Simplify examples

5 files changed, 349 insertions, 405 deletions

diff --git a/example/CMakeLists.txt b/example/CMakeLists.txt
index bf9efd64..f659e5bb 100644
--- a/example/CMakeLists.txt
+++ b/example/CMakeLists.txt
@@ -6,6 +6,7 @@ include_directories(
 
 add_executable(simple
     simple.c
+    shared.c
 )
 
 target_link_libraries(simple
@@ -16,6 +17,7 @@ target_link_libraries(simple
 
 add_executable(rotation
     rotation.c
+    shared.c
     cat.c
 )
 
diff --git a/example/rotation.c b/example/rotation.c
index 24c9f494..2634ea03 100644
--- a/example/rotation.c
+++ b/example/rotation.c
@@ -16,32 +16,17 @@
 #include <wlr/session.h>
 #include <wlr/types.h>
 #include <math.h>
+#include "shared.h"
 #include "cat.h"
 
-struct state {
+struct sample_state {
 	struct wl_list config;
-	struct xkb_keymap *keymap;
-	struct xkb_state *xkb_state;
-	bool exit;
-
-	struct wl_list keyboards;
-	struct wl_listener input_add;
-	struct wl_listener input_remove;
-
-	struct wl_list outputs;
-	struct wl_listener output_add;
-	struct wl_listener output_remove;
-
+	// TODO: Move renderer into shared
 	struct wlr_renderer *renderer;
 	struct wlr_surface *cat_texture;
 };
 
-struct output_state {
-	struct timespec last_frame;
-	struct wl_list link;
-	struct wlr_output *output;
-	struct state *state;
-	struct wl_listener frame;
+struct output_data {
 	float x_offs, y_offs;
 	float x_vel, y_vel;
 };
@@ -52,176 +37,93 @@ struct output_config {
 	struct wl_list link;
 };
 
-struct keyboard_state {
-	struct state *state;
-	struct wlr_input_device *device;
-	struct wl_listener key;
-	struct wl_list link;
-};
-
-static void output_frame(struct wl_listener *listener, void *data) {
-	struct output_state *ostate = wl_container_of(listener, ostate, frame);
-	struct wlr_output *output = ostate->output;
-	struct state *s = ostate->state;
+static void handle_output_frame(struct output_state *output, struct timespec *ts) {
+	struct compositor_state *state = output->compositor;
+	struct sample_state *sample = state->data;
+	struct output_data *odata = output->data;
+	struct wlr_output *wlr_output = output->output;
 
 	int32_t width, height;
-	wlr_output_effective_resolution(output, &width, &height);
+	wlr_output_effective_resolution(wlr_output, &width, &height);
 
-	wlr_renderer_begin(s->renderer, output);
+	wlr_renderer_begin(sample->renderer, wlr_output);
 
 	float matrix[16];
-	for (int y = -128 + (int)ostate->y_offs; y < height; y += 128) {
-		for (int x = -128 + (int)ostate->x_offs; x < width; x += 128) {
-			wlr_surface_get_matrix(s->cat_texture, &matrix,
-				&output->transform_matrix, x, y);
-			wlr_render_with_matrix(s->renderer, s->cat_texture, &matrix);
+	for (int y = -128 + (int)odata->y_offs; y < height; y += 128) {
+		for (int x = -128 + (int)odata->x_offs; x < width; x += 128) {
+			wlr_surface_get_matrix(sample->cat_texture, &matrix,
+				&wlr_output->transform_matrix, x, y);
+			wlr_render_with_matrix(sample->renderer,
+					sample->cat_texture, &matrix);
 		}
 	}
 
-	wlr_renderer_end(s->renderer);
+	wlr_renderer_end(sample->renderer);
 
-	struct timespec now;
-	clock_gettime(CLOCK_MONOTONIC, &now);
-	long ms = (now.tv_sec - ostate->last_frame.tv_sec) * 1000 +
-		(now.tv_nsec - ostate->last_frame.tv_nsec) / 1000000;
+	long ms = (ts->tv_sec - output->last_frame.tv_sec) * 1000 +
+		(ts->tv_nsec - output->last_frame.tv_nsec) / 1000000;
 	float seconds = ms / 1000.0f;
 
-	ostate->x_offs += ostate->x_vel * seconds;
-	ostate->y_offs += ostate->y_vel * seconds;
-	if (ostate->x_offs > 128) ostate->x_offs = 0;
-	if (ostate->y_offs > 128) ostate->y_offs = 0;
-	ostate->last_frame = now;
+	odata->x_offs += odata->x_vel * seconds;
+	odata->y_offs += odata->y_vel * seconds;
+	if (odata->x_offs > 128) odata->x_offs = 0;
+	if (odata->y_offs > 128) odata->y_offs = 0;
 }
 
