backend-pipewire: add PipeWire backend

Add a separate PipeWire backend based on the PipeWire plugin. The backend
requires PipeWire 0.3.x.

The PipeWire backend can be used as a standalone-backend backend for streaming
and composing Wayland clients to PipeWire.

The backend supports the on-demand creation of heads via the
weston_pipewire_output_api_v1. It also supports per-output pixel format
configuration via a gbm-format option.

Multiple PipeWire outputs can be created by setting the num-outputs option in
the [pipewire] section.

Co-authored-by: Michael Tretter <m.tretter@pengutronix.de>
Signed-off-by: Philipp Zabel <p.zabel@pengutronix.de>
Signed-off-by: Michael Tretter <m.tretter@pengutronix.de>

compositor/config-helpers.c

@@ -40,6 +40,7 @@ struct {
 } backend_name_map[] = {
 	{ "drm", "drm-backend.so", WESTON_BACKEND_DRM },
 	{ "headless", "headless-backend.so", WESTON_BACKEND_HEADLESS },
+	{ "pipewire", "pipewire-backend.so", WESTON_BACKEND_PIPEWIRE },
 	{ "rdp", "rdp-backend.so", WESTON_BACKEND_RDP },
 	{ "vnc", "vnc-backend.so", WESTON_BACKEND_VNC },
 	{ "wayland", "wayland-backend.so", WESTON_BACKEND_WAYLAND },

compositor/main.c

@@ -60,6 +60,7 @@
 
 #include <libweston/backend-drm.h>
 #include <libweston/backend-headless.h>
+#include <libweston/backend-pipewire.h>
 #include <libweston/backend-rdp.h>
 #include <libweston/backend-vnc.h>
 #include <libweston/backend-x11.h>
@@ -658,6 +659,9 @@ usage(int error_code)
 #if defined(BUILD_HEADLESS_COMPOSITOR)
 			"\t\t\t\theadless\n"
 #endif
+#if defined(BUILD_PIPEWIRE_COMPOSITOR)
+			"\t\t\t\tpipewire\n"
+#endif
 #if defined(BUILD_RDP_COMPOSITOR)
 			"\t\t\t\trdp\n"
 #endif
@@ -721,6 +725,14 @@ usage(int error_code)
 		"\n");
 #endif
 
+#if defined(BUILD_PIPEWIRE_COMPOSITOR)
+	fprintf(out,
+		"Options for pipewire\n\n"
+		"  --width=WIDTH\t\tWidth of desktop\n"
+		"  --height=HEIGHT\tHeight of desktop\n"
+		"\n");
+#endif
+
 #if defined(BUILD_RDP_COMPOSITOR)
 	fprintf(out,
 		"Options for rdp:\n\n"
@@ -3071,6 +3083,98 @@ load_headless_backend(struct weston_compositor *c,
 	return 0;
 }
 
