X Version 11, Release 7.7
Version 2.0
Copyright © 1991 Network Computing Devices, Inc.
Permission to use, copy, modify, distribute, and sell this documentation for any purpose is hereby granted without fee, provided that the above copyright notice and this permission notice appear in all copies. Network Computing Devices, Inc. makes no representations about the suitability for any purpose of the information in this document. This documentation is provided “as is” without express or implied warranty.
Copyright © 1994 X Consortium
Permission is hereby granted, free of charge, to any person obtaining a copy of this software and associated documentation files (the “Software”), to deal in the Software without restriction, including without limitation the rights to use, copy, modify, merge, publish, distribute, sublicense, and/or sell copies of the Software, and to permit persons to whom the Software is furnished to do so, subject to the following conditions:
The above copyright notice and this permission notice shall be included in all copies or substantial portions of the Software.
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Except as contained in this notice, the name of the X Consortium shall not be used in advertising or otherwise to promote the sale, use or other dealings in this Software without prior written authorization from the X Consortium.
Table of Contents
NoOpListExtensionsQueryExtensionListCataloguesSetCataloguesGetCataloguesSetEventMaskGetEventMaskCreateACFreeACSetAuthorizationSetResolutionGetResolutionListFontsListFontsWithXInfoOpenBitmapFontQueryXInfoQueryXExtents8QueryXExtents16QueryXBitmaps8QueryXBitmaps16CloseFontList of Figures
The management of fonts in large, heterogeneous environments is one of the hardest aspects of using the X Window System [1] . Multiple formats and the lack of a consistent mechanism for exporting font data to all displays on a network prevent the transparent use of applications across different display platforms. The X Font Service protocol is designed to address this and other issues, with specific emphasis on the needs of the core X protocol. Upward-compatible changes (typically in the form of new requests) are expected as consensus is reached on new features (particularly outline font support).
Currently, most X displays use network file protocols such as NFS and TFTP to obtain raw font data which they parse directly. Since a common binary format for this data doesn't exist, displays must be able to interpret a variety of formats if they are to be used with different application hosts. This leads to wasted code and data space and a loss of interoperability as displays are used in unforeseen environments.
By moving the interpretation of font data out of the X server into a separate service on the network, these problems can be greatly reduced. In addition, new technologies, such as dynamically generating bitmaps from scaled or outline fonts, can be provided to all displays transparently. For horizontal text, caching techniques and increased processor power can potentially make rasterization more efficient on large, centralized hosts than on individual displays.
Each font server provides sets of fonts that may be listed and queried for header, property, glyph extents, and bitmap information. This data is transmitted over the network using a binary format (with variations to support different bit- and byte-orders) designed to minimize the amount of processing required by the display. Since the font server, rather than the display, is responsible for parsing the raw font data, new formats can be used by all displays by modifying a single font server.
From the user's point of view, font servers are simply a new type of name in the X font path. Network name services allow descriptive names (such as DEPARTMENT-FONTS or APPLICATION-FONTS) to be translated into proper network addresses. X displays send requests to and read replies from the font server rather than reading directly from files. Since the X Font Service protocol is designed to allow subsets of the font data to be requested, displays may easily implement a variety of strategies for fine-grained demand-loading of glyphs.
In this document, the words client and server refer to the consumer and provider of a font, respectively, unless otherwise indicated. It is important to note that in this context, the X server is also a font client.
The X Font Service protocol does not require any changes to the core X protocol or to any applications. To the user, font servers are simply additional types of font path elements. As such, X servers may connect to multiple font servers, as shown in Figure 2.1. Although the font protocol is geared towards the X Window System, it may be also used by other consumers of font data (such as printer drivers).
Figure 2.1. Connecting to a Font Server
┌────────┐ ┌───────────────┐
│ X1 ├──────────────┤ │
│ Server │ │ Font Server │
└────────┘ ┌───────┤ 1 │
│ └───────────────┘
┌────────┐ │
│ X2 ├──────┘ ┌───────────────┐
│ Server ├──────────────┤ │
└────────┘ │ Font Server │
┌───────┤ 2 │
┌─────────┐ │ └───────────────┘
│ other │ │
│ clients ├──────┘
└─────────┘
Clients communicate with the font server using the request/reply/event model over any mutually-understood virtual stream connection (such as TCP/IP, DECnet, [2] etc.). Font servers are responsible for providing data in the bit and byte orders requested by the client. The set of requests and events provided in the first version of the X Font Service protocol is limited to supporting the needs of the bitmap-oriented core X Window System protocol. Extensions are expected as new needs evolve.
A font server reads raw font data from a variety of sources (possibly including other font servers) and converts it into a common format that is transmitted to the client using the protocol described in Section 4. New font formats are handled by adding new converters to a font server, as shown in Figure 2.2.
Figure 2.2. Where Font Data Comes From
┌────────────┐
│ client │
│ (X server) │
└─────┬──────┘
│
network
│
┌─────────────────────┴──────────────────────┐
│ │
│ font server 1 │
│ │
├─────┬─────┬─────┬─────┬────┬─────┬───┬─────┤
│ bdf │ snf │ pcf │ atm │ f3 │ dwf │ │ │ ... │
└─────┴─────┴─────┴─────┴────┴─────┴─│─┴─────┘
│
network
│
┌─────┴────┐
│ font │
│ server 2 │
└──────────┘
The server may choose to provide named sets of fonts called catalogues. Clients may specify which of the sets should be used in listing or opening a font.
An event mechanism similar to that used in the X protocol is provided for asynchronous notification of clients by the server.
Clients may provide authorization data for the server to be used in determining (according to the server's licensing policy) whether or not access should be granted to particular fonts. This is particularly useful for clients whose authorization changes over time (such as an X server that can verify the identity of the user).
Implementations that wish to provide additional requests or events may use the extension mechanism. Adding to the core font service protocol (with the accompanying change in the major or minor version numbers) is reserved to the X Consortium.
Table of Contents
Font clients that expose font server names to the user are encouraged to provide ways of naming font servers symbolically (e.g. DEPARTMENT-FONTS). However, for environments that lack appropriate name services transport-specific names are necessary. Since these names do occur in the protocol, clients and servers should support at least the applicable formats described below. Formats for additional transports may be registered with the X Consortium.
The following syntax should be used for TCP/IP names:
TCP name ::= tcp/ hostname : ipportnumber [/ cataloguelist]
where hostname is either symbolic (such as
expo.lcs.mit.edu) or numeric
decimal (such as 18.30.0.212).
The ipportnumber is the port on which the
font server is listening for connections.
The cataloguelist string at
the end is optional and specifies a plus-separated list of catalogues
that may be requested. For example:
tcp/expo.lcs.mit.edu:8012/available+special
tcp/18.30.0.212:7890
The following syntax should be used for DECnet names:
DECnet name ::= decnet/ nodename ::font$ objname [/ cataloguelist]
where nodename is either symbolic (such as
SRVNOD) or the
numeric decimal form of the DECnet address (such as
44.70).
The objname is normal, case-insensitive DECnet
object name. The cataloguelist string
at the end is
optional and specifies a plus-separated list of catalogues that may be
requested. For example:
DECNET/SRVNOD::FONT$DEFAULT/AVAILABLE
decnet/44.70::font$other
Table of Contents
NoOpListExtensionsQueryExtensionListCataloguesSetCataloguesGetCataloguesSetEventMaskGetEventMaskCreateACFreeACSetAuthorizationSetResolutionGetResolutionListFontsListFontsWithXInfoOpenBitmapFontQueryXInfoQueryXExtents8QueryXExtents16QueryXBitmaps8QueryXBitmaps16CloseFontThe protocol described below uses the request/reply/error model and is specified using the same conventions outlined in Section 2 of the core X Window System protocol [1]:
Data type names are spelled in upper case with no word separators, as in: FONTID
Alternate values are capitalized with no word separators,
as in: MaxWidth
Structure element declarations are in lower case with hyphens
as word separators, as in: byte-order-msb
Structure element names are referred to in
upper case (e.g. BYTE-ORDER-MSB) when used in
descriptions to set them off from the surrounding
text. When this document is typeset they will be
printed in lower case in a distinct font.
Type declarations have the form “name: type”, as in: CARD8: 8-bit byte
Comma-separated lists of alternate values are enclosed in
braces, as in: { Min, MaxWidth,
Max }
Comma-separated lists of structure elements are enclosed in
brackets, as in: [ byte1: CARD8,
byte2: CARD8 ]
A type with a prefix “LISTof” represents a counted list of elements of that type, as in: LISTofCARD8
The following data types are used in the core X Font Server protocol:
| ACCESSCONTEXT: | ID |
This value is specified in the CreateAC request as the identifier to be used when referring to a particular AccessContext resource within the server. These resources are used by the server to store client-specified authorization information. This information may be used by the server to determine whether or not the client should be granted access to particular font data.
In order to preserve the integrity of font licensing being performed by the font server, care must be taken by a client to properly represent the identity of the true user of the font. Some font clients will in fact be servers (for example, X servers) requesting fonts for their own clients. Other font clients may be doing work on behalf of a number of different users over time (for example, print spoolers).
