add minimalist cairo example

examples/cairo-buffer.c

@@ -0,0 +1,194 @@
+#define _POSIX_C_SOURCE 200112L
+
+#include <stdbool.h>
+#include <stdlib.h>
+#include <time.h>
+#include <cairo.h>
+#include <drm_fourcc.h>
+#include <wayland-server-core.h>
+#include <wlr/backend.h>
+#include <wlr/render/allocator.h>
+#include <wlr/render/wlr_renderer.h>
+#include <wlr/types/wlr_output.h>
+#include <wlr/types/wlr_scene.h>
+#include <wlr/util/log.h>
+#include <wlr/interfaces/wlr_buffer.h>
+
+/* Simple scene-graph example with a custom buffer drawn by Cairo.
+ *
+ * Input is unimplemented. Surfaces are unimplemented. */
+
+struct cairo_buffer {
+	struct wlr_buffer base;
+	cairo_surface_t *surface;
+};
+
+static void cairo_buffer_destroy(struct wlr_buffer *wlr_buffer) {
+	struct cairo_buffer *buffer = wl_container_of(wlr_buffer, buffer, base);
+	cairo_surface_destroy(buffer->surface);
+	free(buffer);
+}
+
+static bool cairo_buffer_begin_data_ptr_access(struct wlr_buffer *wlr_buffer,
+		uint32_t flags, void **data, uint32_t *format, size_t *stride) {
+	struct cairo_buffer *buffer = wl_container_of(wlr_buffer, buffer, base);
+
+	if (flags & WLR_BUFFER_DATA_PTR_ACCESS_WRITE) {
+		return false;
+	}
+
+	*format = DRM_FORMAT_ARGB8888;
+	*data = cairo_image_surface_get_data(buffer->surface);
+	*stride = cairo_image_surface_get_stride(buffer->surface);
+	return true;
+}
+
+static void cairo_buffer_end_data_ptr_access(struct wlr_buffer *wlr_buffer) {
+}
+
+static const struct wlr_buffer_impl cairo_buffer_impl = {
+	.destroy = cairo_buffer_destroy,
+	.begin_data_ptr_access = cairo_buffer_begin_data_ptr_access,
+	.end_data_ptr_access = cairo_buffer_end_data_ptr_access
+};
+
+static struct cairo_buffer *create_cairo_buffer(int width, int height) {
+	struct cairo_buffer *buffer = calloc(1, sizeof(*buffer));
+	if (!buffer) {
+		return NULL;
+	}
+
+	wlr_buffer_init(&buffer->base, &cairo_buffer_impl, width, height);
+
+	buffer->surface = cairo_image_surface_create(CAIRO_FORMAT_ARGB32,
+			width, height);
+	if (cairo_surface_status(buffer->surface) != CAIRO_STATUS_SUCCESS) {
+		free(buffer);
+		return NULL;
+	}
+
+	return buffer;
+}
+
+struct server {
+	struct wl_display *display;
+	struct wlr_backend *backend;
+	struct wlr_renderer *renderer;
+	struct wlr_allocator *allocator;
+	struct wlr_scene *scene;
+
+	struct wl_listener new_output;
+};
+
+struct output {
+	struct wl_list link;
+	struct server *server;
+	struct wlr_output *wlr;
+	struct wlr_scene_output *scene_output;
+
+	struct wl_listener frame;
+};
+
+static void output_handle_frame(struct wl_listener *listener, void *data) {
+	struct output *output = wl_container_of(listener, output, frame);
+
+	wlr_scene_output_commit(output->scene_output, NULL);
+}
+
+static void server_handle_new_output(struct wl_listener *listener, void *data) {
+	struct server *server = wl_container_of(listener, server, new_output);
+	struct wlr_output *wlr_output = data;
+
+	wlr_output_init_render(wlr_output, server->allocator, server->renderer);
+
+	struct output *output = calloc(1, sizeof(struct output));
+	output->wlr = wlr_output;
+	output->server = server;
+	output->frame.notify = output_handle_frame;
+	wl_signal_add(&wlr_output->events.frame, &output->frame);
+
+	output->scene_output = wlr_scene_output_create(server->scene, wlr_output);
