MiniGUI下获取屏幕分辨率用
unsigned int GetGDCapability (HDC hdc, int iItem)
// 屏幕宽度
int screen_width = GetGDCapability(HDC_SCREEN,GDCAP_HPIXEL);
// 屏幕高度
int screen_height =GetGDCapability(HDC_SCREEN,GDCAP_VPIXEL);GetGDCapability 用于返回HDC的参数，如果hdc参数为HDC_SCREEN,返回的就是屏幕DC的相关参数，不同的iItem值返回不同的参数：
GDCAP_COLORNUM
Tell GetGDCapability to return the colors number of the DC. Note the for a DC with 32-bit depth, the function will return 0xFFFFFFFF, not 0x100000000.
GDCAP_HPIXEL
Tell GetGCapability to return the horizontal resolution of the DC.
GDCAP_VPIXEL
Tell GetGDCapability to return the vertical resolution of the DC.
GDCAP_MAXX
Tell GetGDCapability to return the maximal visible x value of the DC.
GDCAP_MAXY
Tell GetGDCapability to return the maximal visible y value of the DC.
GDCAP_DEPTH
Tell GetGDCapability to return the color depth of the DC. The returned value can be 1, 4, 8, 15, 16, 24, or 32.
GDCAP_BITSPP
Tell GetGDCapability to return the bits number for storing a pixle in the DC.
GDCAP_BPP
Tell GetGDCapability to return the bytes number for storing a pixle in the DC.
GDCAP_RMASK
Tell GetGDCapability to return the pixel red color mask for the DC.
GDCAP_GMASK
Tell GetGDCapability to return the pixel green color mask for the DC.
GDCAP_BMASK
Tell GetGDCapability to return the pixel blue color mask for the DC.
GDCAP_AMASK
Tell GetGDCapability to return the pixel alpha color mask for the DC.
GDCAP_PITCH
Tell GetGDCapability to return the pitch (the bytes of one scan line) of the DC.
官方API说明参见：
http://www.minigui.com/api_ref/3.0.12_processes/group__dc__fns.html