Cron support

Makefile

@@ -1,5 +1,5 @@
 TARGET_EXEC := runwhenidle
-LDLIBS=-lXss -lX11 -lwayland-client -lm
+LDLIBS=-lXss -lX11 -lwayland-client
 CC=gcc
 ifeq ($(PREFIX),)
     PREFIX := /usr

main.c

@@ -11,9 +11,11 @@
 #include <signal.h>
 #include <sys/timerfd.h>
 #include <sys/syscall.h>
+#include <dirent.h>
+#include <sys/stat.h>
+#include <pwd.h>
 
 #include <wayland-client.h>
-
 #include "ext-idle-notify-v1-client-protocol.h"
 
 #include <X11/extensions/scrnsaver.h>
@@ -56,6 +58,8 @@ volatile sig_atomic_t command_paused = 0;
 volatile sig_atomic_t sigchld_received = 0;
 pid_t pid;
 
+static int invoked_from_cron = 0;
+
 static struct wl_display *wayland_display = NULL;
 static struct wl_registry *wayland_registry = NULL;
 static struct wl_seat *wayland_seat = NULL;
@@ -64,6 +68,335 @@ static uint32_t wayland_idle_notifier_version = 0;
 static struct ext_idle_notification_v1 *wayland_idle_notification = NULL;
 static int wayland_idle_notify_available = 0;
 