+static int
+pipewire_backend_output_configure(struct weston_output *output)
+{
+	struct wet_output_config defaults = {
+		.width = 640,
+		.height = 480,
+	};
+	struct wet_compositor *compositor = to_wet_compositor(output->compositor);
+	struct wet_output_config *parsed_options = compositor->parsed_options;
+	const struct weston_pipewire_output_api *api = weston_pipewire_output_get_api(output->compositor);
+	struct weston_config *wc = wet_get_config(output->compositor);
+	struct weston_config_section *section;
+	char *gbm_format = NULL;
+	int width;
+	int height;
+
+	assert(parsed_options);
+
+	if (!api) {
+		weston_log("Cannot use weston_pipewire_output_api.\n");
+		return -1;
+	}
+
+	section = weston_config_get_section(wc, "output", "name", output->name);
+
+	parse_simple_mode(output, section, &width, &height, &defaults,
+			  parsed_options);
+
+	if (section)
+		weston_config_section_get_string(section, "gbm-format",
+						 &gbm_format, NULL);
+
+	weston_output_set_scale(output, 1);
+	weston_output_set_transform(output, WL_OUTPUT_TRANSFORM_NORMAL);
+
+	api->set_gbm_format(output, gbm_format);
+	free(gbm_format);
+
+	if (api->output_set_size(output, width, height) < 0) {
+		weston_log("Cannot configure output \"%s\" using weston_pipewire_output_api.\n",
+			   output->name);
+		return -1;
+	}
+	weston_log("pipewire_backend_output_configure.. Done\n");
+
+	return 0;
+}
+
+static void
+weston_pipewire_backend_config_init(struct weston_pipewire_backend_config *config)
+{
+	config->base.struct_version = WESTON_PIPEWIRE_BACKEND_CONFIG_VERSION;
+	config->base.struct_size = sizeof(struct weston_pipewire_backend_config);
+}
+
+static int
+load_pipewire_backend(struct weston_compositor *c,
+		      int *argc, char *argv[], struct weston_config *wc,
+		      enum weston_renderer_type renderer)
+{
+	struct weston_pipewire_backend_config config = {{ 0, }};
+	struct weston_config_section *section;
+	struct wet_output_config *parsed_options = wet_init_parsed_options(c);
+
+	if (!parsed_options)
+		return -1;
+
+	weston_pipewire_backend_config_init(&config);
+
+	const struct weston_option pipewire_options[] = {
+		{ WESTON_OPTION_INTEGER, "width", 0, &parsed_options->width },
+		{ WESTON_OPTION_INTEGER, "height", 0, &parsed_options->height },
+	};
+
+	parse_options(pipewire_options, ARRAY_LENGTH(pipewire_options), argc, argv);
+
+	config.renderer = renderer;
+
+	wet_set_simple_head_configurator(c, pipewire_backend_output_configure);
+
+	section = weston_config_get_section(wc, "core", NULL, NULL);
+	weston_config_section_get_string(section, "gbm-format",
+					 &config.gbm_format, NULL);
+
+	section = weston_config_get_section(wc, "pipewire", NULL, NULL);
+	weston_config_section_get_int(section, "num-outputs",
+				      &config.num_outputs, 1);
+
+	return weston_compositor_load_backend(c, WESTON_BACKEND_PIPEWIRE,
+					      &config.base);
+}
+
 static void
 weston_rdp_backend_config_init(struct weston_rdp_backend_config *config)
 {
@@ -3608,6 +3712,9 @@ load_backend(struct weston_compositor *compositor, const char *name,
 	case WESTON_BACKEND_HEADLESS:
 		return load_headless_backend(compositor, argc, argv, config,
 					     renderer);
+	case WESTON_BACKEND_PIPEWIRE:
+		return load_pipewire_backend(compositor, argc, argv, config,
+					     renderer);
 	case WESTON_BACKEND_RDP:
 		return load_rdp_backend(compositor, argc, argv, config,
 					renderer);

include/libweston/backend-pipewire.h

@@ -0,0 +1,108 @@
+/*
+ * Copyright © 2021-2023 Philipp Zabel <p.zabel@pengutronix.de>
+ *
+ * Permission is hereby granted, free of charge, to any person obtaining
+ * a copy of this software and associated documentation files (the
+ * "Software"), to deal in the Software without restriction, including
+ * without limitation the rights to use, copy, modify, merge, publish,
+ * distribute, sublicense, and/or sell copies of the Software, and to
+ * permit persons to whom the Software is furnished to do so, subject to
+ * the following conditions:
+ *
+ * The above copyright notice and this permission notice (including the
+ * next paragraph) shall be included in all copies or substantial
+ * portions of the Software.
+ *
+ * THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND,
+ * EXPRESS OR IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF
+ * MERCHANTABILITY, FITNESS FOR A PARTICULAR PURPOSE AND
+ * NONINFRINGEMENT.  IN NO EVENT SHALL THE AUTHORS OR COPYRIGHT HOLDERS
+ * BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER LIABILITY, WHETHER IN AN
+ * ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM, OUT OF OR IN
+ * CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE
+ * SOFTWARE.
+ */
+
+#ifndef WESTON_COMPOSITOR_PIPEWIRE_H
+#define WESTON_COMPOSITOR_PIPEWIRE_H
+
+#ifdef  __cplusplus
+extern "C" {
+#endif
+
+#include <libweston/libweston.h>
+#include <libweston/plugin-registry.h>
+
+#define WESTON_PIPEWIRE_OUTPUT_API_NAME "weston_pipewire_output_api_v1"
+
+struct pipewire_config {
+	int32_t width;
+	int32_t height;
+	uint32_t framerate;
+};
+
+struct weston_pipewire_output_api {
+	/** Create a new PipeWire head.
+	 *
+	 * \param compositor The compositor instance.
+	 * \param name       Desired name for the new head
+	 * \param config     The pipewire_config of the new head.
+	 *
+	 * Returns 0 on success, -1 on failure.
+	 */
+	void (*head_create)(struct weston_compositor *compositor,
+			    const char *name,
+			    const struct pipewire_config *config);
+
+	/** Set the size of a PipeWire output to the specified width and height.
+	 *
+	 * If the width or height are set to -1, the size of the underlying
+	 * PipeWire head will be used.
+	 *
+	 * \param output     The weston output for which the size shall be set
+	 * \param width	     Desired width of the output
+	 * \param height     Desired height of the output
+	 *
+	 * Returns 0 on success, -1 on failure.
+	 */
+	int (*output_set_size)(struct weston_output *output,
+			       int width, int height);
+
+	/** The pixel format to be used by the output.
+	 *
+	 * \param output     The weston output for which the pixel format is set
+	 * \param gbm_format String representation of the pixel format
+	 *
+	 * Valid values for the gbm_format are:
+	 * - NULL - The format set at backend creation time will be used;
+	 * - "xrgb8888";
+	 * - "rgb565";
+	 */
+	void (*set_gbm_format)(struct weston_output *output,
+			       const char *gbm_format);
+};
+
+static inline const struct weston_pipewire_output_api *
+weston_pipewire_output_get_api(struct weston_compositor *compositor)
+{
+	const void *api;
+	api = weston_plugin_api_get(compositor, WESTON_PIPEWIRE_OUTPUT_API_NAME,
+				    sizeof(struct weston_pipewire_output_api));
+
+	return (const struct weston_pipewire_output_api *)api;
+}
+
+#define WESTON_PIPEWIRE_BACKEND_CONFIG_VERSION 1
+
+struct weston_pipewire_backend_config {
+	struct weston_backend_config base;
+	enum weston_renderer_type renderer;
+	char *gbm_format;
+	int32_t num_outputs;
+};
+
+#ifdef  __cplusplus
+}
+#endif
+
+#endif /* WESTON_COMPOSITOR_PIPEWIRE_H */

