feat: add lever operation of electrical delay

main.c

@@ -1667,6 +1667,7 @@ void set_electrical_delay(float picoseconds)
     electrical_delay = picoseconds;
     force_set_markmap();
   }
+  redraw_request |= REDRAW_MARKER;
 }
 
 float get_electrical_delay(void)

nanovna.h

@@ -410,7 +410,7 @@ void clear_all_config_prop_data(void);
 
 // lever_mode
 enum lever_mode {
-  LM_MARKER, LM_SEARCH, LM_CENTER, LM_SPAN
+  LM_MARKER, LM_SEARCH, LM_CENTER, LM_SPAN, LM_EDELAY
 };
 
 // marker smith value format

plot.c

@@ -1599,6 +1599,10 @@ cell_draw_marker_info(int m, int n, int w, int h)
     xpos -= m * CELLWIDTH -CELLOFFSETX;
     ypos -= n * CELLHEIGHT;
 
+    if (uistat.lever_mode == LM_EDELAY)
+      cell_drawstring(w, h, S_SARROW, xpos, ypos);
+    xpos += 5;
+
     float light_speed_ps = 299792458e-12; //(m/ps)
     chsnprintf(buf, sizeof buf, "Edelay %Fs %Fm", electrical_delay * 1e-12,
                                                   electrical_delay * light_speed_ps * velocity_factor);

ui.c

@@ -1756,6 +1756,23 @@ lever_move(int status, int mode)
   }
 }
 
+#define STEPRATIO 0.2
+
+static void
+lever_edelay(int status)
+{
+  float value = get_electrical_delay();
+  float ratio = STEPRATIO;
+  if (value < 0)
+    ratio = -ratio;
+  if (status & EVT_UP) {
+    value = (1 - ratio) * value;
+  } else if (status & EVT_DOWN) {
+    value = (1 + ratio) * value;
+  }
+  set_electrical_delay(value);
+}
+
 static void
 ui_process_normal(void)
 {
@@ -1776,6 +1793,9 @@ ui_process_normal(void)
         else
         lever_zoom_span(status);
         break;
+      case LM_EDELAY:
+        lever_edelay(status);
+        break;
       }
     }
   }
@@ -2156,6 +2176,9 @@ touch_lever_mode_select(void)
   }
 
   if (touch_y < 15) {
+    if (touch_x < 160 && get_electrical_delay() != 0.0) {
+      select_lever_mode(LM_EDELAY);
+    } else 
       select_lever_mode(LM_MARKER);
     return TRUE;
   }