LibGUI: Add GVariant class and use it for table model data.

LibGUI/GVariant.cpp

@@ -0,0 +1,69 @@
+#include <LibGUI/GVariant.h>
+
+GVariant::~GVariant()
+{
+    switch (m_type) {
+    case Type::String:
+        if (m_value.as_string)
+            m_value.as_string->release();
+        break;
+    case Type::Bitmap:
+        if (m_value.as_bitmap)
+            m_value.as_bitmap->release();
+        break;
+    default:
+        break;
+    }
+}
+
+GVariant::GVariant(int value)
+    : m_type(Type::Int)
+{
+    m_value.as_int = value;
+}
+
+GVariant::GVariant(float value)
+    : m_type(Type::Float)
+{
+    m_value.as_float = value;
+}
+
+GVariant::GVariant(bool value)
+    : m_type(Type::Bool)
+{
+    m_value.as_bool = value;
+}
+
+GVariant::GVariant(const String& value)
+    : m_type(Type::String)
+{
+    m_value.as_string = const_cast<StringImpl*>(value.impl());
+    AK::retain_if_not_null(m_value.as_string);
+}
+
+GVariant::GVariant(const GraphicsBitmap& value)
+    : m_type(Type::Bitmap)
+{
+    m_value.as_bitmap = const_cast<GraphicsBitmap*>(&value);
+    AK::retain_if_not_null(m_value.as_bitmap);
+}
+
+String GVariant::to_string() const
+{
+    switch (m_type) {
+    case Type::Bool:
+        return as_bool() ? "True" : "False";
+    case Type::Int:
+        return String::format("%d", as_int());
+    case Type::Float:
+        return String::format("%f", as_float());
+    case Type::String:
+        return as_string();
+    case Type::Bitmap:
+        return "[GraphicsBitmap]";
+    case Type::Invalid:
+        break;
+    }
+    ASSERT_NOT_REACHED();
+}
+