add lv_slider_set/get_sym

src/lv_objx/lv_slider.c

@@ -316,6 +316,8 @@ static bool lv_slider_design(lv_obj_t * slider, const lv_area_t * mask, lv_desig
 
         /*If dragged draw to the drag position*/
         if(ext->drag_value != LV_SLIDER_NOT_PRESSED) cur_value = ext->drag_value;
+        bool sym = false;
+        if(ext->bar.sym && ext->bar.min_value < 0 && ext->bar.max_value > 0) sym = true;
 
         if(slider_w >= slider_h) {
             lv_coord_t indic_w = lv_area_get_width(&area_indic);
@@ -335,7 +337,19 @@ static bool lv_slider_design(lv_obj_t * slider, const lv_area_t * mask, lv_desig
             {
                 area_indic.x2 = (int32_t)((int32_t)indic_w * (cur_value - min_value)) / (max_value - min_value);
             }
+
             area_indic.x2 = area_indic.x1 + area_indic.x2 - 1;
+            if(sym) {
+                /*Calculate the coordinate of the zero point*/
+                lv_coord_t zero;
+                zero = area_indic.x1 + (-ext->bar.min_value * slider_w) / (ext->bar.max_value - ext->bar.min_value);
+                if(area_indic.x2 > zero)
+                    area_indic.x1 = zero;
+                else {
+                    area_indic.x1 = area_indic.x2;
+                    area_indic.x2 = zero;
+                }
+            }
 
             /*Draw the indicator but don't draw an ugly 1px wide rectangle on the left on min.
              * value*/
@@ -359,8 +373,21 @@ static bool lv_slider_design(lv_obj_t * slider, const lv_area_t * mask, lv_desig
             {
                 area_indic.y1 = (int32_t)((int32_t)indic_h * (cur_value - min_value)) / (max_value - min_value);
             }
+
             area_indic.y1 = area_indic.y2 - area_indic.y1 + 1;
 
+            if(sym) {
+                /*Calculate the coordinate of the zero point*/
+                lv_coord_t zero;
+                zero = area_indic.y2 - (-ext->bar.min_value * slider_h) / (ext->bar.max_value - ext->bar.min_value);
+                if(area_indic.y1 < zero)
+                    area_indic.y2 = zero;
+                else {
+                    area_indic.y2 = area_indic.y1;
+                    area_indic.y1 = zero;
+                }
+            }
+
             /*Draw the indicator but don't draw an ugly 1px height rectangle on the bottom on min.
              * value*/
             if(area_indic.x1 != area_indic.x2) lv_draw_rect(&area_indic, mask, style_indic, opa_scale);
@@ -386,7 +413,12 @@ static bool lv_slider_design(lv_obj_t * slider, const lv_area_t * mask, lv_desig
 
         if(slider_w >= slider_h) {
             if(ext->knob_in == 0) {
-                knob_area.x1 = area_indic.x2 - slider_h / 2;
+                if(sym == false) {
+                    knob_area.x1 = area_indic.x2 - slider_h / 2;
+                } else {
+                    if(cur_value > 0) knob_area.x1 = area_indic.x2 - slider_h / 2;
+                    else knob_area.x1 = area_indic.x1 - slider_h / 2;
+                }
                 knob_area.x2 = knob_area.x1 + slider_h - 1;
             } else {
 #if LV_USE_ANIMATION
@@ -415,7 +447,12 @@ static bool lv_slider_design(lv_obj_t * slider, const lv_area_t * mask, lv_desig
             knob_area.y2 = slider->coords.y2;
         } else {
             if(ext->knob_in == 0) {
-                knob_area.y1 = area_indic.y1 - slider_w / 2;
+                if(sym == false) {
+                    knob_area.y1 = area_indic.y1 - slider_w / 2;
+                } else {
+                    if(cur_value > 0)  knob_area.y1 = area_indic.y1 - slider_w / 2;
+                    else  knob_area.y1 = area_indic.y2 - slider_w / 2;
+                }
                 knob_area.y2 = knob_area.y1 + slider_w - 1;
             } else {
 #if LV_USE_ANIMATION

src/lv_objx/lv_slider.h

@@ -93,15 +93,26 @@ static inline void lv_slider_set_range(lv_obj_t * slider, int16_t min, int16_t m
 }
 
 /**
- * Set the animation time of the slider
+ * Make the slider symmetric to zero. The indicator will grow from zero instead of the minimum
- * @param slider pointer to a bar object
+ * position.
- * @param anim_time the animation time in milliseconds.
+ * @param slider pointer to a slider object
+ * @param en true: enable disable symmetric behavior; false: disable
  */
 static inline void lv_slider_set_anim_time(lv_obj_t * slider, uint16_t anim_time)
 {
     lv_bar_set_anim_time(slider, anim_time);
 }
 
+/**
+ * Set the animation time of the slider
+ * @param slider pointer to a bar object
+ * @param anim_time the animation time in milliseconds.
+ */
+static inline void lv_slider_set_sym(lv_obj_t * slider, bool en)
+{
+    lv_bar_set_sym(slider, en);
+}
+
 /**
  * Set the 'knob in' attribute of a slider
  * @param slider pointer to slider object
@@ -156,6 +167,26 @@ static inline int16_t lv_slider_get_max_value(const lv_obj_t * slider)
  */
 bool lv_slider_is_dragged(const lv_obj_t * slider);
 
+/**
+ * Get the animation time of the slider
+ * @param slider pointer to a slider object
+ * @return the animation time in milliseconds.
+ */
+static inline uint16_t lv_slider_get_anim_time(lv_obj_t * slider)
+{
+    return lv_bar_get_anim_time(slider);
+}
+
+/**
+ * Get whether the slider is symmetric or not.
+ * @param slider pointer to a bar object
+ * @return true: symmetric is enabled; false: disable
+ */
+static inline bool lv_slider_get_sym(lv_obj_t * slider)
+{
+    return lv_bar_get_sym(slider);
+}
+
 /**
  * Get the 'knob in' attribute of a slider
  * @param slider pointer to slider object