SCons / src / engine / SCons / Tool / xgettext.xml

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<tool name="xgettext">
<summary>
This scons tool is a part of scons &t-link-gettext; toolset. It provides
scons interface to <command>xgettext(1)</command>
program, which extracts internationalized messages from source code. The tool
provides &b-POTUpdate; builder to make  <literal>PO</literal>
<emphasis>Template</emphasis> files. 
</summary>
<sets>
POTSUFFIX
POTUPDATE_ALIAS
XGETTEXTCOM
XGETTEXTCOMSTR
XGETTEXTFLAGS
XGETTEXTFROM
XGETTEXTFROMPREFIX
XGETTEXTFROMSUFFIX
XGETTEXTPATH
XGETTEXTPATHPREFIX
XGETTEXTPATHSUFFIX
_XGETTEXTDOMAIN
_XGETTEXTFROMFLAGS
_XGETTEXTPATHFLAGS
</sets>
<uses>
POTDOMAIN
</uses>
</tool>

<builder name="POTUpdate">
<summary>
The builder belongs to &t-link-xgettext; tool. The builder updates target
<literal>POT</literal> file if exists or creates one if it doesn't. The node is
not built by default (i.e. it is <literal>Ignore</literal>d from
<literal>'.'</literal>), but only on demand (i.e.  when given
<literal>POT</literal> file is required or when special alias is invoked). This
builder adds its targe node (<filename>messages.pot</filename>, say) to a
special alias (<literal>pot-update</literal> by default, see
&cv-link-POTUPDATE_ALIAS;) so you can update/create them easily with
<command>scons pot-update</command>. The file is not written until there is no
real change in internationalized messages (or in comments that enter
<literal>POT</literal> file). 

<note> <para>You may see <command>xgettext(1)</command> being invoked by the
&t-link-xgettext; tool even if there is no real change in internationalized
messages (so the <literal>POT</literal> file is not being updated).  This
happens every time  a source file has changed. In such case we invoke
<command>xgettext(1)</command> and compare its output with the content of
<literal>POT</literal> file to decide whether the file should be updated or
not.</para></note>

<emphasis>Example 1.</emphasis>
Let's create <filename>po/</filename> directory and place following
<filename>SConstruct</filename> script there:
<example>
  # SConstruct in 'po/' subdir
  env = Environment( tools = ['default', 'xgettext'] )
  env.POTUpdate(['foo'], ['../a.cpp', '../b.cpp'])
  env.POTUpdate(['bar'], ['../c.cpp', '../d.cpp'])
</example>      
Then invoke scons few times:
<example>
  user@host:$ scons             # Does not create foo.pot nor bar.pot
  user@host:$ scons foo.pot     # Updates or creates foo.pot
  user@host:$ scons pot-update  # Updates or creates foo.pot and bar.pot
  user@host:$ scons -c          # Does not clean foo.pot nor bar.pot.
</example>
the results shall be as the comments above say.

<emphasis>Example 2.</emphasis>
The &b-POTUpdate; builder may be used with no target specified, in which
case default target <filename>messages.pot</filename> will be used. The
default target may also be overriden by setting &cv-link-POTDOMAIN; construction
variable or providing it as an override to &b-POTUpdate; builder:
<example>    
  # SConstruct script
  env = Environment( tools = ['default', 'xgettext'] )
  env['POTDOMAIN'] = "foo"
  env.POTUpdate(source = ["a.cpp", "b.cpp"]) # Creates foo.pot ...
  env.POTUpdate(POTDOMAIN = "bar", source = ["c.cpp", "d.cpp"]) # and bar.pot
</example>

<emphasis>Example 3.</emphasis>
The sources may be specified within separate file, for example
<filename>POTFILES.in</filename>:
<example>      
  # POTFILES.in in 'po/' subdirectory
  ../a.cpp
  ../b.cpp
  # end of file
</example>    
The name of the file (<filename>POTFILES.in</filename>) containing the list of
sources is provided via &cv-link-XGETTEXTFROM;:
<example>      
  # SConstruct file in 'po/' subdirectory
  env = Environment( tools = ['default', 'xgettext'] )
  env.POTUpdate(XGETTEXTFROM = 'POTFILES.in')
</example>    

<emphasis>Example 4.</emphasis>
You may use &cv-link-XGETTEXTPATH; to define source search path. Assume, for
example, that you have files <filename>a.cpp</filename>,
<filename>b.cpp</filename>, <filename>po/SConstruct</filename>,
<filename>po/POTFILES.in</filename>. Then your <literal>POT</literal>-related
files could look as below:
<example>
  # POTFILES.in in 'po/' subdirectory
  a.cpp
  b.cpp
  # end of file
</example>

<example>
  # SConstruct file in 'po/' subdirectory
  env = Environment( tools = ['default', 'xgettext'] )
  env.POTUpdate(XGETTEXTFROM = 'POTFILES.in', XGETTEXTPATH='../')
</example>

<emphasis>Example 5.</emphasis>
Multiple search directories may be defined within a list, i.e.
<literal>XGETTEXTPATH = ['dir1', 'dir2', ...]</literal>. The order in the list
determines the search order of source files. The path to the first file found
is used.