+
+	struct wlr_output_state state;
+	wlr_output_state_init(&state);
+	wlr_output_state_set_enabled(&state, true);
+	struct wlr_output_mode *mode = wlr_output_preferred_mode(wlr_output);
+	if (mode != NULL) {
+		wlr_output_state_set_mode(&state, mode);
+	}
+	wlr_output_commit_state(wlr_output, &state);
+	wlr_output_state_finish(&state);
+}
+
+int main(void) {
+	wlr_log_init(WLR_DEBUG, NULL);
+
+	struct server server = {0};
+	server.display = wl_display_create();
+	server.backend = wlr_backend_autocreate(server.display, NULL);
+	server.scene = wlr_scene_create();
+
+	server.renderer = wlr_renderer_autocreate(server.backend);
+	wlr_renderer_init_wl_display(server.renderer, server.display);
+
+	server.allocator = wlr_allocator_autocreate(server.backend,
+			server.renderer);
+
+	server.new_output.notify = server_handle_new_output;
+	wl_signal_add(&server.backend->events.new_output, &server.new_output);
+
+	if (!wlr_backend_start(server.backend)) {
+		wl_display_destroy(server.display);
+		return EXIT_FAILURE;
+	}
+
+	struct cairo_buffer *buffer = create_cairo_buffer(256, 256);
+	if (!buffer) {
+		wl_display_destroy(server.display);
+		return EXIT_FAILURE;
+	}
+
+	/* Begin drawing
+	 * From cairo samples at https://www.cairographics.org/samples/ */
+	cairo_t *cr = cairo_create(buffer->surface);
+	cairo_set_source_rgb(cr, 1, 1, 1);
+	cairo_paint(cr);
+	cairo_set_source_rgb(cr, 0, 0, 0);
+
+	double x = 25.6, y = 128.0;
+	double x1 = 102.4, y1 = 230.4,
+			x2 = 153.6, y2 = 25.6,
+			x3 = 230.4, y3 = 128.0;
+
+	cairo_move_to(cr, x, y);
+	cairo_curve_to(cr, x1, y1, x2, y2, x3, y3);
+
+	cairo_set_line_width(cr, 10.0);
+	cairo_stroke(cr);
+
+	cairo_set_source_rgba(cr, 1, 0.2, 0.2, 0.6);
+	cairo_set_line_width(cr, 6.0);
+	cairo_move_to(cr, x, y);
+	cairo_line_to(cr, x1, y1);
+	cairo_move_to(cr, x2, y2);
+	cairo_line_to(cr, x3, y3);
+	cairo_stroke(cr);
+
+	cairo_destroy(cr);
+	/* End drawing */
+
+	struct wlr_scene_buffer *scene_buffer = wlr_scene_buffer_create(
+			&server.scene->tree, &buffer->base);
+	if (!scene_buffer) {
+		wl_display_destroy(server.display);
+		return EXIT_FAILURE;
+	}
+
+	wlr_scene_node_set_position(&scene_buffer->node, 50, 50);
+	wlr_buffer_drop(&buffer->base);
+
+	wl_display_run(server.display);
+
+	wl_display_destroy(server.display);
+	return EXIT_SUCCESS;
+}

examples/meson.build

@@ -6,6 +6,7 @@ libpng = dependency('libpng', required: false, disabler: true)
 egl = dependency('egl', required: false, disabler: true)
 glesv2 = dependency('glesv2', required: false, disabler: true)
 gbm = dependency('gbm', required: false, disabler: true)
+cairo = dependency('cairo', required: false, disabler: true)
 # These versions correspond to ffmpeg 4.0
 libavutil = dependency('libavutil', version: '>=56.14.100', required: false, disabler: true)
 libavcodec = dependency('libavcodec', version: '>=58.18.100', required: false, disabler: true)
@@ -57,6 +58,10 @@ compositors = {
 			'xdg-shell',
 		],
 	},
+	'cairo-buffer': {
+		'src': 'cairo-buffer.c',
+		'dep': cairo,
+	},
 }
 
 clients = {
@@ -199,7 +204,7 @@ foreach name, info : compositors
 	executable(
 		name,
 		[info.get('src'), extra_src],
-		dependencies: [wlroots, libdrm],
+		dependencies: [wlroots, libdrm, info.get('dep', [])],
 		build_by_default: get_option('examples'),
 	)
 endforeach