Motivation for this change

Packaging https://github.com/aruiz/webp-pixbuf-loader , which allows programs using gdk-pixbuf to load webp images.

At this time this package isn't much use. The only programs making use of gdk-pixbuf are GTK apps, and wrapGAppsHook puts them in a wrapper that overrides the $GDK_PIXBUF_MODULE_FILE environment variable. See #42562 (comment)

Still, it works with eog and ristretto:

• configure this package in your configuration.nix
  services.xserver.gdk-pixbuf.modulePackages = [pkgs.webp-pixbuf-loader];
  alternatively, you can find this package in nur.repos.cwyc.webp-pixbuf-loader
• copy the wrapper script to your working directory and remove the line setting $GDK_PIXBUF_MODULE_FILE
cat $(which eog) | sed -e "s/export GDK_PIXBUF_MODULE_FILE=.*//" > ./wrapper.sh
• get a sample file if you have none
  curl https://www.gstatic.com/webp/gallery/1.webp -o sample.webp
• launch it
  ./wrapper.sh sample.webp
  (If your terminal program also launches through the GTK wrapper, then $GDK_PIXBUF_MODULE_FILE might have already been overwritten. In that case you'd have to find what it would have been using nixos-option environment.variables, and set it manually before running.)

Things done

• Built on platform(s)
  • x86_64-linux
  • aarch64-linux
  • x86_64-darwin
  • aarch64-darwin
• For non-Linux: Is sandbox = true set in nix.conf? (See Nix manual)
• Tested, as applicable:
  • NixOS test(s) (look inside nixos/tests)
  • and/or package tests
  • or, for functions and "core" functionality, tests in lib/tests or pkgs/test
  • made sure NixOS tests are linked to the relevant packages
• Tested compilation of all packages that depend on this change using nix-shell -p nixpkgs-review --run "nixpkgs-review rev HEAD". Note: all changes have to be committed, also see nixpkgs-review usage
• Tested basic functionality of all binary files (usually in ./result/bin/)
• 22.05 Release Notes (or backporting 21.11 Release notes)
  • (Package updates) Added a release notes entry if the change is major or breaking
  • (Module updates) Added a release notes entry if the change is significant
  • (Module addition) Added a release notes entry if adding a new NixOS module
  • (Release notes changes) Ran nixos/doc/manual/md-to-db.sh to update generated release notes
• Fits CONTRIBUTING.md.