AccessContexts
must be created (with
CreateAC)
and switched among (with
SetAuthorization)
to represent all of these “font users” properly.
This structure specifies the NAME,
encoded in ISO 8859-1 according
to Section 3,
of another font server that may be useful as a
substitute for this font server.
The SUBSET field indicates
whether or not the alternate server is likely to only contain a
subset of the fonts available from this font server. This
information is returned during the initial connection setup and
may be used by the client to find a backup server in case of
failure.
| AUTH: | [ name: | STRING8, |
data: | LISTofBYTE ] |
This structure specifies the name of an authorization protocol and initial data for that protocol. It is used in the authorization negotiation in the initial connection setup and in the CreateAC request.
| BITMAPFORMAT: | CARD32 |
CARD32 containing the following fields defined by the sets of values given further below
| [ | ||
byte-order-msb: | 1 bit, | |
bit-order-msb: | 1 bit, | |
image-rect: | 2 bits | { Min,
MaxWidth,
Max }, |
zero-pad: | 4 bits, | |
scanline-pad: | 2 bits | { ScanlinePad8,
ScanlinePad16,
ScanlinePad32,
ScanlinePad64 }, |
zero-pad: | 2 bits, | |
scanline-unit: | 2 bits | { ScanlineUnit8,
ScanlineUnit16,
ScanlineUnit32,
ScanlineUnit64 }, |
zero-pad: | 2 bits, | |
zero-pad: | 16 bits, | |
| ] |
This structure specifies how glyph images are transmitted in
response to
QueryXBitmaps8
and
QueryXBitmaps16
requests.
If the BYTE-ORDER-MSB bit
(1 << 0) is set, the Most Significant
Byte of each scanline unit is returned first. Otherwise, the
Least Significant Byte is returned first.
If the BIT-ORDER-MSB bit
(1 << 1) is set, the left-most bit in
each glyph scanline unit is stored in the Most Significant Bit of
each transmitted scanline unit. Otherwise, the left-most bit is
stored in the Least Significant Bit.
The IMAGE-RECT field specifies a rectangle of
pixels within the
glyph image. It contains one of the following alternate values:
ImageRectMin | (0 << 2) |
ImageRectMaxWidth | (1 << 2) |
ImageRectMax | (2 << 2) |
For a glyph with extents XCHARINFO in a font with header
information XFONTINFO, the IMAGE-RECT
values have the following meanings:
The SCANLINE-PAD field specifies the number of
bits (8, 16, 32,
or 64) to which each glyph scanline is padded before transmitting.
It contains one of the following alternate values:
ScanlinePad8 | (0 << 8) |
ScanlinePad16 | (1 << 8) |
ScanlinePad32 | (2 << 8) |
ScanlinePad64 | (3 << 8) |
The SCANLINE-UNIT field specifies the number of
bits (8, 16, 32, or 64) that should be treated as a unit for swapping.
This value must be less than or equal to the number of bits specified by the
SCANLINE-PAD. It contains one of the following
alternate values:
ScanlineUnit8 | (0 << 12) |
ScanlineUnit16 | (1 << 12) |
ScanlineUnit32 | (2 << 12) |
ScanlineUnit64 | (3 << 12) |
BITMAPFORMATs are byte-swapped as CARD32s. All unspecified bits must be zero.
Use of an invalid BITMAPFORMAT causes a Format error to be returned.
| BITMAPFORMATMASK: | CARD32 mask |
This is a mask of bits representing the fields in a BITMAPFORMAT:
ByteOrderMask | (1 << 0) |
BitOrderMask | (1 << 1) |
ImageRectMask | (1 << 2) |
ScanlinePadMask | (1 << 3) |
ScanlineUnitMask | (1 << 4) |
Unspecified bits are required to be zero or else a Format error is returned.
| BYTE: | 8-bit value |
This is an unsigned byte of data whose encoding is determined by the context in which it is used.
| CARD8: | 8-bit unsigned integer | |
| CARD16: | 16-bit unsigned integer | |
| CARD32: | 32-bit unsigned integer |
These are unsigned numbers. The latter two are byte-swapped when the server and client have different byte orders.
| CHAR2B: | [ byte1, byte2: | CARD8 ] |
This structure specifies an individual character code within
either a 2-dimensional matrix (using BYTE1
and BYTE2 as the row and column indices,
respectively) or a vector (using BYTE1 and
BYTE2 as most- and least-significant bytes,
respectively). This data type is treated as a pair of 8-bit values and
is never byte-swapped. Therefore, the client should always transmit
BYTE1 first.
| EVENTMASK: | CARD32 mask |
This is a mask of bits indicating which of an extension's (or the
core's) maskable events the client would like to receive. Each
bit indicates one or more events, and a bit value of one indicates
interest in a corresponding set of events. The following bits are
defined for event masks specified for the core protocol (i.e. an
EXTENSION-OPCODE of zero in
SetEventMask
and
GetEventMask
requests):
CatalogueListChangeMask | (1 << 0) |
FontListChangeMask | (1 << 1) |
If
CatalogueListChangeMask
is set, client is interested in
receiving
CatalogueListNotify
events. If
FontListChangeMask
is set, the client is interested in
receiving
FontListNotify
events.
Extensions that provide additional events may define their own event masks. These event masks have their own scope and may use the same bit values as the core or other extensions.
All unused bits must be set to zero. In
SetEventMask
requests, if
any bits are set that are not defined for the extension (or core)
for which this EVENTMASK is intended (according to the
EXTENSION-OPCODE given in the
SetEventMask
request), an
EventMask
error is generated.
This value is swapped as a CARD32.
| FONTID: | ID |
This is specified by the client in the request
OpenBitmapFont
as the identifier to be used when referring to a particular open
font.
| ID: | CARD32 |
This is a 32-bit value in which the top 3 bits must be clear, and at least 1 other bit must be set (yielding a range of 1 through 229-1). It is specified by the client to represent objects in the server. Identifiers are scoped according to their type are private to the client; thus, the same identifier may be used for both a FONTID and an ACCESSCONTEXT as well as by multiple clients.
An ID of zero is referred to as None.
| INT8: | 8-bit signed integer | |
| INT16: | 16-bit signed integer | |
| INT32: | 32-bit signed integer |
These are signed numbers. The latter two are byte-swapped when the client and server have different byte orders.
| OFFSET32: | [ position: | CARD32, |
length: | CARD32 ] |
This structure indicates a position and length within a block of data.
| PROPINFO: | [ offsets: | LISTofPROPOFFSET, |
data: | LISTofBYTE ] |
This structure describes the list of properties provided by a font. Strings for all of the properties names and values are stored within the data block and are located using a table of offsets and lengths.
This structure is padded to 32-bit alignment.
This structure specifies the position, length, and type of of data for a property.
The NAME field specifies the position and length
(which must be
greater than zero) of the property name relative to the beginning
of the PROPINFO.DATA block for this font.
The interpretation of
the position and length of the VALUE field is
determined by the TYPE field, which contains
one of the following alternate values:
String | 0 |
Unsigned | 1 |
Signed | 2 |
which have the following meanings:
This structure is zero-padded to 32-bit alignment.
| RANGE: | [ min-char, max-char: | CHAR2B ] |
This structure specifies a range of character codes. A single
character is represented by MIN-CHAR equals
MAX-CHAR. If the linear interpretation of
MAX-CHAR is less than that of
MIN-CHAR, or if
MIN-CHAR is less than the font's
XFONTINFO.CHAR-RANGE.MIN-CHAR, or if
MAX-CHAR is greater than the
font's XFONTINFO.CHAR-RANGE.MAX-CHAR,
the range is invalid.
| RESOLUTION: | [ x-resolution: | CARD16, |
y-resolution: | CARD16, | |
decipoint-size: | CARD16 ] |
This structure specifies resolution and point size to be used in
resolving partially-specified scaled font names. The
X-RESOLUTION and
Y-RESOLUTION are measured in
pixels-per-inch and must be greater than zero.
The DECIPOINT-SIZE is the preferred font
size, measured in tenths of a point, and must be greater than zero.
| STRING8: | LISTofCARD8 |
This is a counted list of 1-byte character codes, typically
encoded in ISO 8859-1. A character code
“c” is equivalent to a
CHAR2B structure whose BYTE1
is zero and whose BYTE2 is
“c”.
| TIMESTAMP: | CARD32 |
This is the number of milliseconds that have passed since a server-dependent origin. It is provided in errors and events and is permitted to wrap.
| XCHARINFO: | [ lbearing, rbearing: | INT16, |
width: | INT16, | |
ascent, descent: | INT16, | |
attributes: | CARD16 ] |
This structure specifies the ink extents and horizontal escapement (also known as the set- or logical width) of an individual character. The first five values represent directed distances in a coordinate system whose origin is aligned with the lower-left edge of the left-most pixel of the glyph baseline (i.e. the baseline falls between two pixels as shown in Figure 3-1 of the Bitmap Distribution Format 2.1 Consortium standard [2]).
The LBEARING field specifies the
directed distance measured to the
right from the origin to the left edge of the left-most inked
pixel in the glyph.
The RBEARING field specifies the
directed distance (measured to
the right) from the origin to the right edge of the right-most
inked pixel in the glyph.
