backend: make DRM and libinput backends optional

Co-authored-by: Simon Ser <contact@emersion.fr>

backend/backend.c

@@ -6,10 +6,9 @@
 #include <string.h>
 #include <unistd.h>
 #include <wayland-server-core.h>
-#include <wlr/backend/drm.h>
+
 #include <wlr/backend/headless.h>
 #include <wlr/backend/interface.h>
-#include <wlr/backend/libinput.h>
 #include <wlr/backend/multi.h>
 #include <wlr/backend/noop.h>
 #include <wlr/backend/session.h>
@@ -22,6 +21,14 @@
 #include "render/allocator.h"
 #include "util/signal.h"
 
+#if WLR_HAS_DRM_BACKEND
+#include <wlr/backend/drm.h>
+#endif
+
+#if WLR_HAS_LIBINPUT_BACKEND
+#include <wlr/backend/libinput.h>
+#endif
+
 #if WLR_HAS_X11_BACKEND
 #include <wlr/backend/x11.h>
 #endif
@@ -211,6 +218,7 @@ static struct wlr_backend *attempt_noop_backend(struct wl_display *display) {
 	return backend;
 }
 
+#if WLR_HAS_DRM_BACKEND
 static struct wlr_backend *attempt_drm_backend(struct wl_display *display,
 		struct wlr_backend *backend, struct wlr_session *session) {
 	struct wlr_device *gpus[8];
@@ -240,6 +248,7 @@ static struct wlr_backend *attempt_drm_backend(struct wl_display *display,
 
 	return primary_drm;
 }
+#endif
 
 static struct wlr_backend *attempt_backend_by_name(struct wl_display *display,
 		struct wlr_backend *backend, struct wlr_session **session,
@@ -265,9 +274,17 @@ static struct wlr_backend *attempt_backend_by_name(struct wl_display *display,
 		}
 
 		if (strcmp(name, "libinput") == 0) {
+#if WLR_HAS_LIBINPUT_BACKEND
 			return wlr_libinput_backend_create(display, *session);
+#else
+			return NULL;
+#endif
 		} else {
+#if WLR_HAS_DRM_BACKEND
 			return attempt_drm_backend(display, backend, *session);
+#else
+			return NULL;
+#endif
 		}
 	}
 
@@ -355,6 +372,7 @@ struct wlr_backend *wlr_backend_autocreate(struct wl_display *display) {
 		return NULL;
 	}
 
+#if WLR_HAS_LIBINPUT_BACKEND
 	struct wlr_backend *libinput = wlr_libinput_backend_create(display,
 		multi->session);
 	if (!libinput) {
@@ -364,7 +382,9 @@ struct wlr_backend *wlr_backend_autocreate(struct wl_display *display) {
 		return NULL;
 	}
 	wlr_multi_backend_add(backend, libinput);
+#endif
 
+#if WLR_HAS_DRM_BACKEND
 	struct wlr_backend *primary_drm =
 		attempt_drm_backend(display, backend, multi->session);
 	if (!primary_drm) {
@@ -376,6 +396,7 @@ struct wlr_backend *wlr_backend_autocreate(struct wl_display *display) {
 	}
 
 	return backend;
+#endif
 
 error:
 	wlr_backend_destroy(backend);

backend/drm/meson.build

@@ -8,3 +8,5 @@ wlr_files += files(
 	'renderer.c',
 	'util.c',
 )
+
+features += { 'drm-backend': true }

backend/libinput/meson.build

@@ -1,3 +1,19 @@
+msg = ['Required for libinput backend support.']
+if 'libinput' in backends
+	msg += 'Install "libinput" or disable the libinput backend.'
+endif
+
+libinput = dependency(
+	'libinput',
+	version: '>=1.14.0',
+	required: 'libinput' in backends,
+	not_found_message: '\n'.join(msg),
+)
+
+if not libinput.found()
+	subdir_done()
+endif
+
 wlr_files += files(
 	'backend.c',
 	'events.c',
@@ -8,3 +24,6 @@ wlr_files += files(
 	'tablet_tool.c',
 	'touch.c',
 )
+
+features += { 'libinput-backend': true }
+wlr_deps += libinput

backend/meson.build

@@ -1,11 +1,22 @@
 wlr_files += files('backend.c')
 