-static void output_add(struct wl_listener *listener, void *data) {
-	struct wlr_output *output = data;
-	struct state *state = wl_container_of(listener, state, output_add);
-
-	fprintf(stderr, "Output '%s' added\n", output->name);
-	wlr_output_set_mode(output, output->modes->items[0]);
-
-	struct output_state *ostate = calloc(1, sizeof(struct output_state));
-
-	clock_gettime(CLOCK_MONOTONIC, &ostate->last_frame);
-	ostate->output = output;
-	ostate->state = state;
-	ostate->frame.notify = output_frame;
-	ostate->x_offs = ostate->y_offs = 0;
-	ostate->x_vel = ostate->y_vel = 128;
+static void handle_output_add(struct output_state *output) {
+	struct output_data *odata = calloc(1, sizeof(struct output_data));
+	odata->x_offs = odata->y_offs = 0;
+	odata->x_vel = odata->y_vel = 128;
+	output->data = odata;
+	struct sample_state *state = output->compositor->data;
 
 	struct output_config *conf;
 	wl_list_for_each(conf, &state->config, link) {
-		if (strcmp(conf->name, output->name) == 0) {
-			wlr_output_transform(ostate->output, conf->transform);
+		if (strcmp(conf->name, output->output->name) == 0) {
+			wlr_output_transform(output->output, conf->transform);
 			break;
 		}
 	}
-
-	wl_list_init(&ostate->frame.link);
-	wl_signal_add(&output->events.frame, &ostate->frame);
-	wl_list_insert(&state->outputs, &ostate->link);
 }
 
-static void output_remove(struct wl_listener *listener, void *data) {
-	struct wlr_output *output = data;
-	struct state *state = wl_container_of(listener, state, output_remove);
-	struct output_state *ostate;
-
-	wl_list_for_each(ostate, &state->outputs, link) {
-		if (ostate->output == output) {
-			wl_list_remove(&ostate->link);
-			wl_list_remove(&ostate->frame.link);
-			free(ostate);
-			break;
-		}
-	}
+static void handle_output_remove(struct output_state *output) {
+	free(output->data);
 }
 
-static void update_velocities(struct state *state, float x_diff, float y_diff) {
-	struct output_state *ostate;
-	wl_list_for_each(ostate, &state->outputs, link) {
-		ostate->x_vel += x_diff;
-		ostate->y_vel += y_diff;
+static void update_velocities(struct compositor_state *state,
+		float x_diff, float y_diff) {
+	struct output_state *output;
+	wl_list_for_each(output, &state->outputs, link) {
+		struct output_data *odata = output->data;
+		odata->x_vel += x_diff;
+		odata->y_vel += y_diff;
 	}
 }
 
