Add support for using a system copy of libroaring

Distributions try to avoid using bundled copies of libraries that are
maintained in an API- and ABI-stable way.

Signed-off-by: Simon McVittie <smcv@debian.org>

gtk/gtkbitset.c

@@ -21,7 +21,11 @@
 
 #include "gtkbitset.h"
 
+#ifdef HAVE_LIBROARING
+#include <roaring/roaring.h>
+#else
 #include "roaring.c"
+#endif
 
 /**
  * SECTION:gtkbitset

gtk/meson.build

@@ -968,6 +968,7 @@ gtk_deps = [
   epoxy_dep,
   libm,
   graphene_dep,
+  roaring_dep,
 ]
 
 if harfbuzz_dep.found() and pangoft_dep.found()

meson.build

@@ -683,6 +683,25 @@ else
   endif
 endif
 
+roaring_dep = []
+
+internal_roaring = get_option('internal_roaring')
+if internal_roaring == 'yes'
+  message('Using bundled copy of libroaring as requested.')
+else
+  roaring_dep = dependency('roaring', required: false)
+  if roaring_dep.found()
+    cdata.set('HAVE_LIBROARING', 1)
+  else
+    if internal_roaring == 'no'
+      error('System copy of libroaring not found, but was explicitly requested.')
+    else
+      message('Using bundled copy of libroaring automatically.')
+      roaring_dep = []
+    endif
+  endif
+endif
+
 cloudproviders_enabled = get_option('cloudproviders')
 if cloudproviders_enabled
   cloudproviders_dep = dependency('cloudproviders',

meson_options.txt

@@ -27,6 +27,8 @@ option('profiler', type: 'boolean', value: false,
   description : 'Enable profiler support')
 option('tracker3', type: 'boolean', value: false,
   description : 'Enable Tracker3 filechooser search')
+option('internal_roaring', type : 'combo', choices : ['yes', 'no', 'auto'], value : 'auto',
+  description : 'use bundled copy of libroaring?')
 
 # Print backends
 option('print-backends', type : 'string', value : 'cups,file',