The WIDTH field specifies the
directed distance (measured to the
right) from the origin to the position where the next character
should appear (called the escapement point). This
distance includes any whitespace used for intercharacter padding and is
also referred to as the logical width or
horizontal escapement.
The ASCENT field specifies the
directed distance (measured up)
from the baseline to the top edge of the top-most inked pixel
in the glyph.
The DESCENT field specifies the
directed distance (measured
down) from the baseline to the bottom edge of the bottom-most
inked pixel.
The ATTRIBUTES field specifies
glyph-specific information that
is passed through the application. If this value is not being
used, it should be zero.
The ink bounding box of a glyph is defined to be the smallest
rectangle that encloses all of the inked pixels. This box has
a width of
RBEARING − LBEARING
pixels and a height of
ASCENT + DESCENT pixels.
| XFONTINFO: | [ flags: | CARD32, |
drawing-direction: | { LeftToRight, RightToLeft } | |
char-range: | RANGE, | |
default-char: | CHAR2B, | |
min-bounds: | XCHARINFO, | |
max-bounds: | XCHARINFO, | |
font-ascent: | INT16, | |
font-descent: | INT16, | |
properties: | PROPINFO ] |
This structure specifies attributes related to the font as a whole.
The FLAGS field is a bit mask containing zero
or more of the following boolean values (unspecified bits must be zero):
AllCharactersExist | (1 << 0) |
InkInside | (1 << 1) |
HorizontalOverlap | (1 << 2) |
which have the following meanings:
The DRAWING-DIRECTION field contains a hint
indicating whether most of the character metrics have a positive (or
“LeftToRight”) logical width or a
negative (“RightToLeft”) logical width. It
contains the following alternate values:
LeftToRight | 0 |
RightToLeft | 1 |
The CHAR-RANGE.MIN-CHAR
and CHAR-RANGE.MAX-CHAR fields specify the
first and last character codes that have glyphs encoded in this font.
All fonts must have at least one encoded glyph (in which case the
MIN-CHAR and MAX-CHAR
are equal), but are not required to have glyphs
encoded at all positions between the first and last characters.
The DEFAULT-CHAR field specifies
the character code of the glyph
that the client should substitute for unencoded characters. Requests
for extents or bitmaps for an unencoded character generate zero-filled
metrics and a zero-length glyph bitmap, respectively.
The MIN-BOUNDS and
MAX-BOUNDS fields contain the minimum and maximum
values of each of the extents field of all encoded characters in the
font (i.e. non-existent characters are ignored).
The FONT-ASCENT and
FONT-DESCENT fields specify the font designer's
logical height of the font, above and below the baseline,
respectively. The sum of the two values is often used as the
vertical line spacing of the font. Individual glyphs are permitted
to have ascents and descents that are greater than these values.
The PROPERTIES field contains the
property data associated with this font.
This structure is padded to 32-bit alignment.
This section describes the requests that may be sent by the client and the replies or errors that are generated in response. Versions of the protocol with the same major version are required to be upward-compatible.
Every request on a given connection is implicitly assigned a sequence number, starting with 1, that is used in replies, error, and events. Servers are required to generate replies and errors in the order in which the corresponding requests are received. Servers are permitted to add or remove fonts to the list visible to the client between any two requests, but requests must be processed atomically. Each request packet is at least 4 bytes long and contains the following fields:
major-opcode: | CARD8 | |
minor-opcode: | CARD8 | |
length: | CARD16 |
The MAJOR-OPCODE specifies which core request or
extension package this packet represents. If the
MAJOR-OPCODE corresponds to a core request, the
MINOR-OPCODE contains 8 bits of request-specific data.
Otherwise, the MINOR-OPCODE specifies which extension
request this packet represents. The LENGTH field
specifies the number of 4-byte units contained within the packet
and must be at least one. If this field contains a value greater than one it
is followed by (LENGTH - 1) * 4 bytes
of request-specific data. Unless
otherwise specified, unused bytes are not required to be zero.
If a request packet contains too little or too much data, the server returns
a Length error.
If the server runs out of internal
resources (such as memory) while processing a request, it returns an
Alloc error.
If a server is deficient (and therefore non-compliant) and is unable to
process a request, it may return an
Implementation error.
If a client uses an extension request without previously having issued a
QueryExtension
request for that extension, the server responds with a
Request
error. If the server encounters a request with an unknown
MAJOR-OPCODE or MINOR-OPCODE,
it responds with a
Request
error.
At most one error is generated per request. If more than one error condition
is encountered in processing a requests, the choice of which error is returned
is server-dependent.
Core requests have MAJOR-OPCODE values between 0 and
127, inclusive. Extension requests have MAJOR-OPCODE
values between 128 and 255, inclusive, that are assigned by by the server.
All MINOR-OPCODE values in extension requests are
between 0 and 255, inclusive.
Each reply is at least 8 bytes long and contains the following fields:
type: | CARD8 | value of 0 |
data-or-unused: | CARD8 | |
sequence-number: | CARD16 | |
length: | CARD32 |
The TYPE field has a value of zero.
The DATA-OR-UNUSED field may be used to
encode one byte of reply-specific data (see
Section 5.2 on request encoding).
The least-significant 16 bits of the sequence number of the request that
generated the reply are stored in the SEQUENCE-NUMBER
field. The LENGTH field specifies the number of
4-byte units in this reply packet, including the fields described above,
and must be at least two. If LENGTH is greater
than two, the fields described above are followed by
(LENGTH - 2) * 4 bytes of additional data.
Requests that have replies are described using the following syntax:
RequestName
arg1:type1 arg2:type2 ... argN:typeN ▶ result1:type1 result2:type2 ... resultM:typeM Errors: kind1, kind2 ..., kindK Description
If a request does not generate a reply, the ▶ and result lines are omitted. If a request may generate multiple replies, the ▶ is replaced by a ▶+. In the authorization data exchanges in the initial connection setup and the CreateAC request, ◀ indicates data sent by the client in response to data sent by the server.
The protocol begins with the establishment of a connection over a mutually-understood virtual stream:
byte-order: | BYTE |
client-major-protocol-version: | CARD16 |
client-minor-protocol-version: | CARD16 |
authorization-protocols: | LISTofAUTH |
The initial byte of the connection specifies the
BYTE-ORDER in
which subsequent 16-bit and 32-bit numeric values are to be
transmitted. The octal value 102
(ASCII uppercase “B”)
indicates that the most-significant byte is to be transmitted
first; the octal value 154
(ASCII lowercase “l”)
indicates that the least-significant byte is to be transmitted first.
If any other value is encountered the server closes the
connection without any response.
The CLIENT-MAJOR-PROTOCOL-VERSION and
CLIENT-MINOR-PROTOCOL-VERSION specify
which version of the
font service protocol the client would like to use. If the
client can support multiple versions, the highest version
should be given. This version of the protocol has a
major version of 2 and a minor version of 0.
The AUTHORIZATION-PROTOCOLS
contains a list of protocol names and
optional initial data for which the client can provide
information. The server may use this to determine which
protocol to use or as part of the initial exchange of
authorization data.
| ▶ | |
status: | { Success, Continue,
Busy, Denied } |
server-major-protocol-version: | CARD16 |
server-minor-protocol-version: | CARD16 |
alternate-servers-hint: | LISTofALTERNATESERVER |
authorization-index: | CARD8 |
authorization-data: | LISTofBYTE |
The SERVER-MAJOR-PROTOCOL-VERSION and
SERVER-MINOR-PROTOCOL-VERSION specify
the version of the font
service protocol that the server expects from the client. If
the server supports the version specified by the client, this
version number should be returned. If the client has
requested a higher version than is supported by the server,
the server's highest version should be returned. Otherwise,
if the client has requested a lower version than is supported
by the server, the server's lowest version should be returned.
It is the client's responsibility to decide whether or not it
can match this version of the protocol.
The ALTERNATE-SERVERS-HINT
is a list of other font servers
that may have related sets of fonts (determined by means
outside this protocol, typically by the system administrator).
Clients may choose to contact these font servers if the
connection is rejected or lost.
The STATUS field indicates whether the server accepted,
rejected, or would like more information about the connection.
It has one of the following alternate values:
Success | 0 |
Continue | 1 |
Busy | 2 |
Denied | 3 |
If STATUS is Denied,
the server has rejected the client's authorization information.
If STATUS is Busy, the server has
simply decided that it cannot provide fonts to this client at
this time (it may be able to at a later time). In both cases,
AUTHORIZATION-INDEX is set to zero,
no authorization-data is
returned, and the server closes the connection after sending
the data described so far.
Otherwise the AUTHORIZATION-INDEX is set to the index
(beginning with 1) into the AUTHORIZATION-PROTOCOLS
list of the protocol that the server will use for this connection. If
the server does not want to use any of the given protocols,
this value is set to zero. The AUTHORIZATION-DATA
field is used to send back authorization protocol-dependent data to the
client (such as a challenge, authentication of the server,
etc.).
