RFC 1013
X Window System Protocol, version 11: Alpha update April 1987
Pages: 101
Unclassified
Unclassified
Part 1 of 3 – Pages 1 to 29
Network Working Group Robert W. Scheifler Request for Comments: 1013 June 1987 X WINDOW SYSTEM PROTOCOL, VERSION 11 Alpha Update April 1987 Copyright (c) 1986, 1987 Massachusetts Institute of Technology X Window System is a trademark of M.I.T. Status of this Memo This RFC is distributed to the Internet community for information only. It does not establish an Internet standard. The X window system has been widely reviewed and tested. The internet community is encouraged to experiment with it. Distribution of this memo is unlimited (see copyright notice on page 2).
Permission to use, copy, modify, and distribute this document for any
purpose and without fee is hereby granted, provided that the above
copyright notice appear in all copies and that both that copyright
notice and this permission notice are retained, and that the name of
M.I.T. not be used in advertising or publicity pertaining to this
document without specific, written prior permission. M.I.T. makes no
representations about the suitability of this document or the
protocol defined in this document for any purpose. It is provided
"as is" without express or implied warranty.
Author: Robert W. Scheifler
Laboratory for Computer Science
545 Technology Square, Room 418
Cambridge, MA 02139
Contributors:
Dave Carver (Digital HPW)
Branko Gerovac (Digital HPW)
Jim Gettys (MIT/Project Athena, Digital)
Phil Karlton (Digital WSL)
Scott McGregor (Digital SSG)
Ram Rao (Digital UEG)
David Rosenthal (Sun)
Dave Winchell (Digital UEG)
Implementors of initial server who provided useful input:
Susan Angebranndt (Digital)
Raymond Drewry (Digital)
Todd Newman (Digital)
Invited reviewers who provided useful input:
Andrew Cherenson (Berkeley)
Burns Fisher (Digital)
Dan Garfinkel (HP)
Leo Hourvitz (Next)
Brock Krizan (HP)
David Laidlaw (Stellar)
Dave Mellinger (Interleaf)
Ron Newman (MIT)
John Ousterhout (Berkeley)
Andrew Palay (ITC CMU)
Ralph Swick (MIT)
Craig Taylor (Sun)
Jeffery Vroom (Stellar)
This document does not attempt to provide the rationale or pragmatics
required to fully understand the protocol or to place it in
perspective within a complete system. Knowledge of X Version 10
will certainly aid in understanding this document.
The protocol contains many management mechanisms that are not intended for normal applications. Not all mechanisms are needed to build a particular user interface. It is important to keep in mind that the protocol is intended to provide mechanism, not policy. This document does not attempt to define precise formats or bit encodings. -------------------------------------------------------------------
SECTION 1. TERMINOLOGY
Access control list
X maintains a list of hosts from which client programs may be
run. By default, only programs on the local host may use the
display, plus any hosts specified in an initial list read by
the server. This "access control list" can be changed by
clients on the local host. Some server implementations may
also implement other authorization mechanisms.
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 id corresponding to a string name.
Atoms are used to identify properties, types, and selections.
Backing store
When a server maintains the contents of a window, the
off-screen saved pixels are known as a "backing store".
Bit gravity
When a window is resized, the contents of the window are
not necessarily discarded. It is possible to request the
server (though no guarantees are made) to relocate the
previous contents to some region of the window. This
attraction of window contents for some location of a window
is known as "bit gravity".
Bitmap
A "bitmap" is a pixmap of depth one.
Button grabbing
Buttons on the pointer may 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, byte order is defined by
the server, and clients with different native byte ordering
must swap bytes as necessary. For all other parts of the
protocol, the byte order is defined by the client, and the
server swaps bytes as necessary.
Children
The "children" of a window are its first-level subwindows.
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 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 regions
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".
Color cell
An entry in a colormap is known as a "color cell". An entry
contains three values specifying red, green and blue
intensities. These values are always viewed as 16 bit
unsigned numbers, with zero being minimum intensity. The
values are scaled by the server to match the display
hardware. The components of a cell are coincident with
components of other cells in DirectColor and TrueColor
colormaps.
Colormap
A "colormap" consists of a set of color cells. A pixel value
indexes the color map to produce intensities to be displayed.
Depending on hardware limitations, one or more colormaps may
be installed at one time, such 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
discrete, and in terms of pixels. Each window and pixmap has
its own coordinate system. For a window, the origin is at
the inside upper left, inside the border.
Cursor
A "cursor" is the visible shape of the pointer on a screen.
It consist of a hot spot, a source bitmap, a shape bitmap,
and a pair of colors. The cursor defined for a window
controls the visible appearance when the pinter is in that
window.
Depth
The "depth" of a window or pixmap is number of bits per pixel
it has. The depth of a gcontext is the depth of the root of
the gcontext.
Device
Keyboards, mice, tablets, track-balls, button boxes, etc. are
all collectively known as input "devices". The core protocol
only deals with two devices, "the keyboard" and "the
pointer".
