Conky is a free, lightweight system monitor for X11, Wayland, and macOS that displays system information on the desktop or in alternative output modes (console, file, HTTP). It collects data from /proc, /sys, sysctl, and various APIs to report CPU, memory, disk, network, processes, sensors, audio players, mail, RSS, and more. The architecture is modular: data sources are registered as text objects with scan/print/free callbacks, output backends are selected at runtime (X11, Wayland, ncurses, console, file, HTTP), and Lua scripting provides configuration and extensibility via tolua++ generated bindings. A callback system handles periodic data fetching with deduplication and thread safety, and a priority queue supports top process sorting. The codebase is written in C++ with some C, uses CMake build system, and includes a comprehensive test suite using Catch2. It supports Linux, BSDs, Haiku, Solaris, and macOS with platform-specific backends. The project demonstrates several well-crafted reusable components: a generic priority queue, a callback system for periodic tasks, a typed configuration settings framework with Lua integration, a structured logging wrapper around spdlog, and a macro-generated X11 event variant pattern. These components exhibit non-obvious skill and can be extracted for use in other C++ projects. However, the codebase also shows signs of technical drift with bundled third-party libraries (Vc, tolua++, spdlog) that may lag behind upstream, and some platform-specific backends have incomplete implementations.
feh is a lightweight, configurable X11 image viewer and cataloguer written in C. It provides multiple viewing modes: slideshow, index (montage), thumbnail browser, multiwindow, file list, and wallpaper setting. The application relies on Imlib2 for image loading and rendering, with optional support for libcurl (HTTP/HTTPS), libexif (EXIF metadata), Xinerama (multi-monitor), inotify (auto-reload), and libmagic (MIME detection). The codebase is modular, featuring reusable generic data structures (doubly linked list, hash table, Imlib2 wrapper) and a format specifier system for actions, captions, and titles. It is a mature, stable project with a long history (since 1999) and an extensive test suite using X11::GUITest. However, it shows signs of technical drift: manual memory management, legacy code comments, deprecated options, platform-specific conditionals, and reliance on external tools like dcraw and ImageMagick for certain image formats. The project is actively maintained with regular releases.