If STATUS is Success,
the following section of protocol is omitted. Otherwise, if
STATUS is Continue,
the server expects
more authorization data from the client (i.e. the connection
setup is not finished, so no requests or events may be sent):
| ◀ | |
more-authorization-data: | STRING8 |
| ▶ | |
status: | { Success, Continue, Busy, Denied } |
more-authorization-data: | LISTofBYTE |
The values in STATUS have the same meanings as described
above. This section of protocol is repeated until the server
either accepts (sets STATUS to
Success) or rejects (sets STATUS
to Denied or Busy) the connection.
Once the connection has been accepted and STATUS
is Success,
an implicit AccessContext is created for the authorization
data and the protocol continues with the following data sent
from the server:
| ▶ | |
remaining-length: | CARD32 |
maximum-request-length: | CARD16 |
release-number: | CARD32 |
vendor: | STRING8 |
The REMAINING-LENGTH specifies the length in 4-byte
units of the remaining data to be transmitted to the client. The
MAXIMUM-REQUEST-LENGTH specifies the largest request
size in 4-byte units that is accepted by the server and must have a
value of at least 4096. Requests with a length field larger
than this value are ignored and a
Length
error is returned.
The VENDOR string specifies the name of the
manufacturer of the font server. The
RELEASE-NUMBER specifies the particular
release of the server in a manufacturer-dependent manner.
After the connection is established and the setup information has been exchanged, the client may issue any of requests described below:
| ▶ | |
names: | LISTofSTRING8 |
| Errors: | Alloc |
This request returns the names of the extension packages that are supported by the server. Extension names are case-sensitive and are encoded in ISO 8859-1.
name: | STRING8 |
| ▶ | |
present: | BOOL |
major-version: | CARD16 |
minor-version: | CARD16 |
major-opcode: | CARD8 |
first-event: | CARD8 |
number-events: | CARD8 |
first-error: | CARD8 |
number-errors: | CARD8 |
| Errors: | Alloc |
This request determines whether or not the extension package specified by
NAME (encoded in ISO 8859-1) is
supported by the server and that there is sufficient number of major opcode,
event, and error codes available. If so, then PRESENT
is set to True, MAJOR-VERSION
and MINOR-VERSION are set to the
respective major and minor version numbers of the protocol
that the server would prefer; MAJOR-OPCODE is set to
the value to use in extension requests; FIRST-EVENT
is set to the value of the first extension-specific event code or zero if the
extension does not have any events; NUMBER-EVENTS is
set to the number of new events that the event defines;
FIRST-ERROR
is set to the value of the first extension-specific error code
or zero if the extension does not define any new errors; and
NUMBER-ERRORS is set to the number of
new errors the extension defines.
Otherwise, PRESENT is set to
False and the remaining fields are
set to zero.
The server is free to return different values to different
clients. Therefore, clients must use this request before
issuing any of the requests in the named extension package or
using the
SetEventMask request to express interest in any of
this extension's events. Otherwise, a
Request
error is returned.
pattern: | STRING8 |
max-names: | CARD32 |
| ▶+ | |
replies-following-hint: | CARD32 |
names: | LISTofSTRING8 |
| Errors: | Alloc |
This request returns a list of at most MAX-NAMES names
of collections (called catalogues) of fonts that match
the specified PATTERN. In the pattern (which is encoded
in ISO 8859-1), the
“?” character (octal 77)
matches any single character; the
“*” character (octal 52)
matches any series of zero or more characters; and alphabetic
characters match either upper- or lowercase. The
returned NAMES are encoded in
ISO 8859-1 and may contain
mixed character cases.
If PATTERN is of zero length or
MAX-NAMES is equal to zero,
one reply containing a zero-length list of names is returned.
This may be used to synchronize the client with the server.
Servers are free to add or remove catalogues to the set returned by
ListCatalogues
between any two requests. This request is not
cumulative; repeated uses are processed in isolation and do
result in an iteration through the list.
To reduce the amount of buffering needed by the server, the
list of names may be split across several reply packets, so
long as the names arrive in the same order that they would
have appeared had they been in a single packet. The
REPLIES-FOLLOWING-HINT field in all but the last reply
contains a positive value that specifies the number of
replies that are likely, but not required, to follow. In the
last reply, which may contain zero or more names, this field
is set to zero.
names: | LISTofSTRING8 |
| Errors: | Alloc, Name |
This request sets the list of catalogues whose fonts should be
visible to the client. The union of the fonts provided by
each of the named catalogues forms the set of fonts whose
names match patterns in
ListFonts,
ListFontsWithXInfo,
and
OpenBitmapFont
requests. The catalogue names are
case-insensitive and are encoded in ISO 8859-1. A zero-length
list resets the client's catalogue list to the
server-dependent default.
If any of the catalogue names are invalid, a Name error is returned and the request is ignored.
| ▶ | |
names: | LISTofSTRING8 |
| Errors: | Alloc |
This request returns the current list of catalogue names
(encoded in ISO 8859-1) associated with the client. These
catalogues determine the set of fonts that are visible
to
ListFonts,
ListFontsWithXInfo,
and
OpenBitmapFont.
A zero-length list indicates the server's default set of
fonts. Catalogue names are case-insensitive and may be
returned in mixed case.
This request specifies the set of maskable events that the
extension indicated by EXTENSION-OPCODE
(or zero for the core)
should generate for the client. Event masks are limited in
scope to the extension (or core) for which they are defined,
so expressing interest in events from one or more extensions
requires multiple uses of this request.
The default event mask if
SetEventMask
has not been called
is zero, indicating no interest in any maskable events.
Some events are not maskable and cannot be blocked.
If EXTENSION-OPCODE is not a valid extension
opcode previously returned by
QueryExtension
or zero, a
Request
error is
returned. If EVENT-MASK contains any bits that do not
correspond to valid events for the specified extension (or
core), an
EventMask
error is returned and the request is
ignored.
This request returns the set of maskable core events the
extension indicated by EXTENSION-OPCODE
(or the core if zero)
should generate for the client. Non-maskable events are
always sent to the client.
If EXTENSION-OPCODE is not a valid extension opcode
previously returned by
QueryExtension
or zero, a
Request
error is returned.
ac: | ACCESSCONTEXT |
authorization-protocols: | LISTofAUTH |
| ▶ | |
status: | { Success, Continue, Denied } |
authorization-index: | CARD8 |
authorization-data: | LISTofBYTE |
| Errors: | IDChoice |
This request creates a new
AccessContext
object within the
server containing the specified authorization data. When
this
AccessContext
is selected by the client using the
SetAuthorization
request, the data may be used by the server
to determine whether or not the client should be granted
access to particular font information.
If STATUS is Denied, the server
rejects the client's authorization information and does not associate
AC with any valid AccessContext.
In this case, AUTHORIZATION-INDEX is set
to zero, and zero bytes of AUTHORIZATION-DATA
is returned.
Otherwise, AUTHORIZATION-INDEX is set to the index
(beginning with 1) into the AUTHORIZATION-PROTOCOLS
list of the protocol
that the server will use for this connection. If the server
does not want to use any of the given protocols, this value is
set to zero. The AUTHORIZATION-DATA field is used
to send back authorization protocol-dependent data to the client (such
as a challenge, authentication of the server, etc.).
If STATUS is Continue,
the client is expected to continue
the request by sending the following protocol and receiving
the indicated response from the server. This continues
until STATUS is set to either
Success or Denied.
| ◀ | |
more-authorization-data: | STRING8 |
| ▶ | |
status: | { Success, Continue, Denied } |
more-authorization-data: | LISTofBYTE |
Once the connection has been accepted and STATUS
is Success, the request is complete.
If AC is not in the range
[1..229-1] or is already associated
with an access context, an IDChoice error is returned.
ac: | ACCESSCONTEXT |
| Errors: | AccessContext, Alloc |
This request indicates that the specified AC should
no longer be associated with a valid access context.
If AC is also the current
AccessContext
(as set by the
SetAuthorization
request), an implicit
SetAuthorization
of None is done to
restore the
AccessContext
established for the initial
connection setup. Operations on fonts that were opened under
AC are not affected. The client may reuse the
value of AC in a subsequent
CreateAC
request.
If AC isn't associated with any valid authorization
previously created by
CreateAC, an
AccessContext
error is returned.
ac: | ACCESSCONTEXT |
| Errors: | AccessContext |
This request sets the
AccessContext
to be used for subsequent
requests (except for
QueryXInfo,
QueryXExtents8,
QueryXExtents16,
QueryXBitmaps8,
QueryXBitmaps16
and
CloseFont
which are done under the
AccessContext
of the
corresponding
OpenBitmapFont
).
An AC of None restores the
AccessContext
established for the initial connection setup.
If AC is neither None
nor a value associated with a valid AccessContext
previously created by
CreateAC,
an
AccessContext
error is returned.
resolutions: | LISTofRESOLUTION |
| Errors: | Resolution, Alloc |
This request provides a hint as to the resolution and preferred point size of the drawing surfaces for which the client will be requesting fonts. The server may use this information to set the RESOLUTION_X and RESOLUTION_Y fields of scalable XLFD font names, to order sets of names based on their resolutions, and to choose the server-dependent instance that is used when a partially-specified scalable fontname is opened.