Drawable
Both windows and pixmaps may be used as sources and
destinations in graphics operations. These are collectively
known as "drawables". However, an InputOnly window cannot be
used as a source or destination in a graphics operation.
Event
Clients are informed of information asynchronously via
"events". These events may be either asynchronously generated
from devices, or generated as side effects of client
requests. Events are grouped into types; events are never
sent to a client by the server unless the client has
specificially asked to be informed of that type of event,
but other 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 described using
an "event mask".
Event sychronization
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 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 source
The smallest window containing the pointer is the "source"
of a device related event.
Exposure event
Servers do not guarantee to preserve the contents of windows
when windows are obscured or reconfigur contents of regions
of windows have been lost.
Extension
Named "extensions" to the core protocol can be defined to
extend the system. Extension 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 inter-glyph and inter-line spacing.
Glyph
A "glyph" is an image, typically of a character, in a font.
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 "GC"'s,
such as foreground pixel, background pixel, line width,
clipping region, etc.
Hotspot
A cursor has an associated "hot spot" which defines a point
in the cursor that corresponds to the coordinates reported
for the pointer.
Identifier
Each resource has an "identifier", a unique value associated
with it that clients use to name the resource. An 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, etc.
Input focus
The "input focus" is nominally where keyboard input goes.
Keyboard events are by default sent to the client expressing
interest on the window the pointer is in. This is said to be
a "real estate driven" input focus. It is also possible to
attach the keyboard input to a specific window; events will
then be sent to the appropriate client independent of the
pointer position.
Input manager
Control over keyboard input is typically provided by an
"input manager" client.
InputOnly window
A window that cannot be used for graphics requests.
InputOnly windows are "invisible", and can be used to control
such things as cursors, input event generation, and grabbing.
InputOutput window
The "normal" kind of opaque window, used for both input
and output.
Key grabbing
Keys on the keyboard may 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.
Mapping
A window is said to be "mapped" if a map call has been
performed on it. Unmapped windows are never viewable or
visible.
Modifier keys
Shift, Control, Meta, Super, Hyper, ALT, Compose, Apple,
CapsLock, ShiftLock, and similar keys are called "modifier"
keys.
Obscures
Window A "obscures" window B if both are viewable
InputOutput windows and A is higher in the global stacking
order, and the rectangle defined by the outside edges of
intersects the rectangle defined by the outside edges of B.
Note the (fine) distinction with "occludes". Also note that
window borders are included in the calculation.
Occludes
Window A "occludes" window B if both are mapped and A is
higher in the global stacking order, and the rectangle
defined by the outside edges of A intersects the rectangle
defined by the outside edges of B. Note the (fine)
distinction with "obscures". Also note that window borders
are included in the calculation.
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. For a window,
a pixel value 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, where N
is the depth (z axis) of the pixmap. A pixmap can also be
thought of as a stack of N bitmaps.
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, and
is stored in a graphics context.
Pointer
The "pointer" is the pointing device attached to the cursor,
and tracked on the screens.
Pointer grabbing
A client can actively "grab" control of the pointer, and
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 or tablet, or some
other device with effective dimensional motion. There is
only one visible cursor is defined by the core protocol,
and it tracks whatever pointing device is attached as the
pointer.
Property
Windows may have associated "properties", consisting 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 share information such as resize
hints, program names, and icon formats with a window
manager via properties.
Property list
The "property list" of a window is the list of properties
that have been defined for the window.
Redirecting control
Window managers (or client programs) may wish to 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 is sent back to
the client with a "reply". Both events and replys are
multipexed on the same connection. Most requests do not
generate 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 is bounded by the lifetime of the
connection over which the resource was created.
Root
The "root" of a pixmap or gcontext is the same as the root
of whatever drawable was used when the pixmap or gcontext
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. It cannot be
reconfigured or unmapped, but otherwise 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 client's
windows which, if they are inferiors of one of the client's
windows at connection close, should not be destroyed, and
which should be remapped if it is unmapped. Save sets are
typically used by window managers to avoid lost windows if
the manager should terminate abnormally.
Screen
A server may 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.
Server
The "server" provides the basic windowing mechanism. It
handles IPC connections from clients, demultipexes graphics
requests onto the screens, and multiplexes 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 complete. This is
typically only a transient state for such things as
rubber-banding and pop-up menus, or to execute requests
indivisibly.
Sibling
Children of the same parent window are known as "sibling"
windows.
Stacking order
Sibling windows may "stack" on top of each other. Windows
above both obscure and occlude lower windows. This is
similar to paper on a desk. The relationship between
sibling windows is known as the "stacking order".
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.
Tile
A pixmap can be replicated in two dimensions to "tile"
a region. The pixmap itself is also known as a "tile".
Timestamp
A time value, expressed in milliseconds, typically 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
(named CurrentTime) is never generated by the server;
this value is reserved for use in requests to represent
the current server time.
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.
Unviewable
A window is "unviewable" if it is mapped but some ancestor is
unmapped.
