add lv_draw_free_buf

src/lv_core/lv_refr.c

@@ -217,6 +217,8 @@ void lv_disp_refr_task(lv_task_t * task)
         }
     }
 
+    lv_draw_free_buf();
+
     LV_LOG_TRACE("lv_refr_task: ready");
 }
 

src/lv_draw/lv_draw.c

@@ -58,6 +58,15 @@ void * lv_draw_get_buf(uint32_t size)
     return draw_buf;
 }
 
+void lv_draw_free_buf(void)
+{
+    if(draw_buf) {
+        lv_mem_free(draw_buf);
+        draw_buf = NULL;
+        draw_buf_size = 0;
+    }
+}
+
 
 #if LV_ANTIALIAS
 

src/lv_draw/lv_draw.h

@@ -37,6 +37,8 @@ extern "C" {
 
 void * lv_draw_get_buf(uint32_t size);
 
+void lv_draw_free_buf(void);
+
 #if LV_ANTIALIAS
 
 /**