opencv: move the dependency check to a single place

Previously we were checking for opencv dep in 2 different places,
and the checks would vary in terms of how complex and exhaustive
they were.

Move the check into the libs module and reuse the result later on.

Part-of: <https://gitlab.freedesktop.org/gstreamer/gstreamer/-/merge_requests/3016>

subprojects/gst-plugins-bad/ext/opencv/meson.build

@@ -34,87 +34,7 @@ gstopencv_sources = [
   'gstcvtracker.cpp'
 ]
 
-libopencv_headers = [
-  'opencv2/bgsegm.hpp',
-  'opencv2/calib3d.hpp',
-  'opencv2/core.hpp',
-  'opencv2/imgproc.hpp',
-  'opencv2/objdetect.hpp',
-  'opencv2/opencv.hpp',
-  'opencv2/video.hpp',
-  'opencv2/tracking.hpp',
-]
-
-libopencv4_headers = [
-  'opencv4/opencv2/bgsegm.hpp',
-  'opencv4/opencv2/calib3d.hpp',
-  'opencv4/opencv2/core.hpp',
-  'opencv4/opencv2/imgproc.hpp',
-  'opencv4/opencv2/objdetect.hpp',
-  'opencv4/opencv2/opencv.hpp',
-  'opencv4/opencv2/video.hpp',
-  'opencv4/opencv2/tracking.hpp',
-]
-
-gstopencv_cargs = ['-DGST_HAAR_CASCADES_DIR="@0@"']
-
-opencv_dep = dependency('opencv', version : ['>= 3.0.0', '< 3.5.0'], required : false)
-opencv_found = opencv_dep.found()
-
 if opencv_found
-  foreach h : libopencv_headers
-    if not cxx.has_header(h)
-      message('Needed header "' + h + '" not found')
-      opencv_found = false
-    endif
-  endforeach
-endif
-
-if not opencv_found
-  opencv_dep = dependency('opencv4', version : '>= 4.0.0', required : false)
-  opencv_found = opencv_dep.found()
-  if opencv_found
-    foreach h : libopencv4_headers
-      if not cxx.has_header(h)
-        message('Needed header "' + h + '" not found')
-        opencv_found = false
-      endif
-    endforeach
-  endif
-endif
-
-if opencv_found
-  opencv_prefix = opencv_dep.get_variable('prefix')
-  gstopencv_cargs += ['-DOPENCV_PREFIX="' + opencv_prefix + '"']
-
-  # Check the data dir used by opencv for its xml data files
-  # Use prefix from pkg-config to be compatible with cross-compilation
-  r = run_command('test', '-d', opencv_prefix + '/share/opencv', check: false)
-  if r.returncode() == 0
-    gstopencv_cargs += '-DOPENCV_PATH_NAME="opencv"'
-  else
-    r = run_command('test', '-d', opencv_prefix + '/share/OpenCV', check: false)
-    if r.returncode() == 0
-      gstopencv_cargs += '-DOPENCV_PATH_NAME="OpenCV"'
-    else
-      r = run_command('test', '-d', opencv_prefix + '/share/opencv4', check: false)
-      if r.returncode() == 0
-        gstopencv_cargs += '-DOPENCV_PATH_NAME="opencv4"'
-      else
-        message('Unable to detect OpenCV data directory')
-        opencv_found = false
-      endif
-    endif
-  endif
-endif
-
-if opencv_found
-  # opencv4 seems to ship with .pc file that references non-existent include dir
-  # (/usr/include/opencv4/opencv instead of /usr/include/opencv4/opencv2)
-  # clang 10 complains about the following header in opencv4
-  # /usr/include/opencv4/opencv2/flann/logger.h:83:36: error: format string is not a string literal [-Werror,-Wformat-nonliteral]
-  gstopencv_cargs += cxx.get_supported_arguments(['-Wno-missing-include-dirs', '-Wno-format-nonliteral'])
-
   gstopencv = library('gstopencv',
     gstopencv_sources,
     cpp_args : gst_plugins_bad_args + gstopencv_cargs + [ '-DGST_USE_UNSTABLE_API' ],

subprojects/gst-plugins-bad/gst-libs/gst/opencv/meson.build

@@ -1,3 +1,8 @@
+if get_option('opencv').disabled()
+  gstopencv_dep = disabler()
+  subdir_done()
+endif
+
 opencv_sources = [
   'gstopencvutils.cpp',
   'gstopencvvideofilter.cpp',
@@ -9,22 +14,66 @@ opencv_headers = [
   'gstopencvvideofilter.h',
 ]
 
