James Gettys, Robert W. Scheifler, et al.

“ A window usually but not always has a background pattern, which will be repainted by the window system when uncovered. Child windows obscure their parents, and graphic operations in the parent window usually are clipped by the children. ”

“ All Xlib functions begin with a capital X. The beginnings of all function names and symbols are capitalized. All user-visible data structures begin with a capital X. More generally, anything that a user might dereference begins with a capital X. Macros and other symbols do not begin with a capital X. To distinguish them from all user symbols, each word in the macro is capitalized. All elements of or variables in a data structure are in lowercase. Compound words, where needed, are constructed with underscores (_) . The display argument, where used, is always first in the argument list. ”

“ The X Window System supports one or more screens containing overlapping windows or subwindows. A screen is a physical monitor and hardware that can be color, grayscale, or monochrome.
There can be multiple screens for each display or workstation. A single X server can provide display services for any number of screens. A set of screens for a single user with one keyboard and one pointer (usually a mouse) is called a display. ”

“ Where the x, y, width, and height arguments are used together, the x and y arguments always precede the width and height arguments. Where a mask is accompanied with a structure, the mask always precedes the pointer to the structure in the argument list. ”

“ Although a client usually runs on the same machine as the X server it is talking to, this need not be the case.
Xlib − C Language X Interface is a reference guide to the low-level C language interface to the X Window System protocol. It is neither a tutorial nor a user’s guide to programming the X Window System. Rather, it provides a detailed description of each function in the library as well as a discussion of the related background information. Xlib − C Language X Interface assumes a basic understanding of a graphics window system and of the C programming language. ”

“ The preprocessor symbols are XK_MISCELLANY, XK_XKB_KEYS, XK_3270, XK_LATIN1, XK_LATIN2, XK_LATIN3, XK_LATIN4, XK_KATAKANA, XK_ARABIC, XK_CYRILLIC, XK_GREEK, XK_TECHNICAL, XK_SPECIAL, XK_PUBLISHING, XK_APL, XK_HEBREW, XK_THAI, and XK_KOREAN. This file defines the preprocessor symbols XK_MISCELLANY, XK_XKB_KEYS, XK_LATIN1, XK_LATIN2, XK_LATIN3, XK_LATIN4, and XK_GREEK and then includes . This file declares all the functions, types, and symbols used for extensions, which are described in appendix C. This file automatically includes . ”

“ This decision was made to minimize the bandwidth required for a given level of performance. Coordinates usually are declared as an int in the interface. Values larger than 16 bits are truncated silently. Sizes (width and height) are declared as unsigned quantities. ”