-subdir('drm')
-subdir('headless')
-subdir('libinput')
+all_backends = ['drm', 'libinput', 'x11']
+backends = get_option('backends')
+if 'auto' in backends and get_option('auto_features').enabled()
+	backends = all_backends
+elif 'auto' in backends and get_option('auto_features').disabled()
+	backends = []
+endif
+
+foreach backend : all_backends
+	if backend in backends or 'auto' in backends
+		subdir(backend)
+	endif
+endforeach
+
 subdir('multi')
-subdir('noop')
 subdir('wayland')
-subdir('x11')
+subdir('noop')
+subdir('headless')
 
 subdir('session')

backend/x11/meson.build

@@ -10,17 +10,14 @@ x11_required = [
 	'xcb-xinput',
 ]
 
-msg = []
-if get_option('x11-backend').enabled()
-	msg += 'Install "@0@" or pass "-Dx11-backend=disabled" to disable it.'
-endif
-if not get_option('x11-backend').disabled()
-	msg += 'Required for X11 backend support.'
+msg = ['Required for X11 backend support.']
+if 'x11' in backends
+	msg += 'Install "@0@" or disable the X11 backend.'
 endif
 
 foreach lib : x11_required
 	dep = dependency(lib,
-		required: get_option('x11-backend'),
+		required: 'x11' in backends,
 		not_found_message: '\n'.join(msg).format(lib),
 	)
 	if not dep.found()

include/wlr/config.h.in

@@ -1,6 +1,8 @@
 #ifndef WLR_CONFIG_H
 #define WLR_CONFIG_H
 
+#mesondefine WLR_HAS_DRM_BACKEND
+#mesondefine WLR_HAS_LIBINPUT_BACKEND
 #mesondefine WLR_HAS_X11_BACKEND
 
 #mesondefine WLR_HAS_GLES2_RENDERER

meson.build

@@ -86,7 +86,9 @@ else
 endif
 
 features = {
+	'drm-backend': false,
 	'x11-backend': false,
+	'libinput-backend': false,
 	'xwayland': false,
 	'gles2-renderer': false,
 }
@@ -98,7 +100,6 @@ wayland_server = dependency('wayland-server', version: '>=1.19')
 wayland_client = dependency('wayland-client')
 drm = dependency('libdrm', version: '>=2.4.105')
 gbm = dependency('gbm', version: '>=17.1.0')
-libinput = dependency('libinput', version: '>=1.14.0')
 xkbcommon = dependency('xkbcommon')
 udev = dependency('libudev')
 pixman = dependency('pixman-1')
@@ -111,7 +112,6 @@ wlr_deps = [
 	wayland_client,
 	drm,
 	gbm,
-	libinput,
 	xkbcommon,
 	udev,
 	pixman,

meson_options.txt

@@ -1,6 +1,6 @@
 option('xcb-errors', type: 'feature', value: 'auto', description: 'Use xcb-errors util library')
 option('xwayland', type: 'feature', value: 'auto', yield: true, description: 'Enable support for X11 applications')
-option('x11-backend', type: 'feature', value: 'auto', description: 'Enable X11 backend')
 option('examples', type: 'boolean', value: true, description: 'Build example applications')
 option('icon_directory', description: 'Location used to look for cursors (default: ${datadir}/icons)', type: 'string', value: '')
 option('renderers', type: 'array', choices: ['auto', 'gles2'], value: ['auto'], description: 'Select built-in renderers')
+option('backends', type: 'array', choices: ['auto', 'drm', 'libinput', 'x11'], value: ['auto'], description: 'Select built-in backends')