-static void handle_keysym(struct state *state, xkb_keysym_t sym,
-		enum wlr_key_state key_state) {
-	char name[64];
-	int l = xkb_keysym_get_name(sym, name, sizeof(name));
-	if (l != -1 && l != sizeof(name)) {
-		fprintf(stderr, "Key event: %s %s\n", name,
-				key_state == WLR_KEY_PRESSED ? "pressed" : "released");
-	}
+static void handle_keyboard_key(struct keyboard_state *kbstate,
+		xkb_keysym_t sym, enum wlr_key_state key_state) {
 	// NOTE: It may be better to simply refer to our key state during each frame
 	// and make this change in pixels/sec^2
+	// Also, key repeat
 	if (key_state == WLR_KEY_PRESSED) {
 		switch (sym) {
 		case XKB_KEY_Escape:
-			state->exit = true;
+			kbstate->compositor->exit = true;
 			break;
 		case XKB_KEY_Left:
-			update_velocities(state, -16, 0);
+			update_velocities(kbstate->compositor, -16, 0);
 			break;
 		case XKB_KEY_Right:
-			update_velocities(state, 16, 0);
+			update_velocities(kbstate->compositor, 16, 0);
 			break;
 		case XKB_KEY_Up:
-			update_velocities(state, 0, -16);
+			update_velocities(kbstate->compositor, 0, -16);
 			break;
 		case XKB_KEY_Down:
-			update_velocities(state, 0, 16);
-			break;
-		}
-	}
-}
-
-static void keyboard_key(struct wl_listener *listener, void *data) {
-	struct wlr_keyboard_key *event = data;
-	struct keyboard_state *kbstate = wl_container_of(listener, kbstate, key);
-	uint32_t keycode = event->keycode + 8;
-	const xkb_keysym_t *syms;
-	int nsyms = xkb_state_key_get_syms(kbstate->state->xkb_state, keycode, &syms);
-	for (int i = 0; i < nsyms; ++i) {
-		handle_keysym(kbstate->state, syms[i], event->state);
-	}
-	xkb_state_update_key(kbstate->state->xkb_state, keycode,
-		event->state == WLR_KEY_PRESSED ?  XKB_KEY_DOWN : XKB_KEY_UP);
-}
-
-void input_add(struct wl_listener *listener, void *data) {
-	struct wlr_input_device *device = data;
-	struct state *state = wl_container_of(listener, state, input_add);
-	if (device->type != WLR_INPUT_DEVICE_KEYBOARD) {
-		return;
-	}
-	struct keyboard_state *kbstate = calloc(sizeof(struct keyboard_state), 1);
-	kbstate->device = device;
-	kbstate->state = state;
-	wl_list_init(&kbstate->key.link);
-	kbstate->key.notify = keyboard_key;
-	wl_signal_add(&device->keyboard->events.key, &kbstate->key);
-	wl_list_insert(&state->keyboards, &kbstate->link);
-}
-
-void input_remove(struct wl_listener *listener, void *data) {
-	struct wlr_input_device *device = data;
-	struct state *state = wl_container_of(listener, state, input_add);
-	if (device->type != WLR_INPUT_DEVICE_KEYBOARD) {
-		return;
-	}
-	struct keyboard_state *kbstate = NULL, *_kbstate;
-	wl_list_for_each(_kbstate, &state->keyboards, link) {
-		if (_kbstate->device == device) {
-			kbstate = kbstate;
+			update_velocities(kbstate->compositor, 0, 16);
 			break;
 		}
 	}
-	if (!kbstate) {
-		return; // We are unfamiliar with this keyboard
-	}
-	wl_list_remove(&kbstate->link);
-	wl_list_remove(&kbstate->key.link);
 }
 
 static void usage(const char *name, int ret) {
@@ -291,82 +193,27 @@ static void parse_args(int argc, char *argv[], struct wl_list *config) {
 }
 
 int main(int argc, char *argv[]) {
-	struct state state = {
-		.exit = false,
-		.input_add = { .notify = input_add },
-		.input_remove = { .notify = input_remove },
-		.output_add = { .notify = output_add },
-		.output_remove = { .notify = output_remove }
-	};
-
-	struct xkb_rule_names rules;
-	memset(&rules, 0, sizeof(rules));
-	rules.rules = getenv("XKB_DEFAULT_RULES");
-	rules.model = getenv("XKB_DEFAULT_MODEL");
-	rules.layout = getenv("XKB_DEFAULT_LAYOUT");
-	rules.variant = getenv("XKB_DEFAULT_VARIANT");
-	rules.options = getenv("XKB_DEFAULT_OPTIONS");
-	struct xkb_context *context = xkb_context_new(XKB_CONTEXT_NO_FLAGS);
-	if (!context) {
-		fprintf(stderr, "Failed to create XKB context\n");
-		return 1;
-	}
-	state.keymap =
-		xkb_map_new_from_names(context, &rules, XKB_KEYMAP_COMPILE_NO_FLAGS);
-	if (!state.keymap) {
-		fprintf(stderr, "Failed to create XKB keymap\n");
-		return 1;
-	}
-	xkb_context_unref(context);
-	state.xkb_state = xkb_state_new(state.keymap);
-
-	wl_list_init(&state.keyboards);
-	wl_list_init(&state.input_add.link);
-	wl_list_init(&state.input_remove.link);
-
-	wl_list_init(&state.outputs);
+	struct sample_state state = { 0 };
+	struct compositor_state compositor;
 	wl_list_init(&state.config);
-	wl_list_init(&state.output_add.link);
-	wl_list_init(&state.output_remove.link);
-
 	parse_args(argc, argv, &state.config);
 
