Function FreeBitmapMemory

src/cache.cpp:95–130

	size_t cache_size = 0;

	void FreeBitmapMemory() {
		auto cur_ticks = Game_Clock::GetFrameTime();

		for (auto it = cache.begin(); it != cache.end();) {
			if (it->second.bitmap.use_count() != 1) {
				// Bitmap is referenced
				++it;
				continue;
			}

			auto last_access = cur_ticks - it->second.last_access;
			bool cache_exhausted = cache_size > cache_limit;
			if (cache_exhausted) {
				if (last_access <= 50ms) {
					// Used during the last 3 frames, must be important, keep it.
					++it;
					continue;
				}
			} else if (last_access <= 3s) {
				++it;
				continue;
			}

#ifdef CACHE_DEBUG
			Output::Debug("Freeing memory of {}/{}", std::get<0>(i.first), std::get<1>(i.first));
#endif

			cache_size -= it->second.bitmap->GetSize();

			it = cache.erase(it);
		}

#ifdef CACHE_DEBUG
		Output::Debug("Bitmap cache size: {}", cache_size / 1024.0 / 1024);
#endif
	}

	BitmapRef AddToCache(const std::string& key, BitmapRef bmp) {
		if (bmp) {