+static int is_string_null_or_empty(const char *value) {
+    return value == NULL || value[0] == '\0';
+}
+
+static int file_is_socket(const char *path) {
+    struct stat st;
+    if (stat(path, &st) != 0) {
+        return 0;
+    }
+    return S_ISSOCK(st.st_mode) ? 1 : 0;
+}
+
+static int file_is_readable_regular_file(const char *path) {
+    struct stat st;
+    if (stat(path, &st) != 0) {
+        return 0;
+    }
+    if (!S_ISREG(st.st_mode)) {
+        return 0;
+    }
+    return access(path, R_OK) == 0 ? 1 : 0;
+}
+
+static int directory_exists_and_accessible(const char *path) {
+    struct stat st;
+    if (stat(path, &st) != 0) {
+        return 0;
+    }
+    if (!S_ISDIR(st.st_mode)) {
+        return 0;
+    }
+    return access(path, R_OK | X_OK) == 0 ? 1 : 0;
+}
+
+static int read_process_status_ppid(pid_t target_pid, pid_t *out_ppid) {
+    char status_path[64];
+    snprintf(status_path, sizeof(status_path), "/proc/%d/status", target_pid);
+
+    FILE *fp = fopen(status_path, "r");
+    if (!fp) {
+        return 0;
+    }
+
+    char line[256];
+    while (fgets(line, sizeof(line), fp)) {
+        if (strncmp(line, "PPid:", 5) == 0) {
+            long parsed = strtol(line + 5, NULL, 10);
+            fclose(fp);
+            if (parsed <= 0) {
+                return 0;
+            }
+            *out_ppid = (pid_t)parsed;
+            return 1;
+        }
+    }
+
+    fclose(fp);
+    return 0;
+}
+
+static int read_process_comm(pid_t target_pid, char *out_comm, size_t out_comm_size) {
+    char comm_path[64];
+    snprintf(comm_path, sizeof(comm_path), "/proc/%d/comm", target_pid);
+
+    FILE *fp = fopen(comm_path, "r");
+    if (!fp) {
+        return 0;
+    }
+
+    if (!fgets(out_comm, (int)out_comm_size, fp)) {
+        fclose(fp);
+        return 0;
+    }
+    fclose(fp);
+
+    out_comm[strcspn(out_comm, "\n")] = '\0';
+    return 1;
+}
+
+static int comm_matches_any_cron_name(const char *comm) {
+    const char *cron_names[] = { "cron", "crond", "anacron", "cronie", "fcron", NULL };
+    for (int i = 0; cron_names[i] != NULL; i++) {
+        if (strcmp(comm, cron_names[i]) == 0) {
+            return 1;
+        }
+    }
+    return 0;
+}
+
+static int detect_invoked_from_cron_via_process_tree(void) {
+    pid_t current_pid = getpid();
+
+    for (int depth = 0; depth < 12; depth++) {
+        pid_t parent_pid = 0;
+        if (!read_process_status_ppid(current_pid, &parent_pid)) {
+            break;
+        }
+        if (parent_pid <= 1) {
+            break;
+        }
+
+        char comm[128];
+        if (read_process_comm(parent_pid, comm, sizeof(comm))) {
+            if (comm_matches_any_cron_name(comm)) {
+                return 1;
+            }
+        }
+
+        current_pid = parent_pid;
+    }
+
+    return 0;
+}
+
+static int get_home_directory_for_current_user(char *out_home, size_t out_home_size) {
+    const char *home_env = getenv("HOME");
+    if (!is_string_null_or_empty(home_env)) {
+        snprintf(out_home, out_home_size, "%s", home_env);
+        return 1;
+    }
+
+    struct passwd *pw = getpwuid(getuid());
+    if (!pw || !pw->pw_dir) {
+        return 0;
+    }
+
+    snprintf(out_home, out_home_size, "%s", pw->pw_dir);
+    return 1;
+}
+
+static int build_xauthority_path_from_home_dir(char *xauthority_path,
+                                               size_t xauthority_path_size,
+                                               const char *home_dir) {
+    static const char xauthority_suffix[] = "/.Xauthority";
+    size_t home_dir_length = strnlen(home_dir, xauthority_path_size);
+    size_t suffix_length = sizeof(xauthority_suffix) - 1;
+
+    if (home_dir_length == 0 || home_dir_length >= xauthority_path_size) {
+        return 0;
+    }
+
+    if (home_dir_length + suffix_length + 1 > xauthority_path_size) {
+        return 0;
+    }
+
+    memcpy(xauthority_path, home_dir, home_dir_length);
+    memcpy(xauthority_path + home_dir_length, xauthority_suffix, suffix_length + 1);
+    return 1;
+}
+
+static void ensure_xauthority_is_set_if_possible(void) {
+    if (!is_string_null_or_empty(getenv("XAUTHORITY"))) {
+        return;
+    }
+
+    char home_dir[PATH_MAX];
+    if (!get_home_directory_for_current_user(home_dir, sizeof(home_dir))) {
+        return;
+    }
+
+    char xauthority_path[PATH_MAX];
+    if (!build_xauthority_path_from_home_dir(xauthority_path, sizeof(xauthority_path), home_dir)) {
+        return;
+    }
+
+    if (file_is_readable_regular_file(xauthority_path)) {
+        setenv("XAUTHORITY", xauthority_path, 0);
+    }
+}
+
+
+static int build_default_xdg_runtime_dir_for_current_user(char *out_runtime_dir, size_t out_runtime_dir_size) {
+    uid_t uid = getuid();
+    snprintf(out_runtime_dir, out_runtime_dir_size, "/run/user/%u", (unsigned)uid);
+    if (!directory_exists_and_accessible(out_runtime_dir)) {
+        return 0;
+    }
+    return 1;
+}
+
+static int find_best_wayland_socket_in_runtime_dir(const char *runtime_dir,
+                                                   char *out_socket_path,
+                                                   size_t out_socket_path_size,
+                                                   char *out_socket_name,
+                                                   size_t out_socket_name_size) {
+    DIR *dir = opendir(runtime_dir);
+    if (!dir) {
+        return 0;
+    }
+
+    int found = 0;
+    int best_numeric_suffix = INT_MAX;
+    char best_name[NAME_MAX + 1];
+    best_name[0] = '\0';
+
+    struct dirent *entry;
+    while ((entry = readdir(dir)) != NULL) {
+        if (strncmp(entry->d_name, "wayland-", 8) != 0) {
+            continue;
+        }
+
+        char full_path[PATH_MAX];
+        snprintf(full_path, sizeof(full_path), "%s/%s", runtime_dir, entry->d_name);
+
+        if (!file_is_socket(full_path)) {
+            continue;
+        }
+
+        int numeric_suffix = -1;
+        const char *suffix = entry->d_name + 8;
+        if (*suffix >= '0' && *suffix <= '9') {
+            numeric_suffix = (int)strtol(suffix, NULL, 10);
+        }
+
+        if (!found) {
+            found = 1;
+            best_numeric_suffix = (numeric_suffix >= 0) ? numeric_suffix : INT_MAX;
+            snprintf(best_name, sizeof(best_name), "%s", entry->d_name);
+            continue;
+        }
+
+        if (numeric_suffix >= 0 && numeric_suffix < best_numeric_suffix) {
+            best_numeric_suffix = numeric_suffix;
+            snprintf(best_name, sizeof(best_name), "%s", entry->d_name);
+            continue;
+        }
+
+        if (best_numeric_suffix == INT_MAX && numeric_suffix == -1) {
+            snprintf(best_name, sizeof(best_name), "%s", entry->d_name);
+        }
+    }
+
+    closedir(dir);
+
+    if (!found) {
+        return 0;
+    }
+
+    snprintf(out_socket_path, out_socket_path_size, "%s/%s", runtime_dir, best_name);
+    if (out_socket_name && out_socket_name_size > 0) {
+        snprintf(out_socket_name, out_socket_name_size, "%s", best_name);
+    }
+    return 1;
+}
+
+static int find_best_x11_display_from_socket_dir(char *out_display, size_t out_display_size) {
+    const char *x11_socket_dir = "/tmp/.X11-unix";
+    DIR *dir = opendir(x11_socket_dir);
+    if (!dir) {
+        return 0;
+    }
+
+    int found = 0;
+    int best_display_number = INT_MAX;
+
+    struct dirent *entry;
+    while ((entry = readdir(dir)) != NULL) {
+        if (entry->d_name[0] != 'X') {
+            continue;
+        }
+        const char *digits = entry->d_name + 1;
+        if (*digits < '0' || *digits > '9') {
+            continue;
+        }
+
+        int display_number = (int)strtol(digits, NULL, 10);
+
+        char socket_path[PATH_MAX];
+        snprintf(socket_path, sizeof(socket_path), "%s/%s", x11_socket_dir, entry->d_name);
+
+        if (!file_is_socket(socket_path)) {
+            continue;
+        }
+
+        if (!found || display_number < best_display_number) {
+            found = 1;
+            best_display_number = display_number;
+        }
+    }
+
+    closedir(dir);
+
+    if (!found) {
+        return 0;
+    }
+
+    snprintf(out_display, out_display_size, ":%d", best_display_number);
+    return 1;
+}
+
+static void best_effort_infer_graphical_session_environment_if_missing(void) {
+    if (!is_string_null_or_empty(getenv("WAYLAND_DISPLAY")) || !is_string_null_or_empty(getenv("DISPLAY"))) {
+        return;
+    }
+
+    char inferred_runtime_dir[PATH_MAX];
+    if (is_string_null_or_empty(getenv("XDG_RUNTIME_DIR"))) {
+        if (build_default_xdg_runtime_dir_for_current_user(inferred_runtime_dir, sizeof(inferred_runtime_dir))) {
+            setenv("XDG_RUNTIME_DIR", inferred_runtime_dir, 0);
+        }
+    }
+
+    const char *runtime_dir = getenv("XDG_RUNTIME_DIR");
+    if (!is_string_null_or_empty(runtime_dir) && is_string_null_or_empty(getenv("WAYLAND_DISPLAY"))) {
+        char wayland_socket_path[PATH_MAX];
+        char wayland_socket_name[NAME_MAX + 1];
+        if (find_best_wayland_socket_in_runtime_dir(runtime_dir, wayland_socket_path, sizeof(wayland_socket_path),
+                                                    wayland_socket_name, sizeof(wayland_socket_name))) {
+            setenv("WAYLAND_DISPLAY", wayland_socket_name, 0);
+        }
+    }
+
+    if (is_string_null_or_empty(getenv("DISPLAY"))) {
+        char inferred_display[32];
+        if (find_best_x11_display_from_socket_dir(inferred_display, sizeof(inferred_display))) {
+            setenv("DISPLAY", inferred_display, 0);
+            ensure_xauthority_is_set_if_possible();
+        }
+    }
+
+    if (verbose && invoked_from_cron) {
+        const char *wd = getenv("WAYLAND_DISPLAY");
+        const char *xdg = getenv("XDG_RUNTIME_DIR");
+        const char *dpy = getenv("DISPLAY");
+        fprintf(stderr, "Detected cron context; inferred session vars: XDG_RUNTIME_DIR=%s WAYLAND_DISPLAY=%s DISPLAY=%s\n",
+                xdg ? xdg : "(unset)", wd ? wd : "(unset)", dpy ? dpy : "(unset)");
+    }
+}
+
 static int open_pid_file_descriptor_for_process(pid_t process_id) {
 #if defined(SYS_pidfd_open)
     return (int)syscall(SYS_pidfd_open, process_id, 0);
@@ -190,74 +523,6 @@ void sigchld_handler(int signum) {
     sigchld_received = 1;
 }
 
