Allow negative values in menus

Marlin/ultralcd.cpp

 #define menu_edit_type(_type, _name, _strFunc, scale) \
     void menu_edit_ ## _name () \
     { \
-        if ((int32_t)encoderPosition < minEditValue) \
-            encoderPosition = minEditValue; \
+        if ((int32_t)encoderPosition < 0) \
+            encoderPosition = 0; \
         if ((int32_t)encoderPosition > maxEditValue) \
             encoderPosition = maxEditValue; \
         if (lcdDrawUpdate) \
-            lcd_implementation_drawedit(editLabel, _strFunc(((_type)encoderPosition) / scale)); \
+            lcd_implementation_drawedit(editLabel, _strFunc(((_type)((int32_t)encoderPosition + minEditValue)) / scale)); \
         if (LCD_CLICKED) \
         { \
-            *((_type*)editValue) = ((_type)encoderPosition) / scale; \
+            *((_type*)editValue) = ((_type)((int32_t)encoderPosition + minEditValue)) / scale; \
             lcd_quick_feedback(); \
             currentMenu = prevMenu; \
             encoderPosition = prevEncoderPosition; \
     } \
     void menu_edit_callback_ ## _name () \
     { \
-        if ((int32_t)encoderPosition < minEditValue) \
-            encoderPosition = minEditValue; \
+        if ((int32_t)encoderPosition < 0) \
+            encoderPosition = 0; \
         if ((int32_t)encoderPosition > maxEditValue) \
             encoderPosition = maxEditValue; \
         if (lcdDrawUpdate) \
-            lcd_implementation_drawedit(editLabel, _strFunc(((_type)encoderPosition) / scale)); \
+            lcd_implementation_drawedit(editLabel, _strFunc(((_type)((int32_t)encoderPosition + minEditValue)) / scale)); \
         if (LCD_CLICKED) \
         { \
-            *((_type*)editValue) = ((_type)encoderPosition) / scale; \
+            *((_type*)editValue) = ((_type)((int32_t)encoderPosition + minEditValue)) / scale; \
             lcd_quick_feedback(); \
             currentMenu = prevMenu; \
             encoderPosition = prevEncoderPosition; \
         editLabel = pstr; \
         editValue = ptr; \
         minEditValue = minValue * scale; \
-        maxEditValue = maxValue * scale; \
-        encoderPosition = (*ptr) * scale; \
+        maxEditValue = maxValue * scale - minEditValue; \
+        encoderPosition = (*ptr) * scale - minEditValue; \
     }\
     static void menu_action_setting_edit_callback_ ## _name (const char* pstr, _type* ptr, _type minValue, _type maxValue, menuFunc_t callback) \
     { \
         editLabel = pstr; \
         editValue = ptr; \
         minEditValue = minValue * scale; \
-        maxEditValue = maxValue * scale; \
-        encoderPosition = (*ptr) * scale; \
+        maxEditValue = maxValue * scale - minEditValue; \
+        encoderPosition = (*ptr) * scale - minEditValue; \
         callbackFunc = callback;\
     }
 menu_edit_type(int, int3, itostr3, 1)
   #ifdef SR_LCD_2W_NL // Non latching 2 wire shift register
      pinMode (SR_DATA_PIN, OUTPUT);
      pinMode (SR_CLK_PIN, OUTPUT);
-  #elif defined(SHIFT_CLK) 
+  #elif defined(SHIFT_CLK)
      pinMode(SHIFT_CLK,OUTPUT);
      pinMode(SHIFT_LD,OUTPUT);
      pinMode(SHIFT_EN,OUTPUT);