uart: support backspace for RX input

src/event.cpp

@@ -52,8 +52,11 @@ void read_event() {
     case SDL_MOUSEBUTTONDOWN: mousedown_handler(ev); break;
     case SDL_MOUSEBUTTONUP: mouseup_handler(ev); break;
     case SDL_KEYDOWN:
-      if (ev.key.keysym.sym == SDLK_RETURN && focus_uart_rx_term) {
-        uart_rx_getchar('\n');
+      if (focus_uart_rx_term) {
+        switch (ev.key.keysym.sym) {
+          case SDLK_RETURN: uart_rx_getchar('\n'); break;
+          case SDLK_BACKSPACE: uart_rx_getchar('\b'); break;
+        }
       }
     case SDL_KEYUP:
       if (!focus_uart_rx_term) kb_push_key(ev.key.keysym.scancode, ev.key.type == SDL_KEYDOWN);

src/term.cpp

@@ -80,9 +80,13 @@ void Term::feed_ch(uint8_t ch) {
   if (ch == '\n') {
     newline();
     return;
+  } else if (ch == '\b') {
+    if (cursor_x > 0) cursor_x --;  // FIXME: back to the last line for input
+    lines[y][cursor_x] = ' ';
+    if (is_cursor_on_screen()) set_dirty_char(cursor_y - screen_y, cursor_x);
+    return;
   }
-  uint8_t *l = lines[y];
-  l[cursor_x] = ch;
+  lines[y][cursor_x] = ch;
   cursor_x ++;
   if (cursor_x == w_in_char) newline();
 }

src/uart.cpp

@@ -90,7 +90,11 @@ void UART::rx_getchar(uint8_t ch) {
     rx_input = "";
   }
   else {
-    rx_input += ch;
+    if (ch == '\b') {
+      if (rx_input.empty()) return;
+      rx_input.pop_back();
+    }
+    else { rx_input += ch; }
     rx_term->feed_ch(ch);
   }
   rx_update_gui = true;