If a zero-length list of RESOLUTIONs is given, the server-dependent default value is restored. Otherwise, if elements of all of the specified RESOLUTIONs are non-zero, the default resolutions for this client are changed.
If a RESOLUTION entry contains a zero, a Resolution error is returned and the default resolutions are not changed.
| ▶ | |
resolutions: | LISTofRESOLUTION |
| Errors: | Alloc |
This request returns the current list of default resolutions.
If a client has not performed a
SetResolution,
a server-dependent default value is returned.
pattern: | STRING8 |
max-names: | CARD32 |
| ▶+ | |
replies-following-hint: | CARD32 |
names: | LISTofSTRING8 |
| Errors: | Alloc |
This request returns a list of at most MAX-NAMES
font names that match the specified PATTERN,
according to matching rules
of the X Logical
Font Description Conventions
[3].
In the pattern (which is encoded in ISO 8859-1) the
“?” character (octal 77)
matches any single character; the
“*” character (octal 52)
matches any series of zero or more characters; and
alphabetic characters match either upper- or lowercase. The
returned NAMES are encoded in
ISO 8859-1 and may contain mixed
character cases. Font names are not required to be in XLFD
format.
If PATTERN is of zero length or
MAX-NAMES is equal to zero,
one reply containing a zero-length list of names is returned.
This may be used to synchronize the client with the server.
Servers are free to add or remove fonts to the set returned by
ListFonts
between any two requests. This request is not
cumulative; repeated uses are processed in isolation and do
result in an iteration through the list.
To reduce the amount of buffering needed by the server, the
list of names may be split across several reply packets, so
long as the names arrive in the same order that they would
have appeared had they been in a single packet. The
REPLIES-FOLLOWING-HINT field in all but the last reply
contains a positive value that specifies the number of
replies that are likely, but not required, to follow. In the
last reply, which may contain zero or more names, this field
is set to zero.
pattern: | STRING8 |
pattern: | STRING8 |
pattern: | STRING8 |
max-names: | CARD32 |
| ▶+ | |
replies-following-hint: | CARD32 |
info: | XFONTINFO |
name: | STRING8 |
| Errors: | Alloc |
This request is similar to
ListFonts
except that a separate
reply containing the name, header, and property data is
generated for each matching font name. Following these
replies, if any, a final reply containing a zero-length
NAME and no INFO is sent.
The REPLIES-FOLLOWING-HINT field in all but the
last reply contains a positive value that specifies the number of replies
that are likely, but not required, to follow. In the last
reply, this field is set to zero.
If PATTERN is of zero length or if
MAX-NAMES is equal to zero, only the final reply
containing a zero-length NAME and no
INFO is returned. This may be used to synchronize the
client with the server.
fontid: | FONTID |
pattern: | STRING8 |
format-mask: | BITMAPFORMATMASK |
format-hint: | BITMAPFORMAT |
| ▶ | |
otherid: | FONTID or None |
otherid-valid: | BOOL |
cachable: | BOOL |
| Errors: | IDChoice, Name, Format, AccessContext, Alloc |
This request looks for a server-dependent choice of the
font names that match the specified PATTERN
according to the rules described for
ListFonts.
If no matches are found, a
Name
error is returned. Otherwise, the server attempts to
open the font associated with the chosen name.
Permission to access the font is determined by the server
according the licensing policy used for this font. The server
may use the client's current
AccessContext
(as set by the most
recent
SetAuthorization
request or the original connection
setup) to determine any client-specific sets of permissions.
After the font has been opened, the client is allowed to
specify a new
AccessContext
with
SetAuthorization
or release
the
AccessContext
using
FreeAC
. Subsequent
QueryXInfo,
QueryXExtents8,
QueryXExtents16,
QueryXBitmaps8,
QueryXBitmaps16
and
CloseFont
requests on this FONTID are
performed according to permissions granted at the time of the
OpenBitmapFont
request.
If the server is willing and able to detect that the client
has already opened the font successfully (possibly under a
different name), the OTHERID field
may be set to one of the
identifiers previously used to open the font. The
OTHERID-VALID field indicates whether or not
OTHERID is still associated with an open font:
if it is True, the client may use
OTHERID as an alternative to
FONTID. Otherwise, if
OTHERID-VALID is False,
OTHERID is no longer
open but has not been reused by a subsequent
OpenBitmapFont
request.
If OTHERID is set to None,
then OTHERID-VALID should be set
to False.
The FORMAT-MASK indicates which fields in
FORMAT-HINT
the client is likely to use in subsequent
GetXBitmaps8
and
GetXBitmaps16
requests. Servers may wish to use
this information to precompute certain values.
If CACHABLE is set to True,
the client may cache the font
(so that redundant opens of the same font may be avoided)
and use it with all
AccessContexts
during the life of the
client without violating the font's licensing policy. This
flag is typically set whenever a font is unlicensed or is
licensed on a per-display basis. If CACHABLE
is False, the
client should reopen the font for each
AccessContext.
The server is permitted to add to or remove from the set of
fonts returned by
ListFonts
between any two requests, though
mechanisms outside the protocol. Therefore, it is possible
for this request (which is atomic) to return a different font
than would result from separate a
ListFonts
followed by an
OpenBitmapFont
with a non-wildcarded font name.
If FONTID is not in the range
[1..229-1] or if it is already
associated with an open font, an
IDChoice
error is returned.
If no font is available that matches the specified
PATTERN, a
Name
error is returned. If the font is present but the client
is not permitted access, an
AccessContext
error is returned.
If FORMAT-MASK has any unspecified bits set or if any
of the fields in FORMAT-HINT indicated by
FORMAT-MASK are invalid, a
Format
error is returned.
This request returns the font header and property information
for the open font associated with FONTID.
If FONTID is not associated with any open fonts, a
Font
error
is returned.
This request is equivalent to
QueryXExtents16
except that it
uses 1-byte character codes.
fontid: | FONTID |
range: | BOOL |
chars: | LISTofCHAR2B |
| ▶ | |
extents: | LISTofXCHARINFO |
| Errors: | Font, Range, Alloc |
This request returns a list of glyph extents from the open
font associated with FONTID for the series of characters
specified by RANGE and CHARS.
If RANGE is True,
each succeeding pair of elements in CHARS is
treated as a range of characters for which extents should be
returned. If CHARS contains an odd number of elements,
the font's XFONTINFO.CHAR-RANGE.MAX-CHAR
is implicitly appended to
the list. If CHARS contains no elements, the list is
implicitly replaced with the font's
XFONTINFO.CHAR-RANGE. If
any of the resulting character ranges are invalid, a
Range
error is returned. Otherwise, the character ranges are
concatenated in the order given by CHARS to produce
a set of character codes for which extents are returned.
If RANGE is False,
then CHARS specifies the set of character
codes for which extents are returned. If CHARS is of
zero length, then a zero-length list of extents is returned.
The extents for each character code in the resulting set (which may contain duplicates) are returned in the order in which the character codes appear in the set. At least one metric for each character shall be non-zero unless the character is not encoded in the font, in which case all-zero metrics are returned. A blank, zero-width character can be encoded with non-zero but equal left and right bearings.
If FONTID is not associated with any open fonts, a
Font
error is
returned. If RANGE is True
and CHARS contains any invalid ranges, a
Range
error is returned.
fontid: | FONTID |
range: | BOOL |
chars: | STRING8 |
format: | BITMAPFORMAT |
| ▶+ | |
replies-following-hint: | CARD32 |
offsets: | LISTofOFFSET32 |
bitmaps: | LISTofBYTE |
| Errors: | Font, Range, Format, Alloc |
This request is equivalent to
QueryXBitmaps16
except that it
uses 1-byte character codes.
fontid: | FONTID |
range: | BOOL |
chars: | LISTofCHAR2B |
format: | BITMAPFORMAT |
| ▶+ | |
replies-following-hint: | CARD32 |
offsets: | LISTofOFFSET32 |
bitmaps: | LISTofBYTE |
| Errors: | Font, Range, Format, Alloc |
This request returns a list of glyph bitmaps from the open font associated
with FONTID for the series of characters
specified by RANGE and CHARS.
If RANGE is True, each succeeding
pair of elements in CHARS is
treated as a range of characters for which bitmaps should be
returned. If CHARS contains an odd number of elements,
the font's XFONTINFO.CHAR-RANGE.MAX-CHAR
is implicitly appended to
the list. If CHARS contains no elements, the list is
implicitly replaced with the font's
XFONTINFO.CHAR-RANGE. If
any of the resulting character ranges are invalid, a Range
error is returned. Otherwise, the character ranges are
concatenated in the order given by CHARS to produce
a set of character codes for which bitmaps are returned.
If RANGE is False,
then CHARS specifies the set of character
codes for which bitmaps are returned. If CHARS
is of zero length, then a single reply containing a zero-length list of
offsets and bitmaps is returned.
If any of the resulting character ranges are invalid, a
Range
error is returned. Otherwise, the resulting character ranges
are concatenated in the order given by CHARS
to produce a set of character codes for which bitmaps are returned.
