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\pdf_title "LyX's Development manual"
\pdf_author "LyX Team"
\pdf_subject "LyX's development documentation"
\pdf_keywords "LyX, Documentation, Development"
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\begin_body

\begin_layout Title
Developing LyX
\end_layout

\begin_layout Subtitle
Version 2.2.x
\end_layout

\begin_layout Author
by the LyX Team
\begin_inset Foot
status collapsed

\begin_layout Plain Layout
\noindent
If you have comments or error corrections, please send them to the LyX Documenta
tion mailing list, 
\begin_inset Flex Code
status collapsed

\begin_layout Plain Layout
\noindent
<lyx-docs@lists.lyx.org>
\end_layout

\end_inset

.
\end_layout

\end_inset


\end_layout

\begin_layout Standard
\begin_inset CommandInset toc
LatexCommand tableofcontents

\end_inset


\end_layout

\begin_layout Chapter
Introduction
\end_layout

\begin_layout Standard
This manual documents some aspects of LyX development.
 It is currently rather incomplete, but will hopefully be extended in the
 future.
 Meanwhile, additional information can be found in the 
\begin_inset Flex Code
status collapsed

\begin_layout Plain Layout
development
\end_layout

\end_inset

 subfolder of the LyX source code distribution.
 This document is not translated, since the development language of LyX
 is english.
 If you want to use LyX you don't need to read this manual.
 However, if you want to learn more about how LyX is developed, or even
 want to participate in LyX development, you may find some interesting informati
on.
\end_layout

\begin_layout Chapter
File formats
\end_layout

\begin_layout Standard
LyX uses several custom file formats for configuration files and documents.
 This chapter contains some background concerning these file formats.
 Several file formats are also described in detail in the regular user documenta
tion.
\end_layout

\begin_layout Section
File Format Numbers
\end_layout

\begin_layout Section
When is an update of the .lyx file format number needed?
\end_layout

\begin_layout Standard
When you ware 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.
 Below you can find a list of reasons for file format updates with explanations:
\end_layout

\begin_layout Description
New
\begin_inset space ~
\end_inset

document
\begin_inset space ~
\end_inset

setting Whenever you introduce a new setting that is stored in the document
 header, a file format update is needed.
 This is also true if you add a new valid value to an existing setting,
 e.
\begin_inset space \thinspace{}
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g.
\begin_inset space \space{}
\end_inset

a new language that is stored in 
\begin_inset Flex Code
status collapsed

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\backslash
language
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\end_inset

.
\end_layout

\begin_layout Description
Removed
\begin_inset space ~
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document
\begin_inset space ~
\end_inset

setting If a certain setting becomes obsolete and gets removed, a file format
 update is needed.
\end_layout

\begin_layout Description
New
\begin_inset space ~
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inset Of course a new inset requires a file format update.
\end_layout

\begin_layout Description
New
\begin_inset space ~
\end_inset

style in any layout file or module shipped with LyX, or new shipped layout
 file or module.
 These requirements are currently under discussion and might change in the
 future.
\end_layout

\begin_layout Description
Automatically
\begin_inset space ~
\end_inset

loaded
\begin_inset space ~
\end_inset

math
\begin_inset space ~
\end_inset

package Any new math package that is automatically loaded needs a file format
 update.
 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 defne a local command
 with the same name as a command that triggers an automatic load of a package,
 he needs to be able to switch off the automatic loading of that package.
 This switch is stored by the 
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status collapsed

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use_package
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 header setting.
\end_layout

\begin_layout Standard
If you are still unsure, please ask on the development list.
\end_layout

\begin_layout Section
How to update the file format number of .lyx files
\end_layout

\begin_layout Standard
Once you came to the conclusion that a file format update is needed you
 should use the following procedure to perform the update:
\end_layout

\begin_layout Enumerate
Implement and test the new feature, including the reading and writing of
 .lyx files.
 Note that any file produced at this stage does not use a valid format,
 so do not use this version of LyX for working on any important documents.
\end_layout

\begin_layout Enumerate
Describe the new format in 
\begin_inset Flex Code
status collapsed

\begin_layout Plain Layout
development/FORMAT
\end_layout

\end_inset

.
\end_layout

\begin_layout Enumerate
Update the LyX file format number in 
\begin_inset Flex Code
status collapsed

\begin_layout Plain Layout
src/version.h
\end_layout

\end_inset

.
\end_layout

\begin_layout Enumerate
Add an entry to both format lists (for conversion and reversion) in
\begin_inset Newline newline
\end_inset


\begin_inset Flex Code
status collapsed

\begin_layout Plain Layout
lib/lyx2lyx/lyx_2_2.py
\end_layout

\end_inset

.
 Add a conversion routine if needed (e.
\begin_inset space \thinspace{}
\end_inset

g.
\begin_inset space \space{}
\end_inset

a new header setting always needs a conversion that adds the new setting,
 a new document language does not need one).
 Add a reversion routine if needed.
 While the conversion routine is required to produce a document that is
 equivalent to the old version, the requirements of the reversion are not
 that strict.
 If possible, try to produce a proper reversion, using ERT if needed, but
 for some features this might be too complicated.
 In this case, the minimum requirement of the reversion routine is that
 it produces a valid document which can be read by an older LyX.
 If absolutely needed, even data loss is allowed for the reversion.
\end_layout

