Add display id parameter

Add --display command line parameter to specify a display id.

app/scrcpy.1

@@ -33,6 +33,15 @@ The values are expressed in the device natural orientation (typically, portrait
 .B \-\-max\-size
 value is computed on the cropped size.
 
+.TP
+.BI "\-\-display " id
+Specify the display id to mirror.
+
+The list of possible display ids can be listed by "adb shell dumpsys display"
+(search "mDisplayId=" in the output).
+
+Default is 0.
+
 .TP
 .B \-f, \-\-fullscreen
 Start in fullscreen.

app/src/cli.c

@@ -36,6 +36,15 @@ scrcpy_print_usage(const char *arg0) {
         "        (typically, portrait for a phone, landscape for a tablet).\n"
         "        Any --max-size value is computed on the cropped size.\n"
         "\n"
+        "    --display id\n"
+        "        Specify the display id to mirror.\n"
+        "\n"
+        "        The list of possible display ids can be listed by:\n"
+        "            adb shell dumpsys display\n"
+        "        (search \"mDisplayId=\" in the output)\n"
+        "\n"
+        "        Default is 0.\n"
+        "\n"
         "    -f, --fullscreen\n"
         "        Start in fullscreen.\n"
         "\n"
@@ -363,6 +372,18 @@ parse_port_range(const char *s, struct port_range *port_range) {
     return true;
 }
 
+static bool
+parse_display_id(const char *s, uint16_t *display_id) {
+    long value;
+    bool ok = parse_integer_arg(s, &value, false, 0, 0xFFFF, "display id");
+    if (!ok) {
+        return false;
+    }
+
+    *display_id = (uint16_t) value;
+    return true;
+}
+
 static bool
 parse_record_format(const char *optarg, enum recorder_format *format) {
     if (!strcmp(optarg, "mp4")) {
@@ -407,6 +428,7 @@ guess_record_format(const char *filename) {
 #define OPT_WINDOW_BORDERLESS      1011
 #define OPT_MAX_FPS                1012
 #define OPT_LOCK_VIDEO_ORIENTATION 1013
+#define OPT_DISPLAY_ID             1014
 
 bool
 scrcpy_parse_args(struct scrcpy_cli_args *args, int argc, char *argv[]) {
@@ -414,6 +436,7 @@ scrcpy_parse_args(struct scrcpy_cli_args *args, int argc, char *argv[]) {
         {"always-on-top",          no_argument,       NULL, OPT_ALWAYS_ON_TOP},
         {"bit-rate",               required_argument, NULL, 'b'},
         {"crop",                   required_argument, NULL, OPT_CROP},
+        {"display",                required_argument, NULL, OPT_DISPLAY_ID},
         {"fullscreen",             no_argument,       NULL, 'f'},
         {"help",                   no_argument,       NULL, 'h'},
         {"lock-video-orientation", required_argument, NULL,
@@ -462,6 +485,11 @@ scrcpy_parse_args(struct scrcpy_cli_args *args, int argc, char *argv[]) {
             case OPT_CROP:
                 opts->crop = optarg;
                 break;
+            case OPT_DISPLAY_ID:
+                if (!parse_display_id(optarg, &opts->display_id)) {
+                    return false;
+                }
+                break;
             case 'f':
                 opts->fullscreen = true;
                 break;

app/src/scrcpy.c

@@ -286,6 +286,7 @@ scrcpy(const struct scrcpy_options *options) {
         .max_fps = options->max_fps,
         .lock_video_orientation = options->lock_video_orientation,
         .control = options->control,
+        .display_id = options->display_id,
     };
     if (!server_start(&server, options->serial, &params)) {
         return false;

app/src/scrcpy.h

@@ -25,6 +25,7 @@ struct scrcpy_options {
     int16_t window_y; // WINDOW_POSITION_UNDEFINED for "auto"
     uint16_t window_width;
     uint16_t window_height;
+    uint16_t display_id;
     bool show_touches;
     bool fullscreen;
     bool always_on_top;
@@ -55,6 +56,7 @@ struct scrcpy_options {
     .window_y = WINDOW_POSITION_UNDEFINED, \
     .window_width = 0, \
     .window_height = 0, \
+    .display_id = 0, \
     .show_touches = false, \
     .fullscreen = false, \
     .always_on_top = false, \

app/src/server.c

@@ -234,10 +234,12 @@ execute_server(struct server *server, const struct server_params *params) {
     char bit_rate_string[11];
     char max_fps_string[6];
     char lock_video_orientation_string[3];
+    char display_id_string[6];
     sprintf(max_size_string, "%"PRIu16, params->max_size);
     sprintf(bit_rate_string, "%"PRIu32, params->bit_rate);
     sprintf(max_fps_string, "%"PRIu16, params->max_fps);
     sprintf(lock_video_orientation_string, "%"PRIi8, params->lock_video_orientation);
+    sprintf(display_id_string, "%"PRIu16, params->display_id);
     const char *const cmd[] = {
         "shell",
         "CLASSPATH=" DEVICE_SERVER_PATH,
@@ -264,6 +266,7 @@ execute_server(struct server *server, const struct server_params *params) {
         params->crop ? params->crop : "-",
         "true", // always send frame meta (packet boundaries + timestamp)
         params->control ? "true" : "false",
+        display_id_string,
     };
 #ifdef SERVER_DEBUGGER
     LOGI("Server debugger waiting for a client on device port "

app/src/server.h

@@ -44,6 +44,7 @@ struct server_params {
     uint16_t max_fps;
     int8_t lock_video_orientation;
     bool control;
+    uint16_t display_id;
 };
 
 // init default values