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.
Visible
A region of a window is "visible" if someone looking at the
screen can actually "see" it: the window is viewable and the
region is not occluded by any other window.
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.
XYFormat
The data for a pixmap is said to be in "XYFormat" if it is
organized as a set of bitmaps representing individual bit
planes.
ZFormat
The data for a pixmap is said to be in "ZFormat" if it is
organized as a set of pixel values in scanline order.
SECTION 2. PROTOCOL FORMATS
Request Format
Every request contains an 8-bit "major" opcode, and a 16-bit length
field expressed in units of 4 bytes. Every request consists of 4
bytes of header containing the major opcode, the length field, and a
data byte) followed by zero or more additional bytes of data; the
length field defines the total length of the request, including the
header. The length field in a request must equal the minimum length
required to contain the request; if the specified length is smaller
or larger than the required length, an error is enerated. Unused
bytes in a request are not required to be zero. Major opcodes 128
through 255 are reserved for extensions. Extensions are intended
to contain multiple requests, so extension requests typically have
an additional minor opcode encoded in the "spare" data byte in the
request header, but the placement and interpretation of this minor
opcode, and all other fields in extension requests, are not defined
by the core protocol. Every request is implicitly assigned a sequence
number, starting with one,used in replies, errors, and events.
Reply Format
Every reply contains a 32-bit length field expressed in units of 4
bytes. Every reply consists of 32 bytes, followed by zero or more
additional bytes of data, as specified in the length field. Unused
bytes within a reply are not guaranteed to be zero. Every reply
also contains the least significant 16 bits of the sequence number
of the corresponding request.
Error Format
Error reports are 32 bytes long. Every error includes an 8-bit error
code. Error codes 128 through 255 are reserved for extensions. Every
error also includes the major and minor opcodes of the failed
request, and the least significant 16 bits of the sequence number of
the request. For the following errors (see Section 5), the failing
resource id is also returned: Colormap, Cursor, Drawable, Font,
GContext, IDChoice, Pixmap, and Window. For Atom errors, the failing
atom is returned. For Value errors, the failing value is returned.
Other core errors return no additional data. Unused bytes within
an error are not guaranteed to be zero.
Event Format
Events are 32 bytes long. Unused bytes within an event are not
guaranteed to be zero. Every event contains an 8-bit type code. The
most significant bit in this code is set if the event was generated
from a SendEvent request. Event codes 64 through 127 are reserved for
extensions, although the core protocol does not define a mechanism
for selecting interest in such events. Every core event (with the
exception of KeymapNotify) also contains the least significant 16
bits of the sequence number of the last request issued by the client
that was (or is currently being) processed by the server.
SECTION 3. SYNTAX
The syntax {...} encloses a set of alternatives.
The syntax [...] encloses a set of structure components.
In general, TYPEs are in upper case and AlternativeValues are
capitalized.
Requests in Section 10 are described in the following format:
RequestName
arg1: type1
...
argN: typeN
=>
result1: type1
...
resultM: typeM
Errors: kind1, ..., kindK
Description.
If no => is present in the description, then the request has no
reply (it is asynchronous), although errors may still be reported.
Events in Section 12 are described in the following format:
EventName
value1: type1
...
valueN: typeN
Description.
SECTION 4. COMMON TYPES
LISTofFOO
A type name of the form LISTofFOO means a counted list of elements
of type FOO; the size of the length field may vary (it is not
necessarily the same size as a FOO), in some cases may be implicit,
and is not fully specified in this document.
BITMASK and LISTofVALUE
The types BITMASK and LISTofVALUE are somewhat special. Various
requests contain arguments of the form:
value-mask: BITMASK
value-list: LISTofVALUE
used to allow the client to specify a subset of a heterogeneous
collection of "optional" arguments. The value-mask specifies which
arguments are to be provided; each such argument is assigned a unique
bit position. The representation of the BITMASK will typically
contain more bits than there are defined arguments; unused bits in
the value-mask must be zero (or the server generates a Value error).
The value-list contains one value for each one bit in the mask, from
least to most significant bit in the mask. Each value is represented
with 4 bytes, but the actual value occupies only the least
significant bytes as required; the values of the unused bytes do not
matter.
Or Types
A type of the form "T1 or ... or Tn" means the union of the indicated
types; a single-element type is given as the element without
enclosing braces.
