Add --list-displays

Add an option to list the device displays properly.

app/src/cli.c

@@ -69,6 +69,7 @@ enum {
     OPT_AUDIO_CODEC_OPTIONS,
     OPT_AUDIO_ENCODER,
     OPT_LIST_ENCODERS,
+    OPT_LIST_DISPLAYS,
 };
 
 struct sc_option {
@@ -198,10 +199,9 @@ static const struct sc_option options[] = {
         .longopt_id = OPT_DISPLAY_ID,
         .longopt = "display",
         .argdesc = "id",
-        .text = "Specify the display id to mirror.\n"
-                "The list of possible display ids can be listed by:\n"
-                "    adb shell dumpsys display\n"
-                "(search \"mDisplayId=\" in the output)\n"
+        .text = "Specify the device display id to mirror.\n"
+                "The available display ids can be listed by:\n"
+                "    scrcpy --list-displays\n"
                 "Default is 0.",
     },
     {
@@ -272,6 +272,11 @@ static const struct sc_option options[] = {
                 "This is a workaround for some devices not behaving as "
                 "expected when setting the device clipboard programmatically.",
     },
+    {
+        .longopt_id = OPT_LIST_DISPLAYS,
+        .longopt = "list-displays",
+        .text = "List device displays.",
+    },
     {
         .longopt_id = OPT_LIST_ENCODERS,
         .longopt = "list-encoders",
@@ -1803,6 +1808,9 @@ parse_args_with_getopt(struct scrcpy_cli_args *args, int argc, char *argv[],
             case OPT_LIST_ENCODERS:
                 opts->list_encoders = true;
                 break;
+            case OPT_LIST_DISPLAYS:
+                opts->list_displays = true;
+                break;
             default:
                 // getopt prints the error message on stderr
                 return false;

app/src/options.c

@@ -73,4 +73,5 @@ const struct scrcpy_options scrcpy_options_default = {
     .power_on = true,
     .audio = true,
     .list_encoders = false,
+    .list_displays = false,
 };

app/src/options.h

@@ -155,6 +155,7 @@ struct scrcpy_options {
     bool power_on;
     bool audio;
     bool list_encoders;
+    bool list_displays;
 };
 
 extern const struct scrcpy_options scrcpy_options_default;

app/src/scrcpy.c

@@ -353,6 +353,7 @@ scrcpy(struct scrcpy_options *options) {
         .cleanup = options->cleanup,
         .power_on = options->power_on,
         .list_encoders = options->list_encoders,
+        .list_displays = options->list_displays,
     };
 
     static const struct sc_server_callbacks cbs = {
@@ -370,7 +371,7 @@ scrcpy(struct scrcpy_options *options) {
 
     server_started = true;
 
-    if (options->list_encoders) {
+    if (options->list_encoders || options->list_displays) {
         bool ok = await_for_server(NULL);
         ret = ok ? SCRCPY_EXIT_SUCCESS : SCRCPY_EXIT_FAILURE;
         goto end;

app/src/server.c

@@ -303,6 +303,9 @@ execute_server(struct sc_server *server,
     if (params->list_encoders) {
         ADD_PARAM("list_encoders=true");
     }
+    if (params->list_displays) {
+        ADD_PARAM("list_displays=true");
+    }
 
 #undef ADD_PARAM
 
@@ -856,9 +859,9 @@ run_server(void *data) {
         goto error_connection_failed;
     }
 
-    // If --list-encoders is passed, then the server just prints the encoders
+    // If --list-* is passed, then the server just prints the requested data
     // then exits.
-    if (params->list_encoders) {
+    if (params->list_encoders || params->list_displays) {
         sc_pid pid = execute_server(server, params);
         if (pid == SC_PROCESS_NONE) {
             goto error_connection_failed;

app/src/server.h

@@ -56,6 +56,7 @@ struct sc_server_params {
     bool cleanup;
     bool power_on;
     bool list_encoders;
+    bool list_displays;
 };
 
 struct sc_server {