X Window Programming/XLib/Library Conventions

Library Conventions Xlib follows a number of conventions to make it easier to use and remember. The major conventions are: To differentiate the X symbols from the other symbols, the library uses mixed case for external symbol names. It leaves lowercase for variables and all uppercase for user macros, as per existing convention. All Xlib functions, user-visible data structures, and 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. The beginnings of all function names and symbols are capitalized. All elements of 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. All resource objects, where used, occur at the beginning of the argument list immediately after the display argument. When a graphics context is present together with another type of resource (most commonly, a drawable), the graphics context occurs in the argument list after the other resource. Drawables outrank all other resources. Source arguments always precede the destination arguments in the argument list. The x argument always precedes the y argument in the argument list, and the width argument always precedes the height argument in the argument list. 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.