DEVICE: 32-bit id (<class,model,manufacturer,unit> 8 bits each)
WINDOW: 32-bit id
PIXMAP: 32-bit id
CURSOR: 32-bit id
FONT: 32-bit id
GCONTEXT: 32-bit id
COLORMAP: 32-bit id
DRAWABLE: WINDOW or PIXMAP
ATOM: 32-bit id (top 3 bits guaranteed to be zero)
VISUALID: 32-bit id (top 3 bits guaranteed to be zero)
VALUE: 32-bit quantity (used only in LISTofVALUE)
INT8: 8-bit signed integer
INT16: 16-bit signed integer
INT32: 32-bit signed integer
CARD8: 8-bit unsigned integer
CARD16: 16-bit unsigned integer
CARD32: 32-bit unsigned integer
TIMESTAMP: CARD32
BITGRAVITY: {Forget, Static,
NorthWest, North, NorthEast,
West, Center, East,
SouthWest, South, SouthEast}
WINGRAVITY: {Unmap, Static,
NorthWest, North, NorthEast,
West, Center, East,
SouthWest, South, SouthEast}
BOOL: {True, False}
EVENT: {KeyPress, KeyRelease,
OwnerGrabButton,
ButtonPress, ButtonRelease, EnterWindow, LeaveWindow,
PointerMotion, PointerMotionHint,
Button1Motion, Button2Motion, Button3Motion,
Button4Motion, Button5Motion, ButtonMotion
Exposure, VisibilityChange,
StructureNotify, ResizeRedirect,
SubstructureNotify, SubstructureRedirect,
FocusChange,
PropertyChange, ColormapChange,
KeymapState}
POINTEREVENT: {ButtonPress, ButtonRelease, EnterWindow, LeaveWindow,
PointerMotion, PointerMotionHint,
Button1Motion, Button2Motion, Button3Motion,
Button4Motion, Button5Motion, ButtonMotion
KeymapState}
DEVICEEVENT: {KeyPress, KeyRelease,
ButtonPress, ButtonRelease,
PointerMotion,
Button1Motion, Button2Motion, Button3Motion,
Button4Motion, Button5Motion, ButtonMotion}
KEYCODE: CARD8
BUTTON: CARD8
KEYMASK: {Shift, CapsLock, Control, Mod1, Mod2, Mod3, Mod4, Mod5}
BUTMASK: {Button1, Button2, Button3, Button4, Button5}
KEYBUTMASK: KEYMASK or BUTMASK
STRING8: LISTofCARD8
STRING16: LISTofCHAR2B
CHAR2B: [byte1, byte2: CARD8]
POINT: [x, y: INT16]
RECTANGLE: [x, y: INT16,
width, height: CARD16]
ARC: [x, y: INT16,
width, height: CARD16,
angle1, angle2: INT16]
HOST: [family: {Internet, NS, ECMA, Datakit, DECnet}
address: LISTofCARD8]
The [x,y] coordinates of a RECTANGLE specify the upper left corner.
The primary interpretation of "large" characters in a STRING16 is
that they are composed of two bytes used to index a 2-D matrix;
hence the use of CHAR2B rather than CARD16. This corresponds to
the JIS/ISO method of indexing two-byte characters. It is expected
that most "large" fonts will be defined with two-byte matrix
indexing. For large fonts constructed with linear indexing, a
CHAR2B can be interpreted as a 16-bit number by treating byte1 as
the most significant byte; this means that clients should always
transmit such 16-bit character values most significant byte first,
as the server will never byte-swap CHAR2B quantities.
The length, format, and interpretation of a HOST address are specific
to the family.
SECTION 5. ERRORS
In general, when a request terminates with an error, the request has
no side effects (i.e., there is no partial execution). The only
requests for which this is not true are ChangeWindowAttributes,
ChangeGC, PolyText8, PolyText16, FreeColors, StoreColors, and
ChangeKeyboardControl.
The following error codes can be returned by the various requests:
Access
An attempt to grab a key/button combination already grabbed
by another client.
An attempt to free a colormap entry not allocated by the
client.
An attempt to store into a read-only or an unallocated
colormap entry.
An attempt to modify the access control list from other than
the local (or otherwise authorized) host.
An attempt to select an event type, that at most one client
can select at a time, when another client has already
selected it.
Alloc
The server failed to allocate the requested resource.
Note that this only covers allocation errors at a very coarse
level, and is not intended to (nor can it in practice hope
to) cover all cases of a server running out of allocation
space in the middle of service.
The semantics when a server runs out of allocation space are
left unspecified.
Atom
A value for an ATOM argument does not name a defined ATOM.
Colormap
A value for a COLORMAP argument does not name a defined
COLORMAP.
Cursor
A value for a CURSOR argument does not name a defined CURSOR.
Drawable
A value for a DRAWABLE argument does not name a defined
WINDOW or PIXMAP.
Font
A value for a FONT or <FONT or GCONTEXT> argument does not
name a defined FONT.
GContext
A value for a GCONTEXT argument does not name a defined
GCONTEXT.
IDChoice
The value chosen for a resource identifier is either not
included in the range assigned to the client, or is already
in use.
Implementation
The server does not implement some aspect of the request. A
server which generates this error for a core request is
deficient. As such, this error is not listed for any of the
requests, but clients should be prepared to receive such
errors, and handle or discard them.
Length
The length of a request is shorter or longer than that
required to minimally contain the arguments.
Match
An InputOnly window is used as a DRAWABLE.
Some argument (or pair of arguments) has the correct type and
range, but fails to "match" in some other way required by the
request.
