Hydra vs Wallpaper Cycler

Hydra is a continuous integration service for projects based on Nix. It checks out project source periodically or continuously, builds it, runs tests, and produces reports. Work is organized into jobsets whose inputs can trigger builds when they change; jobsets can also depend on one another. Flake jobsets are supported when their outputs expose a hydraJobs attribute set. Jobs can produce packages, ISO images, or tarballs, and jobset inputs can use Git checkout sources. Hydra also provides a JSON API. It is aimed at Nix and NixOS package developers, not people who only need to use NixOS. Hydra is open source under GPL-3.0 and listed at free. It is self-hosted, with no hosted option listed, and running it is currently supported only on NixOS; the repository recommends the NixOS module for production. Flake evaluation is restricted from accessing files outside the Nix store. Some state is stored in the database, so backups are needed, and the wiki reports that hydra-queue-runner can sometimes leave queued builds unscheduled.

Wallpaper Cycler is a Windows desktop wallpaper manager that changes images after a delay or at specified times. It organizes wallpapers in multilevel categories, which can have time constraints and link to folders to detect new images. Layouts can place calendars, quotes, notes, webcams, other wallpapers, calendar notes, and RSS headlines on the desktop. The software supports more than 20 image formats, including JPG, BMP, TIFF, PNG, GIF, and JPEG 2000. Its random selector uses all wallpapers before repeating one. The maker says it can manage tens of thousands of wallpapers and pause cycling when CPU load is too high. Effects can be extended with third-party DLLs using the included SDK, and third-party control is available through WPCController in version 3.6. Wallpaper Cycler Lite is free; the full single-user version costs $19.95, paid once, with tax not included. A site license costs $495 as a one-time purchase. The trial is limited to 30 runs and does not allow layouts to be exported. Listed system requirements cover Windows XP, 2003, Vista, and 7, excluding Windows 7 Starter.