-	struct wl_display *display = wl_display_create();
-	struct wl_event_loop *event_loop = wl_display_get_event_loop(display);
-
-	struct wlr_session *session = wlr_session_start(display);
-	if (!session) {
-		return 1;
-	}
-
-	struct wlr_backend *wlr = wlr_backend_autocreate(display, session);
-	if (!wlr) {
-		return 1;
-	}
-
-	wl_signal_add(&wlr->events.input_add, &state.input_add);
-	wl_signal_add(&wlr->events.input_remove, &state.input_remove);
-	wl_signal_add(&wlr->events.output_add, &state.output_add);
-	wl_signal_add(&wlr->events.output_remove, &state.output_remove);
-	if (!wlr || !wlr_backend_init(wlr)) {
-		printf("Failed to initialize backend, bailing out\n");
-		return 1;
-	}
+	compositor_init(&compositor);
+	compositor.output_add_cb = handle_output_add;
+	compositor.output_remove_cb = handle_output_remove;
+	compositor.output_frame_cb = handle_output_frame;
+	compositor.keyboard_key_cb = handle_keyboard_key;
 
 	state.renderer = wlr_gles3_renderer_init();
 	state.cat_texture = wlr_render_surface_init(state.renderer);
 	wlr_surface_attach_pixels(state.cat_texture, GL_RGB,
 		cat_tex.width, cat_tex.height, cat_tex.pixel_data);
 
-	while (!state.exit) {
-		wl_event_loop_dispatch(event_loop, 0);
-	}
+	compositor.data = &state;
+	compositor_run(&compositor);
 
-	wlr_backend_destroy(wlr);
-	wlr_session_finish(session);
 	wlr_surface_destroy(state.cat_texture);
 	wlr_renderer_destroy(state.renderer);
-	wl_display_destroy(display);
 
