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Glossary
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\fBAccess control list\fP
.IN "Access control list" "" "@DEF@"
.IP
X maintains a list of hosts from which client programs can be run.
By default,
only programs on the local host and hosts specified in an initial list read
by the server can use the display.
This access control list can be changed by clients on the local host.
Some server implementations can also implement other authorization mechanisms
in addition to or in place of this mechanism.
The action of this mechanism can be conditional based on the authorization
protocol name and data received by the server at connection setup.
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\fBActive grab\fP
.IN "Active grab" "" "@DEF@"
.IP
A grab is active when the pointer or keyboard is actually owned by the
single grabbing client.
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\fBAncestors\fP
.IN "Ancestors" "" "@DEF@"
.IP
If W is an inferior of A, then A is an ancestor of W.
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\fBAtom\fP
.IN "Atom" "" "@DEF@"
.IP
An atom is a unique ID corresponding to a string name.
Atoms are used to identify properties, types, and selections.
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\fBBackground\fP
.IN "Background" "" "@DEF@"
.IP
An
.PN InputOutput
window can have a background, which is defined as a pixmap.
When regions of the window have their contents lost
or invalidated,
the server automatically tiles those regions with the background.
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\fBBacking store\fP
.IN "Backing store" "" "@DEF@"
.IP
When a server maintains the contents of a window,
the pixels saved off-screen are known as a backing store.
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\fBBase font name\fP
.IN "Base font name" "" "@DEF@"
.IP
A font name used to select a family of fonts whose members may be encoded
in various charsets.
The
.PN CharSetRegistry
and
.PN CharSetEncoding
fields of an XLFD name identify the charset of the font.
A base font name may be a full XLFD name, with all fourteen '-' delimiters,
or an abbreviated XLFD name containing only the first 12 fields of an XLFD name,
up to but not including
.PN CharSetRegistry ,
with or without the thirteenth '-', or a non-XLFD name.
Any XLFD fields may contain wild cards.
.IP
When creating an
.PN XFontSet ,
Xlib accepts from the client a list of one or more base font names
which select one or more font families.
They are combined with charset names obtained from the encoding of the locale
to load the fonts required to render text.
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\fBBit gravity\fP
.IN "Bit" "gravity" "@DEF@"
.IP
When a window is resized,
the contents of the window are not necessarily discarded.
It is possible to request that the server relocate the previous contents
to some region of the window (though no guarantees are made).
This attraction of window contents for some location of
a window is known as bit gravity.
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\fBBit plane\fP
.IN "Bit" "plane" "@DEF@"
.IP
When a pixmap or window is thought of as a stack of bitmaps,
each bitmap is called a bit plane or plane.
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\fBBitmap\fP
.IN "Bitmap" "" "@DEF@"
.IP
A bitmap is a pixmap of depth one.
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\fBBorder\fP
.IN "Border" "" "@DEF@"
.IP
An
.PN InputOutput
window can have a border of equal thickness on all four sides of the window.
The contents of the border are defined by a pixmap,
and the server automatically maintains the contents of the border.
Exposure events are never generated for border regions.
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\fBButton grabbing\fP
.IN "Button" "grabbing" "@DEF@"
.IP
Buttons on the pointer can be passively grabbed by a client.
When the button is pressed,
the pointer is then actively grabbed by the client.
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\fBByte order\fP
.IN "Byte" "order" "@DEF@"
.IP
For image (pixmap/bitmap) data,
the server defines the byte order,
and clients with different native byte ordering must swap bytes as
necessary.
For all other parts of the protocol,
the client defines the byte order,
and the server swaps bytes as necessary.
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\fBCharacter\fP
.IN "Character" "" "@DEF@"
.IP
A member of a set of elements used for the organization,
control, or representation of text (ISO2022, as adapted by XPG3).
Note that in ISO2022 terms, a character is not bound to a coded value
until it is identified as part of a coded character set.
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\fBCharacter glyph\fP
.IN "Character glyph" "" "@DEF@"
.IP
The abstract graphical symbol for a character.
Character glyphs may or may not map one-to-one to font glyphs,
and may be context-dependent, varying with the adjacent characters.
Multiple characters may map to a single character glyph.
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\fBCharacter set\fP
.IN "Character set" "" "@DEF@"
.IP
A collection of characters.
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\fBCharset\fP
.IN "Charset" "" "@DEF@"
.IP
An encoding with a uniform, state-independent mapping from characters
to codepoints.
A coded character set.
.IP
For display in X,
there can be a direct mapping from a charset to one font,
if the width of all characters in the charset is either one or two bytes.
A text string encoded in an encoding such as Shift-JIS cannot be passed
directly to the X server, because the text imaging requests accept only
single-width charsets (either 8 or 16 bits).
Charsets which meet these restrictions can serve as ``font charsets''.
