Use $ANDROID_SERIAL if no selector is specified

Like adb, read the ANDROID_SERIAL environment variable to select a
device by serial if no explicit selection (-s, -d, -e or --tcpip=<addr>)
is provided via the command line.

Fixes #3111 <https://github.com/Genymobile/scrcpy/issues/3111>
PR #3113 <https://github.com/Genymobile/scrcpy/pull/3113>

README.md

@@ -448,6 +448,9 @@ scrcpy --serial 0123456789abcdef
 scrcpy -s 0123456789abcdef  # short version
 ```
 
+The serial may also be provided via the environment variable `ANDROID_SERIAL`
+(also used by `adb`).
+
 If the device is connected over TCP/IP:
 
 ```bash

app/scrcpy.1

@@ -355,6 +355,12 @@ Set the initial window height.
 
 Default is 0 (automatic).
 
+.SH EXIT STATUS
+.B scrcpy
+will exit with code 0 on normal program termination. If an initial
+connection cannot be established, the exit code 1 will be returned. If the
+device disconnects while a session is active, exit code 2 will be returned.
+
 .SH SHORTCUTS
 
 In the following list, MOD is the shortcut modifier. By default, it's (left)
@@ -471,6 +477,10 @@ Push file to device (see \fB\-\-push\-target\fR)
 .B ADB
 Path to adb.
 
+.TP
+.B ANDROID_SERIAL
+Device serial to use if no selector (-s, -d, -e or --tcpip=<addr>) is specified.
+
 .TP
 .B SCRCPY_ICON_PATH
 Path to the program icon.

app/src/cli.c

@@ -80,6 +80,11 @@ struct sc_envvar {
     const char *text;
 };
 
+struct sc_exit_status {
+    unsigned value;
+    const char *text;
+};
+
 struct sc_getopt_adapter {
     char *optstring;
     struct option *longopts;
@@ -655,6 +660,11 @@ static const struct sc_envvar envvars[] = {
         .name = "ADB",
         .text = "Path to adb executable",
     },
+    {
+        .name = "ANDROID_SERIAL",
+        .text = "Device serial to use if no selector (-s, -d, -e or "
+                "--tcpip=<addr>) is specified",
+    },
     {
         .name = "SCRCPY_ICON_PATH",
         .text = "Path to the program icon",
@@ -662,7 +672,22 @@ static const struct sc_envvar envvars[] = {
     {
         .name = "SCRCPY_SERVER_PATH",
         .text = "Path to the server binary",
-    }
+    },
+};
+
+static const struct sc_exit_status exit_statuses[] = {
+    {
+        .value = 0,
+        .text = "Normal program termination",
+    },
+    {
+        .value = 1,
+        .text = "Start failure",
+    },
+    {
+        .value = 2,
+        .text = "Device disconnected while running",
+    },
 };
 
 static char *
@@ -901,6 +926,25 @@ print_envvar(const struct sc_envvar *envvar, unsigned cols) {
     free(text);
 }
 
+static void
+print_exit_status(const struct sc_exit_status *status, unsigned cols) {
+    assert(cols > 8); // sc_str_wrap_lines() requires indent < columns
+    assert(status->text);
+
+    // The text starts at 9: 4 ident spaces, 3 chars for numeric value, 2 spaces
+    char *text = sc_str_wrap_lines(status->text, cols, 9);
+    if (!text) {
+        printf("<ERROR>\n");
+        return;
+    }
+
+    assert(strlen(text) >= 9); // Contains at least the initial identation
+
+    // text + 9 to remove the initial indentation
+    printf("    %3d  %s\n", status->value, text + 9);
+    free(text);
+}
+
 void
 scrcpy_print_usage(const char *arg0) {
 #define SC_TERM_COLS_DEFAULT 80
@@ -939,6 +983,11 @@ scrcpy_print_usage(const char *arg0) {
     for (size_t i = 0; i < ARRAY_LEN(envvars); ++i) {
         print_envvar(&envvars[i], cols);
     }
+
+    printf("\nExit status:\n\n");
+    for (size_t i = 0; i < ARRAY_LEN(exit_statuses); ++i) {
+        print_exit_status(&exit_statuses[i], cols);
+    }
 }
 
 static bool

app/src/main.c

@@ -40,19 +40,19 @@ main(int argc, char *argv[]) {
 #endif
 
     if (!scrcpy_parse_args(&args, argc, argv)) {
-        return 1;
+        return SCRCPY_EXIT_FAILURE;
     }
 
     sc_set_log_level(args.opts.log_level);
 
     if (args.help) {
         scrcpy_print_usage(argv[0]);
-        return 0;
+        return SCRCPY_EXIT_SUCCESS;
     }
 
     if (args.version) {
         scrcpy_print_version();
-        return 0;
+        return SCRCPY_EXIT_SUCCESS;
     }
 
