gl: use dependency fallbacks to get at a possible gl-headers subproject

We would make the subproject conditional on the wrap-mode=nodownload
however get_option('wrap-mode') or similar is not available from
meson.build files as the wrap-mode is meant to be used automatically.

Instead use the dependency fallback mechanism to get at the subproject
where possible i.e. when downloading is allows and only add the compat
includes when we have a valid internal dependency from the gl-headers
subproject.

https://bugzilla.gnome.org/show_bug.cgi?id=796534

diff --git a/gst-libs/gst/gl/meson.build b/gst-libs/gst/gl/meson.build
index 4b6a5f0..4bdf0d2 100644 (file)
--- a/gst-libs/gst/gl/meson.build
+++ b/gst-libs/gst/gl/meson.build
@@ -145,6 +145,7 @@ gl_winsys_deps = []
 gl_misc_deps = []
 # Other preprocessor arguments
 gl_cpp_args = []
+gl_includes = []
 
 enabled_gl_apis = []
 enabled_gl_platforms = []
@@ -264,6 +265,20 @@ gl_include_header = '''
 #endif
 '''
 
+# convoluted way of getting at the subproject taking into account the wrap-mode
+# so we don't download a subproject unless allowed
+# FIXME: dependency() needs a valid name to attempt to find otherwise meson
+# short-circuits and will always fail and never look into the fallback
+# subproject. https://github.com/mesonbuild/meson/issues/3754
+gl_header_dep = dependency('gl-headers-not-findable', method : 'pkg-config',
+    fallback : ['gl-headers', 'gl_headers_dummy_dep'], required : false)
+if gl_header_dep.type_name() == 'internal'
+  # this will only contain the includes of headers that are not found
+  compat_includes = subproject('gl-headers').get_variable('compatibility_includes')
+else
+  compat_includes = []
+endif
+
 # Desktop OpenGL checks
 gl_dep = unneeded_dep
 glx_dep = unneeded_dep
@@ -280,13 +295,17 @@ if need_api_opengl != 'no' or need_platform_glx != 'no'
       gl_dep = cc.find_library('GL', required : false)
     endif
 
-    if not cc.has_header('GL/gl.h')
+    if not cc.has_header('GL/gl.h', include_directories : compat_includes)
       gl_dep = unneeded_dep
     endif
 
     if not gl_dep.found() and need_api_opengl == 'yes'
       error ('Could not find requested OpenGL library')
     endif
+
+    if gl_dep.found()
+      gl_includes += [compat_includes]
+    endif
   endif
 
   glx_dep = gl_dep
@@ -331,16 +350,20 @@ if need_api_gles2 != 'no'
       gles2_dep = cc.find_library('GLESv2', required : false)
 #    endif
 
-     if not cc.has_header('GLES2/gl2.h')
+     if not cc.has_header('GLES2/gl2.h', include_directories : compat_includes)
        gles2_dep = unneeded_dep
      endif
 
     if not gles2_dep.found() and need_api_gles2 == 'yes'
       error ('Could not find requested OpenGL ES library')
     endif
+
+    if gles2_dep.found()
+      gl_includes += [compat_includes]
+    endif
   endif
 
-  gles3_h = gles2_dep.found() and cc.has_header('GLES3/gl3.h', dependencies : gles2_dep)
+  gles3_h = gles2_dep.found() and cc.has_header('GLES3/gl3.h', dependencies : gles2_dep, include_directories : compat_includes)
 
   gles_includes = '''
 #ifdef HAVE_IOS /* FIXME */
@@ -348,7 +371,8 @@ if need_api_gles2 != 'no'
 # include <OpenGLES/ES2/glext.h>
 #else'''
   if gles3_h
-    gles3ext3_h = gles3_h and cc.has_header('GLES3/gl3ext.h', dependencies : gles2_dep)
+    gl_includes += [compat_includes]
+    gles3ext3_h = gles3_h and cc.has_header('GLES3/gl3ext.h', dependencies : gles2_dep, include_directories : compat_includes)
     gles_includes += '''
 # include <GLES3/gl3.h>
 # include <GLES2/gl2ext.h>'''
@@ -371,7 +395,7 @@ if gles2_dep.found() and gl_dep.found()
   gl_include_block = gl_include_header + gles_includes + opengl_includes
   # TODO: Revert to passing gl_include_block via prefix: once
   # https://github.com/mesonbuild/meson/issues/2364 is fixed
-  if not cc.compiles(gl_include_block + '\n' + 'void f (void) {}',dependencies : [gles2_dep, gl_dep])
+  if not cc.compiles(gl_include_block + '\n' + 'void f (void) {}',dependencies : [gles2_dep, gl_dep], include_directories : compat_includes)
     message ('Cannot include both OpenGL and OpenGL ES headers')
     if need_api_gles2 != 'yes'
       gles2_dep = unneeded_dep
@@ -568,15 +592,16 @@ if need_platform_wgl == 'yes'
   endif
 endif
 