Font charsets strictly speaking map font indices to font glyphs,
not characters to character glyphs.
.IP
Note that a single font charset is sometimes used as the encoding of a locale,
for example, ISO8859-1.
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\fBChildren\fP
.IN "Children" "" "@DEF@"
.IP
The children of a window are its first-level subwindows.
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\fBClass\fP
.IN "Class" "" "@DEF@"
.IP
Windows can be of different classes or types.
See the entries for
.PN InputOnly
and
.PN InputOutput
windows for further information about valid window types.
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\fBClient\fP
.IN "Client" "" "@DEF@"
.IP
An application program connects to the window system server by some
interprocess communication (IPC) path, such as a TCP connection or a
shared memory buffer.
This program is referred to as a client of the window system server.
More precisely,
the client is the IPC path itself.
A program with multiple paths open to the server is viewed as
multiple clients by the protocol.
Resource lifetimes are controlled by
connection lifetimes, not by program lifetimes.
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\fBClipping region\fP
.IN "Clipping region" "" "@DEF@"
.IP
In a graphics context,
a bitmap or list of rectangles can be specified
to restrict output to a particular region of the window.
The image defined by the bitmap or rectangles is called a clipping region.
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\fBCoded character\fP
.IN "Coded character" "" "@DEF@"
.IP
A character bound to a codepoint.
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\fBCoded character set\fP
.IN "Coded character set" "" "@DEF@"
.IP
A set of unambiguous rules that establishes a character set
and the one-to-one relationship between each character of the set
and its bit representation.
(ISO2022, as adapted by XPG3)
A definition of a one-to-one mapping of a set of characters to a set of
codepoints.
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\fBCodepoint\fP
.IN "Codepoint" "" "@DEF@"
.IP
The coded representation of a single character in a coded character set.
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\fBColormap\fP
.IN "Colormap" "" "@DEF@"
.IP
A colormap consists of a set of entries defining color values.
The colormap associated with a window is used to display the contents of
the window; each pixel value indexes the colormap to produce an RGB value
that drives the guns of a monitor.
Depending on hardware limitations,
one or more colormaps can be installed at one time so
that windows associated with those maps display with true colors.
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\fBConnection\fP
.IN "Connection" "" "@DEF@"
.IP
The IPC path between the server and client program is known as a connection.
A client program typically (but not necessarily) has one
connection to the server over which requests and events are sent.
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\fBContainment\fP
.IN "Containment" "" "@DEF@"
.IP
A window contains the pointer if the window is viewable and the
hotspot of the cursor is within a visible region of the window or a
visible region of one of its inferiors.
The border of the window is included as part of the window for containment.
The pointer is in a window if the window contains the pointer
but no inferior contains the pointer.
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\fBCoordinate system\fP
.IN "Coordinate system" "" "@DEF@"
.IP
The coordinate system has X horizontal and Y vertical,
with the origin [0, 0] at the upper left.
Coordinates are integral and coincide with pixel centers.
Each window and pixmap has its own coordinate system.
For a window,
the origin is inside the border at the inside upper-left corner.
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\fBCursor\fP
.IN "Cursor" "" "@DEF@"
.IP
A cursor is the visible shape of the pointer on a screen.
It consists of a hotspot, a source bitmap, a shape bitmap,
and a pair of colors.
The cursor defined for a window controls the visible
appearance when the pointer is in that window.
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\fBDepth\fP
.IN "Depth" "" "@DEF@"
.IP
The depth of a window or pixmap is the number of bits per pixel it has.
The depth of a graphics context is the depth of the drawables it can be
used in conjunction with graphics output.
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\fBDevice\fP
.IN "Device" "" "@DEF@"
.IP
Keyboards, mice, tablets, track-balls, button boxes, and so on are all
collectively known as input devices.
Pointers can have one or more buttons
(the most common number is three).
The core protocol only deals with two devices: the keyboard
and the pointer.
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\fBDirectColor\fP
.IN "DirectColor" "" "@DEF@"
.IP
.PN DirectColor
is a class of colormap in which a pixel value is decomposed into three
separate subfields for indexing.
The first subfield indexes an array to produce red intensity values.
The second subfield indexes a second array to produce blue intensity values.
The third subfield indexes a third array to produce green intensity values.
The RGB (red, green, and blue) values in the colormap entry can be
changed dynamically.
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\fBDisplay\fP
.IN "Display" "" "@DEF@"
.IP
A server, together with its screens and input devices, is called a display.
The Xlib
.PN Display
.IN "Display" "structure"
structure contains all information about the particular display and its screens
as well as the state that Xlib needs to communicate with the display over a
particular connection.
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\fBDrawable\fP
.IN "Drawable" "" "@DEF@"
.IP
Both windows and pixmaps can be used as sources and destinations
in graphics operations.