 #ifdef SCRCPY_LAVF_REQUIRES_REGISTER_ALL
@@ -66,17 +66,17 @@ main(int argc, char *argv[]) {
 #endif
 
     if (avformat_network_init()) {
-        return 1;
+        return SCRCPY_EXIT_FAILURE;
     }
 
 #ifdef HAVE_USB
-    bool ok = args.opts.otg ? scrcpy_otg(&args.opts)
+    enum scrcpy_exit_code ret = args.opts.otg ? scrcpy_otg(&args.opts)
                                               : scrcpy(&args.opts);
 #else
-    bool ok = scrcpy(&args.opts);
+    enum scrcpy_exit_code ret = scrcpy(&args.opts);
 #endif
 
     avformat_network_deinit(); // ignore failure
 
-    return ok ? 0 : 1;
+    return ret;
 }

app/src/scrcpy.c

@@ -149,38 +149,41 @@ sdl_configure(bool display, bool disable_screensaver) {
     }
 }
 
-static bool
+static enum scrcpy_exit_code
 event_loop(struct scrcpy *s) {
     SDL_Event event;
     while (SDL_WaitEvent(&event)) {
         switch (event.type) {
             case EVENT_STREAM_STOPPED:
                 LOGW("Device disconnected");
-                return false;
+                return SCRCPY_EXIT_DISCONNECTED;
             case SDL_QUIT:
                 LOGD("User requested to quit");
-                return true;
+                return SCRCPY_EXIT_SUCCESS;
             default:
                 sc_screen_handle_event(&s->screen, &event);
                 break;
         }
     }
-    return false;
+    return SCRCPY_EXIT_FAILURE;
 }
 
+// Return true on success, false on error
 static bool
-await_for_server(void) {
+await_for_server(bool *connected) {
     SDL_Event event;
     while (SDL_WaitEvent(&event)) {
         switch (event.type) {
             case SDL_QUIT:
                 LOGD("User requested to quit");
-                return false;
+                *connected = false;
+                return true;
             case EVENT_SERVER_CONNECTION_FAILED:
                 LOGE("Server connection failed");
                 return false;
             case EVENT_SERVER_CONNECTED:
                 LOGD("Server connected");
+                *connected = true;
                 return true;
             default:
                 break;
@@ -262,7 +265,7 @@ sc_server_on_disconnected(struct sc_server *server, void *userdata) {
     // event
 }
 
-bool
+enum scrcpy_exit_code
 scrcpy(struct scrcpy_options *options) {
     static struct scrcpy scrcpy;
     struct scrcpy *s = &scrcpy;
@@ -270,12 +273,12 @@ scrcpy(struct scrcpy_options *options) {
     // Minimal SDL initialization
     if (SDL_Init(SDL_INIT_EVENTS)) {
         LOGE("Could not initialize SDL: %s", SDL_GetError());
-        return false;
+        return SCRCPY_EXIT_FAILURE;
     }
 
     atexit(SDL_Quit);
 
-    bool ret = false;
+    enum scrcpy_exit_code ret = SCRCPY_EXIT_FAILURE;
 
     bool server_started = false;
     bool file_pusher_initialized = false;
@@ -329,7 +332,7 @@ scrcpy(struct scrcpy_options *options) {
         .on_disconnected = sc_server_on_disconnected,
     };
     if (!sc_server_init(&s->server, &params, &cbs, NULL)) {
-        return false;
+        return SCRCPY_EXIT_FAILURE;
     }
 
     if (!sc_server_start(&s->server)) {
@@ -351,7 +354,14 @@ scrcpy(struct scrcpy_options *options) {
     sdl_configure(options->display, options->disable_screensaver);
 
     // Await for server without blocking Ctrl+C handling
-    if (!await_for_server()) {
+    bool connected;
+    if (!await_for_server(&connected)) {
+        goto end;
+    }
+
+    if (!connected) {
+        // This is not an error, user requested to quit
+        ret = SCRCPY_EXIT_SUCCESS;
         goto end;
     }
 

app/src/scrcpy.h

@@ -6,7 +6,18 @@
 #include <stdbool.h>
 #include "options.h"
 
-bool
+enum scrcpy_exit_code {
+    // Normal program termination
+    SCRCPY_EXIT_SUCCESS,
+
+    // No connection could be established
+    SCRCPY_EXIT_FAILURE,
+
+    // Device was disconnected while running
+    SCRCPY_EXIT_DISCONNECTED,
+};
+
+enum scrcpy_exit_code
 scrcpy(struct scrcpy_options *options);
 
