Misc (#19)

* get image returns optional<Mat> instead of unique_ptr<Mat>

* introduce complexity

* rename image load function

* add example for a basic reader for binary image files

* fix windows build?

* add a status bar underneath the menu bar

* use status bar in custom_0 example app

* clang formats

* packing w/ pragma push

* add "Save As" functions to image views

* resize over reserve

* rm local override uri

* add simple thread pool

* rename to simple_thread_pool

* get rid of useless renderlib

* document version inc

* extract hardcoded values to in-header

* clang format patch

* clone registered image in custom_0

* document binary-file header

* minor fixes

* clang format

* rm unused render cmake

lib/app/rendering/RenderImageManager.hpp

@@ -0,0 +1,74 @@
+#pragma once
+#include <memory>
+#include <mutex>
+#include <unordered_map>
+#include <unordered_set>
+
+#include "IPixelariumImageView.hpp"
+#include "ImageViewFactory.hpp"
+#include "resources/resource.hpp"
+#include "utilities/ILog.hpp"
+
+// This is intended as an additional abstraction
+// aggregating views that should be rendered (or not)
+namespace pixelarium::application
+{
+/// @brief Instead of directly using the view, we
+/// proxy it through a wrapper. This allows for arbitrary additional data
+/// to be added in future
+struct RenderImageStateWrapper
+{
+    std::unique_ptr<IPixelariumImageView> view;
+    const bool* show_state;
+};
+
+/// @brief Manage instances of IPixelariumImageView.
+///
+/// This class is used to keep track of what must be rendered.
+/// It manages a set of IPixelariumImageView instances that can be traversed
+/// via its Enumerate() function.
+/// Views that shall not be rendered anymore should be marked for deletion
+/// with MarkForDeletion()
+class RenderImageManager
+{
+    using Pool = resources::ImageResourcePool;
+
+   public:
+    explicit RenderImageManager(Pool& pool, const utils::log::ILog& log)
+        : view_factory_(std::make_unique<ImageViewFactory>(pool, log)), log_(log)
+    {
+    }
+
+    void Clear() noexcept;
+
+    void Add(resources::ResourceKey key) noexcept;
+
+    bool Remove(resources::ResourceKey key) noexcept;
+
+    // can't be const because func mutates the state
+    template <typename Callable>
+        requires std::invocable<Callable, resources::ResourceKey, RenderImageStateWrapper&>
+    void Enumerate(Callable&& func)
+    {
+        for (auto& [key, val] : this->render_image_map_)
+        {
+            if (val.view != nullptr)
+            {
+                func(key, val);
+            }
+        }
+    }
+
+    void MarkForDeletion(resources::ResourceKey key);
+
+    void UpdateCollection();
+
+   private:
+    std::unordered_map<resources::ResourceKey, RenderImageStateWrapper> render_image_map_;
+    std::unique_ptr<ImageViewFactory> view_factory_;
+    std::mutex mut_;
+    std::unordered_set<resources::ResourceKey> keys_to_delete_;
+
+    const utils::log::ILog& log_;
+};
+}  // namespace pixelarium::application