Name
A font or color of the specified name does not exist.
Pixmap
A value for a PIXMAP argument does not name a defined PIXMAP.
Property
The requested property does not exist for the specified
window.
Request
The major or minor opcode does not specify a valid request.
Value
Some numeric value falls outside the range of values accepted
by the request. Unless a specific range is specified for an
argument, the full range defined by the argument's type is
accepted. Any argument defined as a set of alternatives can
generate this error.
Window
A value for a WINDOW argument does not name a defined WINDOW.
Note: the Atom, Colormap, Cursor, Drawable, Font, GContext, Pixmap,
and Window errors are also used when the argument type is extended
by union with a set of fixed alternatives, e.g.,<Window or
PointerRoot or None>.
SECTION 6. KEYBOARDS
Keycodes are always in the inclusive range [8,255].
For keyboards with both left-side and right-side modifier keys (e.g.,
Shift and Control), the mask bits in the protocol always define the
OR of the keys. If electronically distinguishable, they can have
separate up/down events generated, and clients that want to
distinguish can track the individual states manually.
<As part of the core we need to define a universal association
between keycaps and keycodes. A keycap is the graphical information
imprinted on a keyboard key, e.g., "$ 4", "T", "+ =".>
SECTION 7. POINTERS
Buttons are always numbered starting with one.
SECTION 8. PREDEFINED ATOMS
Predefined atoms are not strictly necessary, and may not be useful in
all environments, but will eliminate many InternAtom requests in most
applications. The core protocol imposes no semantics on these names,
except as they are used in FONTPROP structures (see QueryFont). Note
that upper/lower case matters.
BITMAP ICON_SIZE RGB_GREEN_MAP
COMMAND ITALIC_ANGLE RGB_RED_MAP
COPYRIGHT MAX_SPACE SECONDARY
CUT_BUFFER0 MIN_SPACE SIZE_HINTS
CUT_BUFFER1 NAME STRIKEOUT_ASCENT
CUT_BUFFER2 NORMAL_HINTS STRIKEOUT_DESCENT
CUT_BUFFER3 NORM_SPACE STRING
CUT_BUFFER4 PIXMAP SUBSCRIPT_X
CUT_BUFFER5 POINT_SIZE SUBSCRIPT_Y
CUT_BUFFER6 PRIMARY SUPERSCRIPT_X
CUT_BUFFER7 QUAD_WIDTH SUPERSCRIPT_Y
DEFAULT_CHAR RECTANGLE UNDERLINE_POSITION
END_SPACE RESIZE_HINT UNDERLINE_THICKNESS
FACE_NAME RESOLUTION WEIGHT
FAMILY_NAME RGB_BEST_MAP WINDOW
FONT_ASCENT RGB_BLUE_MAP WM_HINTS
FONT_DESCENT RGB_COLOR_MAP X_HEIGHT
ICON RGB_DEFAULT_MAP ZOOM_HINTS
ICON_NAME
SECTION 9. CONNECTION SETUP
For remote clients, the X protocol can be built on top of any
reliable byte stream. For TCP connections, displays on a given host
a numbered starting from 0, and the server for display N listens and
accepts connections on port 6000+N.
The client must send an initial byte of data to identify the byte
order to be employed. The value of the byte must be octal 102 or
154. The value 102 (ASCII uppercase B) means values are transmitted
most significant byte first, and value 154 (ASCII lowercase l) means
values are transmitted least significant byte first. Except where
explicitly noted in the protocol, all 16-bit and 32-bit quantities
sent by the client must be transmitted with this byte order, and all
16-bit and 32-bit quantities returned by the server will be
transmitted with this byte order.
Following the byte-order byte, the following information is sent by
the client at connection setup:
protocol-major-version: CARD16
protocol-minor-version: CARD16
authorization-protocol-name: STRING8
authorization-protocol-data: STRING8
The version numbers indicate what version of the protocol the
client expects the server to implement. See below for an
explanation. The authorization name indicates what
authorization protocol the client expects the server to use,
and the data is specific to that protocol. Specification of
valid authorization mechanisms is not part of the core X
protocol. It is hoped that eventually one authorization
protocol will be agreed upon. In the mean time, a server
that implements a different protocol than the client expects,
or a server that only implements the host-based mechanism,
will simply ignore this information.
Received by the client at connection setup:
success: BOOL
protocol-major-version: CARD16
protocol-minor-version: CARD16
length: CARD16
Length is the amount of additional data to follow, in units
of 4 bytes. The version numbers are an escape hatch in case
future revisions of the protocol are necessary. In general,
the major version would increment for incompatible changes,
and the minor version would increment for small upward
compatible changes. Barring changes, the major version
will be eleven, and the minor version will be zero. The
protocol version numbers returned indicate the protocol the
server actually supports. This might not equal the version
sent by the client. The server can (but need not) refuse
connections from clients that offer a different version
than the server supports. A server can (but need not)
support more than one version simultaneously.