Let's create <filename>0/1/po/SConstruct</filename> script:
<example>
  # SConstruct file in '0/1/po/' subdirectory
  env = Environment( tools = ['default', 'xgettext'] )
  env.POTUpdate(XGETTEXTFROM = 'POTFILES.in', XGETTEXTPATH=['../', '../../'])
</example>
and <filename>0/1/po/POTFILES.in</filename>:
<example>
  # POTFILES.in in '0/1/po/' subdirectory
  a.cpp
  # end of file
</example>
Write two <filename>*.cpp</filename> files, the first one is
<filename>0/a.cpp</filename>:
<example>
  /* 0/a.cpp */
  gettext("Hello from ../../a.cpp")
</example>
and the second is <filename>0/1/a.cpp</filename>:
<example>
  /* 0/1/a.cpp */
  gettext("Hello from ../a.cpp")
</example>
then run scons. You'll obtain <literal>0/1/po/messages.pot</literal> with the
message <literal>"Hello from ../a.cpp"</literal>. When you reverse order in
<varname>$XGETTEXTFOM</varname>, i.e. when you write SConscript as
<example>
  # SConstruct file in '0/1/po/' subdirectory
  env = Environment( tools = ['default', 'xgettext'] )
  env.POTUpdate(XGETTEXTFROM = 'POTFILES.in', XGETTEXTPATH=['../../', '../'])
</example> then the <filename>messages.pot</filename> will contain
<literal>msgid "Hello from ../../a.cpp"</literal> line and not 
<literal>msgid "Hello from ../a.cpp"</literal>.

</summary>

</builder>

<!-- %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%% -->
<cvar name="POTSUFFIX">
<summary>
Suffix used for PO Template files (default: <literal>'.pot'</literal>).
See &t-link-xgettext; tool and &b-link-POTUpdate; builder.
</summary>
</cvar>
<!-- %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%% -->
<cvar name="POTUPDATE_ALIAS">
<summary>
Name of the common phony target for all PO Templates created with
&b-link-POUpdate; (default: <literal>'pot-update'</literal>).
See &t-link-xgettext; tool and &b-link-POTUpdate; builder.
</summary>
</cvar>
<!-- %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%% -->
<cvar name="XGETTEXT">
<summary>
Path to <command>xgettext(1)</command> program (found via
<function>Detect()</function>).
See &t-link-xgettext; tool and &b-link-POTUpdate; builder.
</summary>
</cvar>
<!-- %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%% -->
<cvar name="XGETTEXTCOM">
<summary>
Complete xgettext command line.
See &t-link-xgettext; tool and &b-link-POTUpdate; builder.
</summary>
</cvar>
<!-- %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%% -->
<cvar name="XGETTEXTCOMSTR">
<summary>
A string that is shown when <command>xgettext(1)</command> command is invoked
(default: <literal>''</literal>, which means "print &cv-link-XGETTEXTCOM;").
See &t-link-xgettext; tool and &b-link-POTUpdate; builder.
</summary>
</cvar>
<!-- %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%% -->
<cvar name="XGETTEXTFLAGS">
<summary>
Additional flags to <command>xgettext(1)</command>.
See &t-link-xgettext; tool and &b-link-POTUpdate; builder.
</summary>
</cvar>
<!-- %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%% -->
<cvar name="XGETTEXTFROM">
<summary>
Name of file containing list of <command>xgettext(1)</command>'s source
files. Autotools' users know this as <filename>POTFILES.in</filename> so they
will in most cases set <literal>XGETTEXTFROM="POTFILES.in"</literal> here.
The &cv-XGETTEXTFROM; files have same syntax and semantics as the well known
GNU <filename>POTFILES.in</filename>.
See &t-link-xgettext; tool and &b-link-POTUpdate; builder.
</summary>
</cvar>
<!-- %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%% -->
<cvar name="XGETTEXTPATH">
<summary>
List of directories, there <command>xgettext(1)</command> will look for
source files (default: <literal>[]</literal>).
<note><para>
This variable works only together with &cv-link-XGETTEXTFROM;
</para></note>
See also &t-link-xgettext; tool and &b-link-POTUpdate; builder.
</summary>
</cvar>
<!-- %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%% -->
<cvar name="XGETTEXTPATHPREFIX">
<summary>
This flag is used to add single search path to
<command>xgettext(1)</command>'s commandline (default:
<literal>'-D'</literal>).
</summary>
</cvar>
<!-- %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%% -->
<cvar name="XGETTEXTPATHSUFFIX">
<summary>
(default: <literal>''</literal>)
</summary>
</cvar>
<!-- %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%% -->
<cvar name="XGETTEXTFROMPREFIX">
<summary>
This flag is used to add single &cv-link-XGETTEXTFROM; file to
<command>xgettext(1)</command>'s commandline (default:
<literal>'-f'</literal>).
</summary>
</cvar>
<!-- %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%% -->
<cvar name="XGETTEXTFROMSUFFIX">
<summary>
(default: <literal>''</literal>)
</summary>
</cvar>
<!-- %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%% -->
<cvar name="_XGETTEXTDOMAIN">
<summary>
Internal "macro". Generates <command>xgettext</command> domain name
form source and target (default: <literal>'${TARGET.filebase}'</literal>).
</summary>
</cvar>
<!-- %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%% -->
<cvar name="_XGETTEXTFROMFLAGS">
<summary>
Internal "macro". Genrates list of <literal>-D&lt;dir&gt;</literal> flags
from the &cv-link-XGETTEXTPATH; list.
</summary>
</cvar>
<!-- %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%% -->
<cvar name="_XGETTEXTPATHFLAGS">
<summary>
Internal "macro". Generates list of <literal>-f&lt;file&gt;</literal> flags
from &cv-link-XGETTEXTFROM;.
</summary>
</cvar>

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