CHARON(1) CHARON(1)
NAME
charon - web browser
SYNOPSIS
charon [ -option [value] ] [url]
DESCRIPTION
Charon is the Inferno graphical web browser, supporting a
variety of web standards for the download, viewing, automa-
tion and navigation of web based information and images.
The browser runs under the wm(1) window manager, or directly
on the draw(3) and cons(3) devices. When charon starts, it
checks to see if wm is running; if it is then charon creates
a new wm window for its display, otherwise it uses the whole
area of the display device.
Charon implements an image cache to help reduce the overhead
of revisiting pages. The image cache resides in memory for
the duration of a session. The cache is managed by discard-
ing least recently used images once the cache bounds have
been reached. Currently, charon does not provide a general
purpose web cache; all other resources have to be reloaded
when needed.
Navigation
Charon provides navigation controls familiar to any web-
surfer: back, forward, reload, home, stop and URL entry.
Navigation of web-based information is by means of following
HTML links, this is done by clicking on them using mouse
button-1, or the touch-screen. Clicking mouse button-2 on a
link causes its address to be displayed in the status line
of charon's display. Navigation to other information is
achieved by clicking on the URL entry field and typing the
address of the resource, followed by the Enter key.
The retrieval and processing of the current page is immedi-
ately terminated by clicking the Stop button.
As resources are browsed, a history of their web addresses
(URLs) is built up. At any time you can navigate forwards
and backwards through this list using the Forward and Back
buttons. Additionally, clicking the History button, dis-
plays the entire history list as a set of links enabling the
user to quickly jump to any position in the list.
Sometimes, it is not possible to retrieve all of the compo-
nents of a web document at the time that it is requested.
Often this is because the remote server is very busy or not
available. This can result in the presentation of the
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document being incomplete or even corrupted. Clicking the
Reload button causes charon to attempt to retrieve the cur-
rent document and all of its components again.
Charon displays a progress panel to indicate the download
status of each of the components of the current document.
The progress panel is displayed at the bottom of the charon
window. Each component of the current document is repre-
sented by a rectangular block in the progress panel. As the
download of a component progresses, its corresponding block
is gradually filled in. If an error occurs while download-
ing or processing the component, its block is coloured red.
The component address and amount downloaded, or reason for
failure, can be obtained by clicking mouse button-1 on its
progress block.
Web Standards
Standards are the life-blood of the World-Wide-Web; without
them, the web could not exist. Web standards are under con-
stant review with revised editions and complete new stan-
dards being published all of the time. This section lists
the standards supported by charon at the time of writing
this manual entry. The version of the standard is given, if
appropriate, alongside any comments on its implementation.
Protocols HTTP versions 1.0 and 1.1
HTTPS: SSL Protocol versions 2.0 and 3.0.
X.509.v3 server certificates.
FTP: charon supports retrieval of plain text
files only, directory listings are not gener-
ated.
FILE: Charon attempts to determine the file
type by a combination of the filename exten-
sion and examination of the first few bytes
of the file. Directory listings are not gen-
erated.
HTML It is intended that charon supports HTML ver-
sion 3.2, but in reality there is no single
standard! Charon attempts to be as close as
possible to Netscape Navigator Version 3 in
terms of its markup support. Obvious bugs in
Navigator 3 and the Netscape security model
have not been adopted.
JavaScript Charon implements ECMAscript-262 2nd Edition,
which is roughly equivalent to JavaScript1.1.
The ECMA-262 standard does not define the
host objects and classes that should
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implemented by the browser. Charon imple-
ments the set of host objects and classes of
Netscape Navigator version 3.
Encodings US_Ascii, ISO_8859_1, UTF_8, Unicode (big-
endian)
Images GIF87a and GIF89a - animated GIFs always
loop.
JPEG, XBitmap, Inferno BIT image(6) format.
Configuration
While using charon, a sub-set of the configuration options
can be modified. Clicking the Configuration button displays
a config popup window, enabling the user to modify the cur-
rent values of the available options.
The full set of configuration options can be modified on the
command line or in a configuration file. Comand line
options are processed after the configuration file. The
configuration file is loaded from /usr/user/charon/config
where user is obtained by reading the file /dev/user. If
this file does not exist, the file
/services/config/charon.cfg is read instead. Options are
processed in order; some options override settings affected
by others and so the order in which they are used is impor-
tant.
Options are specified using a key, value pair. On the com-
mand line this takes the form:
-key value
Where -key and value are individual items in the argument
list to charon.
In the config file options take the form:
key=value
Where value is the remainder of the input line after the `='
character. Any text lines in the config file that start
with a `#' character are ignored as comment lines.
OPTIONS
userdir
The directory where charon expects to find its configu-
ration files such as, bookmark and cookie files. The
default value is /usr/user/charon/ where user is
obtained by reading the file /dev/user.
starturl
Specifies the URL of the first document to be displayed
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CHARON(1) CHARON(1)
by charon at startup. The default value is
file://localhost/services/webget/start.html
homeurl
Specifies the URL of the document to retrieve when the
Home button is clicked. The homeurl can only be changed
if the change_homeurl option is enabled. Setting
homeurl also set the value of the starturl option. The
default value is
file://localhost/services/webget/start.html
change_homeurl
Enables editing of the Home URL in the configuration
popup window. A non-zero integer value enables this
option, all other values disable it This option also
enables the homeurl option. The default value is 1.
helpurl
Specifies the URL of the document to retrieve when the
Help button is clicked. The default value is
file://localhost/services/webget/help.html
httpproxy
Specifies the host name and port of a web proxy server.
