PixelPaint: Create Filter base class

All the filters will need a wrapper around them, and this is going to be
their base class

Userland/Applications/PixelPaint/CMakeLists.txt

@@ -17,6 +17,7 @@ set(SOURCES
     FilterGallery.cpp
     FilterGalleryGML.h
     FilterModel.cpp
+    Filters/Filter.cpp
     Image.cpp
     ImageEditor.cpp
     Layer.cpp

Userland/Applications/PixelPaint/Filters/Filter.cpp

@@ -0,0 +1,28 @@
+/*
+ * Copyright (c) 2022, Tobias Christiansen <tobyase@serenityos.org>
+ *
+ * SPDX-License-Identifier: BSD-2-Clause
+ */
+
+#include "Filter.h"
+#include <LibGUI/BoxLayout.h>
+#include <LibGUI/Label.h>
+
+namespace PixelPaint {
+
+RefPtr<GUI::Widget> Filter::get_settings_widget()
+{
+    if (!m_settings_widget) {
+        m_settings_widget = GUI::Widget::construct();
+        m_settings_widget->set_layout<GUI::VerticalBoxLayout>();
+
+        auto& name_label = m_settings_widget->add<GUI::Label>(filter_name());
+        name_label.set_text_alignment(Gfx::TextAlignment::TopLeft);
+
+        m_settings_widget->add<GUI::Widget>();
+    }
+
+    return m_settings_widget.ptr();
+}
+
+}

Userland/Applications/PixelPaint/Filters/Filter.h

@@ -0,0 +1,33 @@
+/*
+ * Copyright (c) 2022, Tobias Christiansen <tobyase@serenityos.org>
+ *
+ * SPDX-License-Identifier: BSD-2-Clause
+ */
+
+#pragma once
+
+#include "../ImageEditor.h"
+#include "../Layer.h"
+#include <LibGUI/Widget.h>
+
+namespace PixelPaint {
+
+class Filter {
+public:
+    virtual void apply() const = 0;
+    virtual RefPtr<GUI::Widget> get_settings_widget();
+
+    virtual StringView filter_name() = 0;
+
+    virtual ~Filter() {};
+
+    Filter(ImageEditor* editor)
+        : m_editor(editor) {};
+
+protected:
+    ImageEditor* m_editor { nullptr };
+    StringView m_filter_name;
+    RefPtr<GUI::Widget> m_settings_widget { nullptr };
+};
+
+}