\begin_layout Enumerate
Since tex2lyx has several implicit file format dependencies caused by sharing
 code with LyX, updating the file format of .lyx files produced by tex2lyx
 at the same time as updating the main .lyx file format is strongly recommended.
 Therefore, a compiler warning will be issued if the LyX and tex2lyx .lyx
 file format numbers differ.
 In many cases the tex2lyx update requires only the first and last item
 of the list below:
\end_layout

\begin_deeper
\begin_layout Enumerate
Update the tex2lyx file format number in 
\begin_inset Flex Code
status collapsed

\begin_layout Plain Layout
src/version.h
\end_layout

\end_inset

.
\end_layout

\begin_layout Enumerate
If the lyx2lyx conversion from the old to the new format is empty, or if
 tex2lyx does not yet output the changed feature, you do not need any further
 tex2lyx changes.
 Otherwise, search for the changed feature in tex2lyx, and adjust the output
 according to the lyx2lyx changes.
\end_layout

\begin_layout Enumerate
Update the tex2lyx test references as described in 
\begin_inset CommandInset ref
LatexCommand formatted
reference "sec:Updating-test-references"

\end_inset

.
\end_layout

\end_deeper
\begin_layout Enumerate
If you did not implement full tex2lyx support of the new feature, add a
 line to 
\begin_inset Flex Code
status collapsed

\begin_layout Plain Layout
src/tex2lyx/TODO.txt
\end_layout

\end_inset

 describing the missing bits.
 Note that it is perfectly fine if you do not add full tex2lyx support for
 a new feature: The updating recommendation above is only issued for the
 syntax of the produced .lyx file.
 It is no problem if some features supported by LyX are still output as
 ERT by tex2lyx, since the problems in the past that resulted in the update
 recommendation were related to mixed version syntax, not ERT.
\end_layout

\begin_layout Section
Backporting new styles to the stable version
\end_layout

\begin_layout Standard
Starting with the stable LyX 2.1 branch, there is a mechanism in place to
 backport new styles to the stable version without the need to update the
 file format.
 The basic idea is that the new style definition is automatically copied
 to the document preamble, so that it can even be used by older minor revisions
 that did not yet include the style.
 To backport a new style to the stable version, the following steps are
 needed:
\end_layout

\begin_layout Enumerate
Add the line 
\begin_inset Flex Code
status collapsed

\begin_layout Plain Layout
ForceLocal -1
\end_layout

\end_inset

 to the style definition in the development version.
\end_layout

\begin_layout Enumerate
Copy the style definition to the stable version, but use 
\begin_inset Flex Code
status collapsed

\begin_layout Plain Layout
ForceLocal 1
\end_layout

\end_inset

 instead.
 If needed adjust the format to the one used by the stable version (see
 the customization manual for details of the layout file format).
\end_layout

\begin_layout Enumerate
For each update of the style in a later stable version, increase the argument
 of 
\begin_inset Flex Code
status collapsed

\begin_layout Plain Layout
ForceLocal
\end_layout

\end_inset

 by one (in the stable version, the development version should not be touched).
\end_layout

\begin_layout Standard
For details about the 
\begin_inset Flex Code
status collapsed

\begin_layout Plain Layout
ForceLocal
\end_layout

\end_inset

 flag see the customization manual.
 No 
\begin_inset Flex Code
status collapsed

\begin_layout Plain Layout
lyx2lyx
\end_layout

\end_inset

 support is needed for backported styles: Since the style of the development
 version has an infinite version number, it will always be used.
 Furthermore, since its version number is less than one, the style will
 not be written anymore to the document header for files saved by the new
 version.
\end_layout

\begin_layout Chapter
Tests
\end_layout

\begin_layout Standard
Automated tests are an important tool to detect bugs and regressions in
 software development.
 Some projects like gcc even require each bug fix to be accompanied by a
 test case for the automatic test suite, that would detect this bug.
 Testing interactive features automatically is of course very hard, but
 core functionality like document import and export can be tested quite
 easily, and some tests of this kind exist.
\end_layout

\begin_layout Section
LyX tests
\end_layout

\begin_layout Standard
Some tests are located in the 
\begin_inset Flex Code
status collapsed

\begin_layout Plain Layout
development/autotests
\end_layout

\end_inset

 subfolder of the LyX source code distribution.
\end_layout

\begin_layout Subsection
Running the tests
\end_layout

\begin_layout Standard
The LyX tests can be run by the commands 
\begin_inset Flex Code
status collapsed

\begin_layout Plain Layout
make test
\end_layout

\end_inset

 (cmake) in the 
\begin_inset Flex Code
status collapsed

\begin_layout Plain Layout
autotests
\end_layout

\end_inset

 subfolder of the build directory.
\begin_inset Note Note
status open

\begin_layout Plain Layout
FIXME: Is this possible with autotools?
\end_layout

\end_inset


\end_layout

\begin_layout Section
tex2lyx tests
\end_layout

\begin_layout Standard
The tex2lyx tests are located in the 
\begin_inset Flex Code
status collapsed

