Fix warnings

Fix warnings reported with -Dwarning_level=2.

app/src/receiver.c

@@ -23,7 +23,7 @@ receiver_destroy(struct receiver *receiver) {
 }
 
 static void
-process_msg(struct receiver *receiver, struct device_msg *msg) {
+process_msg(struct device_msg *msg) {
     switch (msg->type) {
         case DEVICE_MSG_TYPE_CLIPBOARD:
             LOGI("Device clipboard copied");
@@ -33,7 +33,7 @@ process_msg(struct receiver *receiver, struct device_msg *msg) {
 }
 
 static ssize_t
-process_msgs(struct receiver *receiver, const unsigned char *buf, size_t len) {
+process_msgs(const unsigned char *buf, size_t len) {
     size_t head = 0;
     for (;;) {
         struct device_msg msg;
@@ -45,7 +45,7 @@ process_msgs(struct receiver *receiver, const unsigned char *buf, size_t len) {
             return head;
         }
 
-        process_msg(receiver, &msg);
+        process_msg(&msg);
         device_msg_destroy(&msg);
 
         head += r;
@@ -72,7 +72,7 @@ run_receiver(void *data) {
             break;
         }
 
-        ssize_t consumed = process_msgs(receiver, buf, r);
+        ssize_t consumed = process_msgs(buf, r);
         if (consumed == -1) {
             // an error occurred
             break;

app/src/scrcpy.c

@@ -201,6 +201,7 @@ handle_event(SDL_Event *event, bool control) {
 
 static bool
 event_loop(bool display, bool control) {
+    (void) display;
 #ifdef CONTINUOUS_RESIZING_WORKAROUND
     if (display) {
         SDL_AddEventWatch(event_watcher, NULL);
@@ -256,6 +257,7 @@ sdl_priority_from_av_level(int level) {
 
 static void
 av_log_callback(void *avcl, int level, const char *fmt, va_list vl) {
+    (void) avcl;
     SDL_LogPriority priority = sdl_priority_from_av_level(level);
     if (priority == 0) {
         return;

app/src/screen.c

@@ -185,8 +185,8 @@ screen_init_rendering(struct screen *screen, const char *window_title,
         window_flags |= SDL_WINDOW_BORDERLESS;
     }
 
-    int x = window_x != -1 ? window_x : SDL_WINDOWPOS_UNDEFINED;
-    int y = window_y != -1 ? window_y : SDL_WINDOWPOS_UNDEFINED;
+    int x = window_x != -1 ? window_x : (int) SDL_WINDOWPOS_UNDEFINED;
+    int y = window_y != -1 ? window_y : (int) SDL_WINDOWPOS_UNDEFINED;
     screen->window = SDL_CreateWindow(window_title, x, y,
                                       window_size.width, window_size.height,
                                       window_flags);