Restructure source and resource files (#46)

importantly, res is now res/res and css is now res/css

src/components/draglistbox.hpp

@@ -0,0 +1,45 @@
+#pragma once
+#include <gtkmm.h>
+
+class DragListBox : public Gtk::ListBox {
+public:
+    DragListBox();
+
+    void row_drag_begin(Gtk::Widget *widget, const Glib::RefPtr<Gdk::DragContext> &context);
+
+    bool on_drag_motion(const Glib::RefPtr<Gdk::DragContext> &context, gint x, gint y, guint time) override;
+
+    void on_drag_leave(const Glib::RefPtr<Gdk::DragContext> &context, guint time) override;
+
+    void check_scroll(gint y);
+
+    bool scroll();
+
+    void on_drag_data_received(const Glib::RefPtr<Gdk::DragContext> &context, int x, int y, const Gtk::SelectionData &selection_data, guint info, guint time) override;
+
+    void add_draggable(Gtk::ListBoxRow *widget);
+
+private:
+    Gtk::ListBoxRow *m_hover_row = nullptr;
+    Gtk::ListBoxRow *m_drag_row = nullptr;
+    bool m_top = false;
+    int m_hover_top = 0;
+    int m_hover_bottom = 0;
+    bool m_should_scroll = false;
+    bool m_scrolling = false;
+    bool m_scroll_up = false;
+
+    constexpr static int SCROLL_STEP_SIZE = 8;
+    constexpr static int SCROLL_DISTANCE = 30;
+    constexpr static int SCROLL_DELAY = 50;
+
+    const std::vector<Gtk::TargetEntry> m_entries = {
+        Gtk::TargetEntry("GTK_LIST_BOX_ROW", Gtk::TARGET_SAME_APP, 0),
+    };
+
+    using type_signal_on_drop = sigc::signal<bool, Gtk::ListBoxRow *, int /* new index */>;
+    type_signal_on_drop m_signal_on_drop;
+
+public:
+    type_signal_on_drop signal_on_drop(); // return true to prevent drop
+};