These windows and pixmaps are collectively known as drawables.
However, an
.PN InputOnly
window cannot be used as a source or destination in a
graphics operation.
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\fBEncoding\fP
.IN "Encoding" "" "@DEF@"
.IP
A set of unambiguous rules that establishes a character set
and a relationship between the characters and their representations.
The character set does not have to be fixed to a finite pre-defined set of
characters.
The representations do not have to be of uniform length.
Examples are an ISO2022 graphic set, a state-independent
or state-dependent combination of graphic sets, possibly including control
sets, the X Compound Text encoding, and the UTF-8 ISO10646/Unicode encoding.
.IP
In X, encodings are identified by a string
which appears as: the
.PN CharSetRegistry
and
.PN CharSetEncoding
components of an XLFD
name; the name of a charset of the locale for which a font could not be
found; or an atom which identifies the encoding of a text property or
which names an encoding for a text selection target type.
Encoding names should be composed of characters from the X Portable
Character Set.
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\fBEscapement\fP
.IN "Escapement" "" "@DEF@"
.IP
The escapement of a string is the distance in pixels in the
primary draw direction from the drawing origin to the origin of the next
character (that is, the one following the given string) to be drawn.
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\fBEvent\fP
.IN "Event" "" "@DEF@"
.IP
Clients are informed of information asynchronously by means of events.
These events can be either asynchronously generated from devices or
generated as side effects of client requests.
Events are grouped into types.
The server never sends an event to a client unless the
client has specifically asked to be informed of that type of event.
However, clients can force events to be sent to other clients.
Events are typically reported relative to a window.
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\fBEvent mask\fP
.IN "Event" "mask" "@DEF@"
.IP
Events are requested relative to a window.
The set of event types a client requests relative to a window is described
by using an event mask.
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\fBEvent propagation\fP
.IN "Event" "propagation" "@DEF@"
.IP
Device-related events propagate from the source window to ancestor
windows until some client has expressed interest in handling that type
of event or until the event is discarded explicitly.
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\fBEvent source\fP
.IN "Event" "source" "@DEF@"
.IP
The deepest viewable window that the pointer is in is called
the source of a device-related event.
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\fBEvent synchronization\fP
.IN "Event" "synchronization" "@DEF@"
.IP
There are certain race conditions possible when demultiplexing device
events to clients (in particular, deciding where pointer and keyboard
events should be sent when in the middle of window management
operations).
The event synchronization mechanism allows synchronous processing of
device events.
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\fBExposure event\fP
.IN "Event" "Exposure" "@DEF@"
.IP
Servers do not guarantee to preserve the contents of windows when
windows are obscured or reconfigured.
Exposure events are sent to clients to inform them when contents of regions
of windows have been lost.
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\fBExtension\fP
.IN "Extension" "" "@DEF@"
.IP
Named extensions to the core protocol can be defined to extend the system.
Extensions to output requests, resources, and event types are all possible
and expected.
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\fBFont\fP
.IN "Font" "" "@DEF@"
.IP
A font is an array of glyphs (typically characters).
The protocol does no translation or interpretation of character sets.
The client simply indicates values used to index the glyph array.
A font contains additional metric information to determine interglyph
and interline spacing.
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\fBFont glyph\fP
.IN "Font glyph" "" "@DEF@"
.IP
The abstract graphical symbol for an index into a font.
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\fBFrozen events\fP
.IN "Frozen events" "" "@DEF@"
.IP
Clients can freeze event processing during keyboard and pointer grabs.
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\fBGC\fP
.IN "GC" "" "@DEF@"
.IP
GC is an abbreviation for graphics context.
See \fBGraphics context\fP.
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\fBGlyph\fP
.IN "Glyph" "" "@DEF@"
.IP
An identified abstract graphical symbol independent of any actual image.
(ISO/IEC/DIS 9541-1)
An abstract visual representation of a graphic character,
not bound to a codepoint.
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\fBGlyph image\fP
.IN "Glyph image" "" "@DEF@"
.IP
An image of a glyph, as obtained from a glyph representation displayed
on a presentation surface.
(ISO/IEC/DIS 9541-1)
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\fBGrab\fP
.IN "Grab" "" "@DEF@"
.IP
Keyboard keys, the keyboard, pointer buttons, the pointer,
and the server can be grabbed for exclusive use by a client.
In general,
these facilities are not intended to be used by normal applications
but are intended for various input and window managers to implement various
styles of user interfaces.
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\fBGraphics context\fP
.IN "Graphics context" "" "@DEF@"
.IP
Various information for graphics output is stored in a graphics
context (GC), such as foreground pixel, background
pixel, line width, clipping region, and so on.
A graphics context can only
be used with drawables that have the same root and the same depth as
the graphics context.
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\fBGravity\fP
.IN "Gravity" "" "@DEF@"
.IP
The contents of windows and windows themselves have a gravity,
which determines how the contents move when a window is resized.