-long long pause_or_resume_command_depending_on_user_activity(
-        long long sleep_time_ms,
-        unsigned long user_idle_time_ms) {
-    if (user_idle_time_ms >= user_idle_timeout_ms) {
-        if (debug)
-            fprintf(stderr, "Idle time: %lums, idle timeout: %lums, user is inactive\n", user_idle_time_ms,
-                    user_idle_timeout_ms);
-        if (command_paused) {
-            sleep_time_ms = POLLING_INTERVAL_MS; //reset to default value
-            if (verbose) {
-                fprintf(stderr, "Idle time: %lums, idle timeout: %lums, resuming command\n", user_idle_time_ms,
-                        user_idle_timeout_ms);
-            }
-            if (!quiet) {
-                printf("Lack of user activity detected. ");
-                //intentionally no new line here, resume_command will print the rest of the message.
-            }
-            resume_command_recursively(pid);
-            command_paused = 0;
-        }
-    } else {
-        struct timespec time_when_starting_to_pause;
-        int command_was_paused_this_iteration = 0;
-        // User is active
-        if (!command_paused) {
-            clock_gettime(CLOCK_MONOTONIC, &time_when_starting_to_pause);
-            if (verbose) {
-                fprintf(stderr, "Idle time: %lums.\n", user_idle_time_ms);
-            }
-            pause_command_recursively(pid);
-            if (debug) fprintf(stderr, "Command paused\n");
-            command_paused = 1;
-            command_was_paused_this_iteration = 1;
-        }
-        sleep_time_ms = user_idle_timeout_ms - user_idle_time_ms;
-        if (debug) fprintf(stderr, "Target sleep time: %llums\n", sleep_time_ms);
-        if (command_was_paused_this_iteration) {
-            if (debug) fprintf(stderr, "Command was paused this iteration\n");
-            struct timespec time_before_sleep;
-            clock_gettime(CLOCK_MONOTONIC, &time_before_sleep);
-            long long pausing_time_ms = get_elapsed_time_ms(time_when_starting_to_pause, time_before_sleep);
-            if (debug)
-                fprintf(stderr,
-                        "Target sleep time before taking into account time it took to pause: %lldms, time it took to pause: %lldms\n",
-                        sleep_time_ms, pausing_time_ms);
-            sleep_time_ms = sleep_time_ms - pausing_time_ms;
-
-        }
-
-        if (sleep_time_ms < POLLING_INTERVAL_MS) {
-            if (debug)
-                fprintf(stderr,
-                        "Target sleep time %lldms is less than polling interval %lldms, resetting it to polling interval\n",
-                        sleep_time_ms, POLLING_INTERVAL_MS);
-            sleep_time_ms = POLLING_INTERVAL_MS;
-        }
-        if (verbose) {
-            fprintf(
-                    stderr,
-                    "Polling every second is temporarily disabled due to user activity, idle time: %lums, next activity check scheduled in %lldms\n",
-                    user_idle_time_ms,
-                    sleep_time_ms
-            );
-        }
-    }
-    return sleep_time_ms;
-}
-
 static void wayland_idle_notification_idled(void *data, struct ext_idle_notification_v1 *notification) {
     (void)data;
     (void)notification;
@@ -341,8 +606,45 @@ static const struct wl_registry_listener wayland_registry_listener = {
         .global_remove = wayland_registry_global_remove
 };
 
