meson: allow building libcamera from source as a subproject

Many distributions provide outdated libcamera versions. This change should also help making changes to libcamera itself.

System libcamera is kept a default to avoid breaking existing build processes relying to packaged libcamera.

.gitignore

@@ -15,6 +15,11 @@ subprojects/lua*
 subprojects/wireplumber
 subprojects/media-session
 subprojects/packagecache
+subprojects/googletest*
+subprojects/gtest.wrap
+subprojects/libyaml.wrap
+subprojects/libyaml
+subprojects/libcamera
 
 # Created by https://www.gitignore.io/api/vim
 

meson_options.txt

@@ -168,6 +168,8 @@ option('libcamera',
        description: 'Enable libcamera spa plugin integration',
        type: 'feature',
        value: 'auto')
+option('system-libcamera', type : 'boolean', value : 'true',
+       description : 'Use libcamera from the system instead of building from source')
 option('videoconvert',
        description: 'Enable videoconvert spa plugin integration',
        type: 'feature',

spa/meson.build

@@ -89,7 +89,12 @@ if get_option('spa-plugins').allowed()
   vulkan_headers = cc.has_header('vulkan/vulkan.h', dependencies : vulkan_dep)
   #summary({'Vulkan': vulkan_headers}, bool_yn: true, section: 'Misc dependencies')
 
-  libcamera_dep = dependency('libcamera', required: get_option('libcamera'))
+  if get_option('system-libcamera')
+    libcamera_dep = dependency('libcamera', required: get_option('libcamera'))
+  else
+    libcamera_proj = subproject('libcamera')
+    libcamera_dep = libcamera_proj.get_variable('libcamera_public')
+  endif
   summary({'libcamera': libcamera_dep.found()}, bool_yn: true, section: 'Backend')
 
   tinycompress_dep = cc.find_library('tinycompress', has_headers: ['tinycompress/tinycompress.h' ], required: get_option('compress-offload'))

subprojects/libcamera.wrap

@@ -0,0 +1,3 @@
+[wrap-git]
+url = https://git.libcamera.org/libcamera/libcamera.git
+revision = head