See \fBBit gravity\fP and \fBWindow gravity\fP.
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\fBGrayScale\fP
.IN "GrayScale" "" "@DEF@"
.IP
.PN GrayScale
can be viewed as a degenerate case of
.PN PseudoColor ,
in which the red, green, and blue values in any given colormap entry
are equal and thus, produce shades of gray.
The gray values can be changed dynamically.
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\fBHost Portable Character Encoding\fP
.IN "Host Portable Character Encoding" "" "@DEF@"
.IP
The encoding of the X Portable Character Set on the host.
The encoding itself is not defined by this standard,
but the encoding must be the same in all locales supported by Xlib on the host.
If a string is said to be in the Host Portable Character Encoding,
then it only contains characters from the X Portable Character Set,
in the host encoding.
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\fBHotspot\fP
.IN "Hotspot" "" "@DEF@"
.IP
A cursor has an associated hotspot, which defines the point in the
cursor corresponding to the coordinates reported for the pointer.
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\fBIdentifier\fP
.IN "Identifier" "" "@DEF@"
.IP
An identifier is a unique value associated with a resource
that clients use to name that resource.
The identifier can be used over any connection to name the resource.
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\fBInferiors\fP
.IN "Inferiors" "" "@DEF@"
.IP
The inferiors of a window are all of the subwindows nested below it:
the children, the children's children, and so on.
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\fBInput focus\fP
.IN "Input" "focus" "@DEF@"
.IP
The input focus is usually a window defining the scope for processing
of keyboard input.
If a generated keyboard event usually would be reported to this window
or one of its inferiors,
the event is reported as usual.
Otherwise, the event is reported with respect to the focus window.
The input focus also can be set such that all keyboard events are discarded
and such that the focus window is dynamically taken to be the root window
of whatever screen the pointer is on at each keyboard event.
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\fBInput manager\fP
.IN "Input" "manager" "@DEF@"
.IP
Control over keyboard input is typically provided by an input manager
client, which usually is part of a window manager.
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\fBInputOnly window\fP
.IN "Window" "InputOnly" "@DEF@"
.IP
An
.PN InputOnly
window is a window that cannot be used for graphics requests.
.PN InputOnly
windows are invisible and are used to control such things as cursors,
input event generation, and grabbing.
.PN InputOnly
windows cannot have
.PN InputOutput
windows as inferiors.
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\fBInputOutput window\fP
.IN "Window" "InputOutput" "@DEF@"
.IP
An
.PN InputOutput
window is the normal kind of window that is used for both input and output.
.PN InputOutput
windows can have both
.PN InputOutput
and
.PN InputOnly
windows as inferiors.
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\fBInternationalization\fP
.IN "Internationalization" "" "@DEF@"
.IP
The process of making software adaptable to the requirements
of different native languages, local customs, and character string encodings.
Making a computer program adaptable to different locales
without program source modifications or recompilation.
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\fBISO2022\fP
.IN "ISO2022" "" "@DEF@"
.IP
ISO standard for code extension techniques for 7-bit and 8-bit coded
character sets.
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\fBKey grabbing\fP
.IN "Key" "grabbing" "@DEF@"
.IP
Keys on the keyboard can be passively grabbed by a client.
When the key is pressed,
the keyboard is then actively grabbed by the client.
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\fBKeyboard grabbing\fP
.IN "Keyboard" "grabbing" "@DEF@"
.IP
A client can actively grab control of the keyboard, and key events
will be sent to that client rather than the client the events would
normally have been sent to.
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\fBKeysym\fP
.IN "Keysym" "" "@DEF@"
.IP
An encoding of a symbol on a keycap on a keyboard.
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\fBLatin-1\fP
.IN "Latin-1" "" "@DEF@"
.IP
The coded character set defined by the ISO8859-1 standard.
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\fBLatin Portable Character Encoding\fP
.IN "Latin Portable Character Encoding" "" "@DEF@"
.IP
The encoding of the X Portable Character Set using the Latin-1 codepoints
plus ASCII control characters.
If a string is said to be in the Latin Portable Character Encoding,
then it only contains characters from the X Portable Character Set,
not all of Latin-1.
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\fBLocale\fP
.IN "Locale" "" "@DEF@"
.IP
The international environment of a computer program defining the ``localized''
behavior of that program at run-time.
This information can be established from one or more sets of localization data.
ANSI C defines locale-specific processing by C system library calls.
See ANSI C and the X/Open Portability Guide specifications for more details.
In this specification, on implementations that conform to the ANSI C library,
the ``current locale'' is the current setting of the LC_CTYPE
.PN setlocale
category.
Associated with each locale is a text encoding. When text is processed
in the context of a locale, the text must be in the encoding of the locale.
