gnu: Add glad.

* gnu/packages/gl.scm (glad): New variable.

gnu/packages/gl.scm

@@ -12,7 +12,7 @@
 ;;; Copyright © 2019 Pierre Neidhardt <mail@ambrevar.xyz>
 ;;; Copyright © 2020 Marius Bakke <mbakke@fastmail.com>
 ;;; Copyright © 2020 Giacomo Leidi <goodoldpaul@autistici.org>
-;;; Copyright © 2020, 2021 Maxim Cournoyer <maxim.cournoyer@gmail.com>
+;;; Copyright © 2020, 2021, 2022 Maxim Cournoyer <maxim.cournoyer@gmail.com>
 ;;; Copyright © 2020 Kei Kebreau <kkebreau@posteo.net>
 ;;; Copyright © 2021 Ivan Gankevich <i.gankevich@spbu.ru>
 ;;; Copyright © 2021 John Kehayias <john.kehayias@protonmail.com>
@@ -63,6 +63,7 @@
   #:use-module (guix build-system gnu)
   #:use-module (guix build-system cmake)
   #:use-module (guix build-system meson)
+  #:use-module (guix build-system python)
   #:use-module (guix build-system waf)
   #:use-module ((guix licenses) #:prefix license:)
   #:use-module (guix packages)
@@ -181,6 +182,38 @@ rendering modes are: Bitmaps, Anti-aliased pixmaps, Texture maps, Outlines,
 Polygon meshes, and Extruded polygon meshes.")
     (license license:x11)))
 
+(define-public glad
+  (package
+    (name "glad")
+    (version "0.1.36")
+    (source
+     (origin
+       ;; We fetch the sources from the repository since the PyPI archive
+       ;; doesn't contain the CMakeLists.txt file which is useful for
+       ;; integration with other software, such as the openboardview package.
+       (method git-fetch)
+       (uri (git-reference
+             (url "https://github.com/Dav1dde/glad")
+             (commit (string-append "v" version))))
+       (file-name (git-file-name name version))
+       (sha256
+        (base32
+         "0m55ya1zrmg6n2cljkajy80ilmi5sblln8742fm0k1sw9k7hzn8n"))))
+    (build-system python-build-system)
+    (arguments
+     `(#:phases
+       (modify-phases %standard-phases
+         (add-after 'install 'install-cmakelists.txt
+           (lambda* (#:key outputs #:allow-other-keys)
+             (let* ((out (assoc-ref outputs "out"))
+                    (share (string-append out "/share/" ,name)))
+               (install-file "CMakeLists.txt" share)))))))
+    (home-page "https://github.com/Dav1dde/glad")
+    (synopsis "Multi-language GL/GLES/EGL/GLX/WGL loader generator")
+    (description "Glad uses the official Khronos XML specifications to
+generate a GL/GLES/EGL/GLX/WGL loader tailored for specific requirements.")
+    (license license:expat)))
+
 (define-public s2tc
   (package
     (name "s2tc")