+static struct wl_display *connect_to_wayland_best_effort(void) {
+    struct wl_display *display = wl_display_connect(NULL);
+    if (display) {
+        return display;
+    }
+
+    const char *runtime_dir = getenv("XDG_RUNTIME_DIR");
+    char inferred_runtime_dir[PATH_MAX];
+    if (is_string_null_or_empty(runtime_dir)) {
+        if (!build_default_xdg_runtime_dir_for_current_user(inferred_runtime_dir, sizeof(inferred_runtime_dir))) {
+            return NULL;
+        }
+        runtime_dir = inferred_runtime_dir;
+    }
+
+    char wayland_socket_path[PATH_MAX];
+    char wayland_socket_name[NAME_MAX + 1];
+    if (!find_best_wayland_socket_in_runtime_dir(runtime_dir, wayland_socket_path, sizeof(wayland_socket_path),
+                                                 wayland_socket_name, sizeof(wayland_socket_name))) {
+        return NULL;
+    }
+
+    display = wl_display_connect(wayland_socket_path);
+    if (!display) {
+        return NULL;
+    }
+
+    if (is_string_null_or_empty(getenv("XDG_RUNTIME_DIR"))) {
+        setenv("XDG_RUNTIME_DIR", runtime_dir, 0);
+    }
+    if (is_string_null_or_empty(getenv("WAYLAND_DISPLAY"))) {
+        setenv("WAYLAND_DISPLAY", wayland_socket_name, 0);
+    }
+
+    return display;
+}
+
 static int try_initialize_wayland_idle_backend(void) {
-    wayland_display = wl_display_connect(NULL);
+    wayland_display = connect_to_wayland_best_effort();
     if (!wayland_display) {
         return 0;
     }
@@ -358,10 +660,8 @@ static int try_initialize_wayland_idle_backend(void) {
     wl_display_roundtrip(wayland_display);
 
