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@@ -0,0 +1,206 @@ +IJS 0.35 + +News as of 0.35: +11 Feb 2004 + +The autoconf build system has been moderized and we now use +libtool for portable shared library building. Thanks to Roger +Leigh for helping with that. + +Also a bug with ColorSpace field was corrected, thanks to David +Suffield. + +News as of 0.34: +22 Apr 2002 + +The source files now have official MIT license banners. Thanks to +www.opensource.org for hosting the ur-text of this license. Also +some clarifications on namespace management in the spec. + +There is now an IJS website, graciously hosted by linuxprinting.org. +http://www.linuxprinting.org/ijs/ + +There have been some minor improvements in the makefile. + +News as of 0.33: + +The buffer size has been increased to 4096. It should probably be +dynamically allocated, though. Minor clarification in BitsPerSample +language in spec (thanks to Jackie Chang for pointing out the +ambiguity). + +News as of 0.32: + +The xres and yres fields of ph are now floats. + +The example server now supports margins. A few small bugs have +been cleaned up as well. + +News as of 0.31: + +A number of small cleanups in the code. The example client and server +support more querying and enumeration, but not yet margins. + +There is a new API for the client to query the negotiated version +number. + +The ijs_exec_unix module now sets the SIGPIPE signal to ignore. This +way, if the client abnormally exits, it allows the error to propagate +through the read() or write() call to the pipe, rather than +immediately killing the client. + +News as of 0.30: + +It now builds as a library. Also, there is basic autoconf support (but +not automake or libtool). It's probably best to link the static +library for now. I'm open to suggestions - I'm open to drinking the +entire pitcher of auto* Kool-Aid, but we probably won't use libtool +in Ghostscript builds. + +This release fixes a number of bugs and improves portability. In +particular, server errors should now bubble up to the client, and +the termination logic has been patched according to David Suffield, +who discovered a race condition there. Thanks to David and Russell +for patches. + +The spec is now in a reasonable draft. See ijs_spec.sgml and +ijs_spec.pdf. Comments and suggestions are welcome. + +The example client and server have _not_ yet been updated to use +the newer features of the ijs spec. Patches are welcome. + +News as of 0.29: + +I've added a number of things discussed on the mailing list, including +listing and enumerating parameters, as well as a job abstraction. +The client interface has changed a bit - job id's are now present +in most callbacks, colorspace is now presented only as a string, and +there are quite a few more callbacks. + +I've started a skeleton of a protocol spec in DocBook. + +Note, there's a potential race condition in EXIT noted by David +Suffield. The fix hasn't yet been merged in from his work. + +News as of 0.2: + +This version integrates set_param and get_param, and has moved the +"page header" processing to use set_param. + +Also, there are both Windows (MS VC++) and Unix makefiles. Use +"make -f unix.mak" to build on Unix. Thanks to Russell Lang for +Windows portability work. + + +Introduction + +This is an early snapshot of IJS. I expect the protocols and API's to +evolve somewhat, and things like error handling are still far from +perfect. However, I'm pretty happy that this is going in the right +direction. + +I am doing this prerelease so that authors of various packages related +to raster-based printing can start thinking about how to integrate it. +Ideally, all producers of printable raster data should be able to +function as an ijs client, and all consumers should be able to +function as an ijs server. This release is about as functional as +piping pnm's, which is primitive, but the way a lot of drivers still +work. + + +What is IJS? + +IJS is, first and foremost, a protocol for transmission of raster page +images. This snapshot provides a reference implementation of the +protocol, the design of which is still in flux. When the protocol +specification is published, it will be authoritative. Applications +should feel free to link against the library provided in this package, +adapt that code for their own needs, or roll a completely new +implementation. + +The protocol is a fairly traditional client-server design. In general, +the client sends one or more page images to the server, along with +various metadata. Communication is through simple "commands", which +are essentially size-prefixed packets. The client sends a command to +the server, then waits for a response command, either ACK or NAK. + +The server "speaks" IJS through stdin and stdout. One consequence of +this design decision is that the server can be invoked remotely, for +example through ssh. It's not clear yet how useful this will be, but +at least people can experiment with it. + +Currently, all data goes through the stdin and stdout pipes. It is +envisioned that a shared memory transport will also be provided, +transparently. IJS will fall back to pipes if shared memory is not +available for any reason. + +I'm not yet convinced that the performance win for shared memory is +significant. I would like to benchmark domain sockets as well, as they +are likely to provide better performance than pipes, and are also +highly desirable for cases where the server runs as a persistent +daemon. + +This tarball provides an "IJS library" in the form of ijs, ijs_client, +and ijs_server. It also provides an example client (capable of reading +pnmraw files) and an example server (capable of generating +PostScript). I imagine that the example programs will be useful for +development and testing, but that end-users probably won't find a need +for them. + +To try IJS, compile and run "./ijs_client_example -s +./ijs_server_example -pOutputFile=/tmp/tmp.ps foo.ppm". This will +invoke ./ijs_server_example, which will in turn generate a /tmp/tmp.ps +file. + +The ijs_client_example takes a -p command line argument for setting +parameters, and a -r argument for setting resolution. Here is a +typical command line: + +./ijs_client_example -s ./ijs_server_example -pOutputFile=/tmp/tmp.ps \ + -r300 in.ppm + +The syntax of -p is a sequence of key=value pairs, separated by +commas. A backslash in the value escapes the next character (allowing +embedded commas in the value). Thus, '-pfoo=bar, quux=a\,b' sets the +key "foo" to the value "bar, and the key "quux" to the value "a,b". + + +FAQ + +What does IJS stand for? + +It stands for "raster printer driver architecture." It's spelled +U+30EA U+13DA, to avoid confusion, and to save space in UTF-16 +encodings. + +Actually, the name derives from HPIJS, which presumably stands for HP +InkJet Server. The name pays homage to HPIJS for the inspiration, +while communicating that it's not specific to HP printers. + +Licensing + +All source code in this distribution is released under the MIT +License. I want everybody to be able to use this. + + +More stuff to write: + +Actual specification for the protocol (in draft). + +Client spawns server, invoker invokes client and server, and +persistent server daemon modes. + +Negotation of extensions (goal is interoperability between versions). +(Actually, the PING/PONG protocol as it exists negotiates version +numbers). + +TODO: + +Shared memory transport. + +Should have an alternate mode in which the client is passed the pipe +information, rather than having to spawn the server. + +wait() cleanup of invoked server. + +Package library up as libijs.a, .so (partially done) |