feat(spinbox ) add function to set cursor to specific position (#2314)

* Spinbox set cursor to specific position (funct.)

* changed exp10 to lv_pow(10

* Update lv_spinbox.c

resolved indentation

* Update spinbox.md

Added lv_spinbox_set_pos description

Co-authored-by: Sebastian Dyker <sebastian.dyker@walther-systemtechnik.com>

docs/widgets/extra/spinbox.md

@@ -20,6 +20,8 @@ The parts of the Spinbox are identical to the [Text area](/widgets/core/textarea
 
 `lv_spinbox_set_step(spinbox, 100)` sets which digits to change on increment/decrement. Only multiples of ten can be set, and not for example 3. 
 
+`lv_spinbox_set_pos(spinbox, 1)` sets the cursor to a specific digit to change on increment/decrement. For example position '0' sets the cursor to the least significant digit.
+
 ### Format
 
 `lv_spinbox_set_digit_format(spinbox, digit_count, separator_position)` sets the number format. `digit_count` is the number of digits excluding the decimal separator and the sign.

src/extra/widgets/spinbox/lv_spinbox.c

@@ -145,6 +145,23 @@ void lv_spinbox_set_range(lv_obj_t * obj, int32_t range_min, int32_t range_max)
     lv_spinbox_updatevalue(obj);
 }
 
+/**
+ * Set cursor position to a specific digit for edition
+ * @param spinbox pointer to spinbox
+ * @param pos selected position in spinbox
+ */
+void lv_spinbox_set_pos(lv_obj_t * obj, uint8_t pos)
+{
+
+    lv_spinbox_t * spinbox = (lv_spinbox_t *)obj;
+    int32_t step_limit;
+    step_limit       = LV_MAX(spinbox->range_max, (spinbox->range_min < 0 ? (-spinbox->range_min) : spinbox->range_min));
+    int32_t new_step = spinbox->step * lv_pow(10, pos);
+    if(pos <= 0) spinbox->step = 1;
+    else if(new_step <= step_limit) spinbox->step = new_step; 
+	
+    lv_spinbox_updatevalue(obj);
+}
 /*=====================
  * Getter functions
  *====================*/

src/extra/widgets/spinbox/lv_spinbox.h

@@ -99,6 +99,12 @@ void lv_spinbox_set_step(lv_obj_t * obj, uint32_t step);
  */
 void lv_spinbox_set_range(lv_obj_t * obj, int32_t range_min, int32_t range_max);
 
+/**
+ * Set cursor position to a specific digit for edition
+ * @param spinbox pointer to spinbox
+ * @param pos selected position in spinbox
+ */
+void lv_spinbox_set_pos(lv_obj_t * obj, uint8_t pos);
 /*=====================
  * Getter functions
  *====================*/