feat: add marker operation groupdelay->edelay

nanovna.h

@@ -206,6 +206,7 @@ void draw_battery_status(void);
 
 void set_electrical_delay(float picoseconds);
 float get_electrical_delay(void);
+float groupdelay_from_array(int i, float array[101][2]);
 
 // marker
 

plot.c

@@ -503,7 +503,7 @@ cartesian_scale(float re, float im, int *xp, int *yp, float scale)
   *yp = HEIGHT/2 - y;
 }
 
-static float
+float
 groupdelay_from_array(int i, float array[101][2])
 {
   if (i == 0) {

ui.c

@@ -818,11 +818,13 @@ menu_marker_op_cb(int item)
   case 3: /* MARKERS->SPAN */
     {
       if (previous_marker == -1 || active_marker == previous_marker) {
+        // if only 1 marker is active, keep center freq and make span the marker comes to the edge  
         int32_t center = get_sweep_frequency(ST_CENTER);
         int32_t span = center - freq;
         if (span < 0) span = -span;
         set_sweep_frequency(ST_SPAN, span * 2);
       } else {
+        // if 2 or more marker active, set start and stop freq to each marker
         int32_t freq2 = get_marker_frequency(previous_marker);
         if (freq2 < 0)
           return;
@@ -835,6 +837,13 @@ menu_marker_op_cb(int item)
       }
     }
     break;
+  case 4: /* MARKERS->EDELAY */
+    { 
+      float (*array)[2] = measured[trace[uistat.current_trace].channel];
+      float v = groupdelay_from_array(markers[active_marker].index, array);
+      set_electrical_delay(electrical_delay + (v / 1e-12));
+    }
+    break;
   }
   ui_mode_normal();
   draw_cal_status();
@@ -1052,6 +1061,7 @@ const menuitem_t menu_marker_ops[] = {
   { MT_CALLBACK, S_RARROW"STOP", menu_marker_op_cb },
   { MT_CALLBACK, S_RARROW"CENTER", menu_marker_op_cb },
   { MT_CALLBACK, S_RARROW"SPAN", menu_marker_op_cb },
+  { MT_CALLBACK, S_RARROW"EDELAY", menu_marker_op_cb },
   { MT_CANCEL, S_LARROW" BACK", NULL },
   { MT_NONE, NULL, NULL } // sentinel
 };