\begin_layout Plain Layout
src/tex2lyx/test
\end_layout

\end_inset

 subfolder of the LyX source code distribution.
 The actual testing is performed by the simple python script 
\begin_inset Flex Code
status collapsed

\begin_layout Plain Layout
src/tex2lyx/test/runtests.py
\end_layout

\end_inset

.
 Each test consists of two files: 
\begin_inset Flex Code
status collapsed

\begin_layout Plain Layout
<test name>.tex
\end_layout

\end_inset

 contains the LaTeX code that should be tested.
 
\begin_inset Flex Code
status collapsed

\begin_layout Plain Layout
<test name>.lyx.lyx
\end_layout

\end_inset

 contains the expected output of tex2lyx.
 When a test is run, the actual produced output is compared with the stored
 reference output.
 The test passes if both are identical.
 The test machinery is also able to generate a file 
\begin_inset Flex Code
status collapsed

\begin_layout Plain Layout
<test name>.lyx.tex
\end_layout

\end_inset

 by exporting the produced .lyx file with LyX again.
 This may be useful for roundtrip comparisons.
\end_layout

\begin_layout Subsection
Running the tests
\end_layout

\begin_layout Standard
The tex2lyx tests can be run by the commands 
\begin_inset Flex Code
status collapsed

\begin_layout Plain Layout
make test
\end_layout

\end_inset

 (cmake) or 
\begin_inset Flex Code
status collapsed

\begin_layout Plain Layout
make alltests
\end_layout

\end_inset

 (autotools) in the 
\begin_inset Flex Code
status collapsed

\begin_layout Plain Layout
src/tex2lyx
\end_layout

\end_inset

 subfolder of the build directory.
 If a test fails, the differences between the expected and actual results
 are output in unified diff format.
\end_layout

\begin_layout Subsection
Updating test references
\begin_inset CommandInset label
LatexCommand label
name "sec:Updating-test-references"

\end_inset


\end_layout

\begin_layout Standard
In some cases a changed tex2lyx output is not a test failure, but wanted,
 e.
\begin_inset space \thinspace{}
\end_inset

g.
\begin_inset space \space{}
\end_inset

if a tex2lyx bug was fixed, or a new feature was added.
 In these cases the stored references need to be updated.
 To do so, call 
\begin_inset Flex Code
status collapsed

\begin_layout Plain Layout
make updatetests
\end_layout

\end_inset

 (autotools) 
\begin_inset Note Note
status open

\begin_layout Plain Layout
FIXME: Add cmake command
\end_layout

\end_inset

 in the 
\begin_inset Flex Code
status collapsed

\begin_layout Plain Layout
src/tex2lyx
\end_layout

\end_inset

 subfolder of the build directory.
 For convenience, this command does also produce re-exported roundtrip .lyx.tex
 files.
 Please examine the changed output carefully before committing the changed
 files to the repository: Since the test machinery does not do a roundtrip
 test .tex 
\begin_inset Formula $\Rightarrow$
\end_inset

 .lyx 
\begin_inset Formula $\Rightarrow$
\end_inset

 .tex, and does not compare the produced dvi or pdf output, it assumes that
 the stored .lyx reference produces correct output if processed by LyX.
 There is only one chance to detect wrong output: before committing a new
 reference.
 Once it is committed, it is quite difficult to verify whether it is correct.
\end_layout

\begin_layout Subsection
Adding a new test
\end_layout

\begin_layout Standard
In many cases tests for new features may be added to one of the existing
 test files, but sometimes this is not possible or not wanted.
 Then a new test file needs to be added:
\end_layout

\begin_layout Enumerate
Create the new file 
\begin_inset Flex Code
status collapsed

\begin_layout Plain Layout
src/tex2lyx/test/<test name>.tex
\end_layout

\end_inset

 and run tex2lyx in roundtrip mode to produce the file 
\begin_inset Flex Code
status collapsed

\begin_layout Plain Layout
src/tex2lyx/test/<test name>.lyx.lyx
\end_layout

\end_inset

.
 This file will be the new reference.
\end_layout

\begin_layout Enumerate
Once you confirmed that the tex2lyx output is correct, add the new files
 to the corresponding lists in 
\begin_inset Flex Code
status collapsed

\begin_layout Plain Layout
src/tex2lyx/test/runtests.py
\end_layout

\end_inset

, 
\begin_inset Flex Code
status collapsed

\begin_layout Plain Layout
src/tex2lyx/Makefile.am
\end_layout

\end_inset

 and 
\begin_inset Flex Code
status collapsed

\begin_layout Plain Layout
src/tex2lyx/test/CMakeLists.txt
\end_layout

\end_inset

.
\end_layout

\begin_layout Enumerate
Commit the changes to the repository, or send a patch to the development
 list and ask for committing if you do not have commit rights.
\end_layout

\end_body
\end_document