James Gettys, Robert W. Scheifler, et al.

“ If you later draw into the pixmap used for the border, what happens is undefined because the X implementation is free either to make a copy of the pixmap or to use the same pixmap. If you specify a border-pixel, it overrides either the default border-pixmap or any value you may have set in the border-pixmap. All pixels in the window's border will be set to the border-pixel. Setting a new border, whether by setting border-pixel or by setting border-pixmap, overrides any previous border.
Output to a window is always clipped to the inside of the window. ”

“ The border tile origin is always the same as the background tile origin.
You can also set the border-pixmap to a pixmap of any size (some may be faster than others) or to CopyFromParent (default) . You can set the border-pixel to any pixel value (no default) .
If you set a border-pixmap, it overrides the default. The border-pixmap and the window must have the same depth, or a BadMatch error results. If you set the border-pixmap to CopyFromParent, the parent window's border-pixmap is copied. Subsequent changes to the parent window's border attribute do not affect the child window. ”

“ In the X Window System, a window is a rectangular area on the screen that lets you view graphic output. Client applications can display overlapping and nested windows on one or more screens that are driven by X servers on one or more machines. Clients who want to create windows must first connect their program to the X server by calling XOpenDisplay. ”

“ The XDestroySubwindows function destroys all inferior windows of the specified window, in bottom-to-top stacking order. It causes the X server to generate a DestroyNotify event for each window. If any mapped subwindows were actually destroyed, XDestroySubwindows causes the X server to generate Expose events on the specified window. This is much more efficient than deleting many windows one at a time because much of the work need be performed only once for all of the windows, rather than for each window. ”

“ For PseudoColor, a pixel value indexes a colormap to produce independent RGB values, and the RGB values can be changed dynamically. GrayScale is treated the same way as PseudoColor except that the primary that drives the screen is undefined. Thus, the client should always store the same value for red, green, and blue in the colormaps. For DirectColor, a pixel value is decomposed into separate RGB subfields, and each subfield separately indexes the colormap for the corresponding value. The RGB values can be changed dynamically. ”

“ If a window has a background (almost all do) , it obscures the other window for purposes of output.
Attempts to output to the obscured area do nothing, and no input events (for example, pointer motion) are generated for the obscured area.
Windows also have associated property lists (see section 4.3) . Both InputOutput and InputOnly windows have the following common attributes, which are the only attributes of an InputOnly window:
win-gravity event-mask do-not-propagate-mask override-redirect cursor If you specify any other attributes for an InputOnly window, a BadMatch error results. ”

“ InputOnly windows are used for controlling input events in situations where InputOutput windows are unnecessary. InputOnly windows are invisible; can only be used to control such things as cursors, input event generation, and grabbing ”