The server is free to return the glyph bitmaps in multiple replies to reduce the amount of buffering that is necessary. In this situation, the set of characters obtained above is partitioned into an implementation-dependent number of ordered, non-overlapping subsets containing runs of one or more consecutive characters. The global ordering of characters must be maintained such that concatenating the subsets in order that they were produced yields the original set. A reply is generated for each subset, in the order that it was produced.
For each character in a subset, an image of that character's glyph is described by a rectangle of bits corresponding to the pixels specified by FORMAT.IMAGE-RECT. Within the image, set and clear bits represent inked and non-inked pixels, respectively.
Each scanline of a glyph image, from top to bottom, is zero-padded on the right to a multiple of the number of bits specified by FORMAT.SCANLINE-PAD. The scanline is then divided from left to right into a sequence of FORMAT.SCANLINE-UNIT bits. The bits of each unit are then arranged such that the left-most pixel is stored in the most- or least-significant bit, according to FORMAT.BIT-ORDER-MSB. The bytes of each unit are then arranged such that the most- or least-significant byte, according to FORMAT.BYTE-ORDER-MSB, is transmitted first. Finally, the units are arranged such that the left-most is transmitted first and the right-most is transmitted last.
The individual images within a subset are then concatenated in
a server-dependent order to form the BITMAPS data
of the reply. If a glyph image is duplicated within a reply, the
server is free to return fewer (but at least one) copies of
the image. If a character is not encoded within the font, a
zero-length bitmap is substituted for this character. Each
glyph image must begin at a bit position that is a multiple of
the FORMAT.SCANLINE-UNIT.
The OFFSETS array in a reply contains one entry
for each character in the subset being returned, in the order that the
characters appear in the subset. Each entry specifies the
starting location in bytes and size in bytes of the
corresponding glyph image in the BITMAPS data of that
reply (i.e. an offset may not refer to data in another reply).
The REPLIES-FOLLOWING-HINT field in all but the
last reply contains a positive value that specifies the number of replies
that are likely, but not required, to follow. In the last
reply, which may contain data for zero or more characters,
this field is set to zero.
If FONTID is not associated with any open fonts,
a Font
error is returned. If RANGE is
True and CHARS contains any
invalid ranges, a
Range error
is returned. If FORMAT is invalid, a
Format error
is returned.
This request indicates that the specified FONTID
should no longer be associated with an open font. The server is free to
release any client-specific storage or licenses allocated for
the font. The client may reuse the value of FONTID
in a subsequent
OpenBitmapFont
request.
If FONTID is not associated with any open fonts, a
Font
error is returned.
When a connection is closed, a
CloseFont
is done on all fonts
that are open on the connection. In addition, the server is
free to release any storage or licenses allocated on behalf of
the client that made the connection.
All errors are at least 16 bytes long and contain the following fields:
type: | CARD8 | value of 1 |
error-code: | CARD8 | |
sequence-number: | CARD16 | |
length: | CARD32 | |
timestamp: | TIMESTAMP | |
major-opcode: | CARD8 | |
minor-opcode: | CARD8 | |
data-or-unused: | CARD16 |
The TYPE field has a value of one. The ERROR-CODE field specifies which error occurred. Core errors codes are in the range 0 through 127, extension error codes are in the range 128 through 255. The SEQUENCE-NUMBER field contains the least significant 16 bits of the sequence number of the request that caused the error. The LENGTH field specifies the length of the error packet in 4-byte units and must have a value of at least 4. The TIMESTAMP specifies the server time when the error occurred. The MAJOR-OPCODE and MINOR-OPCODE (zero for core requests) fields specify the type of request that generated the error. The DATA-OR-UNUSED field may be used for 16 bits of error-specific information. If LENGTH is greater than four, these fields are followed by (LENGTH - 4) * 4 bytes of extra data.
The following errors are defined for the core protocol:
data-or-unused: | CARD16 | unused |
This error is generated by any request that has an unknown
combination of major and minor request numbers, or by any
extension request that is issued before a
QueryExtension
of that extension.
data-or-unused: | CARD16 | unused |
format: | BITMAPFORMAT | bad format value |
This error is generated by the use of an invalid BITMAPFORMAT
in the
OpenBitmapFont,
QueryXBitmaps8, and
QueryXBitmaps16
requests.
The value that caused the error is included as extra data.
data-or-unused: | CARD16 | unused |
fontid: | FONTID | bad font identifier |
This error is generated by an invalid FONTID in the
QueryXInfo,
QueryXExtents8,
QueryXExtents16,
QueryXBitmaps8,
QueryXBitmaps16
and
CloseFont
requests. The value that caused
the error is included as extra data.
data-or-unused: | CARD16 | unused |
range: | RANGE | bad range |
This error is generated by an invalid RANGE in the
QueryXExtents8,
QueryXExtents16,
QueryXBitmaps8
and
QueryXBitmaps16
requests. The
value that caused the error is included as extra data.
data-or-unused: | CARD16 | unused |
event-mask: | EVENTMASK | bad event mask |
This error is generated by an invalid EVENTMASK in the
SetEventMask
request. The value that caused the error is
included as extra data.
data-or-unused: | CARD16 | unused |
ac: | ACCESSCONTEXT | unaccepted AccessContext |
This error is generated by an invalid ACCESSCONTEXT in the
FreeAC
or
SetAuthorization
request or by an
OpenBitmapFont
request performed without sufficient authorization. In the
first two cases, the ACCESSCONTEXT of the errant request is
returned as extra data. In the third case, the current
ACCESSCONTEXT is returned as extra data.
data-or-unused: | CARD16 | unused |
id: | ID | bad identifier |
This error is generated by an invalid or already associated
ACCESSCONTEXT identifier in a
CreateAC
request or FONTID identifier
in an
OpenBitmapFont
request. The value that caused the error
is included as extra data.
data-or-unused: | CARD16 | unused |
This error is generated by a font name pattern that matches
no fonts in an
OpenBitmapFont
request or no catalogue names in a
SetCatalogues
request.
data-or-unused: | CARD16 | X value of errant resolution |
y-resolution: | CARD16 | Y value of errant resolution |
point-size: | CARD16 | point size of errant resolution |
This error is generated in response to an invalid RESOLUTION
structure in a
SetResolution
request. The value that caused the
error is included in the DATA-OR-UNUSED field and as extra data.
data-or-unused: | CARD16 | unused |
This error is generated by any request for which the server lacks sufficient resources (especially memory).
data-or-unused: | CARD16 | unused |
length: | CARD32 | bad length value |
This error is generated by any request that has a length field greater than (MAXIMUM-REQUEST-LENGTH * 4) bytes. The value that caused the error is included as extra data.
Events may be generated in response to requests or at the server's discretion after the initial connection setup information has been exchanged. Each event is at least 12 bytes long and contains the following fields:
type: | CARD8 | value of 2 |
event-code: | CARD8 | |
sequence-number: | CARD16 | |
length: | CARD32 | |
timestamp: | TIMESTAMP |
The TYPE field contains the value 2. The EVENT-CODE field specifies the number of the event and is in the range 0-127 for core events or the range 128-255 for extensions. The SEQUENCE-NUMBER field specifies the least significant 16 bits of the sequence number of the last request to have been processed by the server. The LENGTH field specifies the number of 4-byte units in this event packet and must always have a value of at least 3. The TIMESTAMP field specifies the server time when the event occurred. If LENGTH is greater than three, these fields are followed by (LENGTH - 3) * 4 bytes of additional data.
Events are described using the following syntax:
EventName
arg1:type1 ... argN:typeN Description
If an event does not provide any extra arguments, the
arg1...argN
lines are omitted from the description.
The core X Font Service protocol defines the following events:
This unsolicited, nonmaskable event may be sent by the
server to verify that the connection has not been broken
(for transports that do not provide this information).
Clients should acknowledge receipt of this request
by sending any request (such as
NoOp
).
This event is sent to clients that have included
CatalogueListChangeMaskTrue if new catalogues have
been added to the server, otherwise it is False. The
DELETED field is True if any existing catalogues have
been removed from the server, otherwise it is False.
This event is sent to clients that have included
FontListChangeMaskTrue if new
fonts have been added to any of the catalogues currently
used by the client, otherwise it is False. The DELETED
field is True if any existing fonts have been removed
from any of catalogues used by the client, otherwise it
is False.
Table of Contents
Numbers that are prefixed with “#x”
are in hexadecimal (base 16). All other
numbers are in decimal. Requests, replies, errors, events, and compound types
are described using the syntax:
Name
count contents name
...
count contents name
where COUNT is the number of bytes in the data stream occupied by this field, CONTENTS is the name of the type as given in Section 4 or the value if this field contains a constant, and NAME is a description of this field.
Objects containing counted lists use a lowercase single-letter variable (whose scope is limited to the request, reply, event, or error in which it is found) to represent the number of objects in the list. These variables, and any expressions in which they are used, should be treated as unsigned integers. Multiple copies of an object are indicated by CONTENTS prefix “LISTof”.
