
+    virtual int key_column() const { return -1; }
+    virtual GSortOrder sort_order() const { return GSortOrder::None; }
+    virtual void set_key_column_and_sort_order(int, GSortOrder) {}
+
+    void register_view(Badge<GAbstractView>, GAbstractView&);
+    void unregister_view(Badge<GAbstractView>, GAbstractView&);
+
+    Function<void(GModel&)> on_model_update;
+    Function<void(const GModelIndex&)> on_selection_changed;
+
+protected:
+    GModel();
+
+    void for_each_view(Function<void(GAbstractView&)>);
+    void did_update();
+
+    GModelIndex create_index(int row, int column, void* data = nullptr) const;
+
+private:
+    HashTable<GAbstractView*> m_views;
+    GModelIndex m_selected_index;
+};
+
+inline GModelIndex GModelIndex::parent() const
+{
+    return m_model ? m_model->parent_index(*this) : GModelIndex();
+}