 	struct output_config *ptr, *tmp;
 	wl_list_for_each_safe(ptr, tmp, &state.config, link) {
diff --git a/example/shared.c b/example/shared.c
new file mode 100644
index 00000000..58266214
--- /dev/null
+++ b/example/shared.c
@@ -0,0 +1,203 @@
+#define _POSIX_C_SOURCE 199309L
+#include <string.h>
+#include <stdlib.h>
+#include <time.h>
+#include <stdlib.h>
+#include <stdio.h>
+#include <stdbool.h>
+#include <xkbcommon/xkbcommon.h>
+#include <wayland-server-protocol.h>
+#include <wlr/backend.h>
+#include <wlr/session.h>
+#include <wlr/types.h>
+#include "shared.h"
+
+static void keyboard_key_notify(struct wl_listener *listener, void *data) {
+	struct wlr_keyboard_key *event = data;
+	struct keyboard_state *kbstate = wl_container_of(listener, kbstate, key);
+	uint32_t keycode = event->keycode + 8;
+	enum wlr_key_state key_state = event->state;
+	const xkb_keysym_t *syms;
+	int nsyms = xkb_state_key_get_syms(kbstate->xkb_state, keycode, &syms);
+	for (int i = 0; i < nsyms; ++i) {
+		xkb_keysym_t sym = syms[i];
+		char name[64];
+		int l = xkb_keysym_get_name(sym, name, sizeof(name));
+		if (l != -1 && l != sizeof(name)) {
+			fprintf(stderr, "Key event: %s %s\n", name,
+					key_state == WLR_KEY_PRESSED ? "pressed" : "released");
+		}
+		if (kbstate->compositor->keyboard_key_cb) {
+			kbstate->compositor->keyboard_key_cb(kbstate, sym, key_state);
+		}
+	}
+	xkb_state_update_key(kbstate->xkb_state, keycode,
+		event->state == WLR_KEY_PRESSED ?  XKB_KEY_DOWN : XKB_KEY_UP);
+}
+
+static void input_add_notify(struct wl_listener *listener, void *data) {
+	struct wlr_input_device *device = data;
+	struct compositor_state *state = wl_container_of(listener, state, input_add);
+	if (device->type != WLR_INPUT_DEVICE_KEYBOARD) {
+		return;
+	}
+	struct keyboard_state *kbstate = calloc(sizeof(struct keyboard_state), 1);
+	kbstate->device = device;
+	kbstate->compositor = state;
+	wl_list_init(&kbstate->key.link);
+	kbstate->key.notify = keyboard_key_notify;
+	wl_signal_add(&device->keyboard->events.key, &kbstate->key);
+	wl_list_insert(&state->keyboards, &kbstate->link);
+
+	struct xkb_rule_names rules;
+	memset(&rules, 0, sizeof(rules));
+	rules.rules = getenv("XKB_DEFAULT_RULES");
+	rules.model = getenv("XKB_DEFAULT_MODEL");
+	rules.layout = getenv("XKB_DEFAULT_LAYOUT");
+	rules.variant = getenv("XKB_DEFAULT_VARIANT");
+	rules.options = getenv("XKB_DEFAULT_OPTIONS");
+	struct xkb_context *context = xkb_context_new(XKB_CONTEXT_NO_FLAGS);
+	if (!context) {
+		fprintf(stderr, "Failed to create XKB context\n");
+		exit(1);
+	}
+	kbstate->keymap = xkb_map_new_from_names(
+			context, &rules, XKB_KEYMAP_COMPILE_NO_FLAGS);
+	if (!kbstate->keymap) {
+		fprintf(stderr, "Failed to create XKB keymap\n");
+		exit(1);
+	}
+	xkb_context_unref(context);
+	kbstate->xkb_state = xkb_state_new(kbstate->keymap);
+	if (!kbstate->xkb_state) {
+		fprintf(stderr, "Failed to create XKB state\n");
+		exit(1);
+	}
+}
+
+static void input_remove_notify(struct wl_listener *listener, void *data) {
+	struct wlr_input_device *device = data;
+	struct compositor_state *state = wl_container_of(listener, state, input_add);
+	if (device->type != WLR_INPUT_DEVICE_KEYBOARD) {
+		return;
+	}
+	struct keyboard_state *kbstate = NULL, *_kbstate;
+	wl_list_for_each(_kbstate, &state->keyboards, link) {
+		if (_kbstate->device == device) {
+			kbstate = kbstate;
+			break;
+		}
+	}
+	if (!kbstate) {
+		return; // We are unfamiliar with this keyboard
+	}
+	wl_list_remove(&kbstate->link);
+	wl_list_remove(&kbstate->key.link);
+}
+
+static void output_frame_notify(struct wl_listener *listener, void *data) {
+	struct output_state *output = wl_container_of(listener, output, frame);
+	struct compositor_state *compositor = output->compositor;
+
+	struct timespec now;
+	clock_gettime(CLOCK_MONOTONIC, &now);
+	if (compositor->output_frame_cb) {
+		compositor->output_frame_cb(output, &now);
+	}
+
+	output->last_frame = now;
+	compositor->last_frame = now;
+}
+
+static void output_add_notify(struct wl_listener *listener, void *data) {
+	struct wlr_output *output = data;
+	struct compositor_state *state = wl_container_of(listener, state, output_add);
+	fprintf(stderr, "Output '%s' added\n", output->name);
+	fprintf(stderr, "%s %s %"PRId32"mm x %"PRId32"mm\n", output->make, output->model,
+		output->phys_width, output->phys_height);
+	wlr_output_set_mode(output, output->modes->items[0]);
+	struct output_state *ostate = calloc(1, sizeof(struct output_state));
+	clock_gettime(CLOCK_MONOTONIC, &ostate->last_frame);
+	ostate->output = output;