-# XXX: untested
 if need_platform_wgl != 'no' and need_win_win32 != 'no'
   gdi_dep = cc.find_library('gdi32', required : false)
   # FIXME: Revert back to has_header once it gains prefix support
   wglext_h = cc.has_header_symbol('GL/wglext.h', 'WGL_WGLEXT_VERSION',
                                   prefix : '''#include <windows.h>
-                                              #include <GL/gl.h>''')
+                                              #include <GL/gl.h>''',
+                                  include_directories : compat_includes)
 
   if wglext_h and gdi_dep.found() and gl_dep.found()
+    gl_includes += [compat_includes]
     gl_platform_deps += gdi_dep
     gl_sources += [
       'win32/win32_message_source.c',
@@ -649,7 +674,7 @@ if need_platform_egl != 'no' and need_win_viv_fb != 'no'
 endif
 
 # TODO: Add rest of gl config here.
-# iOS, OS X, win32 specific support
+# iOS, OS X specific support
 
 build_gstgl = true
 if enabled_gl_apis.length() == 0
@@ -667,28 +692,28 @@ endif
 
 if build_gstgl
   # find some types that may or may not be defined
-  if cc.has_type('GLeglImageOES', prefix : gl_include_block, dependencies : gl_lib_deps)
+  if cc.has_type('GLeglImageOES', prefix : gl_include_block, dependencies : gl_lib_deps, include_directories : gl_includes)
     glconf.set('GST_GL_HAVE_GLEGLIMAGEOES', 1)
   endif
-  if cc.has_type('GLchar', prefix : gl_include_block, dependencies : gl_lib_deps)
+  if cc.has_type('GLchar', prefix : gl_include_block, dependencies : gl_lib_deps, include_directories : gl_includes)
     glconf.set('GST_GL_HAVE_GLCHAR', 1)
   endif
-  if cc.has_type('GLsizeiptr', prefix : gl_include_block, dependencies : gl_lib_deps)
+  if cc.has_type('GLsizeiptr', prefix : gl_include_block, dependencies : gl_lib_deps, include_directories : gl_includes)
     glconf.set('GST_GL_HAVE_GLSIZEIPTR', 1)
   endif
-  if cc.has_type('GLintptr', prefix : gl_include_block, dependencies : gl_lib_deps)
+  if cc.has_type('GLintptr', prefix : gl_include_block, dependencies : gl_lib_deps, include_directories : gl_includes)
     glconf.set('GST_GL_HAVE_GLINTPTR', 1)
   endif
-  if cc.has_type('GLsync', prefix : gl_include_block, dependencies : gl_lib_deps)
+  if cc.has_type('GLsync', prefix : gl_include_block, dependencies : gl_lib_deps, include_directories : gl_includes)
     glconf.set('GST_GL_HAVE_GLSYNC', 1)
   endif
-  if cc.has_type('GLuint64', prefix : gl_include_block, dependencies : gl_lib_deps)
+  if cc.has_type('GLuint64', prefix : gl_include_block, dependencies : gl_lib_deps, include_directories : gl_includes)
     glconf.set('GST_GL_HAVE_GLUINT64', 1)
   endif
-  if cc.has_type('GLint64', prefix : gl_include_block, dependencies : gl_lib_deps)
+  if cc.has_type('GLint64', prefix : gl_include_block, dependencies : gl_lib_deps, include_directories : gl_includes)
     glconf.set('GST_GL_HAVE_GLINT64', 1)
   endif
-  if egl_dep.found() and cc.has_type('EGLAttrib', prefix : gl_include_block + egl_includes, dependencies : gl_lib_deps + [egl_dep])
+  if egl_dep.found() and cc.has_type('EGLAttrib', prefix : gl_include_block + egl_includes, dependencies : gl_lib_deps + [egl_dep], include_directories : gl_includes)
     glconf.set('GST_GL_HAVE_EGLATTRIB', 1)
   endif
 
@@ -711,7 +736,7 @@ if build_gstgl
   gstgl = library('gstgl-' + api_version,
     gl_sources,
     c_args : gst_plugins_base_args + gl_cpp_args,
-    include_directories : [configinc, libsinc],
+    include_directories : [configinc, libsinc, gl_includes],
     version : libversion,
     soversion : soversion,
     install : true,
@@ -736,7 +761,7 @@ if build_gstgl
 
 
   gstgl_dep = declare_dependency(link_with : gstgl,
-    include_directories : [libsinc],
+    include_directories : [libsinc, compat_includes],
     sources: gen_sources,
     dependencies : [video_dep, gst_base_dep] + gl_winsys_deps)
 endif