 #endif

app/src/server.c

@@ -706,9 +706,17 @@ run_server(void *data) {
             selector.type = SC_ADB_DEVICE_SELECT_USB;
         } else if (params->select_tcpip) {
             selector.type = SC_ADB_DEVICE_SELECT_TCPIP;
+        } else {
+            // No explicit selection, check $ANDROID_SERIAL
+            const char *env_serial = getenv("ANDROID_SERIAL");
+            if (env_serial) {
+                LOGI("Using ANDROID_SERIAL: %s", env_serial);
+                selector.type = SC_ADB_DEVICE_SELECT_SERIAL;
+                selector.serial = env_serial;
             } else {
                 selector.type = SC_ADB_DEVICE_SELECT_ALL;
             }
+        }
         struct sc_adb_device device;
         ok = sc_adb_select_device(&server->intr, &selector, 0, &device);
         if (!ok) {

app/src/usb/hid_keyboard.c

@@ -340,7 +340,7 @@ push_mod_lock_state(struct sc_hid_keyboard *kb, uint16_t mods_state) {
 
     if (!sc_aoa_push_hid_event(kb->aoa, &hid_event)) {
         sc_hid_event_destroy(&hid_event);
-        LOGW("Could request HID event");
+        LOGW("Could not request HID event (mod lock state)");
         return false;
     }
 
@@ -382,7 +382,7 @@ sc_key_processor_process_key(struct sc_key_processor *kp,
 
         if (!sc_aoa_push_hid_event(kb->aoa, &hid_event)) {
             sc_hid_event_destroy(&hid_event);
-            LOGW("Could request HID event");
+            LOGW("Could not request HID event (key)");
         }
     }
 }

app/src/usb/hid_mouse.c

@@ -181,7 +181,7 @@ sc_mouse_processor_process_mouse_motion(struct sc_mouse_processor *mp,
 
     if (!sc_aoa_push_hid_event(mouse->aoa, &hid_event)) {
         sc_hid_event_destroy(&hid_event);
-        LOGW("Could request HID event");
+        LOGW("Could not request HID event (mouse motion)");
     }
 }
 
@@ -203,7 +203,7 @@ sc_mouse_processor_process_mouse_click(struct sc_mouse_processor *mp,
 
     if (!sc_aoa_push_hid_event(mouse->aoa, &hid_event)) {
         sc_hid_event_destroy(&hid_event);
-        LOGW("Could request HID event");
+        LOGW("Could not request HID event (mouse click)");
     }
 }
 
@@ -228,7 +228,7 @@ sc_mouse_processor_process_mouse_scroll(struct sc_mouse_processor *mp,
 
     if (!sc_aoa_push_hid_event(mouse->aoa, &hid_event)) {
         sc_hid_event_destroy(&hid_event);
-        LOGW("Could request HID event");
+        LOGW("Could not request HID event (mouse scroll)");
     }
 }
 

app/src/usb/scrcpy_otg.c

@@ -29,26 +29,26 @@ sc_usb_on_disconnected(struct sc_usb *usb, void *userdata) {
     }
 }
 
-static bool
+static enum scrcpy_exit_code
 event_loop(struct scrcpy_otg *s) {
     SDL_Event event;
     while (SDL_WaitEvent(&event)) {
         switch (event.type) {
             case EVENT_USB_DEVICE_DISCONNECTED:
                 LOGW("Device disconnected");
-                return false;
+                return SCRCPY_EXIT_DISCONNECTED;
             case SDL_QUIT:
                 LOGD("User requested to quit");
-                return true;
+                return SCRCPY_EXIT_SUCCESS;
             default:
                 sc_screen_otg_handle_event(&s->screen_otg, &event);
                 break;
         }
     }
-    return false;
+    return SCRCPY_EXIT_FAILURE;
 }
 
-bool
+enum scrcpy_exit_code
 scrcpy_otg(struct scrcpy_options *options) {
     static struct scrcpy_otg scrcpy_otg;
     struct scrcpy_otg *s = &scrcpy_otg;
@@ -67,7 +67,7 @@ scrcpy_otg(struct scrcpy_options *options) {
         LOGW("Could not enable mouse focus clickthrough");
     }
 
-    bool ret = false;
+    enum scrcpy_exit_code ret = SCRCPY_EXIT_FAILURE;
 
     struct sc_hid_keyboard *keyboard = NULL;
     struct sc_hid_mouse *mouse = NULL;
@@ -90,7 +90,7 @@ scrcpy_otg(struct scrcpy_options *options) {
     };
     bool ok = sc_usb_init(&s->usb);
     if (!ok) {
-        return false;
+        return SCRCPY_EXIT_FAILURE;
     }
 
     struct sc_usb_device usb_device;

app/src/usb/scrcpy_otg.h

@@ -3,10 +3,10 @@
 
 #include "common.h"
 
-#include <stdbool.h>
 #include "options.h"
+#include "scrcpy.h"
 
-bool
+enum scrcpy_exit_code
 scrcpy_otg(struct scrcpy_options *options);
 
 #endif

app/src/usb/usb.c

@@ -15,6 +15,7 @@ read_string(libusb_device_handle *handle, uint8_t desc_index) {
                                            (unsigned char *) buffer,
                                            sizeof(buffer));
     if (result < 0) {
+        LOGD("Read string: libusb error: %s", libusb_strerror(result));
         return NULL;
     }