fix(scale): don't return early on main drawing when having 1 or less ticks (#10010)

src/widgets/scale/lv_scale.c

@@ -1017,10 +1017,18 @@ static void scale_calculate_main_compensation(lv_obj_t * obj)
 
     const uint32_t total_tick_count = scale->total_tick_count;
 
-    if(total_tick_count <= 1) return;
     /* Not supported in round modes */
     if(LV_SCALE_MODE_ROUND_OUTER == scale->mode || LV_SCALE_MODE_ROUND_INNER == scale->mode) return;
 
+    /* Reset compensation when scale has 1 or less ticks on vertical and horizontal scales */
+    if(total_tick_count <= 1) {
+        /* Store initial tick width to be used in the main line drawing */
+        scale_store_main_line_tick_width_compensation(obj, 0U, false, 0U, 0U);
+
+        /* Store last tick width to be used in the main line drawing */
+        scale_store_main_line_tick_width_compensation(obj, total_tick_count, false, 0U, 0U);
+    }
+
     /* Major tick style */
     lv_draw_line_dsc_t major_tick_dsc;
     lv_draw_line_dsc_init(&major_tick_dsc);
@@ -1075,8 +1083,6 @@ static void scale_draw_main(lv_obj_t * obj, lv_event_t * event)
     lv_scale_t * scale = (lv_scale_t *)obj;
     lv_layer_t * layer = lv_event_get_layer(event);
 
-    if(scale->total_tick_count <= 1) return;
-
     if((LV_SCALE_MODE_VERTICAL_LEFT == scale->mode || LV_SCALE_MODE_VERTICAL_RIGHT == scale->mode)
        || (LV_SCALE_MODE_HORIZONTAL_BOTTOM == scale->mode || LV_SCALE_MODE_HORIZONTAL_TOP == scale->mode)) {
 

tests/src/test_cases/widgets/test_scale.c

@@ -637,4 +637,23 @@ void test_scale_properties(void)
 #endif
 }
 
+void test_scale_with_1_tick(void)
+{
+    /* When the scale has 1 (or less) ticks, only the main part should be drawn,
+     * no ticks nor labels are expected to be drawn. */
+    lv_obj_t * lv_obj_t_id = lv_scale_create(lv_screen_active());
+    lv_obj_set_style_height(lv_obj_t_id, lv_pct(100), LV_PART_MAIN);
+    lv_obj_set_style_width(lv_obj_t_id, lv_pct(100), LV_PART_MAIN);
+    lv_obj_set_style_align(lv_obj_t_id, LV_ALIGN_CENTER, LV_PART_MAIN);
+    lv_obj_set_style_bg_opa(lv_obj_t_id, LV_OPA_TRANSP, LV_PART_MAIN);
+    lv_obj_set_style_radius(lv_obj_t_id, LV_RADIUS_CIRCLE, 0);
+    lv_scale_set_mode(lv_obj_t_id, LV_SCALE_MODE_ROUND_INNER);
+    lv_scale_set_range(lv_obj_t_id, 0, 100);
+    lv_scale_set_angle_range(lv_obj_t_id, 180);
+    lv_scale_set_rotation(lv_obj_t_id, 270);
+    lv_scale_set_total_tick_count(lv_obj_t_id, 1);
+
+    TEST_ASSERT_EQUAL_SCREENSHOT("widgets/scale_9.png");
+}
+
 #endif