meson: Add option to control building wayland-scanner

Wayland requires a binary, wayland-scanner, to be run during the build
process. For any configuration other than native builds (including
cross compiling and even 32-bit x86 builds on an x86-64 build machine)
Wayland's build process builds and uses its own wayland-scanner.

For any builds using a cross file, wayland-scanner is built for the host
machine and therefore cannot be executed during the build of the Wayland
libraries. Instead builds using a cross file must execute the build
machine's wayland-scanner (typically /usr/bin/wayland-scanner).

As such, to build Wayland's libraries for a non-native ABI a package
manager must build and install /usr/bin/wayland-scanner first. But then
the build for the native ABI then rebuilds wayland-scanner itself and
doesn't use the system's, and worse, wants to install its own, which
conflicts with the /usr/bin/wayland-scanner already installed!

So, add the -Dscanner=... option to control whether to install
wayland-scanner.

Signed-off-by: Matt Turner <mattst88@gmail.com>

meson.build

@@ -84,12 +84,12 @@ if get_option('libraries')
 	subdir('cursor')
 	subdir('egl')
 	subdir('tests')
-endif
-
 	if get_option('documentation')
 		subdir('doc')
 	endif
+endif
 
+if get_option('scanner')
 	install_data([
 		'wayland-scanner.mk',
 		'protocol/wayland.xml',
@@ -100,3 +100,4 @@ install_data(
 		[ 'wayland-scanner.m4' ],
 		install_dir: join_paths(get_option('prefix'), get_option('datadir'), 'aclocal'),
 	)
+endif

meson_options.txt

@@ -2,6 +2,10 @@ option('libraries',
   description: 'Compile Wayland libraries',
   type: 'boolean',
   value: 'true')
+option('scanner',
+  description: 'Compile wayland-scanner binary',
+  type: 'boolean',
+  value: 'true')
 option('documentation',
   description: 'Build the documentation (requires Doxygen, dot, xmlto, xsltproc)',
   type: 'boolean',

src/meson.build

@@ -4,12 +4,6 @@ wayland_version_h.set('WAYLAND_VERSION', meson.project_version())
 wayland_version_h.set('WAYLAND_VERSION_MAJOR', wayland_version[0].to_int())
 wayland_version_h.set('WAYLAND_VERSION_MINOR', wayland_version[1].to_int())
 wayland_version_h.set('WAYLAND_VERSION_MICRO', wayland_version[2].to_int())
-configure_file(
-	input: 'wayland-version.h.in',
-	output: 'wayland-version.h',
-	configuration: wayland_version_h,
-	install_dir: join_paths(get_option('prefix'), get_option('includedir'))
-)
 
 wayland_util = static_library(
 	'wayland-util',
@@ -21,8 +15,15 @@ wayland_util_dep = declare_dependency(
 	include_directories: include_directories('.')
 )
 
+if get_option('scanner')
 	# wayland-scanner
 
+	configure_file(
+		input: 'wayland-version.h.in',
+		output: 'wayland-version.h',
+		configuration: wayland_version_h,
+	)
+
 	configure_file(
 		input: '../protocol/wayland.dtd',
 		output: 'wayland.dtd.embed',
@@ -53,8 +54,9 @@ pkgconfig.generate(
 		],
 		filebase: 'wayland-scanner'
 	)
+endif
 
-if meson.is_cross_build()
+if meson.is_cross_build() or not get_option('scanner')
 	scanner_dep = dependency('wayland-scanner', native: true, version: meson.project_version())
 	wayland_scanner_for_build = find_program(scanner_dep.get_pkgconfig_variable('wayland_scanner'))
 else
@@ -62,6 +64,19 @@ else
 endif
 
 if get_option('libraries')
+	# wayland libraries
+
+	# Duplicated inside the "if get_option('scanner')" block above since we
+	# still need the wayland-version.h to build the scanner, but do not want
+	# to install it. Meson 0.50 adds "install: bool" which will let us
+	# deduplicate this block.
+	configure_file(
+		input: 'wayland-version.h.in',
+		output: 'wayland-version.h',
+		configuration: wayland_version_h,
+		install_dir: join_paths(get_option('prefix'), get_option('includedir'))
+	)
+
 	mathlib_dep = cc.find_library('m', required: false)
 	threads_dep = dependency('threads', required: false)
 

tests/meson.build

@@ -76,6 +76,7 @@ test(
 
 sed_path = find_program('sed').path()
 
+if get_option('scanner')
 	test(
 		'scanner-test',
 		find_program('scanner-test.sh'),
@@ -86,6 +87,7 @@ test(
 			'WAYLAND_SCANNER=@0@'.format(wayland_scanner.full_path()),
 		],
 	)
+endif
 
 tests = {
 	'array-test': [],