include/libweston/libweston.h

@@ -2252,6 +2252,7 @@ weston_compositor_add_destroy_listener_once(struct weston_compositor *compositor
 enum weston_compositor_backend {
 	WESTON_BACKEND_DRM,
 	WESTON_BACKEND_HEADLESS,
+	WESTON_BACKEND_PIPEWIRE,
 	WESTON_BACKEND_RDP,
 	WESTON_BACKEND_VNC,
 	WESTON_BACKEND_WAYLAND,

include/libweston/meson.build

@@ -15,6 +15,7 @@ install_headers(
 
 backend_drm_h =      files('backend-drm.h')
 backend_headless_h = files('backend-headless.h')
+backend_pipewire_h = files('backend-pipewire.h')
 backend_rdp_h =      files('backend-rdp.h')
 backend_vnc_h =      files('backend-vnc.h')
 backend_wayland_h =  files('backend-wayland.h')

libweston/backend-pipewire/meson.build

@@ -0,0 +1,35 @@
+if not get_option('backend-pipewire')
+	subdir_done()
+endif
+user_hint = 'If you rather not build this, set \'-Dbackend-pipewire=false\'.'
+
+config_h.set('BUILD_PIPEWIRE_COMPOSITOR', '1')
+
+dep_libpipewire = dependency('libpipewire-0.3', required: false)
+if not dep_libpipewire.found()
+	error('PipeWire backend requires libpipewire 0.3 which was not found. ' + user_hint)
+endif
+
+dep_libspa = dependency('libspa-0.2', required: false)
+if not dep_libspa.found()
+	error('Pipewire plugin requires libspa 0.2 which was not found. ' + user_hint)
+endif
+
+deps_pipewire = [
+	dep_libweston_private,
+	dep_libpipewire,
+	dep_libspa,
+	dep_libdrm_headers,
+]
+
+plugin_pipewire = shared_library(
+	'pipewire-backend',
+	[ 'pipewire.c' ],
+	include_directories: common_inc,
+	dependencies: deps_pipewire,
+	name_prefix: '',
+	install: true,
+	install_dir: dir_module_libweston
+)
+env_modmap += 'pipewire-backend.so=@0@;'.format(plugin_pipewire.full_path())
+install_headers(backend_pipewire_h, subdir: dir_include_libweston_install)

libweston/compositor.c

@@ -9024,6 +9024,7 @@ weston_compositor_get_user_data(struct weston_compositor *compositor)
 static const char * const backend_map[] = {
 	[WESTON_BACKEND_DRM] =		"drm-backend.so",
 	[WESTON_BACKEND_HEADLESS] =	"headless-backend.so",
+	[WESTON_BACKEND_PIPEWIRE] =	"pipewire-backend.so",
 	[WESTON_BACKEND_RDP] =		"rdp-backend.so",
 	[WESTON_BACKEND_VNC] =		"vnc-backend.so",
 	[WESTON_BACKEND_WAYLAND] =	"wayland-backend.so",

libweston/meson.build

@@ -268,6 +268,7 @@ subdir('color-lcms')
 subdir('renderer-gl')
 subdir('backend-drm')
 subdir('backend-headless')
+subdir('backend-pipewire')
 subdir('backend-rdp')
 subdir('backend-vnc')
 subdir('backend-wayland')

meson_options.txt

@@ -20,6 +20,12 @@ option(
 	value: true,
 	description: 'Weston backend: headless (testing)'
 )
+option(
+	'backend-pipewire',
+	type: 'boolean',
+	value: true,
+	description: 'PipeWire backend: screencasting via PipeWire'
+)
 option(
 	'backend-rdp',
 	type: 'boolean',