1·The garbage collector moves valid blocks to the tail of the log, skips invalid or obsolete blocks, and erases them (see Figure 2).
垃圾收集器将有效块移动到日志的尾部,跳过无效或废弃块,并擦除它们(参见图 2)。
2·In particular, it erases the original image of the control and then repaints it in the new location.
尤其是,它擦除控件的原有图像然后再在新位置重新绘制图像。