屏幕默认的显示比例是100%，但是有些用户喜欢调到“中等”或“较大”，这样的话，就可能导致我们开发的应用超出屏幕边界。因此，我们要获取屏幕显示比例，做出相应的处理。
Primary display DPI scale factor
Similarly, you can get the pixel density by using the LOGPIXELSX and LOGPIXELSY indices:
syntax
// Get desktop dc
desktopDc = GetDC(NULL);
// Get native resolution
horizontalDPI = GetDeviceCaps(desktopDc,LOGPIXELSX);
verticalDPI = GetDeviceCaps(desktopDc,LOGPIXELSY);
These results are returned in a coordinate system in which 96 corresponds to 100%, as shown inTable 2 DPI Scale Factors.