Unused bytes (whose value is undefined) will have a blank CONTENTS field and a NAME field of “unused”. Zeroed bytes (whose value must be zero) will have a blank CONTENTS field and a NAME field of “zero”. The expression pad(e) refers to the number of bytes needed to round a value “e” up to the closed multiple of four:
pad(e) = (4 - (e mod 4)) mod 4
ACCESSCONTEXT 4 CARD32 access context with at least one of the following bits set: #x1fffffff but none of the following bits set: #xe0000000 zero ALTERNATESERVER 1 BOOL subset 1 n length of name n STRING8 name p unused, p=pad(n+2) AUTH 2 n length of name 2 d length of data n STRING8 name p unused, p=pad(n) d STRING8 data q unused, q=pad(d) BITMAPFORMAT 4 CARD32 value, union of the following bits: #x00000001 ByteOrderMSB #x00000002 BitOrderMSB #x00000000ImageRectMin#x00000004ImageRectMaxWidth#x00000008ImageRectMax#x00000000ScanlinePad8#x00000100ScanlinePad16#x00000200ScanlinePad32#x00000300ScanlinePad64#x00000000ScanlineUnit8#x00001000ScanlineUnit16#x00002000ScanlineUnit32#x00003000ScanlineUnit64except for the following bits which must be zero: #xffffccf0 zero and the following of which at most one bit may be set: #x0000000c at most one bit can be set BITMAPFORMATMASK 4 CARD32 value, mask of the following bits: #x00000001ByteOrderMask#x00000002BitOrderMask#x00000004ImageRectMask#x00000008ScanlinePadMask#x00000010ScanlineUnitMaskexcept for the following bits which must be zero: #xffffffe0 zero BOOL 1 BOOL boolean, one of the following values: 0False1TrueBYTE 1 BYTE unsigned byte of data CARD8 1 CARD8 8-bit unsigned integer CARD16 2 CARD16 16-bit unsigned integer CARD32 4 CARD32 32-bit unsigned integer CHAR2B 1 CARD8 byte1 1 CARD8 byte2 EVENTMASK 4 CARD32 event mask for core events, this is union of the following bits: #00000001CatalogueListChangeMask#00000002FontListChangeMaskbut none of the following bits set: #fffffffc extensions define their own sets of bits FONTID 4 CARD32 font identifier with at least one of the following bits set: #x1fffffff but none of the following bits set: #xe0000000 zero INT8 1 INT8 8-bit signed integer INT16 2 INT16 16-bit signed integer INT32 4 INT32 32-bit signed integer OFFSET32 4 CARD32 position (or integer value) 4 CARD32 length PROPINFO 4 n number of PROPOFFSET components 4 m number of bytes of property data 20*n PROPOFFSET property offsets into data block m LISTofBYTE property data block PROPOFFSET 8 OFFSET32 name in data block 8 OFFSET32 value in data block 1 CARD8 type, one of the following values: 0String1Unsigned2Signed3 zero RANGE 2 CHAR2B minimum character code 2 CHAR2B maximum character code RESOLUTION 2 CARD16 x resolution in pixels per inch 2 CARD16 y resolution in pixels per inch 2 CARD16 point size in decipoints STRNAME 1 n length of name n STRING8 name STRING8 n LISTofBYTE array of 8-bit character values TIMESTAMP 4 CARD32 milliseconds since server time origin XCHARINFO 2 INT16 left bearing 2 INT16 right bearing 2 INT16 width 2 INT16 ascent 2 INT16 descent 2 CARD16 attributes XFONTINFO 4 CARD32 flags, union of the following bits: #x00000001AllCharactersExist#x00000002InkInside#x00000004HorizontalOverlapbut none of the following bits set: #xfffffff8 zero 4 RANGE range of characters in font 1 CARD8 drawing direction 0LeftToRight1RightToLeft1 unused 2 CHAR2B default character 12 XCHARINFO minimum bounds 12 XCHARINFO maximum bounds 2 INT16 font ascent 2 INT16 font descent n PROPINFO property data
1 BYTE byteorder, one of the values: #x42 MostSignificant Byte first #x6c LeastSignificant Byte first 1 CARD8 numberof auth in auth-data 2 2 client-major-protocol-version 2 0 client-minor-protocol-version 2 a/4 lengthof auth-data a LISTofAUTH auth-data ▶ 2 CARD16 status 0Success1Continue2Busy3Denied2 2 major version 2 0 version 1 CARD8 numberof alternate-servers-hint 1 CARD8 authorization-index 2 a/4 lengthof alternate-servers-hint 2 (d+q)/4 lengthof authorization-data a LISTofALTERNATESERVER alternate-servers-hint d LISTofBYTE authorization-data q unused, q=pad(d)
If STATUS is Busy or Denied, the protocol stops and the connection is
closed. If STATUS is Continue, the client is expected to respond with
additional data, to which the server responds with
a new status value and more data. This dialog continues until the status
is set to Success, or until the server sets STATUS to Busy or Denied
and closes the connection:
◀ 4 1+(d+q)/4 length d LISTofBYTE more-authorization-data q unused, q=pad(d) ▶ 4 2+(d+q)/4 length 2 CARD16 status 0Success1Continue2Busy3Denied2 unused d LISTofBYTE more-authorization-data q unused, q=pad(d)
When STATUS is Success, the protocol resumes with the following
sent by the server:
4 3+(v+w)/4 length of rest of data 2 CARD16 maximum-request-length 2 v length of vendor string 4 CARD32 release-number v STRING8 vendor-string w unused, w=pad(v)
Once the connection has been established, the client may send the following requests:
NoOp1 0 major-opcode 1 unused 2 1 lengthListExtensions1 1 major-opcode 1 unused 2 1 length ▶ 1 0 type reply 1 CARD8 numberof names 2 CARD16 sequence-number 4 2+(n+p)/4 length n LISTofSTRNAME names p unused, p=pad(n)QueryExtension1 2 major-opcode 1 n length of name 2 1+(n+p)/4 length n STRING8 name p unused, p=pad(n) ▶ 1 0 type reply 1 BOOL present 2 CARD16 sequence-number 4 5 length 2 CARD16 major-version 2 CARD16 minor-version 1 CARD8 major-opcode 1 CARD8 first-event 1 CARD8 number-events 1 CARD8 first-error 1 CARD8 number-errors 3 unusedListCatalogues1 3 major-opcode 1 unused 2 3+(n+p)/4 length 4 CARD32 max-names 2 n length of pattern 2 unused n STRING8 pattern p unused, p=pad(n) ▶+ 1 0 type reply 1 unused 2 CARD16 sequence-number 4 4+(n+p)/4 length 4 CARD32 replies-following-hint 4 CARD32 numberof catalogue-names n LISTofSTRNAME catalogue-names p unused, p=pad(n)SetCatalogues1 4 major-opcode 1 CARD8 numberof catalogue-names 2 1+(n+p)/4 length n LISTofSTRNAME catalogue-names p unused, p=pad(n)GetCatalogues1 5 major-opcode 1 unused 2 1 length ▶ 1 0 type reply 1 CARD8 numberof catalogue-names 2 CARD16 sequence-number 4 2+(n+p)/4 length n LISTofSTRNAME catalogue-names p unused, p=pad(n)SetEventMask1 6 major-opcode 1 CARD8 extension-opcode 2 2 length 4 EVENTMASK event-maskGetEventMask1 7 major-opcode 1 CARD8 extension-opcode 2 1 length ▶ 1 0 type reply 1 unused 2 CARD16 sequence-number 4 3 length 4 EVENTMASK event-maskCreateAC1 8 major-opcode 1 CARD8 numberof authorization-protocols 2 2+a/4 length 4 ACCESSCONTEXT ac a LISTofAUTH authorization-protocols ▶ 1 0 type reply 1 CARD8 authorization-index 2 CARD16 sequence-number 4 3+(d+q)/4 length 2 CARD16 status 0Success1Continue2Busy3Denied2 unused d LISTofBYTE authorization-data q unused, q=pad(d)
If STATUS is Continue, the client is expected to respond with additional
data, to which the server
responds with a new status value and more data. This dialog continues
until the status is set to
Success, Busy, or Denied at which point the request is finished.