+	ostate->compositor = state;
+	ostate->frame.notify = output_frame_notify;
+	wl_list_init(&ostate->frame.link);
+	wl_signal_add(&output->events.frame, &ostate->frame);
+	wl_list_insert(&state->outputs, &ostate->link);
+	if (state->output_add_cb) {
+		state->output_add_cb(ostate);
+	}
+}
+
+static void output_remove_notify(struct wl_listener *listener, void *data) {
+	struct wlr_output *output = data;
+	struct compositor_state *state = wl_container_of(listener, state, output_remove);
+	struct output_state *ostate = NULL, *_ostate;
+	wl_list_for_each(_ostate, &state->outputs, link) {
+		if (_ostate->output == output) {
+			ostate = _ostate;
+			break;
+		}
+	}
+	if (!ostate) {
+		return; // We are unfamiliar with this output
+	}
+	if (state->output_remove_cb) {
+		state->output_remove_cb(ostate);
+	}
+	wl_list_remove(&ostate->link);
+	wl_list_remove(&ostate->frame.link);
+}
+
+void compositor_init(struct compositor_state *state) {
+	memset(state, 0, sizeof(struct compositor_state));
+
+	state->display = wl_display_create();
+	state->event_loop = wl_display_get_event_loop(state->display);
+	state->session = wlr_session_start(state->display);
+	if (!state->session
+			|| !state->display
+			|| !state->event_loop) {
+		exit(1);
+	}
+
+	wl_list_init(&state->keyboards);
+	wl_list_init(&state->input_add.link);
+	state->input_add.notify = input_add_notify;
+	wl_list_init(&state->input_remove.link);
+	state->input_remove.notify = input_remove_notify;
+
+	wl_list_init(&state->outputs);
+	wl_list_init(&state->output_add.link);
+	state->output_add.notify = output_add_notify;
+	wl_list_init(&state->output_remove.link);
+	state->output_remove.notify = output_remove_notify;
+
+	struct wlr_backend *wlr = wlr_backend_autocreate(
+			state->display, state->session);
+	if (!wlr) {
+		exit(1);
+	}
+	wl_signal_add(&wlr->events.input_add, &state->input_add);
+	wl_signal_add(&wlr->events.input_remove, &state->input_remove);
+	wl_signal_add(&wlr->events.output_add, &state->output_add);
+	wl_signal_add(&wlr->events.output_remove, &state->output_remove);
+	state->backend = wlr;
+
+	clock_gettime(CLOCK_MONOTONIC, &state->last_frame);
+}
+
+void compositor_run(struct compositor_state *state) {
+	if (!wlr_backend_init(state->backend)) {
+		fprintf(stderr, "Failed to initialize backend\n");
+		exit(1);
+	}
+
+	while (!state->exit) {
+		wl_event_loop_dispatch(state->event_loop, 0);
+	}
+
+	wlr_backend_destroy(state->backend);
+	wlr_session_finish(state->session);
+	wl_display_destroy(state->display);
+}
diff --git a/example/shared.h b/example/shared.h
new file mode 100644
index 00000000..bafbee16
--- /dev/null
+++ b/example/shared.h
@@ -0,0 +1,61 @@
+#ifndef _EXAMPLE_SHARED_H
+#define _EXAMPLE_SHARED_H
+#define _POSIX_C_SOURCE 199309L
+#include <time.h>
+#include <stdbool.h>
+#include <xkbcommon/xkbcommon.h>
+#include <wayland-server-protocol.h>
+#include <wlr/backend.h>
+#include <wlr/session.h>
+#include <wlr/types.h>
+
+struct output_state {
+	struct compositor_state *compositor;
+	struct wlr_output *output;
+	struct wl_listener frame;
+	struct timespec last_frame;
+	struct wl_list link;
+	void *data;
+};
+
+struct keyboard_state {
+	struct compositor_state *compositor;
+	struct wlr_input_device *device;
+	struct wl_listener key;
+	struct wl_list link;
+	struct xkb_keymap *keymap;
+	struct xkb_state *xkb_state;
+	void *data;
+};
+
+struct compositor_state {
+	void (*output_add_cb)(struct output_state *s);
+	void (*keyboard_add_cb)(struct keyboard_state *s);
+	void (*output_frame_cb)(struct output_state *s, struct timespec *ts);
+	void (*output_remove_cb)(struct output_state *s);
+	void (*keyboard_remove_cb)(struct keyboard_state *s);
+	void (*keyboard_key_cb)(struct keyboard_state *s, xkb_keysym_t sym,
+			enum wlr_key_state key_state);
+
+	struct wl_display *display;
+	struct wl_event_loop *event_loop;
+	struct wlr_backend *backend;
+	struct wlr_session *session;
+
+	struct wl_list keyboards;
+	struct wl_listener input_add;
+	struct wl_listener input_remove;
+
+	struct timespec last_frame;
+	struct wl_listener output_add;
+	struct wl_listener output_remove;
+	struct wl_list outputs;
+
+	bool exit;
+	void *data;
+};
+
+void compositor_init(struct compositor_state *state);
+void compositor_run(struct compositor_state *state);
+
+#endif
diff --git a/example/simple.c b/example/simple.c
index 331a0d08..5a5a1300 100644
--- a/example/simple.c
+++ b/example/simple.c
@@ -10,220 +10,51 @@
 #include <wlr/session.h>
 #include <wlr/types.h>
 #include <xkbcommon/xkbcommon.h>
+#include "shared.h"
 
