simulator: add USB serial input field

movement/movement.c

@@ -25,7 +25,11 @@
 #include <stdio.h>
 #include <string.h>
 #include <limits.h>
+#include <string.h>
+#include <stdlib.h>
+#include <stdio.h>
 #include "watch.h"
+#include "filesystem.h"
 #include "movement.h"
 
 #ifndef MOVEMENT_FIRMWARE
@@ -423,6 +427,32 @@ bool app_loop(void) {
         }
     }
 
+    // if we are plugged into USB, handle the file browser tasks
+    if (watch_is_usb_enabled()) {
+        char line[256] = {0};
+#if __EMSCRIPTEN__
+        // This is a terrible hack; ideally this should be handled deeper in the watch library.
+        // Alas, emscripten treats read() as something that should pop up an input box, so I
+        // wasn't able to implement this over there. I sense that this relates to read() being
+        // the wrong way to read data from USB (like we should be using fgets or something), but
+        // until I untangle that, this will have to do.
+        char *received_data = (char*)EM_ASM_INT({
+            var len = lengthBytesUTF8(tx) + 1;
+            var s = _malloc(len);
+            stringToUTF8(tx, s, len);
+            return s;
+        });
+        memcpy(line, received_data, min(255, strlen(received_data)));
+        free(received_data);
+        EM_ASM({
+            tx = "";
+        });
+#else
+        read(0, line, 256);
+#endif
+        if (strlen(line)) printf(line);
+    }
+
     event.subsecond = 0;
 
     return can_sleep && (movement_state.light_ticks == -1) && !movement_state.is_buzzing;