◀ 4 1+(d+q)/4 length d LISTofBYTE more-authorization-data q unused, q=pad(d) ▶ 4 2+(d+q)/4 length 2 CARD16 status 0Success1Continue2Busy3Denied2 unused d LISTofBYTE authorization-data q unused, q=pad(d)FreeAC1 9 major-opcode 1 unused 2 2 length 4 ACCESSCONTEXT acSetAuthorization1 10 major-opcode 1 unused 2 2 length 4 ACCESSCONTEXT acSetResolution1 11 major-opcode 1 n number of resolutions 2 1+(6*n+p)/4 length 6*n LISTofRESOLUTION resolutions p p=pad(6*n)GetResolution1 12 major-opcode 1 unused 2 1 length ▶ 1 0 type reply 1 n number of resolutions 2 CARD16 sequence-number 4 2+(6*n+p)/4 length 6*n LISTofRESOLUTION resolutions p p=pad(6*n)ListFonts1 13 major-opcode 1 unused 2 3+(n+p)/4 length 4 CARD32 max-names 2 n length of pattern 2 unused n STRING8 pattern p unused, p=pad(n) ▶+ 1 0 type reply 1 unused 2 CARD16 sequence-number 4 4+(n+p)/4 length 4 CARD32 replies-following-hint 4 CARD32 numberof font-names n LISTofSTRNAME font-names p unused, p=pad(n)ListFontsWithXInfo1 14 major-opcode 1 unused 2 3+(n+p)/4 length 4 CARD32 max-names 2 n length of pattern 2 unused n STRING8 pattern p unused, p=pad(n) ▶+ (except for last in series) 1 0 type reply 1 n length of name 2 CARD16 sequence-number 4 3+(n+p+f)/4 length 4 CARD32 replies-hint f XFONTINFO fontinfo n STRING8 name p unused, p=pad(n) ▶ (last in series) 1 0 type reply 1 0 last-reply indicator 2 CARD16 sequence-number 4 2 reply lengthOpenBitmapFont1 15 major-opcode 1 unused 2 4+(n+p)/4 length 4 FONTID fontid 4 BITMAPFORMATMASK format-mask 4 BITMAPFORMAT format n STRNAME pattern p unused, p=pad(n) ▶ 1 0 type reply 1 BOOL otherid-valid 2 CARD16 sequence-number 4 4 length 4 FONTID otherid 1 BOOL cachable 3 unusedQueryXInfo1 16 major-opcode 1 unused 2 2 length 4 FONTID fontid ▶ 1 0 type reply 1 unused 2 CARD16 sequence-number 4 2+f/4 length f XFONTINFO fontinfo p unused, p=pad(f)QueryXExtents81 17 major-opcode 1 BOOL range 2 3+(n+p)/4 length 4 FONTID fontid 4 n number chars entries n STRING8 chars p unused, p=pad(n) ▶ 1 0 type reply 1 unused 2 CARD16 sequence-number 4 3+3*n length 4 n number of extents 12*n LISTofXCHARINFO extentsQueryXExtents161 18 major-opcode 1 BOOL range 2 3+(2*n+p)/4 length 4 FONTID fontid 4 n number chars entries 2*n LISTofCHAR2B chars p unused, p=pad(2*n) ▶ 1 0 type reply 1 unused 2 CARD16 sequence-number 4 3+3*n length 4 n number of extents 12*n LISTofXCHARINFO extentsQueryXBitmaps81 19 major-opcode 1 BOOL range 2 4+(n+p)/4 length 4 FONTID fontid 4 BITMAPFORMAT format 4 n number of chars entries n STRING8 chars p unused, p=pad(n) ▶+ 1 0 type reply 1 unused 2 CARD16 sequence-number 4 5+2*n+(m+p)/4 length 4 CARD32 replies-following-hint 4 n number of offsets 4 m number of bytes of glyph images 8*n LISTofOFFSET32 offsets m LISTofBYTE glyphimages p unused, p=pad(m)QueryXBitmaps161 20 major-opcode 1 BOOL range 2 4+(2*n+p)/4 length 4 FONTID fontid 4 BITMAPFORMAT format 4 n number of chars entries 2*n LISTofCHAR2B chars p unused, p=pad(2*n) ▶ 1 0 type reply 1 unused 2 CARD16 sequence-number 4 5+2*n+(m+p)/4 length 4 CARD32 replies-following-hint 4 n number of offsets 4 m number of bytes of glyph images 8*n LISTofOFFSET32 offsets m LISTofBYTE glyphimages p unused, p=pad(m)CloseFont1 21 major-opcode 1 unused 2 2 length 4 FONTID fontid
Request 1 1 type error 1 0 Request 2 CARD16 sequence-number 4 4 length 4 TIMESTAMP timestamp 1 CARD8 major-opcode 1 CARD8 minor-opcode 2 unused Format 1 1 type error 1 1 Format 2 CARD16 sequence-number 4 5 length 4 TIMESTAMP timestamp 1 CARD8 major-opcode 1 CARD8 minor-opcode 2 unused 4 BITMAPFORMAT bad-format Font 1 1 type error 1 2 Font 2 CARD16 sequence-number 4 5 length 4 TIMESTAMP timestamp 1 CARD8 major-opcode 1 CARD8 minor-opcode 2 unused 4 FONTID bad-fontid Range 1 1 type error 1 3 Range 2 CARD16 sequence-number 4 5 length 4 TIMESTAMP timestamp 1 CARD8 major-opcode 1 CARD8 minor-opcode 2 unused 4 RANGE bad-range EventMask 1 1 type error 1 4 EventMask 2 CARD16 sequence-number 4 5 length 4 TIMESTAMP timestamp 1 CARD8 major-opcode 1 CARD8 minor-opcode 2 unused 4 EVENTMASK event-mask AccessContext 1 1 type error 1 5 AccessContext 2 CARD16 sequence-number 4 5 length 4 TIMESTAMP timestamp 1 CARD8 major-opcode 1 CARD8 minor-opcode 2 unused 4 ACCESSCONTEXT access context IDChoice 1 1 type error 1 6 IDChoice 2 CARD16 sequence-number 4 5 length 4 TIMESTAMP timestamp 1 CARD8 major-opcode 1 CARD8 minor-opcode 2 unused 4 FONTID bad-fontid Name 1 1 type error 1 7 Name 2 CARD16 sequence-number 4 4 length 4 TIMESTAMP timestamp 1 CARD8 major-opcode 1 CARD8 minor-opcode 2 unused Resolution 1 1 type error 1 8 Resolution 2 CARD16 sequence-number 4 5 length 4 TIMESTAMP timestamp 1 CARD8 major-opcode 1 CARD8 minor-opcode 6 RESOLUTION resolution Alloc 1 1 type error 1 9 Alloc 2 CARD16 sequence-number 4 4 length 4 TIMESTAMP timestamp 1 CARD8 major-opcode 1 CARD8 minor-opcode 2 unused Length 1 1 type error 1 10 Length 2 CARD16 sequence-number 4 5 length 4 TIMESTAMP timestamp 1 CARD8 major-opcode 1 CARD8 minor-opcode 2 unused 4 CARD32 bad-length Implementation 1 1 type error 1 11 Implementation 2 CARD16 sequence-number 4 4 length 4 TIMESTAMP timestamp 1 CARD8 major-opcode 1 CARD8 minor-opcode 2 unused
KeepAlive1 2 type event 1 0 event KeepAlive 2 CARD16 sequence-number 4 3 length 4 TIMESTAMP timestampCatalogueListNotify1 2 type event 1 1 event CatalogueListNotify 2 CARD16 sequence-number 4 4 length 4 TIMESTAMP timestamp 1 BOOL added 1 BOOL deleted 2 unusedFontListNotify1 2 type event 1 2 event FontListNotify 2 CARD16 sequence-number 4 4 length 4 TIMESTAMP timestamp 1 BOOL added 1 BOOL deleted 2 unused
This document represents the culmination of several years of debate and experiments done under the auspices of the MIT X Consortium font working group. Although this was a group effort, the author remains responsible for any errors or omissions. The protocol presented here was primarily designed by Jim Fulton, Keith Packard, and Bob Scheifler. Special thanks goes to Ned Batchelder, Jim Flowers, and Axel Deininger for their invigorating comments which never failed to make this a better document. Stephen Gildea edited version 2 of this document. Finally, David Lemke deserves great credit for designing and coding the sample implementation.
All of the following documents are X Consortium standards available from the X Consortium.
The authorization data passed by the client in the initial connection setup information may be used by the font server to implement restrictions on which fonts may be accessed. Furthermore, the font server is free to refuse new connections at any time.
Configuration or management of the license restrictions is outside the scope of the font service protocol and is done in a server-dependent manner. Possible policies might include, but are not limited to, combinations of the following:
anyone may access any fonts. The server neither refuses any connections nor generates AccessContext errors on any fonts. For environments without specially-licensed fonts, this is sufficient.
only those clients connecting from a known set of machines are permitted access. The server could get the address of the connection and look in a list of allowed machines.
only a known set of users may access the fonts. The server can use the authorization data (such as a Kerberos ticket or a Secure RPC credential) to verify the identity of the user and then look in a list of allowed users.
only a certain number of clients may use a given font at any one time. Additional clients would receive AccessContext errors if they attempt to open the font. This is only effective if the initial clients keep the font open for the entire time that it is being used (even if all of the data has been transmitted and is being cached).
a particular font may only be accessed a limited number of times before its license must be renewed. Each time the font is opened, the server decrements a counter. When the counter reaches zero, all further attempts to open the font return an AccessContext error.
It should be noted that chaining of font servers (obtaining font data from other font servers) may conflict with certain license policies.
Font server implementations will probably wish to use techniques such as the following to avoid limits on the number of simultaneous connections:
The initial connection information returned by the font server contains the names of other font servers that may be used as substitutes. A font server may refuse to accept a connection, indicating that the client should try one of the alternatives instead.
On operating systems that support processing forking, font servers might choose to fork so that the child can continue processing the existing connections and the parent can accept new connections. Such implementations are encouraged to use shared memory so that in-memory font databases can be shared.
On operating systems that support passing stream file descriptors between processes, cooperating font servers could collect connections in a single process when there are few connections and spread them among several processes as the load increases.
If a font client is unable to connect to a server (as opposed to having the connection terminated), it should retry for an implementation-dependent length of time (see Xlib's handling of ECONNREFUSED in XConnDis.c).