Additional data received if authorization fails:
reason: STRING8
Additional data received if authorization is accepted:
vendor: STRING8
release-number: CARD32
resource-id-base, resource-id-mask: CARD32
image-byte-order: {LSBFirst, MSBFirst}
bitmap-format-scanline-unit: {8, 16, 32}
bitmap-format-scanline-pad: {8, 16, 32}
bitmap-format-bit-order: {LeastSignificant, MostSignificant}
pixmap-formats: LISTofFORMAT
roots: LISTofSCREEN
keyboard: DEVICE
pointer: DEVICE
motion-buffer-size: CARD32
maximum-request-length: CARD16
where
FORMAT: [depth: CARD8,
bits-per-pixel: {4, 8, 16, 24, 32}
scanline-pad: {8, 16, 32}]
SCREEN: [root: WINDOW
device: DEVICE
width-in-pixels, height-in-pixels: CARD16
width-in-millimeters,height-in-millimeters:CARD16
allowed-depths: LISTofDEPTH
root-depth: CARD8
root-visual: VISUALID
default-colormap: COLORMAP
white-pixel, black-pixel: CARD32
min-installed-maps, max-installed-maps: CARD16
backing-stores: {Never, WhenMapped, Always}
save-unders: BOOL
current-input-masks: SETofEVENT]
DEPTH: [depth: CARD8
visuals: LISTofVISUALTYPE]
VISUALTYPE: [visual-id: VISUALID
class: {StaticGray, StaticColor,
TrueColor,GrayScale, PseudoColor,
DirectColor}
red-mask, green-mask, blue-mask: CARD32
bits-per-rgb-value: CARD8
colormap-entries: CARD16]
Per server information:
The vendor string gives some indentification of the owner of the
server implementation. The semantics of the release-number is
controlled by the vendor.
The resource-id-mask contains a single contiguous set of bits (at
least 18); the client allocates resource ids by choosing a value
with (only) some subset of these bits set, and ORing it with
resource-id-base. Only values constructed in this way can be
used to name newly created resources over this connection.
Resource ids never have the top 3 bits set. The client is not
restricted to linear or contiguous allocation of resource ids.
Once an id has been freed, it can be reused, but this should not
be necessary. An id must be unique with respect to the ids of
all other resources, not just other resources of the same type.
Although the server is in general responsible for byte swapping
data to match the client, images are always transmitted and
received in formats (including byte order) specified by the
server. The byte order for images is given by image-byte-order,
and applies to each scanline unit in XYFormat (bitmap) format,
and to each pixel value in ZFormat.
A bitmap is represented in scanline order. Each scanline is padded
to a multiple of bits as given by bitmap-format-scanline-pad. The
pad bits are of arbitrary value. The scanline is quantized in multiples of bits as given by bitmap-format-scanline-unit. Within each unit, the leftmost bit in the bitmap is either the least or most significant bit in the unit, as given by bitmap-format-bit-order. If a pixmap is represented in XYFormat, each plane is represented as a bitmap, and the planes appear from most to least significant in bit order. For each pixmap depth supported by some screen, pixmap-formats lists the ZFormat used to represent images of that depth. In ZFormat, the pixels are in scanline order, left to right within a scanline. The number of bits used to hold each pixel is given by bits-per-pixel, and may be larger than strictly required by the depth. When the bits-per-pixel is 4, the order of nibbles in the byte is the same as the image byte-order. Each scanline is padded to a multiple of bits as given by scanline-pad. How a pointing device roams the screens is up to the server implementation, and is transparent to the protocol. No geometry among screens is defined. The server may retain the recent history of pointer motion, and to a finer granularity than is reported by MotionNotify events. Such history is available via the GetPointerMotions request. The approximate size of the history buffer is given by motion-buffer-size. Maximum-request-length specifies the maximum length of a request, in 4-byte units, accepted by the server; i.e., this is the maximum value that can appear in the length field of a request. Requests larger than this generate a Length error, and the server will read and simply discard the entire request. Maximum-request-length will always be at least 4096 (i.e., requests of length up to and including 16384 bytes will be accepted by all servers). Per screen information: The allowed-depths specifies what pixmap and window depths are supported. Pixmaps are supported for each depth listed, and windows of that depth are supported if at least one visual type is listed for the depth. A pixmap depth of one is always supported and listed, but windows of depth one might not be supported. A depth of zero is never listed, but zero-depth InputOnly windows are always supported. Root-depth and root-visual specify the depth and visual type of the root window. Width-in-pixels and height-in-pixels specify the size of the root window (which cannot be changed). The class of the root window is always InputOutput. Width-in-millimeters and height-in-millimeters can be used to determine the physical size and the aspect ratio.
