Restructure source and resource files (#46)

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

src/imgmanager.hpp

@@ -0,0 +1,38 @@
+#pragma once
+#include <string>
+#include <unordered_map>
+#include <functional>
+#include <queue>
+#include <gtkmm.h>
+#include "filecache.hpp"
+
+class ImageManager {
+public:
+    ImageManager();
+
+    using callback_anim_type = sigc::slot<void(Glib::RefPtr<Gdk::PixbufAnimation>)>;
+    using callback_type = sigc::slot<void(Glib::RefPtr<Gdk::Pixbuf>)>;
+
+    Cache &GetCache();
+    void ClearCache();
+    void LoadFromURL(std::string url, callback_type cb);
+    // animations need dimensions before loading since there is no (easy) way to scale a PixbufAnimation
+    void LoadAnimationFromURL(std::string url, int w, int h, callback_anim_type cb);
+    void Prefetch(std::string url);
+    Glib::RefPtr<Gdk::Pixbuf> GetFromURLIfCached(std::string url);
+    Glib::RefPtr<Gdk::PixbufAnimation> GetAnimationFromURLIfCached(std::string url, int w, int h);
+    Glib::RefPtr<Gdk::Pixbuf> GetPlaceholder(int size);
+
+private:
+    Glib::RefPtr<Gdk::Pixbuf> ReadFileToPixbuf(std::string path);
+    Glib::RefPtr<Gdk::PixbufAnimation> ReadFileToPixbufAnimation(std::string path, int w, int h);
+
+    mutable std::mutex m_load_mutex;
+    void RunCallbacks();
+    Glib::Dispatcher m_cb_dispatcher;
+    mutable std::mutex m_cb_mutex;
+    std::queue<std::function<void()>> m_cb_queue;
+
+    std::unordered_map<std::string, Glib::RefPtr<Gdk::Pixbuf>> m_pixs;
+    Cache m_cache;
+};