meson: re-add incorrect pkg-config files with GLVND for backward compatibility

This is a bit counter-intuitive, but the issue is that GLVND is broken
in versions <= 1.1.1, so we need to keep wrongly providing these files
to cover up their mistake, otherwise the rest of the world ends up
broken.

Suggested-by: Dylan Baker <dylan@pnwbakers.com>
Cc: mesa-stable@lists.freedesktop.org
Signed-off-by: Eric Engestrom <eric.engestrom@intel.com>
Reviewed-by: Dylan Baker <dylan@pnwbakers.com>

meson.build

@@ -1328,6 +1328,10 @@ endif
 dep_glvnd = null_dep
 if with_glvnd
   dep_glvnd = dependency('libglvnd', version : '>= 0.2.0')
+  # GLVND until commit 0dfaea2bcb7cdcc785f9 ("Add pkg-config files for EGL, GL,
+  # GLES, and GLX.") was missing its pkg-config files, forcing every vendor to
+  # provide them and the distro maintainers to resolve the conflict.
+  glvnd_missing_pc_files = dep_glvnd.version().version_compare('< 1.2.0')
   pre_args += '-DUSE_LIBGLVND=1'
 endif
 

src/egl/meson.build

@@ -173,17 +173,24 @@ libegl = shared_library(
   version : egl_lib_version,
 )
 
-if not with_glvnd
+# If using glvnd the pkg-config header should not point to EGL_mesa, it should
+# point to EGL. glvnd is only available on unix like platforms so adding -l
+# should be safe here
+if with_glvnd and glvnd_missing_pc_files
+  _egl = '-L${libdir} -lEGL'
+else
+  _egl = libegl
+endif
+
 pkg.generate(
   name : 'egl',
   description : 'Mesa EGL Library',
   version : meson.project_version(),
-    libraries : libegl,
+  libraries : _egl,
   libraries_private: gl_priv_libs,
   requires_private : gl_priv_reqs,
   extra_cflags : gl_pkgconfig_c_flags,
 )
-endif
 
 if with_tests and prog_nm.found()
   if with_glvnd

src/mapi/meson.build

@@ -35,7 +35,7 @@ if with_shared_glapi
 else
   libglapi = []
 endif
-if not with_glvnd
+if not with_glvnd or glvnd_missing_pc_files
   if with_gles1
     subdir('es1api')
   endif

src/meson.build

@@ -111,12 +111,22 @@ endif
 
 # This must be after at least mesa, glx, and gallium, since libgl will be
 # defined in one of those subdirs depending on the glx provider.
-if with_glx != 'disabled' and not with_glvnd
+if with_glx != 'disabled'
+  # If using glvnd the pkg-config header should not point to GL_mesa, it should
+  # point to GL. glvnd is only available on unix like platforms so adding -l
+  # should be safe here
+  # TODO: in the glvnd case glvnd itself should really be providing this.
+  if with_glvnd and glvnd_missing_pc_files
+    _gl = '-L${libdir} -lGL'
+  else
+    _gl = libgl
+  endif
+
   pkg.generate(
     name : 'gl',
     description : 'Mesa OpenGL Library',
     version : meson.project_version(),
-    libraries : libgl,
+    libraries : _gl,
     libraries_private : gl_priv_libs,
     requires_private : gl_priv_reqs,
     variables : ['glx_tls=yes'],