The default-colormap is the one initially associated with the root window. Clients with minimal color requirements creating windows of the same depth as the root may want to allocate from this map by default. Black-pixel and white-pixel can be used in implementing a "monochrome" application. These pixel values are for permanently allocated entries in the default-colormap; the actual RGB values may be settable on some screens. The border of the root window is initially a pixmap filled with the black-pixel. The initial background of the root window is a pixmap filled with some unspecified two-color pattern using black-pixel and white-pixel. Min-installed-maps specifies the number of maps that can be guaranteed to installed simultaneously (with InstallColormap), regardless of the number of entries allocated in each map. Max-installed-maps specifies the maximum number of maps that might possibly be installed simultaneously, depending on their allocations. For the typical case of a single hardware colormap, both values will be one. Backing-stores indicates when the server supports backing stores for this screen, although it may be storage limited in the number of windows it can support at once. If save-unders is True, then the a server can support the save-under mode in CreateWindow and ChangeWindowAttributes, although again it may be storage limited. The current-input-events is what GetWindowAttributes would return for the all-event-masks for the root window. Per visual-type information: A given visual type might be listed for more than one depth, or for more than one screen. For PseudoColor, a pixel value indexes a colormap to produce independent RGB values; the RGB values can be changed dynamically. GrayScale is treated the same as PseudoColor, except which primary drives the screen is undefined, so the client should always store the same value for red, green, and blue in 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. TrueColor is treated the same as DirectColor, except the colormap has predefined read-only RGB values, which are server-dependent, but provide (near-)linear ramps in each primary. StaticColor is treated the same as PseudoColor, except the colormap has predefined read-only RGB values, which are server-dependent. StaticGray is treated the same as StaticColor, except the red,
green, and blue values are equal for any single pixel value,
resulting in shades of gray. StaticGray with a two-entry colormap
can be thought of as "monochrome".
The red-mask, green-mask, and blue-mask are only defined for
DirectColor and TrueColor; each has one contiguous set of bits, with
no intersections.
The bits-per-rgb-value specifies the log base 2 of the approximate
number of distinct color values (individually) of red, green, and
blue. Actual RGB values are always passed in the protocol within a
16-bit spectrum.
The colormap-entries defines the number of available colormap entries
in a newly created colormap. For DirectColor and TrueColor, this
will usually be the size of an individual pixel subfield.
SECTION 10. REQUESTS
CreateWindow
wid, parent: WINDOW
class: {InputOutput, InputOnly, CopyFromParent}
depth: CARD8
visual: VISUALID or CopyFromParent
x, y: INT16
width, height, border-width: CARD16
value-mask: BITMASK
value-list: LISTofVALUE
Errors: IDChoice, Window, Pixmap, Colormap, Cursor, Match,
Value, Alloc
Creates an unmapped window, and assigns the identifier wid
to it.
A class of CopyFromParent means the class is taken from the
parent. A depth of zero for class InputOutput or
CopyFromParent means the depth is taken from the parent.
A visual of CopyFromParent means the visual type is taken
from the parent. For class InputOutput, the visual type
and depth must be a combination supported for the screen
(else a Match error); the depth need not be the same as the
parent, but the parent must not be of class InputOnly (else
a Match error). For class InputOnly, the depth must be
zero (else a Match error), and the visual must be one
supported for the screen (else a Match error), but the
parent may have any depth and class.
The server essentially acts as if InputOnly windows do not
exist for the purposes of graphics requests, exposure
processing, and VisibilityNotify events. An InputOnly window
cannot be used as a drawable (as a source or destination for
graphics requests). InputOnly and InputOutput windows act
identically in other respects (properties, grabs, input
control, and so on).
The window is placed on top in the stacking order with
respect to siblings. The x and y coordinates are relative
to the parent's origin, and specify the position of the upper
left outer corner of the window (not the origin). The width
and height specify the inside size, not including the border,
and must be non-zero. The border-width for an InputOnly
window must be zero (else a Match error).
The value-mask and value-list specify attributes of the
window that are to be explicitly initialized. The possible
values are:
background-pixmap: PIXMAP or None or ParentRelative
background-pixel: CARD32
border-pixmap: PIXMAP or CopyFromParent
border-pixel: CARD32
bit-gravity: BITGRAVITY
win-gravity: WINGRAVITY
backing-store: {NotUseful, WhenMapped, Always}
backing-bit-planes: CARD32
backing-pixel: CARD32
save-under: BOOL
event-mask: SETofEVENT
do-not-propagate-mask: SETofDEVICEEVENT
override-redirect: BOOL
colormap: COLORMAP or CopyFromParent
cursor: CURSOR or None
The default values, when attributes are not explicitly
initialized, are:
background-pixmap: None
border-pixmap: CopyFromParent
bit-gravity: Forget
win-gravity: NorthWest
backing-store: NotUseful
backing-bit-planes: all ones
backing-pixel: zero
save-under: False
event-mask: {} (empty set)
do-not-propagate-mask: {} (empty set)
override-redirect: False
colormap: CopyFromParent
cursor: None
Only the following attributes are defined for InputOnly
windows: win-gravity, event-mask, do-not-propagate-mask,
and cursor. It is a Match error to specify any other
attributes for InputOnly windows.
