build: install headers with enums

Generate and install headers containing enums. See [1].

Meson requires us to generate headers in a "include/wayland-protocols"
directory, so that include paths can be properly set up when used
as a sub-project.

[1]: wayland!312



Signed-off-by: Simon Ser <contact@emersion.fr>

include/wayland-protocols/meson.build

+header_install_dir = get_option('includedir') / 'wayland-protocols'
+foreach protocol_file : protocol_files
+	header_name = fs.name(protocol_file).replace('.xml', '-enum.h')
+	custom_target(
+		header_name,
+		output: header_name,
+		input: '../..' / protocol_file,
+		command: [
+			prog_scanner,
+			'--strict',
+			'enum-header',
+			'@INPUT@',
+			'@OUTPUT@',
+		],
+		install: true,
+		install_dir: header_install_dir,
+	)
+endforeach

meson.build

 project('wayland-protocols',
 	version: '1.37',
-	meson_version: '>= 0.55.0',
+	meson_version: '>= 0.58.0',
 	license: 'MIT/Expat',
 )
 
@@ -8,6 +8,9 @@ wayland_protocols_version = meson.project_version()
 
 fs = import('fs')
 
+dep_scanner = dependency('wayland-scanner', version: '>=1.20.0', native: true, fallback: 'wayland')
+prog_scanner = find_program(dep_scanner.get_variable(pkgconfig: 'wayland_scanner', internal: 'wayland_scanner'))
+
 stable_protocols = {
 	'presentation-time': [''],
 	'viewporter': [''],
@@ -108,6 +111,12 @@ foreach protocol_file : protocol_files
 	)
 endforeach
 
+include_dirs = []
+if dep_scanner.version().version_compare('>=1.22.90')
+	subdir('include/wayland-protocols')
+	include_dirs = ['include']
+endif
+
 wayland_protocols_srcdir = meson.current_source_dir()
 
 pkgconfig_configuration = configuration_data()
@@ -132,6 +141,7 @@ configure_file(
 )
 
 wayland_protocols = declare_dependency(
+	include_directories: include_dirs,
 	variables: {
 		'pkgdatadir': wayland_protocols_srcdir,
 	},
@@ -142,3 +152,7 @@ meson.override_dependency('wayland-protocols', wayland_protocols)
 if get_option('tests')
 	subdir('tests')
 endif
+
+summary({
+	'Headers': include_dirs.length() > 0,
+}, bool_yn: true)

tests/meson.build

 prog_scan_sh = find_program('scan.sh')
-dep_scanner = dependency('wayland-scanner', version: '>=1.20.0', native: true, fallback: 'wayland')
-prog_scanner = find_program(dep_scanner.get_variable(pkgconfig: 'wayland_scanner', internal: 'wayland_scanner'))
 
 libwayland = [
 	dependency('wayland-client'),