The current locale affects Xlib in its:
.RS
.IP \(bu 5
Encoding and processing of input method text
.IP \(bu 5
Encoding of resource files and values
.IP \(bu 5
Encoding and imaging of text strings
.IP \(bu 5
Encoding and decoding for inter-client text communication
.RE
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\fBLocale name\fP
.IN "Locale name" "" "@DEF@"
.IP
The identifier used to select the desired locale for the host C library
and X library functions.
On ANSI C library compliant systems,
the locale argument to the
.PN setlocale
function.
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\fBLocalization\fP
.IN "Localization" "" "@DEF@"
.IP
The process of establishing information within a computer system specific
to the operation of particular native languages, local customs
and coded character sets.
(XPG3)
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\fBMapped\fP
.IN "Mapped window" "" "@DEF@"
.IP
A window is said to be mapped if a map call has been performed on it.
Unmapped windows and their inferiors are never viewable or visible.
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\fBModifier keys\fP
.IN "Modifier keys" "" "@DEF@"
.IP
Shift, Control, Meta, Super, Hyper, Alt, Compose, Apple, CapsLock,
ShiftLock, and similar keys are called modifier keys.
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\fBMonochrome\fP
.IN "Monochrome" "" "@DEF@"
.IP
Monochrome is a special case of
.PN StaticGray
in which there are only two colormap entries.
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\fBMultibyte\fP
.IN "Multibyte" "" "@DEF@"
.IP
A character whose codepoint is stored in more than one byte;
any encoding which can contain multibyte characters;
text in a multibyte encoding.
The ``char *'' null-terminated string datatype in ANSI C.
Note that references in this document to multibyte strings
imply only that the strings \fImay\fP contain multibyte characters.
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\fBObscure\fP
.IN "Obscure" "" "@DEF@"
.IP
A window is obscured if some other window obscures it.
A window can be partially obscured and so still have visible regions.
Window A obscures window B if both are viewable
.PN InputOutput
windows, if A is higher in the global stacking order,
and if the rectangle defined by the outside
edges of A intersects the rectangle defined by the outside edges of B.
Note the distinction between obscures and occludes.
Also note that window borders are included in the calculation.
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\fBOcclude\fP
.IN "Occlude" "" "@DEF@"
.IP
A window is occluded if some other window occludes it.
Window A occludes window B if both are mapped,
if A is higher in the global stacking order,
and if the rectangle defined by the outside edges of A intersects the rectangle defined
by the outside edges of B.
Note the distinction between occludes and obscures.
Also note that window borders are included in the calculation
and that
.PN InputOnly
windows never obscure other windows but can occlude other windows.
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\fBPadding\fP
.IN "Padding" "" "@DEF@"
.IP
Some padding bytes are inserted in the data stream to maintain
alignment of the protocol requests on natural boundaries.
This increases ease of portability to some machine architectures.
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\fBParent window\fP
.IN "Window" "parent" "@DEF@"
.IP
If C is a child of P, then P is the parent of C.
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\fBPassive grab\fP
.IN "Passive grab" "" "@DEF@"
.IP
Grabbing a key or button is a passive grab.
The grab activates when the key or button is actually pressed.
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\fBPixel value\fP
.IN "Pixel value" "" "@DEF@"
.IP
A pixel is an N-bit value,
where N is the number of bit planes used in a particular window or pixmap
(that is, is the depth of the window or pixmap).
A pixel in a window indexes a colormap to derive an actual color to be
displayed.
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\fBPixmap\fP
.IN "Pixmap" "" "@DEF@"
.EQ
delim %%
.EN
.IP
A pixmap is a three-dimensional array of bits.
A pixmap is normally thought of as a two-dimensional array of pixels,
where each pixel can be a value from 0 to %2 sup N %\-1,
and where N is the depth (z axis) of the pixmap.
A pixmap can also be thought of as a stack of N bitmaps.
A pixmap can only be used on the screen that it was created in.
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\fBPlane\fP
.IN "Plane" "" "@DEF@"
.IP
When a pixmap or window is thought of as a stack of bitmaps, each
bitmap is called a plane or bit plane.
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\fBPlane mask\fP
.IN "Plane" "mask" "@DEF@"
.IP
Graphics operations can be restricted to only affect a subset of bit
planes of a destination.
A plane mask is a bit mask describing which planes are to be modified.
The plane mask is stored in a graphics context.
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\fBPointer\fP
.IN "Pointer" "" "@DEF@"
.IP
The pointer is the pointing device currently attached to the cursor
and tracked on the screens.
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\fBPointer grabbing\fP
.IN "Pointer" "grabbing" "@DEF@"
.IP
A client can actively grab control of the pointer.
Then button and motion events will be sent to that client
rather than the client the events would normally have been sent to.
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\fBPointing device\fP
.IN "Pointing device" "" "@DEF@"
.IP
A pointing device is typically a mouse, tablet, or some other
device with effective dimensional motion.
The core protocol defines only one visible cursor,
which tracks whatever pointing device is attached as the pointer.
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\fBPOSIX\fP
.IN "POSIX" "" "@DEF@"
.IP
Portable Operating System Interface, ISO/IEC 9945-1 (IEEE Std 1003.1).
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\fBPOSIX Portable Filename Character Set\fP
.IN "POSIX Portable Filename Character Set" "" "@DEF@"
.IP
The set of 65 characters which can be used in naming files on a POSIX-compliant
host that are correctly processed in all locales.
The set is:
.IP
.Ds 0
a..z A..Z 0..9 ._-
.De
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\fBProperty\fP
.IN "Property" "" "@DEF@"
.IP
Windows can have associated properties that consist of a name, a type,
a data format, and some data.
The protocol places no interpretation on properties.
They are intended as a general-purpose naming mechanism for clients.
For example, clients might use properties to share information such as resize
hints, program names, and icon formats with a window manager.
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\fBProperty list\fP
.IN "Property list" "" "@DEF@"
.IP
The property list of a window is the list of properties that have
been defined for the window.
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\fBPseudoColor\fP
.IN "PseudoColor" "" "@DEF@"
.IP
.PN PseudoColor
is a class of colormap in which a pixel value indexes the colormap entry to
produce an independent RGB value;
that is, the colormap is viewed as an array of triples (RGB values).
The RGB values can be changed dynamically.
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\fBRectangle\fP
.IN "Rectangle" "" "@DEF@"
.IP
A rectangle specified by [x,y,w,h] has an infinitely thin
outline path with corners at [x,y], [x+w,y], [x+w,y+h], and [x, y+h].
When a rectangle is filled,
the lower-right edges are not drawn.
For example,
if w=h=0,
nothing would be drawn.
For w=h=1,
a single pixel would be drawn.
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\fBRedirecting control\fP
.IN "Redirecting control" "" "@DEF@"
.IP
Window managers (or client programs) may enforce window layout
policy in various ways.
When a client attempts to change the size or position of a window,
the operation may be redirected to a specified client
rather than the operation actually being performed.
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\fBReply\fP
.IN "Reply" "" "@DEF@"
.IP
Information requested by a client program using the X protocol
is sent back to the client with a reply.
Both events and replies are multiplexed on the same connection.
Most requests do not generate replies,
but some requests generate multiple replies.
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\fBRequest\fP
.IN "Request" "" "@DEF@"
.IP
A command to the server is called a request.
It is a single block of data sent over a connection.
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\fBResource\fP
.IN "Resource" "" "@DEF@"
.IP
Windows, pixmaps, cursors, fonts, graphics contexts, and colormaps are
known as resources.
They all have unique identifiers associated with them for naming purposes.
The lifetime of a resource usually is bounded by the lifetime of the
connection over which the resource was created.
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\fBRGB values\fP
.IN "RGB values" "" "@DEF@"
.IP
RGB values are the red, green, and blue intensity values that are used
to define a color.
These values are always represented as 16-bit, unsigned numbers, with 0
the minimum intensity and 65535 the maximum intensity.
The X server scales these values to match the display hardware.
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\fBRoot\fP
.IN "Root" "" "@DEF@"
.IP
The root of a pixmap or graphics context is the same as the root
of whatever drawable was used when the pixmap or GC was created.
The root of a window is the root window under which the window was created.
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\fBRoot window\fP
.IN "Window" "root" "@DEF@"
.IP
Each screen has a root window covering it.
The root window cannot be reconfigured or unmapped,
but otherwise it acts as a full-fledged window.
A root window has no parent.
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\fBSave set\fP
.IN "Save set" "" "@DEF@"
.IP
The save set of a client is a list of other clients' windows that,
if they are inferiors of one of the client's windows at connection
close, should not be destroyed and that should be remapped
if currently unmapped.
Save sets are typically used by window managers to avoid
lost windows if the manager should terminate abnormally.
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\fBScanline\fP
.IN "Scanline" "" "@DEF@"
.IP
A scanline is a list of pixel or bit values viewed as a horizontal
row (all values having the same y coordinate) of an image, with the
values ordered by increasing the x coordinate.
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\fBScanline order\fP
.IN "Scanline" "order" "@DEF@"
.IP
An image represented in scanline order contains scanlines ordered by
increasing the y coordinate.
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\fBScreen\fP
.IN "Screen" "" "@DEF@"
.IP
A server can provide several independent screens,
which typically have physically independent monitors.
This would be the expected configuration when there is only a single keyboard
and pointer shared among the screens.
A
.PN Screen
.IN "Screen" "structure"
structure contains the information about that screen
and is linked to the
.PN Display
.IN "Display" "structure"
structure.
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\fBSelection\fP
.IN "Selection" "" "@DEF@"
.IP
A selection can be thought of as an indirect property with dynamic
type.
That is, rather than having the property stored in the X server,
it is maintained by some client (the owner).
A selection is global and is thought of as belonging to the user
and being maintained by clients,
rather than being private to a particular window subhierarchy
or a particular set of clients.
When a client asks for the contents of
a selection, it specifies a selection target type,
which can be used to control the transmitted representation of the contents.
For example, if the selection is ``the last thing the user clicked on,''
and that is currently an image, then the target type might specify
whether the contents of the image should be sent in XY format or
Z format.
.IP
The target type can also be used to control the class of
contents transmitted; for example,
asking for the ``looks'' (fonts, line
spacing, indentation, and so forth) of a paragraph selection, rather than the
text of the paragraph.
The target type can also be used for other
purposes.
The protocol does not constrain the semantics.
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\fBServer\fP
.IN "Server" "" "@DEF@"
.IP
The server, which is also referred to as the X server,
provides the basic windowing mechanism.
It handles IPC connections from clients,
multiplexes graphics requests onto the screens,
and demultiplexes input back to the appropriate clients.
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\fBServer grabbing\fP
.IN "Server" "grabbing" "@DEF@"
.IP
The server can be grabbed by a single client for exclusive use.
This prevents processing of any requests from other client connections until
the grab is completed.
This is typically only a transient state for such things as rubber-banding,
pop-up menus, or executing requests indivisibly.
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\fBShift sequence\fP
.IN "Shift sequence" "" "@DEF@"
.IP
ISO2022 defines control characters and escape sequences
which temporarily (single shift) or permanently (locking shift) cause a
different character set to be in effect (``invoking'' a character set).
.KE
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\fBSibling\fP
.IN "Sibling" "" "@DEF@"
.IP
Children of the same parent window are known as sibling windows.
.KE
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\fBStacking order\fP
.IN "Stacking order" "" "@DEF@"
.IP
Sibling windows, similar to sheets of paper on a desk,
can stack on top of each other.
Windows above both obscure and occlude lower windows.
The relationship between sibling windows is known as the stacking order.
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\fBState-dependent encoding\fP
.IN "State-dependent encoding" "" "@DEF@"
.IP
An encoding in which an invocation of a charset can apply to multiple
characters in sequence.
A state-dependent encoding begins in an ``initial state''
and enters other ``shift states'' when specific ``shift sequences''
are encountered in the byte sequence.
In ISO2022 terms,
this means use of locking shifts, not single shifts.
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\fBState-independent encoding\fP
.IN "State-independent encoding" "" "@DEF@"
.IP
Any encoding in which the invocations of the charsets are fixed,
or span only a single character.
In ISO2022 terms,
this means use of at most single shifts, not locking shifts.
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\fBStaticColor\fP
.IN "StaticColor" "" "@DEF@"
.IP
.PN StaticColor
can be viewed as a degenerate case of
.PN PseudoColor
in which the RGB values are predefined and read-only.
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\fBStaticGray\fP
.IN "StaticGray" "" "@DEF@"
.IP
.PN StaticGray
can be viewed as a degenerate case of
.PN GrayScale
in which the gray values are predefined and read-only.
The values are typically linear or near-linear increasing ramps.
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\fBStatus\fP
.IN "Status" "" "@DEF@"
.IP
Many Xlib functions return a success status.
If the function does not succeed,
however, its arguments are not disturbed.
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\fBStipple\fP
.IN "Stipple" "" "@DEF@"
.IP
A stipple pattern is a bitmap that is used to tile a region to serve
as an additional clip mask for a fill operation with the foreground
color.
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\fBSTRING encoding\fP
.IN "STRING encoding" "" "@DEF@"
.IP
Latin-1, plus tab and newline.
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\fBString Equivalence\fP
.IN "String Equivalence" "" "@DEF@"
.IP
Two ISO Latin-1 STRING8 values are considered equal if they are the same
length and if corresponding bytes are either equal or are equivalent as
follows: decimal values 65 to 90 inclusive (characters ``A'' to ``Z'') are
pairwise equivalent to decimal values 97 to 122 inclusive
(characters ``a'' to ``z''), decimal values 192 to 214 inclusive
(characters ``A grave'' to ``O diaeresis'') are pairwise equivalent to decimal
values 224 to 246 inclusive (characters ``a grave'' to ``o diaeresis''),
and decimal values 216 to 222 inclusive (characters ``O oblique'' to ``THORN'')
are pairwise equivalent to decimal values 246 to 254 inclusive
(characters ``o oblique'' to ``thorn'').
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\fBTile\fP
.IN "Tile" "" "@DEF@"
.IP
A pixmap can be replicated in two dimensions to tile a region.
The pixmap itself is also known as a tile.
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\fBTimestamp\fP
.IN "Timestamp" "" "@DEF@"
.IP
A timestamp is a time value expressed in milliseconds.
It is typically the time since the last server reset.
Timestamp values wrap around (after about 49.7 days).
The server, given its current time is represented by timestamp T,
always interprets timestamps from clients by treating half
of the timestamp space as being earlier in time than T
and half of the timestamp space as being later in time than T.
One timestamp value, represented by the constant
.PN CurrentTime ,
is never generated by the server.
This value is reserved for use in requests to represent the current server time.
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\fBTrueColor\fP
.IN "TrueColor" "" "@DEF@"
.IP
.PN TrueColor
can be viewed as a degenerate case of
.PN DirectColor
in which the subfields in the pixel value directly encode the corresponding RGB
values.
That is, the colormap has predefined read-only RGB values.
The values are typically linear or near-linear increasing ramps.
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\fBType\fP
.IN "Type" "" "@DEF@"
.IP
A type is an arbitrary atom used to identify the interpretation of property
data.
Types are completely uninterpreted by the server.
They are solely for the benefit of clients.
X predefines type atoms for many frequently used types,
and clients also can define new types.
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\fBViewable\fP
.IN "Viewable" "" "@DEF@"
.IP
A window is viewable if it and all of its ancestors are mapped.
This does not imply that any portion of the window is actually visible.
Graphics requests can be performed on a window when it is not
viewable, but output will not be retained unless the server is maintaining
backing store.
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\fBVisible\fP
.IN "Visible" "" "@DEF@"
.IP
A region of a window is visible if someone looking at the screen can
actually see it; that is, the window is viewable and the region is not occluded
by any other window.
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\fBWhitespace\fP
.IN "Whitespace" "" "@DEF@"
.IP
Any spacing character.
On implementations that conform to the ANSI C library,
whitespace is any character for which
.PN isspace
returns true.
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\fBWindow gravity\fP
.IN "Window" "gravity" "@DEF@"
.IP
When windows are resized,
subwindows may be repositioned automatically relative to some position in the
window.
This attraction of a subwindow to some part of its parent is known
as window gravity.
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\fBWindow manager\fP
.IN "Window" "manager" "@DEF@"
.IP
Manipulation of windows on the screen and much of the user interface
(policy) is typically provided by a window manager client.
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\fBX Portable Character Set\fP
.IN "X Portable Character Set" "" "@DEF@"
.IP
A basic set of 97 characters which are assumed to exist in all
locales supported by Xlib. This set contains the following characters:
.IP
.Ds 0
.EQ
delim DD
.EN
a..z A..Z 0..9
!"#$%&'()*+,-./:;<=>?@[\\]^_`{|}~
<space>, <tab>, and <newline>
.EQ
delim %%
.EN
.De
.IP
This is the left/lower half (also called the G0 set)
of the graphic character set of ISO8859-1 plus <space>, <tab>, and <newline>.
It is also the set of graphic characters in 7-bit ASCII plus the same
three control characters.
The actual encoding of these characters on the host is system dependent;
see the Host Portable Character Encoding.
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\fBXLFD\fP
.IN "XLFD" "" "@DEF@"
.IP
The X Logical Font Description Conventions that define a standard syntax
for structured font names.
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\fBXY format\fP
.IN "XY format" "" "@DEF@"
.IP
The data for a pixmap is said to be in XY format if it is organized as
a set of bitmaps representing individual bit planes with the planes
appearing from most-significant to least-significant bit order.
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\fBZ format\fP
.IN "Z format" "" "@DEF@"
.IP
The data for a pixmap is said to be in Z format if it is organized as
a set of pixel values in scanline order.
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\fBReferences\fP
.LP
ANSI Programming Language - C: ANSI X3.159-1989, December 14, 1989.
.LP
Draft Proposed Multibyte Extension of ANSI C, Draft 1.1, November 30,
1989, SC22/C WG/SWG IPSJ/ITSCJ Japan.
.LP
ISO2022: Information processing - ISO 7-bit and 8-bit coded character
sets - Code extension techniques.
.LP
ISO8859-1: Information processing - 8-bit single-byte coded graphic
character sets - Part 1: Latin alphabet No. 1.
.LP
POSIX: Information Technology - Portable Operating System Interface (POSIX) -
Part 1: System Application Program Interface (API) [C Language],
ISO/IEC 9945-1.
.LP
Text of ISO/IEC/DIS 9541-1, Information Processing - Font Information
Interchange - Part 1: Architecture.
.LP
X/Open Portability Guide, Issue 3, December 1988 (XPG3), X/Open Company,
Ltd, Prentice-Hall, Inc. 1989. ISBN 0-13-685835-8.
(See especially Volume 3: XSI Supplementary Definitions.)
.bp