- to get image on window
 XGetImage() : get XImage from Drawable(Window)
 XGetPixel() : get pixel unsigned long from XImage
 XQueryColor() : get RGB info from pixel unsigned long
 XWriteBitmapFile() : ???

- backingstore
 DoesBackingStore(screen)

- handle with exposure events
 XQLength() : get queue length

- handle with colors
 BlackPixel macro :

- to get window opened to appropriate position
 WidthOfScreen macro :
 XParseGeometry() : get some xyvalues from DISPLAY ???
 give WM appropriate info.

- to write japanese text
 XDrawString[16]()
 XTextExtents[16]()
 # kokode XLoadQueryFont to sita koto ga ikite kuru
