Check password without blocking

comm.c

@@ -6,7 +6,7 @@
 #include "log.h"
 #include "swaylock.h"
 
-static int comm[2][2];
+static int comm[2][2] = {{-1, -1}, {-1, -1}};
 
 ssize_t read_comm_request(char **buf_ptr) {
 	size_t size;
@@ -69,28 +69,41 @@ bool spawn_comm_child(void) {
 	return true;
 }
 
-bool attempt_password(struct swaylock_password *pw) {
+bool write_comm_request(struct swaylock_password *pw) {
 	bool result = false;
+
 	size_t len = pw->len + 1;
 	size_t offs = 0;
 	if (write(comm[0][1], &len, sizeof(len)) < 0) {
 		swaylock_log_errno(LOG_ERROR, "Failed to request pw check");
-		goto ret;
+		goto out;
 	}
+
 	do {
 		ssize_t amt = write(comm[0][1], &pw->buffer[offs], len - offs);
 		if (amt < 0) {
 			swaylock_log_errno(LOG_ERROR, "Failed to write pw buffer");
-			goto ret;
+			goto out;
 		}
 		offs += amt;
 	} while (offs < len);
-	if (read(comm[1][0], &result, sizeof(result)) != sizeof(result)) {
-		swaylock_log_errno(LOG_ERROR, "Failed to read pw result");
-		goto ret;
-	}
-	swaylock_log(LOG_DEBUG, "pw result: %d", result);
-ret:
+
+	result = true;
+
+out:
 	clear_password_buffer(pw);
 	return result;
 }
+
+bool read_comm_reply(void) {
+	bool result = false;
+	if (read(comm[1][0], &result, sizeof(result)) != sizeof(result)) {
+		swaylock_log_errno(LOG_ERROR, "Failed to read pw result");
+		result = false;
+	}
+	return result;
+}
+
+int get_comm_reply_fd(void) {
+	return comm[1][0];
+}

include/comm.h

@@ -1,8 +1,18 @@
 #ifndef _SWAYLOCK_COMM_H
 #define _SWAYLOCK_COMM_H
 
+#include <stdbool.h>
+
+struct swaylock_password;
+
 bool spawn_comm_child(void);
 ssize_t read_comm_request(char **buf_ptr);
 bool write_comm_reply(bool success);
+// Requests the provided password to be checked. The password is always cleared
+// when the function returns.
+bool write_comm_request(struct swaylock_password *pw);
+bool read_comm_reply(void);
+// FD to poll for password authentication replies.
+int get_comm_reply_fd(void);
 
 #endif

include/swaylock.h

@@ -62,7 +62,6 @@ struct swaylock_state {
 	struct loop *eventloop;
 	struct loop_timer *clear_indicator_timer; // clears the indicator
 	struct loop_timer *clear_password_timer;  // clears the password buffer
-	struct loop_timer *verify_password_timer;
 	struct wl_display *display;
 	struct wl_compositor *compositor;
 	struct zwlr_layer_shell_v1 *layer_shell;
@@ -110,8 +109,8 @@ 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);
-bool attempt_password(struct swaylock_password *pw);
 void clear_password_buffer(struct swaylock_password *pw);
+void schedule_indicator_clear(struct swaylock_state *state);
 
 void initialize_pw_backend(void);
 void run_pw_backend_child(void);

main.c

@@ -17,6 +17,7 @@
 #include <wordexp.h>
 #include "background-image.h"
 #include "cairo.h"
+#include "comm.h"
 #include "log.h"
 #include "loop.h"
 #include "pool-buffer.h"
@@ -956,6 +957,17 @@ static void display_in(int fd, short mask, void *data) {
 	}
 }
 
+static void comm_in(int fd, short mask, void *data) {
+	if (read_comm_reply()) {
+		// Authentication succeeded
+		state.run_display = false;
+	} else {
+		state.auth_state = AUTH_STATE_INVALID;
+		schedule_indicator_clear(&state);
+		damage_state(&state);
+	}
+}
+
 int main(int argc, char **argv) {
 	swaylock_log_init(LOG_ERROR);
 	initialize_pw_backend();
@@ -1081,6 +1093,8 @@ int main(int argc, char **argv) {
 	loop_add_fd(state.eventloop, wl_display_get_fd(state.display), POLLIN,
 			display_in, NULL);
 
+	loop_add_fd(state.eventloop, get_comm_reply_fd(), POLLIN, comm_in, NULL);
+
 	state.run_display = true;
 	while (state.run_display) {
 		errno = 0;

password.c

@@ -5,6 +5,7 @@
 #include <string.h>
 #include <unistd.h>
 #include <xkbcommon/xkbcommon.h>
+#include "comm.h"
 #include "log.h"
 #include "loop.h"
 #include "seat.h"
@@ -51,7 +52,7 @@ static void clear_indicator(void *data) {
 	damage_state(state);
 }
 
-static void schedule_indicator_clear(struct swaylock_state *state) {
+void schedule_indicator_clear(struct swaylock_state *state) {
 	if (state->clear_indicator_timer) {
 		loop_remove_timer(state->eventloop, state->clear_indicator_timer);
 	}
@@ -76,57 +77,28 @@ static void schedule_password_clear(struct swaylock_state *state) {
 			state->eventloop, 10000, clear_password, state);
 }
 
-static void handle_preverify_timeout(void *data) {
-	struct swaylock_state *state = data;
-	state->verify_password_timer = NULL;
-}
-
 static void submit_password(struct swaylock_state *state) {
 	if (state->args.ignore_empty && state->password.len == 0) {
 		return;
 	}
 
 	state->auth_state = AUTH_STATE_VALIDATING;
-	damage_state(state);
 
-	// We generally want to wait until all surfaces are showing the
-	// "verifying" state before we go and verify the password, because
-	// verifying it is a blocking operation. However, if the surface is on
-	// an output with DPMS off then it won't update, so we set a timer.
-	state->verify_password_timer = loop_add_timer(
-			state->eventloop, 50, handle_preverify_timeout, state);
-
-	while (state->run_display && state->verify_password_timer) {
-		errno = 0;
-		if (wl_display_flush(state->display) == -1 && errno != EAGAIN) {
-			break;
-		}
-		loop_poll(state->eventloop);
-
-		bool ok = 1;
-		struct swaylock_surface *surface;
-		wl_list_for_each(surface, &state->surfaces, link) {
-			if (surface->dirty) {
-				ok = 0;
-			}
-		}
-		if (ok) {
-			break;
-		}
-	}
-	wl_display_flush(state->display);
-
-	if (attempt_password(&state->password)) {
-		state->run_display = false;
-		return;
-	}
+	if (!write_comm_request(&state->password)) {
 		state->auth_state = AUTH_STATE_INVALID;
-	damage_state(state);
 		schedule_indicator_clear(state);
+	}
+
+	damage_state(state);
 }
 
 void swaylock_handle_key(struct swaylock_state *state,
 		xkb_keysym_t keysym, uint32_t codepoint) {
+	// Ignore input events if validating
+	if (state->auth_state == AUTH_STATE_VALIDATING) {
+		return;
+	}
+
 	switch (keysym) {
 	case XKB_KEY_KP_Enter: /* fallthrough */
 	case XKB_KEY_Return: