- Access control list
- 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.
- Active grab
- A grab is active when the
pointer or keyboard
is actually owned by the single grabbing client.
- Ancestors
- If W is an inferior of A, then A is an
ancestor of W.
- Atom
- An atom is a unique identifier
corresponding to a string name. Atoms are used to identify
properties, types, and
selections.
- Background
- An 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.
- Backing store
- When a server maintains the contents of a window,
the pixels saved off-screen are known as a
backing store.
- Base font name
- A font name used to select a family of
fonts whose members may be encoded in various
charsets. The CharSetRegistry
and 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 13 fields of an XLFD name, up
to but not including CharSetRegistry, with or without
the thirteenth '-', or a non-XLFD name. Any XLFD fields may contain
wild cards.
When creating an 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.
- Bit gravity
- 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.
- Bit plane
- When a pixmap or window is thought of as a stack
of bitmaps, each bitmap is called a bit plane or
plane.
- Bitmap
- A bitmap is a pixmap of depth
one.
- Border
- An 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.
- Button grabbing
- 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.
- Byte order
- 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.
- Character
- 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.
- Character glyph
- 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.
- Character set
- A collection of characters.
- Charset
- An encoding with a uniform, state-independent mapping from
characters to codepoints.
A coded character set.
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.
Note that a single font charset is sometimes used as the encoding of a locale,
for example, ISO8859-1.
- Children
- The children of a window are its first-level subwindows.
- Class
- Windows can be of different classes or types.
See the entries for InputOnly
and InputOutput windows
for further information about valid window types.
- Client
- 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.
- Clipping region
- 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.
- Coded character
- A character bound to a
codepoint.
- Coded character set
- 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.
- Codepoint
- The coded representation of a single character
in a coded character set.
- Colormap
- 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.
- Connection
- 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.
- Containment
- 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.
- Coordinate system
- 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.
- Cursor
- 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.
- Depth
- 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.
- Device
- 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.
- DirectColor
- 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.
- Display
- A server, together with its
screens and input devices, is
called a display. The Xlib Display 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.
- Drawable
- 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
InputOnly window
cannot be used as a source or destination in a graphics operation.
- Encoding
- 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, and the
X Compound Text encoding.
In X, encodings are identified by a string which appears as: the
CharSetRegistry and 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.
- Escapement
- 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.
- Event
- 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.
- Event mask
- 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.
- Event propagation
- 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.
- Event synchronization
- 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.
- Event source
- The deepest viewable window that the
pointer is in is called the source of a
device-related event.
- Exposure event
- 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.
- Extension
- 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.
- Font
- 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.
- Frozen events
- Clients can freeze event
processing during keyboard and
pointer grabs.
- Font glyph
- The abstract graphical symbol for an index into a font.
- GC
- GC is an abbreviation for graphics context. See
Graphics context.
- Glyph
- 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.
- Glyph image
- An image of a glyph, as obtained from a
glyph representation displayed on a presentation
surface.(ISO/IEC/DIS 9541-1)
- Grab
- 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.
- Graphics context
- 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.
- Gravity
- The contents of windows and windows themselves have a gravity, which
determines how the contents move when a window is resized. See
Bit gravity and
Window gravity.
- GrayScale
- GrayScale can be viewed as a degenerate case of
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.
- Host Portable
Character Encoding
- 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.
- Hotspot
- A cursor has an associated hotspot, which defines the
point in the cursor corresponding to the
coordinates reported for the
pointer.
- Identifier
- 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.
- Inferiors
- The inferiors of a window are all of the subwindows nested below it: the
children, the children's children, and so on.
- Input focus
- 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.
- Input manager
- Control over keyboard input is typically provided by an input manager
client, which usually is part of a
window manager.
- InputOnly window
- An InputOnly window is a window that cannot be used for
graphics requests. InputOnly windows are
invisible and are used to control such things as
cursors, input event generation, and
grabbing. InputOnly windows cannot have
InputOutput windows as
inferiors.
- InputOutput window
- An InputOutput window is the normal kind of window that is used
for both input and output. InputOutput windows can have both
InputOutput and
InputOnly windows as
inferiors.
- Internationalization
- 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.
- ISO2022
- ISO standard for code extension techniques for 7-bit and 8-bit coded
character sets.
- Key grabbing
- 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.
- Keyboard grabbing
- 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.
- Keysym
- An encoding of a symbol on a keycap on a keyboard.
- Latin-1
- The coded character set defined by the
ISO8859-1 standard.
- Latin
Portable Character Encoding
- 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.
- Locale
- 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 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:
- Encoding and processing of input method text
- Encoding of resource files and values
- Encoding and imaging of text strings
- Encoding and decoding for inter-client text communication
- Localization
- The process of establishing information within a computer system specific
to the operation of particular native languages, local customs and coded
character sets. (XPG3)
- Locale name
- 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 setlocale function.
- Mapped window
- 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.
- Modifier keys
- Shift, Control, Meta, Super, Hyper, Alt, Compose, Apple, CapsLock,
ShiftLock, and similar keys are called modifier keys.
- Monochrome
- Monochrome is a special case of
StaticGray
in which there are only two colormap entries.
- Multibyte
- 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 may contain multibyte characters.
- Obscure
- 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
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.
- Occlude
- 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
InputOnly windows never obscure
other windows but can occlude other windows.
- Padding
- 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.
- Parent window
- If C is a child of P, then P is the parent of C.
- Passive grab
- Grabbing a key or button is a passive grab. The grab
activates when the key
or button is actually pressed.
- Pixel value
- 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.
- Pixmap
- 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^(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.
- Plane
- When a pixmap or window is thought of as a stack of
bitmaps, each bitmap is called a plane or
bit plane.
- Plane mask
- 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.
- Pointer
- The pointer is the pointing device currently
attached to the cursor and tracked on the
screens.
- Pointer grabbing
- 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.
- Pointing device
- 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.
- POSIX
- Portable Operating System Interface, ISO/IEC 9945-1
(IEEE Std 1003.1).
- POSIX Portable
Filename Character Set
- 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:
a..z A..Z 0..9 ._-
- Property
- 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.
- Property list
- The property list of a window is the list of
properties that have been defined for the window.
- PseudoColor
- 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.
- Rectangle
- 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.
- Redirecting control
- 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.
- Reply
- 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.
- Request
- A command to the server is called a request. It is a
single block of data sent over a connection.
- Resource
- 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.
- RGB values
- 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.
- Root
- 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.
- Root window
- 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.
- Save set
- 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.
- Scanline
- 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.
- Scanline order
- An image represented in scanline order contains
scanlines ordered by increasing the y coordinate.
- Screen
- 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 Screen
structure contains the information about that screen and is linked to the
Display structure.
- Selection
- 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.
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.
- Server
- 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.
- Server grabbing
- 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.
- Shift sequence
- 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).
- Sibling
- Children of the same
parent window are known as sibling windows.
- Stacking order
- 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.
- State-dependent
encoding
- 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.
- State-independent
encoding
- 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.
- StaticColor
- StaticColor can be viewed as a degenerate case of
PseudoColor in which the
RGB values are predefined and read-only.
- StaticGray
- StaticGray can be viewed as a degenerate case of
GrayScale in which the gray values are
predefined and read-only. The values are typically linear or near-linear
increasing ramps.
- Status
- Many Xlib functions return a success status. If the function does not
succeed, however, its arguments are not disturbed.
- Stipple
- 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.
- STRING encoding
- Latin-1, plus tab and newline.
- String equivalence
- 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").
- Tile
- A pixmap can be replicated in two dimensions to tile
a region. The pixmap itself is also known as a tile.
- Timestamp
- 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
CurrentTime, is never generated by the server. This value is
reserved for use in requests to represent the current
server time.
- TrueColor
- TrueColor can be viewed as a degenerate case of
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.
- Type
- 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.
- Viewable
- 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.
- Visible
- 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.
- Whitespace
- Any spacing character. On implementations that
conform to the ANSI C library, whitespace is any character for which
isspace returns true.
- Window gravity
- 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.
- Window manager
- Manipulation of windows on the screen and much of the
user interface (policy) is typically provided by a window manager
client.
- X Portable Character
Set
- A basic set of 97 characters which are assumed to
exist in all locales supported by Xlib. This set contains
the following characters:
a..z A..Z 0..9
!"#$%&'()*+,-./:;<=>?@[\\]^_`{|}~
<space>, <tab>, and <newline>
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.
- XLFD
- The X Logical Font Description Conventions that define a standard syntax
for structured font names.
- XY format
- 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.
- Z format
- 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.
Ken has published over two dozen technical papers on the X Window System.
Most are available over the World Wide Web at
http://www.rahul.net/kenton/bib.html.
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