swaylock: implement a proper render loop

include/swaylock/swaylock.h

@@ -56,6 +56,7 @@ struct swaylock_surface {
 	struct zwlr_layer_surface_v1 *layer_surface;
 	struct pool_buffer buffers[2];
 	struct pool_buffer *current_buffer;
+	bool frame_pending, dirty;
 	uint32_t width, height;
 	int32_t scale;
 	char *output_name;
@@ -74,5 +75,7 @@ void swaylock_handle_key(struct swaylock_state *state,
 		xkb_keysym_t keysym, uint32_t codepoint);
 void render_frame(struct swaylock_surface *surface);
 void render_frames(struct swaylock_state *state);
+void damage_surface(struct swaylock_surface *surface);
+void damage_state(struct swaylock_state *state);
 
 #endif

swaylock/main.c

@@ -131,14 +131,58 @@ static const struct zwlr_layer_surface_v1_listener layer_surface_listener = {
 	.closed = layer_surface_closed,
 };
 
-static void handle_wl_output_geometry(void *data, struct wl_output *output, int32_t x,
+static const struct wl_callback_listener surface_frame_listener;
-		int32_t y, int32_t width_mm, int32_t height_mm, int32_t subpixel,
+
-		const char *make, const char *model, int32_t transform) {
+static void surface_frame_handle_done(void *data, struct wl_callback *callback,
+		uint32_t time) {
+	struct swaylock_surface *surface = data;
+
+	wl_callback_destroy(callback);
+	surface->frame_pending = false;
+
+	if (surface->dirty) {
+		// Schedule a frame in case the surface is damaged again
+		struct wl_callback *callback = wl_surface_frame(surface->surface);
+		wl_callback_add_listener(callback, &surface_frame_listener, surface);
+		surface->frame_pending = true;
+
+		render_frame(surface);
+		surface->dirty = false;
+	}
+}
+
+static const struct wl_callback_listener surface_frame_listener = {
+	.done = surface_frame_handle_done,
+};
+
+void damage_surface(struct swaylock_surface *surface) {
+	surface->dirty = true;
+	if (surface->frame_pending) {
+		return;
+	}
+
+	struct wl_callback *callback = wl_surface_frame(surface->surface);
+	wl_callback_add_listener(callback, &surface_frame_listener, surface);
+	surface->frame_pending = true;
+	wl_surface_commit(surface->surface);
+}
+
+void damage_state(struct swaylock_state *state) {
+	struct swaylock_surface *surface;
+	wl_list_for_each(surface, &state->surfaces, link) {
+		damage_surface(surface);
+	}
+}
+
+static void handle_wl_output_geometry(void *data, struct wl_output *output,
+		int32_t x, int32_t y, int32_t width_mm, int32_t height_mm,
+		int32_t subpixel, const char *make, const char *model,
+		int32_t transform) {
 	// Who cares
 }
 
-static void handle_wl_output_mode(void *data, struct wl_output *output, uint32_t flags,
+static void handle_wl_output_mode(void *data, struct wl_output *output,
-		int32_t width, int32_t height, int32_t refresh) {
+		uint32_t flags, int32_t width, int32_t height, int32_t refresh) {
 	// Who cares
 }
 
@@ -151,7 +195,7 @@ static void handle_wl_output_scale(void *data, struct wl_output *output,
 	struct swaylock_surface *surface = data;
 	surface->scale = factor;
 	if (surface->state->run_display) {
-		render_frames(surface->state);
+		damage_surface(surface);
 	}
 }
 

swaylock/password.c

@@ -96,14 +96,14 @@ void swaylock_handle_key(struct swaylock_state *state,
 	case XKB_KEY_KP_Enter: /* fallthrough */
 	case XKB_KEY_Return:
 		state->auth_state = AUTH_STATE_VALIDATING;
-			render_frames(state);
+		damage_state(state);
 		wl_display_roundtrip(state->display);
 		if (attempt_password(&state->password)) {
 			state->run_display = false;
 			break;
 		}
 		state->auth_state = AUTH_STATE_INVALID;
-			render_frames(state);
+		damage_state(state);
 		break;
 	case XKB_KEY_Delete:
 	case XKB_KEY_BackSpace:
@@ -112,19 +112,19 @@ void swaylock_handle_key(struct swaylock_state *state,
 		} else {
 			state->auth_state = AUTH_STATE_CLEAR;
 		}
-			render_frames(state);
+		damage_state(state);
 		break;
 	case XKB_KEY_Escape:
 		clear_password_buffer(&state->password);
 		state->auth_state = AUTH_STATE_CLEAR;
-			render_frames(state);
+		damage_state(state);
 		break;
 	case XKB_KEY_Caps_Lock:
 		/* The state is getting active after this
 		 * so we need to manually toggle it */
 		state->xkb.caps_lock = !state->xkb.caps_lock;
 		state->auth_state = AUTH_STATE_INPUT_NOP;
-			render_frames(state);
+		damage_state(state);
 		break;
 	case XKB_KEY_Shift_L:
 	case XKB_KEY_Shift_R:
@@ -137,13 +137,13 @@ void swaylock_handle_key(struct swaylock_state *state,
 	case XKB_KEY_Super_L:
 	case XKB_KEY_Super_R:
 		state->auth_state = AUTH_STATE_INPUT_NOP;
-			render_frames(state);
+		damage_state(state);
 		break;
 	default:
 		if (codepoint) {
 			append_ch(&state->password, codepoint);
 			state->auth_state = AUTH_STATE_INPUT;
-				render_frames(state);
+			damage_state(state);
 		}
 		break;
 	}

swaylock/render.c

@@ -23,6 +23,10 @@ void render_frame(struct swaylock_surface *surface) {
 
 	surface->current_buffer = get_next_buffer(state->shm,
 			surface->buffers, buffer_width, buffer_height);
+	if (surface->current_buffer == NULL) {
+		return;
+	}
+
 	cairo_t *cairo = surface->current_buffer->cairo;
 	cairo_identity_matrix(cairo);