Add hacky save "feature" (until I make a real one)

field.c

@@ -54,7 +54,7 @@ void field_fput(Field* f, FILE* stream) {
     Glyph* row_p = f_buffer + f_width * iy;
     for (Usz ix = 0; ix < f_width; ++ix) {
       char c = row_p[ix];
-      out_buffer[ix] = glyph_char_is_valid(c) ? c : '!';
+      out_buffer[ix] = glyph_char_is_valid(c) ? c : '?';
     }
     out_buffer[f_width] = '\n';
     out_buffer[f_width + 1] = '\0';

tui_main.c

@@ -1459,6 +1459,16 @@ void app_input_cmd(App_state* a, App_input_cmd ev) {
   }
 }
 
+bool app_hacky_try_save(App_state* a) {
+  if (!a->filename) return false;
+  if (a->field.height == 0 || a->field.width == 0) return false;
+  FILE* f = fopen(a->filename, "w");
+  if (!f) return false;
+  field_fput(&a->field, f);
+  fclose(f);
+  return true;
+}
+
 enum {
   Argopt_margins = UCHAR_MAX + 1,
   Argopt_osc_server,
@@ -1839,6 +1849,10 @@ int main(int argc, char** argv) {
       app_input_character(&app_state, '.');
       break;
 
+    case KEY_F(2):
+      app_hacky_try_save(&app_state);
+      break;
+
     default:
       if (key >= CHAR_MIN && key <= CHAR_MAX && is_valid_glyph((Glyph)key)) {
         app_input_character(&app_state, (char)key);