-if get_option('opencv').disabled()
+libopencv_headers = [
-  gstopencv_dep = disabler()
+  'opencv2/bgsegm.hpp',
-  subdir_done()
+  'opencv2/calib3d.hpp',
+  'opencv2/core.hpp',
+  'opencv2/imgproc.hpp',
+  'opencv2/objdetect.hpp',
+  'opencv2/opencv.hpp',
+  'opencv2/video.hpp',
+  'opencv2/tracking.hpp',
+]
+
+gstopencv_cargs = ['-DGST_HAAR_CASCADES_DIR="@0@"']
+
+opencv_dep = dependency('opencv', version : ['>= 3.0.0', '< 3.5.0'], required : false)
+opencv_found = opencv_dep.found()
+if not opencv_found
+  opencv_dep = dependency('opencv4', version : ['>= 4.0.0'], required : false)
+  opencv_found = opencv_dep.found()
 endif
 
-opencv_dep = dependency('opencv', version : '>= 3.0.0', required : false)
+if opencv_found
-if not opencv_dep.found()
+  foreach h : libopencv_headers
-  opencv_dep = dependency('opencv4', version : '>= 4.0.0', required : false)
+    if not cxx.has_header(h, dependencies: opencv_dep)
+      message('Needed header "' + h + '" not found')
+      opencv_found = false
+    endif
+  endforeach
 endif
-if opencv_dep.found()
+
+if opencv_found
+  opencv_prefix = opencv_dep.get_variable('prefix')
+  gstopencv_cargs += ['-DOPENCV_PREFIX="' + opencv_prefix + '"']
   # opencv4 seems to ship with .pc file that references non-existent include dir
   # (/usr/include/opencv4/opencv instead of /usr/include/opencv4/opencv2)
   # clang 10 complains about the following header in opencv4
   # /usr/include/opencv4/opencv2/flann/logger.h:83:36: error: format string is not a string literal [-Werror,-Wformat-nonliteral]
-  gstopencv_cargs = cxx.get_supported_arguments(['-Wno-missing-include-dirs', '-Wno-format-nonliteral'])
+  gstopencv_cargs += cxx.get_supported_arguments(['-Wno-missing-include-dirs', '-Wno-format-nonliteral'])
 
+  # Check the data dir used by opencv for its xml data files
+  # Use prefix from pkg-config to be compatible with cross-compilation
+  r = run_command('test', '-d', opencv_prefix + '/share/opencv', check: false)
+  if r.returncode() == 0
+    gstopencv_cargs += '-DOPENCV_PATH_NAME="opencv"'
+  else
+    r = run_command('test', '-d', opencv_prefix + '/share/OpenCV', check: false)
+    if r.returncode() == 0
+      gstopencv_cargs += '-DOPENCV_PATH_NAME="OpenCV"'
+    else
+      r = run_command('test', '-d', opencv_prefix + '/share/opencv4', check: false)
+      if r.returncode() == 0
+        gstopencv_cargs += '-DOPENCV_PATH_NAME="opencv4"'
+      else
+        message('Unable to detect OpenCV data directory')
+        opencv_found = false
+      endif
+    endif
+  endif
+endif
+
+if opencv_found
   pkg_name = 'gstreamer-opencv-1.0'
   gstopencv = library('gstopencv-' + api_version,
     opencv_sources,
@@ -48,6 +97,4 @@ if opencv_dep.found()
   install_headers(opencv_headers, subdir : 'gstreamer-1.0/gst/opencv')
 elif get_option('opencv').enabled()
   error('OpenCV support enabled but required dependencies were not found.')
-else
-  gstopencv_dep = disabler()
 endif