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181 lines
8.1 KiB
Plaintext
181 lines
8.1 KiB
Plaintext
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Introduction to MIME handling
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-----------------------------
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At some time along the 0.4 prereleases, ELinks replaced the old Links file
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configuration system with its own one. Now, the configuration is stored in
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elinks.conf, much more complete and featuring a new syntax. You can set most
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options from the UI (so usually there is no need to deal with elinks.conf),
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and that used to be true for setting MIME handlers and extensions as well; but
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now the associations menu is gone temporarily, forcing you to set the handlers
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from the configuration file.
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The comments provided within elinks.conf for the MIME options are not much
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helpful, and those options may seem a bit obscure or confusing at first. This
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document is a basic introduction to setting of MIME associations for ELinks.
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If you want to know how to automatically launch a program to view some kind of
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file (like images), then read on. Some basic knowledge of MIME is recommended.
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Handling MIME types, the ELinks way
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~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
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What are MIME types and why may you want to use them?
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^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
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If, while browsing with ELinks, you need to display files that it can't show
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(like images or PDF documents), then you will likely want to pass them to
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other programs that are suitable for this task. While you may do it manually
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(saving the file to disk, running the auxiliary program to show it and then
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removing the file when finished), ELinks provides a method to do this
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automatically using MIME types.
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ELinks usually knows what the MIME type is for any file (which is a kind of
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description of its format), thus you only need to specify how to manage the
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MIME types for the files you want to open. If you don't tell ELinks how to
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manage a given MIME type then it will show you on screen the contents of the
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file (as if it was ASCII text) instead of calling an external program to show
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them.
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Associating files to MIME types
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^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
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If the file is fetched from a web server then this web server should tell
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ELinks what its MIME type is, so you should have generally no need to care
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about it. However, the web server might send an incorrect type, or you may be
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retrieving it by FTP or from your local filesystem, so sometimes ELinks needs
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to guess it.
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The easiest method to guess a MIME type for a file is to just look at its name
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trusting it was given the right extension. ELinks supports this, letting you
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to specify a type for any given extension.
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Managing a given MIME type
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^^^^^^^^^^^^^^^^^^^^^^^^^^
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This usually means specifying programs to open files of this type and the
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conditions in which those programs may be used. For instance, you may want to
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use zgv (a popular svgalib image viewer) when you are using the text console,
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but xli (a image viewer for X) when running the X window system.
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Binding it to a handler
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+++++++++++++++++++++++
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Instead of directly attaching a program to a MIME type, ELinks lets you
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associate an abstract handler to each type. Then you can specify which
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programs implement the handler and how are they used.
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For instance, you may create an image_viewer handler and assign it to MIME
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types image/jpeg, image/png and image/gif. Then you would associate to
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image_viewer the programs you would like to use for viewing images and the
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details on how to use them. This is less cumbersome than repeating all these
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details for each MIME type.
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Specifying the details for a handler
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^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
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There are three issues to specify for a handler: the program associated to it,
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whether you want confirmation before using it and whether you want the
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terminal to be blocked while it is being used.
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When specifying any of these issues, you must tell ELinks the situation in
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which it gets applied, which is typically either the text console or the X
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window system. So you can specify that you don't want confirmation before
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running the program when running X, and that you want it otherwise.
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Similarly, when you are attaching a program (name it foo) to this handler you
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must tell if it's for X or not (you can attach a second program for the other
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choice if you want).
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Attaching a program to it::
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You must tell ELinks the exact command for running it (with any
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options you wish). In place of the filename you must enter %.
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Choosing whether you want confirmation before applying it::
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This is rather simple. If you choose not to do so, then the handler
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will be automatically called upon when you demand ELinks to show
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something attached to this handler. Otherwise, if you ask for
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confirmation, you will be prompted to open it with a external program,
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with additional choices that include cancelling the operation and
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viewing it with ELinks. E.g: you may use this option for programs
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written in C so that you may always choose if you want to read the
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source with ELinks, or if you want to save it, or if you want to use
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indent to display it with less.
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Choosing whether to block the terminal::
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If you don't want to allow going back to ELinks (or any other program
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from the same terminal) before the external program ends, then you
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should ask to block the terminal.
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Setting up elinks.conf
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~~~~~~~~~~~~~~~~~~~~~~
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If you have old configuration files from old ELinks versions or from Links,
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then you may use the conf-links2elinks.pl script (which is placed at
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contrib/conv/ on the source distribution) to convert them to the new format.
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If you don't use it you will need to edit the configuration file, and here you
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will find how.
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Associating a file extension to a MIME type
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^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
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You can still do this with the UI, from the the Setup->File Extensions
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submenu.
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If you want to do so from the configuration file, enter set mime.extension.ext
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= "type", replacing ext with the appropriate file extension, and type with its
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MIME type. E.g. you may want to have set mime.extension.jpg = "image/jpeg".
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Defining a handler
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^^^^^^^^^^^^^^^^^^
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For each handler you must define three items, specifying in what context the
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value of the item should be applied. You must enter set
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mime.handler.handler-name.item.context = value, replacing handler-name with
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the name for the handler you are defining, item with the item you are defining
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for this handler, context with the context this item value is to be applied,
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and value with the value you want to assign to the item. You must do so for
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each of the available items: program, ask and block.
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The value for program is a string with the exact command you want to be issued
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to view the file, placing % were you would put the file name. The values for
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ask and block are either 0 (no) or 1 (yes). Available contexts include unix
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and unix-xwin, which mean UNIX text terminal and X respectively (others can be
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os2, win32, beos, riscos, ...). The latter does not mean you are running
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ELinks from X, just that the DISPLAY variable is set so that ELinks may run an
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X program.
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To illustrate it, here is an example. Suppose you want to define the
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image_viewer handler which should be used to view images. The configuration
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file may look like this:
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--------------------------------------------------------------------------------
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set mime.handler.image_viewer.unix.ask = 1
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set mime.handler.image_viewer.unix-xwin.ask = 0
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set mime.handler.image_viewer.unix.block = 1
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set mime.handler.image_viewer.unix-xwin.block = 0
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set mime.handler.image_viewer.unix.program = "zgv %"
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set mime.handler.image_viewer.unix-xwin.program = "xli %"
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--------------------------------------------------------------------------------
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In this example the image_viewer handler uses the svgalib image viewer zgv
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when X is not available, and the X image viewer xli when it is. The terminal
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would be blocked when X is not available and it would not be when it's
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available. Finally, ELinks would ask for confirmation before using the handler
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only with X not available.
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Associating a MIME type to a handler
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^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
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Just enter set mime.type.class.name = "handler", replacing class with the
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class for the mime type, name with the specific name within that class, and
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handler with the name for the handler you want to assign to the MIME type.
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E.g. you may want to have set mime.type.image.jpeg = "image_viewer".
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