1.可分别设置组合框中编辑框和下拉列表框的字体、字体颜色、字体大小

2.可设置只读属性

3.可根据下拉列表项的文本长度扩宽下拉列表宽度

4.重绘下拉列表，包括边框和具有焦点的项

5.下拉列表项中提供了删除功能，非只读时显示并可删除

6.重绘了编辑框边框，背景自绘可自行扩展

7.根据组合框高度设置字体能达到伪垂直居中效果，主要就是需要这个-1 can be set combo box edit box and drop-down list box, font, font color, font size, (2) can be set to read-only attribute 3. According to the drop-down list item text length widening dropdown width 4. Redraw the drop-down list including borders and items with focus 5 provides a drop-down list item delete function, not read-only and can be removed when the display 6. redraw the edit box border, background, since the painting can expand their own 7. According to the combo box to set the font height Pseudo vertically to achieve the effect, mainly need this