The address is given in the form of a URL, where the
optional port number can be specified after the server
name by separating them by a colon `:'. The default
value is the empty string, specifying that no web proxy
server should be used.
noproxy or noproxydoms
Specifies a list of network domains for which a web
proxy should not be used. The domains in the list can
be separated by semicolon, comma, space or tab charac-
ters. The default value is the empty list.
usessl
Extends SSL support. Accepted values are ``v2'' and
``v3''. Initially SSL support is configured off.
Enabling version 1 or version 2 support restricts SSL
support to that specific version. Specifying the option
twice, once with each of the options, enables dual ver-
sion SSL support whereby the remote server is probed to
determine which version it supports. Some servers only
support one of the versions and may not tolerate the
special version2/3 probe.
buttons
Specifies the set of buttons that appear on the window
manager title-bar. The buttons are given as a list of
button names separated by comma, space or tab charac-
ters. Valid button names are help, resize and hide.
The default value is for all buttons to be displayed.
defaultwidth or width
Set the initial window width. This option is only mean-
ingful when running under the window manager. If the
specified width exceeds the screen width then the screen
width is used. The default value is 630.
defaultheight or height
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Set the initial height of the main display panel, this
does not include the height of the control and progress
panels. This option is only meaningful when running
under the window manager. If the total height of the
charon window exceeds the screen height, the main dis-
play panel height will be reduced to fit. The default
value is 450.
x and/or y
Set the initial window position. These options are only
meaningful when running under the window manager. The
default value for both options is 0.
imagelvl
Specify how to handle image components of a document.
This option takes a numeric argument. A value of 0 pre-
vents images from being downloaded or displayed. A
value of 1 will download and display images but not ani-
mate GIFS - only the first frame of an animated GIF will
be displayed. A value of 2 or more enables full image
processing. The default value enables full image pro-
cessing.
imagecachenum
Specify the maximum number of images that can remain
resident in the image cache. The default value is 60.
imagecachemem
Specify the maximum amount of image memory available to
the image cache in bytes. The cache is managed such
that neither the imagecachenum nor imagecachemem limits
are exceeded. The image cache tries to ensure that no
more than 80% of available system image memory is taken
by the cache, irrespective of the value of this option.
The default value is 80% of the system image memory that
was available when charon was started.
docookies
Enable cookie handling. A non-zero numeric value
enables cookie handling, all other values disable it.
The cookie cache is maintained in the cookies file in
the userdir directory. The default value is 0, cookie
handling disabled.
doscripts
Enable JavaScript support. A non-zero numeric value
enables JavaScript, all other values disable it. The
default value is 0, JavaScript processing disabled.
showprogress
A non-zero numeric value results in the progress panel
being displayed. All other values hide the progress
panel, leaving more vertical space for the main display
area. The default value is 1, causing the progress
panel to be displayed
http
Set the version of HTTP to use when communicating with
web servers. Supported versions are 1.0 and 1.1. Any
value other than 1.1 results in HTTP1.0 being used. The
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default value is 1.0.
nthreads
Specifies the maximum number of concurrent downloads of
document components. Generally, if this number is
higher, pages will complete faster as charon will not
have to wait for the download of one component to com-
plete before another can be started. The downside is
that a higher number of concurrent downloads will use
more memory during the download process. The default
value is 4.
FILES
/services/config/charon.cfg The default configuration file.
userdir/config The user specific configuration
file. userdir is given by the
value of the userdir option.
userdir/cookies The cookie cache. userdir is
given by the value of the
userdir option.
/services/webget/start.html The default start page.
/services/webget/help.html The default help page.
SOURCE
/appl/charon/ The main charon source files.
/appl/lib/ecmascript/ Javascript (ECMA-262) implementation.
BUGS
Charon has more than its fair share of real bugs. The fol-
lowing list documents the problems that are most likely to
be encountered.
Charon implements its table layout as per the algorithm
described in rfc1942. This sometimes results in table-based
documents being laid out differently to other browsers.
JavaScript is a source of many problems. Many scripts do
not specify the language version they employ. Additionally
different language versions and browsers imply a different
set of host objects and classes. Such differences often
give rise to syntax or null reference errors. This whole
situation places a great burden on the script author to
write safe and compliant scripts; unfortunately authors are
rarely aware of this burden!
The following elements of JavaScript1.1 are not fully imple-
mented:
Document.applets, Document.embeds and Document.plugins: Java
Applets are not supported, the arrays are always empty.
Document.onunload: The property exists and can be assigned
to, but the event is never raised.
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Window.open(): A new window is never opened. If a URL is
specified for the new window, the current document will be
replaced with that of the new URL.
Other annoyances include:
Window resize forces a complete document reload.
Frames in a frameset are processed one at a time, not con-
currently.
It is not possible to save downloaded data to file. This is
particularly annoying for MIME types that charon does not
support.
The history list can get confused, especially when following
links in framesets before the complete frameset has been
downloaded.
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