build: Coalesce print backends options into one

Instead of having separate options for each print backend, we can use
the same approach as the input method modules: a single option, with a
comma-separated list of print backends.

meson.build

@@ -704,6 +704,7 @@ summary = [
   '',
   '  Enabled backends: @0@'.format(pkg_targets.strip()),
   '    Vulkan support: @0@'.format(have_vulkan),
+  '    Print backends: @0@'.format(' '.join(print_backends)),
   '             Tests: @0@'.format(get_option('build-tests')),
   '     Documentation: @0@'.format(get_option('documentation')),
   '             Demos: @0@'.format(get_option('demos')),

meson_options.txt

@@ -1,5 +1,4 @@
-option('colord', type: 'combo', choices : ['yes', 'no', 'auto'], value : 'auto',
-  description : 'Build colord support code')
+# GDK backends
 option('enable-x11-backend', type: 'boolean', value: 'true',
   description : 'Enable the X11 gdk backend')
 option('enable-wayland-backend', type: 'boolean', value: 'true',
@@ -10,30 +9,36 @@ option('enable-win32-backend', type: 'boolean', value: 'false',
   description : 'Enable the Windows gdk backend')
 option('enable-quartz-backend', type: 'boolean', value: 'false',
   description : 'Enable the macOS gdk backend')
+
+# Optional dependencies
 option('enable-vulkan', type: 'combo', choices : ['yes', 'no', 'auto'], value : 'auto',
   description : 'Enable support for the Vulkan graphics API')
-option('enable-test-print-backend', type: 'combo', choices : ['yes', 'no', 'auto'], value : 'no',
-  description : 'Enable the test print backend')
-option('enable-cups-print-backend', type: 'combo', choices : ['yes', 'no', 'auto'], value : 'auto',
-  description : 'Enable the CUPS print backend')
-option('enable-papi-print-backend', type: 'combo', choices : ['yes', 'no', 'auto'], value : 'auto',
-  description : 'Enable the papi print backend')
-option('enable-cloudprint-print-backend', type: 'combo', choices : ['yes', 'no', 'auto'], value : 'auto',
-  description : 'Enable the cloudprint print backend')
-option('enable-cloudproviders', type: 'boolean', value: false,
-  description : 'Enable the cloudproviders support')
 option('enable-xinerama', type: 'combo', choices : ['yes', 'no', 'auto'], value : 'auto',
   description : 'Enable support for the Xinerama extension')
+option('enable-cloudproviders', type: 'boolean', value: false,
+  description : 'Enable the cloudproviders support')
+
+# Print backends
+option('print-backends', type : 'string', value : 'cups,papi',
+  description : 'Build the specified print backends (comma-separated list, "all", or "none")')
+option('colord', type: 'combo', choices : ['yes', 'no', 'auto'], value : 'auto',
+  description : 'Build colord support for the CUPS printing backend')
+
+# Modules
 option('dynamic-modules', type: 'boolean', value : true,
   description : 'Allow dynamic module loading')
 option('included-immodules', type: 'string', value : 'none',
   description : 'Build the specified input methods (comma-separated list, "all", or "none")')
+
+# Documentation and introspection
 option('documentation', type: 'boolean', value: 'false',
   description : 'Build API reference and tools documentation')
 option('man-pages', type: 'boolean', value: 'false',
   description : 'Build man pages for installed tools')
 option('introspection', type: 'boolean', value: 'true',
   description : 'Build introspection data (requires gobject-introspection)')
+
+# Demos and binaries
 option('demos', type: 'boolean', value: 'true',
   description : 'Build demos and example programs')
 option('build-tests', type: 'boolean', value: 'true',

modules/printbackends/meson.build

@@ -1,7 +1,23 @@
+all_print_backends = [
+  'cups',
+  'papi',
+  'cloudprint',
+  'test',
+]
+
+enabled_print_backends = get_option('print-backends').split(',')
+
+if enabled_print_backends.contains('none')
+  enabled_print_backends = []
+elif enabled_print_backends.contains('all')
+  enabled_print_backends = all_print_backends
+endif
+
+# The 'file' print backend cannot be disabled
 print_backends = ['file']
 
 # Checks to see if we should compile with CUPS backend for GTK+
-enable_cups = get_option('enable-cups-print-backend')
+enable_cups = enabled_print_backends.contains('cups')
 if enable_cups != 'no'
   want_cups = enable_cups == 'yes'
   #cups_config = find_program('cups-config', required : want_cups)
@@ -37,7 +53,7 @@ if enable_cups != 'no'
 endif
 
 # Checks to see if we should compile with PAPI backend for GTK+
-enable_papi = get_option('enable-papi-print-backend')
+enable_papi = enabled_print_backends.contains('papi')
 if enable_papi != 'no'
   want_papi = enable_papi == 'yes'
   libpapi = cc.find_library('libpapi', required : false)
@@ -49,7 +65,7 @@ if enable_papi != 'no'
 endif
 
 # Checks to see if we should compile with cloudprint backend for GTK+
-enable_cloudprint = get_option('enable-cloudprint-print-backend')
+enable_cloudprint = enabled_print_backends.contains('cloudprint')
 if enable_cloudprint != 'no'
   want_cloudprint = enable_cloudprint == 'yes'
   rest_dep = dependency('rest-0.7', required : want_cloudprint)
@@ -72,10 +88,11 @@ if os_unix
   endif
 endif
 
-if get_option('enable-test-print-backend') == 'yes'
+if enabled_print_backends.contains('test')
   print_backends += ['test']
 endif
 
+# Automatic fall-back to the lpr backend
 if not print_backends.contains('papi') and not print_backends.contains('cups')
   print_backends += ['lpr']
 endif