If background-pixmap is given, it overrides the default
background-pixel. The background pixmap and the window must
have the same root and the same depth (else a Match error).
Any size pixmap can be used, although some sizes may be
faster than others. If background None is specifed, the
window has no defined background. If background
ParentRelative is specified, the parent's background is
used, but the window must have the same depth as the parent
(else a Match error); if the parent has background None,
then the window will also have background None. A copy
of the parent's background is not made; the parent's
background is reexamined each time the window background is
required. If background-pixel is given, it overrides the
default and any background-pixmap given, and a pixmap of
undefined size filled with background-pixel is used for the
background. For a ParentRelative background, the
background tile origin always aligns with the parent's
background tile origin; otherwise the background tile
origin is always the window origin.
When regions of the window are exposed and the server has
not retained the contents, the server automatically tiles
the regions with the window's background unless the window
has a background of None, in which case the previous screen
contents are simply left in place. Exposure events are then
generated for the regions, even if the background is None.
The border tile origin is always the same as the background
tile origin. If border-pixmap is given, it overrides the
default border-pixel. The border pixmap and the window must
have the same root and the same depth (else a Match error).
Any size pixmap can be used, although some sizes may faster
than others. If CopyFromParent is given, the parent's border
pixmap is copied (subsequent changes to the parent do not
affect the child), but the window must have the same depth
as the parent (else a Match error). If border-pixel is
given, it overrides the default and any border-pixmap given,
and a pixmap of undefined size filled with border-pixel is
used for the border.
Output to a window is always clipped to the inside of the
window, so that the border is never affected.
The bit-gravity defines which region of the window should be
retained if the window is resized, and win-gravity defines
how the window should be repositioned if the parent is
resized; see ConfigureWindow.
A backing-store of WhenMapped advises the server that
maintaining contents of obscured regions when the window
is mapped would be beneficial. A backing-store of Always
advises the server that maintaining contents even when the
window is unmapped would be beneficial. Note that, even if
the window is larger than its parent, the server should
maintain complete contents, not just the region within the
parent boundaries. If the server maintains contents,
Exposure events will not be generated, but the server may
stop maintaining contents at any time. A value of NotUseful
advises the server that maintaining contents is unnecessary,
although a server may still choose to maintain contents.
Backing-bit-planes indicates (with one bits) which bit
planes of the window hold dynamic data that must be preserved
in backing-stores. Backing-pixel specifies what value to use
in planes not covered by backing-bit-planes. The server is
free to only save the specified bit planes in the
backing-store, and regenerate the remaining planes with the
specified pixel value.
If save-under is True, the server is advised that, when
this window is mapped, saving the contents of windows it
obscures would be beneficial.
The event-mask defines which events the client is interested
in for this window (or, for some event types, inferiors of
the window). The do-not-propagate-mask defines which events
should not be propagated to ancestor windows when no client
has the event type selected in this window.
Override-redirect specifies whether map and configure
request on this window should override a SubstructureRedirect
on the parent, typically to inform a window manager not to
tamper with the window.
The colormap specifies the colormap, that best reflects the
"true" colors of the window. Servers capable of supporting
hardware colormaps may use this information, and window
managers may use it for InstallColormap requests. The
colormap must have the same visual type as the window
(else a match error). If CopyFromParent is specified, the
parents's colormap is copied (subsequent changes to the
parent do not affect the child), but the window must have
the same visual type as the parent (else a Match error) an
the parent must not have a colormap of None (else a Match
error).
If a cursor is specified, it will be used whenever the
pointer is in the window. If None is specified, the
parent's cursor will be used when the pointer is in the
window, and any change in the parent's cursor will
cause an immediate change in the display cursor.
This request generates a CreateNotify event.
The background and border pixmaps and the cursor may be
freed immediately if no further explicit references to
them are to be made.
Subsequent drawing into the background or border pixmap has
an undefined effect on the window state; the server might or
might not make a copy of the pixmap.
ChangeWindowAttributes
window: WINDOW
value-mask: BITMASK
value-list: LISTofVALUE
Errors: Window, Pixmap, Colormap, Cursor, Match, Value,
Access
The value-mask and value-list specify which attributes are
to be changed. The values and restrictions are the same
as for CreateWindow.
Changing the background does not cause the window contents
to be changed. Setting the border, or changing the
background such that border tile origin changes, causes the
border to be repainted. Changing the background of a root
window to None or ParentRelative restores the default
background pixmap. Changing the border of a root window to
CopyFromParent restores the default border pixmap.
Changing the back-store of an obsecured window to
WhenMapped or Always, or changing the backing-bit-planes,
backing-pixel, or save-under of a mapped window, may have
no immediate effect.
Multiple clients can select input on the same window; their
event-masks are disjoint. When an event is generated it
will be reported to all interested clients. However, at
most one client at a time can select for
SubstructureRedirect, at most one client at a time can
select for ResizeRedirectr, and at most one client at a
time can select for ButtonPress.
There is only one do-not-propagate-mask for a window, not
one per client.
(next page on part 2)