#LyX 2.4 created this file. For more info see https://www.lyx.org/
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\pdf_title "LyX's Development manual"
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\begin_layout Title
Developing \SpecialChar LyX

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Version 2.3.x
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File formats
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\begin_layout Subsection
When is an update of the .lyx file format number needed?
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LatexCommand label
name "sec:When-is-an"

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\end_layout

\begin_layout Standard
When you are working on a new feature you may ask yourself whether it needs
 an update of the .lyx file format number.
 Whether an update is needed or not is not always obvious.
 Rule of thumb: 
\end_layout

\begin_layout Quote
Whenever there is the danger that a previous version of LyX cannot open
 a file using the new feature, a file format update is needed.
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\begin_layout Standard
The file format change allows lyx2lyx rules to implement backwards compatibility.
 Below you can find a list of reasons for file format updates with explanations:
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\begin_layout Description
New
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document
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setting Whenever you introduce a new setting that is stored in the document
 header, a file format update is needed.
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\begin_layout Description
Removed
\begin_inset space ~
\end_inset

document
\begin_inset space ~
\end_inset

setting If a certain setting becomes obsolete and gets removed, a file format
 update is needed.
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\begin_layout Description
New
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valid
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value
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for
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an
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existing
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setting, e.
\begin_inset space \thinspace{}
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g.
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\begin_layout Description
\paragraph_spacing single
Automatically
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loaded
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math
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package The reason for this is that there is no true ERT inset for math
 formulas: Each command is parsed, and if a user happens to define a local
 command with the same name as a command that triggers an automatic load
 of a package, they need to be able to switch off the automatic loading
 of that package.
 This switch is stored by the 
\begin_inset Flex Code
status collapsed

\begin_layout Plain Layout
use_package
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\end_inset

 header setting.
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\begin_layout Description
New
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language that is stored in 
\begin_inset Flex Code
status collapsed

\begin_layout Plain Layout

\backslash
language
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.
 
\begin_inset Note Note
status collapsed

\begin_layout Plain Layout
This requirement is under discussion.
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\end_deeper
\begin_layout Description
New
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inset Of course a new inset requires a file format update.
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\begin_layout Description
New
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style If a new style or inset layout is added to any layout file or module
 shipped with \SpecialChar LyX
, then a new file format is needed in the master (development)
 branch.
 It is possible to backport new styles to the stable version without a file
 format change.
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\begin_layout Description
Removed
\begin_inset space ~
\end_inset

style If a style or inset layout is removed in any layout file or module
 shipped with \SpecialChar LyX
, a new file format is required.
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\begin_layout Standard
However, 
\series bold
new
\series default
 layouts and modules do 
\series bold
not
\series default
 require a file format update (changed 03/16).
 
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\begin_layout Standard
If you are still unsure, please ask on the development list.
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\begin_layout Paragraph
\begin_inset CommandInset label
LatexCommand label
name "par:export-test-output-formats"

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Output formats
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\begin_layout Standard
The following output formats are currently tested for each sample document:
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\labelwidthstring 00.00.0000
LyX:
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\begin_deeper
\begin_layout Labeling
\labelwidthstring 00.00.0000
lyx16 LyX 1.6 file format (lyx2lyx)
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\begin_layout Labeling
\labelwidthstring 00.00.0000
lyx21 LyX 2.1 file format (lyx2lyx)
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\begin_layout Labeling
\labelwidthstring 00.00.0000
xhtml LyXHTML (native LyX HTML export)
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\end_deeper
\begin_layout Labeling
\labelwidthstring 00.00.0000
LyX
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+
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LaTeX:
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\labelwidthstring pdf5msystemFM
dvi DVI (8-bit latex)
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\begin_layout Labeling
\labelwidthstring pdf5msystemFM
dvi3_texF DVI (LuaTeX with 8-bit TeX fonts)
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\begin_layout Labeling
\labelwidthstring pdf5msystemFM
dvi3_systemF DVI (LuaTeX with Unicode fonts)
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\begin_layout Labeling
\labelwidthstring pdf5msystemFM
pdf2 PDF (pdflatex)
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\begin_layout Labeling
\labelwidthstring pdf5msystemFM
pdf4_texF PDF (XeTeX with 8-bit TeX fonts)
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\begin_layout Labeling
\labelwidthstring pdf5msystemFM
pdf4_systemF PDF (XeTeX with Unicode fonts)
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\begin_layout Labeling
\labelwidthstring pdf5msystemFM
pdf5_texF PDF (LuaTeX with 8-bit TeX fonts)
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\begin_layout Labeling
\labelwidthstring pdf5msystemFM
pdf5_systemF PDF (LuaTeX with Unicode fonts)
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\labelwidthstring 00.00.0000
LyX
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+
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LaTeX
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+
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postprocessing:
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\begin_deeper
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pdf DVI -> PS (dvips) -> PDF (ps2pdf)
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\begin_layout Labeling
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pdf3 DVI -> PDF (dvipdfm)
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not
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tested: (or only if set as default output format in the document source)
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\begin_deeper
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latex LaTeX (plain)
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\begin_layout Labeling
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luatex LaTeX (LuaTeX)
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\begin_layout Labeling
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dviluatex LaTeX (dviluatex)
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\begin_layout Labeling
\labelwidthstring pdf5msystemFM
pdflatex LaTeX (pdflatex)
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\begin_layout Labeling
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platex LaTeX (pLaTeX)
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\begin_layout Labeling
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xetex LaTeX (XeTeX) 
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\begin_layout Labeling
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eps3 EPS (encapsulated Postscript) (cropped)
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\begin_layout Labeling
\labelwidthstring pdf5msystemFM
ps DVI -> Postscript (dvips)
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\begin_layout Labeling
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odf
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\begin_layout Labeling
\labelwidthstring pdf5msystemFM
text (nor text2, ..., text4)
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\begin_layout Labeling
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textparagraph
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\begin_layout Labeling
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word
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\begin_layout Labeling
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word2
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\begin_layout Labeling
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wordhtml
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\end_deeper
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