How do I upgrade my existing LyX system to version 1.6.x?
---------------------------------------------------------

* Upgrading from LyX 1.4.x and earlier:

The biggest change in 1.5 is the switch to Unicode. Please refer to
the section "Document transfer" below for some things you might take
into account before upgrading.

The format of the preferences file has changed slightly. LyX 1.5.x is
able to read old preferences files, but it will save them in the new
format, so it is not possible to run LyX 1.4.x and 1.5.x with the same
personal configuration directory. If you are upgrading from 1.4.x and 
do not intend to continue using 1.4.x, you should delete your existing 
preferences file and allow LyX to create a new one.

The list of recently open files is now stored in a different location.
It will therefore be reset when upgrading from LyX 1.4.x.

The format of the layout files has also changed, but LyX 1.5.x uses a
converter layout2layout.py written in python that will convert old layout
files on the fly (see below, section "Document transfer").

* Upgrading from LyX 1.3.x:

The format of the external template file has changed substantially with 
LyX 1.4.0. Automatic conversion is not available, so you need to convert 
your external templates manually. The new format of the external template
configuration file is described in chapter 6.5 of the Customization Guide.

* Upgrading from LyX 1.2.x:

Since 1.3.0, you have to do the following changes:

One of the perennial bug bears of LyX users in the past has been that
they have had to run Edit->Reconfigure when starting their new version
of the code for the first time. Strange and wonderful things would
often result if they forgot to do this, so LyX 1.3.0 now runs
Edit->Reconfigure automatically the first time the program is run.

If you have your own layout files, you may need to update them a little:

- floats are now defined in the layout file, using the "Float"..."End"
  construct. In most cases, adding "Input stdfloats.inc" to your layout
  file is enough.

- counters are also defined in the layout files, using the
  "Counter"..."End" construct. As for floats, adding "Input
  stdfloats.inc" is probably a good idea.

* Upgrading from LyX 1.1.x:

- all layout files should have a "DefaultStyle" entry

- the "Latex" font style does not exist anymore. If you really need
  its functionality, consider using the "PassThru" keyword instead.

The new layout format keywords are described in the Customization
manual.

If you have your own binding files (especially math.bind), you will
have to update them

- math-insert now takes a latex macro name as argument, so that
  "math-insert sqrt" should now be "\math-insert \sqrt"

- math-greek-toggle is now gone, and should be replaced by explicit
  bindings like

  \bind "M-m g a"      "math-insert \alpha"


Build requirements
------------------

LyX 1.5 uses the Qt 4.x toolkit (version 4.1.1 or newer). Contrary to 
previous versions of LyX, it won't build against Qt 2.x or 3.x.
Furthermore, the XForms frontend was dropped.

LyX's graphics handling system has changed substantially. If you
do not have the JPEG library installed, you may need to install
it before you can use the graphics capabilities of LyX. If you
do not have the ImageMagick command-line tools installed, you
will need to modify the default set up of LyX, or install them,
in order to get previews of your document's graphics.

Document transfer
-----------------

* Compatibility with older documents/layouts

LyX 1.5.x uses an external python script, lyx2lyx, to import documents
written using previous versions of LyX. All versions of LyX as far back as
0.12 are supported, so any klyx users still holding out for an alternative
to xforms will finally be able to put their dinosaur to rest ;-)

Of course, this means that you must have python (at least version 2.3)
installed in order to use LyX 1.5.x with your old documents.

lyx2lyx also has the framework in place to be able to convert documents
to an earlier format (which requires python 2.3.4 at least). However,
these converters have only been written for the conversion from 1.5.x 
to 1.4.x and 1.3.x, so versions of LyX older than 1.3.0 will NOT be able 
to read documents saved with LyX 1.5.x. The conversion from 1.5.x to 
1.4.x/1.3.x is lossless as long as no new features are used. lyx2lyx 
tries hard to find something equivalent for new features such as boxes, 
but this is known to fail sometimes. LyX 1.4.5.1 contains an updated 
lyx2lyx that can read documents in 1.5.x format. LyX 1.5.x can also 
export to 1.4.x format for document transfer to older 1.4.x releases.

Furthermore, LyX uses a converter layout2layout.py, also written in python 
that will convert old layout files on the fly. You can also call it manually 
on your layout files if you want to convert them to 1.5.x format permanently.

* Preparing for Unicode:

As of version 1.5.0, LyX uses Unicode internally. This is a major change that
affects documents and layouts likewise. We have tried to do out best to make the
transition as smooth as possible for you. However, there are some caveats:

- User layout files must be converted to UTF-8

  In previous versions, layout styles were allowed to use non-ASCII names
  using the local encodings. LyX-1.5 now assumes that all layout files are
  UTF-8 encoded. This means that non-ASCII style names are still allowed
  but they must be valid UTF-8 strings. One way of doing the conversion
  is to use iconv. Using bash, the script below should work:

     #! /bin/sh

     cd /path/to/layouts
     for l in *
     do
       cp "$l" tmp.txt
       iconv -f latin1 -t utf8 tmp.txt -o "$l"
     done
     rm -f tmp.txt

- Inset encodings and Conversion from earlier LyX versions

  As part of the transition to unicode, lyx2lyx (the scripts used for converting 
  back and forth between different versions of the lyx files) converts old .lyx 
  files, which may use a number of different encodings, to UTF-8. This conversion 
  depends on correctly identifying the language of the text. There were previously 
  some edge-cases (insets embedded in different-language text type scenarios) in 
  which the language was incorrectly identified, which caused some text to 
  appear incorrectly after having upgraded from older versions. This has now been
  fixed. Unfortunately, however, the fix cannot be applied to files which have
  already been converted past format 249. So if you have already converted 
  your old files (using a development version or release candidate), this fix
  won't help, unless you still have the originals lying around (and haven't 
  yet made too many changes to the newer versions ;) ).

Generally, it is probably wise to keep a backup of the old version of your 
files, at least until you are sure that the upgrade went smoothly (which it 
almost always will).

* Languages/encodings and insets

One of the bugs fixed in LyX 1.5.0 is that previously, there were certain 
specific cases in which the LaTeX generated did not correctly reflect 
language/encoding transitions in and around insets (footnotes, LyX notes).
After much deliberation, it was decided not to change older files such that
they will still reflect the old LaTeX output; rather, they will now correctly
reflect the situation as it appears in the GUI. This means, however, that if 
you mangled the text in the GUI in the older versions, in order that it
generate the correct LaTeX output, the LaTeX will now generate the mangled 
text. If this is problematic for you, please get in touch with us on the
developers mailing list, we do have some possible solutions for this.

The effects of this will be more pronounced for RTL (Hebrew, Arabic, Farsi) 
users -- though they affect users of other languages as well.

* Floatflt in 1.2.x and older

If you were previously (in LyX 1.1.x) using the floatflt paragraph
option to wrap text around a figure, it was necessary to modify this
for LyX 1.2.0 manually, as described in the manuals. The feature has
been re-implemented as "Floating figure" inset in 1.3.0. Old files will
be converted automatically, but you may want to convert the
1.2.x-style ERT constructs with the native solution (see section 3.8
of the Extended Features manual).

* Babel changes since 1.2.x

Since LyX 1.2.0, the babel package is loaded after the user-defined
preamble (because some packages really need to be loaded before
babel). If you relied, on babel being loaded before your own
definitions, you can add an extra "\usepackage{babel}" statement at
the beginning of your preamble.

http://bugzilla.lyx.org/show_bug.cgi?id=315