-struct state {
+struct sample_state {
 	float color[3];
 	int dec;
-	bool exit;
-	struct timespec last_frame;
-	struct xkb_keymap *keymap;
-	struct xkb_state *xkb_state;
-
-	struct wl_list keyboards;
-	struct wl_listener input_add;
-	struct wl_listener input_remove;
-
-	struct wl_listener output_add;
-	struct wl_listener output_remove;
-	struct wl_list outputs;
-};
-
-struct output_state {
-	struct state *state;
-	struct wlr_output *output;
-	struct wl_listener frame;
-	struct wl_list link;
-};
-
-struct keyboard_state {
-	struct state *state;
-	struct wlr_input_device *device;
-	struct wl_listener key;
-	struct wl_list link;
 };
 
-void output_frame(struct wl_listener *listener, void *data) {
-	struct output_state *ostate = wl_container_of(listener, ostate, frame);
-	struct state *s = ostate->state;
-
-	struct timespec now;
-	clock_gettime(CLOCK_MONOTONIC, &now);
+void handle_output_frame(struct output_state *output, struct timespec *ts) {
+	struct compositor_state *state = output->compositor;
+	struct sample_state *sample = state->data;
 
-	long ms = (now.tv_sec - s->last_frame.tv_sec) * 1000 +
-		(now.tv_nsec - s->last_frame.tv_nsec) / 1000000;
-	int inc = (s->dec + 1) % 3;
+	long ms = (ts->tv_sec - state->last_frame.tv_sec) * 1000 +
+		(ts->tv_nsec - state->last_frame.tv_nsec) / 1000000;
+	int inc = (sample->dec + 1) % 3;
 
-	s->color[inc] += ms / 2000.0f;
-	s->color[s->dec] -= ms / 2000.0f;
+	sample->color[inc] += ms / 2000.0f;
+	sample->color[sample->dec] -= ms / 2000.0f;
 
-	if (s->color[s->dec] < 0.0f) {
-		s->color[inc] = 1.0f;
-		s->color[s->dec] = 0.0f;
-		s->dec = inc;
+	if (sample->color[sample->dec] < 0.0f) {
+		sample->color[inc] = 1.0f;
+		sample->color[sample->dec] = 0.0f;
+		sample->dec = inc;
 	}
 
-	s->last_frame = now;
-
-	glClearColor(s->color[0], s->color[1], s->color[2], 1.0);
+	glClearColor(sample->color[0], sample->color[1], sample->color[2], 1.0);
 	glClear(GL_COLOR_BUFFER_BIT);
 }
 
-void output_add(struct wl_listener *listener, void *data) {
-	struct wlr_output *output = data;
-	struct state *state = wl_container_of(listener, state, output_add);
-	fprintf(stderr, "Output '%s' added\n", output->name);
-	fprintf(stderr, "%s %s %"PRId32"mm x %"PRId32"mm\n", output->make, output->model,
-		output->phys_width, output->phys_height);
-	wlr_output_set_mode(output, output->modes->items[0]);
-	struct output_state *ostate = calloc(1, sizeof(struct output_state));
-	ostate->output = output;
-	ostate->state = state;
-	ostate->frame.notify = output_frame;
-	wl_list_init(&ostate->frame.link);
-	wl_signal_add(&output->events.frame, &ostate->frame);
-	wl_list_insert(&state->outputs, &ostate->link);
-}
-
-void output_remove(struct wl_listener *listener, void *data) {
-	struct wlr_output *output = data;
-	struct state *state = wl_container_of(listener, state, output_remove);
-	struct output_state *ostate = NULL, *_ostate;
-	wl_list_for_each(_ostate, &state->outputs, link) {
-		if (_ostate->output == output) {
-			ostate = _ostate;
-			break;
-		}
-	}
-	if (!ostate) {
-		return; // We are unfamiliar with this output
-	}
-	wl_list_remove(&ostate->link);
-	wl_list_remove(&ostate->frame.link);
-}
-
-static void handle_keysym(struct state *state, xkb_keysym_t sym,
-		enum wlr_key_state key_state) {
-	char name[64];
-	int l = xkb_keysym_get_name(sym, name, sizeof(name));
-	if (l != -1 && l != sizeof(name)) {
-		fprintf(stderr, "Key event: %s %s\n", name,
-				key_state == WLR_KEY_PRESSED ? "pressed" : "released");
-	}
+static void handle_keyboard_key(struct keyboard_state *kbstate,
+		xkb_keysym_t sym, enum wlr_key_state key_state) {
 	if (sym == XKB_KEY_Escape) {
-		state->exit = true;
-	}
-}
-
-static void keyboard_key(struct wl_listener *listener, void *data) {
-	struct wlr_keyboard_key *event = data;
-	struct keyboard_state *kbstate = wl_container_of(listener, kbstate, key);
-	uint32_t keycode = event->keycode + 8;
-	const xkb_keysym_t *syms;
-	int nsyms = xkb_state_key_get_syms(kbstate->state->xkb_state, keycode, &syms);
-	for (int i = 0; i < nsyms; ++i) {
-		handle_keysym(kbstate->state, syms[i], event->state);
-	}
-	xkb_state_update_key(kbstate->state->xkb_state, keycode,
-		event->state == WLR_KEY_PRESSED ?  XKB_KEY_DOWN : XKB_KEY_UP);
-}
-
-void input_add(struct wl_listener *listener, void *data) {
-	struct wlr_input_device *device = data;
-	struct state *state = wl_container_of(listener, state, input_add);
-	if (device->type != WLR_INPUT_DEVICE_KEYBOARD) {
-		return;
-	}
-	struct keyboard_state *kbstate = calloc(sizeof(struct keyboard_state), 1);
-	kbstate->device = device;
-	kbstate->state = state;
-	wl_list_init(&kbstate->key.link);
-	kbstate->key.notify = keyboard_key;
-	wl_signal_add(&device->keyboard->events.key, &kbstate->key);
-	wl_list_insert(&state->keyboards, &kbstate->link);
-}
-
-void input_remove(struct wl_listener *listener, void *data) {
-	struct wlr_input_device *device = data;
-	struct state *state = wl_container_of(listener, state, input_add);
-	if (device->type != WLR_INPUT_DEVICE_KEYBOARD) {
-		return;
+		kbstate->compositor->exit = true;
 	}
-	struct keyboard_state *kbstate = NULL, *_kbstate;
-	wl_list_for_each(_kbstate, &state->keyboards, link) {
-		if (_kbstate->device == device) {
-			kbstate = kbstate;
-			break;
-		}
-	}
-	if (!kbstate) {
-		return; // We are unfamiliar with this keyboard
-	}
-	wl_list_remove(&kbstate->link);
-	wl_list_remove(&kbstate->key.link);
 }
 