     if (wayland_seat == NULL || wayland_idle_notifier == NULL) {
-        if (wayland_registry) {
-            wl_registry_destroy(wayland_registry);
-            wayland_registry = NULL;
-        }
+        wl_registry_destroy(wayland_registry);
+        wayland_registry = NULL;
         wl_display_disconnect(wayland_display);
         wayland_display = NULL;
         wayland_seat = NULL;
@@ -431,10 +731,6 @@ static int run_wayland_idle_event_loop(void) {
         };
     }
 
-    if (verbose) {
-        fprintf(stderr, "Wayland backend: waiting for idle notifications\n");
-    }
-
     while (1) {
         if (interruption_received) {
             if (start_monitor_timer_file_descriptor >= 0) close(start_monitor_timer_file_descriptor);
@@ -464,10 +760,6 @@ static int run_wayland_idle_event_loop(void) {
             consume_timer_file_descriptor(start_monitor_timer_file_descriptor);
             monitoring_started = 1;
 
-            if (verbose) {
-                fprintf(stderr, "Starting to monitor user activity (Wayland ext-idle-notify-v1)\n");
-            }
-
             if (start_wayland_idle_notification_object() < 0) {
                 fprintf_error("Failed to create Wayland idle notification object, user will be considered idle.\n");
             } else {
@@ -517,9 +809,31 @@ static int run_wayland_idle_event_loop(void) {
     }
 }
 
+static Display *open_x11_display_best_effort(void) {
+    Display *display = XOpenDisplay(NULL);
+    if (display) {
+        return display;
+    }
+
+    if (!is_string_null_or_empty(getenv("DISPLAY"))) {
+        return NULL;
+    }
+
+    char inferred_display[32];
+    if (!find_best_x11_display_from_socket_dir(inferred_display, sizeof(inferred_display))) {
+        return NULL;
+    }
+
+    setenv("DISPLAY", inferred_display, 0);
+    ensure_xauthority_is_set_if_possible();
+    return XOpenDisplay(NULL);
+}
+
 int main(int argc, char *argv[]) {
     parse_command_line_arguments(argc, argv);
 
+    invoked_from_cron = detect_invoked_from_cron_via_process_tree();
+
     if (external_pid == 0) {
         pid = run_shell_command(shell_command_to_run);
     } else {
@@ -535,6 +849,8 @@ int main(int argc, char *argv[]) {
     signal(SIGTERM, sigterm_handler);
     signal(SIGCHLD, sigchld_handler);
 
+    best_effort_infer_graphical_session_environment_if_missing();
+
     if (try_initialize_wayland_idle_backend()) {
         int wayland_loop_result = run_wayland_idle_event_loop();
 
@@ -562,7 +878,7 @@ int main(int argc, char *argv[]) {
         return wayland_loop_result;
     }
 
-    x_display = XOpenDisplay(NULL);
+    x_display = open_x11_display_best_effort();
     if (!x_display) {
         xscreensaver_is_available = 0;
         fprintf_error("Couldn't open an X11 display!\n");
@@ -615,9 +931,20 @@ int main(int argc, char *argv[]) {
         exit_if_pid_has_finished(pid);
 
         if (monitoring_started) {
-            sleep_time_ms = pause_or_resume_command_depending_on_user_activity(
-                    sleep_time_ms,
-                    user_idle_time_ms);
+            if (user_idle_time_ms >= user_idle_timeout_ms) {
+                if (command_paused) {
+                    if (!quiet) {
+                        printf("Lack of user activity detected. ");
+                    }
+                    resume_command_recursively(pid);
+                    command_paused = 0;
+                }
+            } else {
+                if (!command_paused) {
+                    pause_command_recursively(pid);
+                    command_paused = 1;
+                }
+            }
         }
         if (debug) fprintf(stderr, "Sleeping for %lldms\n", sleep_time_ms);
         sleep_for_milliseconds(sleep_time_ms);