在vc++环境下实现画板的功能，可以更改输出的颜色，线条的线型和粗细；可以输出字体，退格换行；可以更改对话框的颜色和对话框的字体颜色。-In vc++ environment to achieve Sketchpad features, you can change the output of color, line thickness and line style may output the font, backspace wra