 int main() {
-	struct state state = {
+	struct sample_state state = {
 		.color = { 1.0, 0.0, 0.0 },
 		.dec = 0,
-		.exit = false,
-		.input_add = { .notify = input_add },
-		.input_remove = { .notify = input_remove },
-		.output_add = { .notify = output_add },
-		.output_remove = { .notify = output_remove },
 	};
+	struct compositor_state compositor;
 
-	struct xkb_rule_names rules;
-	memset(&rules, 0, sizeof(rules));
-	rules.rules = getenv("XKB_DEFAULT_RULES");
-	rules.model = getenv("XKB_DEFAULT_MODEL");
-	rules.layout = getenv("XKB_DEFAULT_LAYOUT");
-	rules.variant = getenv("XKB_DEFAULT_VARIANT");
-	rules.options = getenv("XKB_DEFAULT_OPTIONS");
-	struct xkb_context *context = xkb_context_new(XKB_CONTEXT_NO_FLAGS);
-	if (!context) {
-		fprintf(stderr, "Failed to create XKB context\n");
-		return 1;
-	}
-	state.keymap =
-		xkb_map_new_from_names(context, &rules, XKB_KEYMAP_COMPILE_NO_FLAGS);
-	if (!state.keymap) {
-		fprintf(stderr, "Failed to create XKB keymap\n");
-		return 1;
-	}
-	xkb_context_unref(context);
-	state.xkb_state = xkb_state_new(state.keymap);
-
-	wl_list_init(&state.keyboards);
-	wl_list_init(&state.input_add.link);
-	wl_list_init(&state.input_remove.link);
-
-	wl_list_init(&state.outputs);
-	wl_list_init(&state.output_remove.link);
-	wl_list_init(&state.output_remove.link);
-	clock_gettime(CLOCK_MONOTONIC, &state.last_frame);
-
-	struct wl_display *display = wl_display_create();
-	struct wl_event_loop *event_loop = wl_display_get_event_loop(display);
-
-	struct wlr_session *session = wlr_session_start(display);
-	if (!session) {
-		return 1;
-	}
-
-	struct wlr_backend *wlr = wlr_backend_autocreate(display, session);
-	wl_signal_add(&wlr->events.input_add, &state.input_add);
-	wl_signal_add(&wlr->events.input_remove, &state.input_remove);
-	wl_signal_add(&wlr->events.output_add, &state.output_add);
-	wl_signal_add(&wlr->events.output_remove, &state.output_remove);
-	if (!wlr || !wlr_backend_init(wlr)) {
-		return 1;
-	}
-
-	while (!state.exit) {
-		wl_event_loop_dispatch(event_loop, 0);
-	}
-
-	wlr_backend_destroy(wlr);
-	wl_display_destroy(display);
+	compositor_init(&compositor);
+	compositor.output_frame_cb = handle_output_frame;
+	compositor.keyboard_key_cb = handle_keyboard_key;
+	compositor.data = &state;
+	compositor_run(&compositor);
 }