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# Updating Existing PO Files

## Invoking the `msgmerge` Program

## Translated Entries

Each PO file entry for which the `msgstr` field has been filled with a translation, and which is not marked as fuzzy (see section Fuzzy Entries), is a said to be a translated entry. Only translated entries will later be compiled by GNU `msgfmt` and become usable in programs. Other entry types will be excluded; translation will not occur for them.

Some commands are more specifically related to translated entry processing.

`t`
  Find the next translated entry.
`M-t`
  Find the previous translated entry.

The commands `t` (`po-next-translated-entry`) and `M-t` (`po-previous-transted-entry`) move forwards or backwards, chasing for an translated entry. If none is found, the search is extended and wraps around in the PO file buffer.

Translated entries usually result from the translator having edited in a translation for them, section Modifying Translations. However, if the variable `po-auto-fuzzy-on-edit` is not `nil`, the entry having received a new translation first becomes a fuzzy entry, which ought to be later unfuzzied before becoming an official, genuine translated entry. See section Fuzzy Entries.

## Fuzzy Entries

Each PO file entry may have a set of attributes, which are qualities given an name and explicitly associated with the entry translation, using a special system comment. One of these attributes has the name `fuzzy`, and entries having this attribute are said to have a fuzzy translation. They are called fuzzy entries, for short.

Fuzzy entries, even if they account for translated entries for most other purposes, usually call for revision by the translator. Those may be produced by applying the program `msgmerge` to update an older translated PO files according to a new PO template file, when this tool hypothesises that some new `msgid` has been modified only slightly out of an older one, and chooses to pair what it thinks to be the old translation for the new modified entry. The slight alteration in the original string (the `msgid` string) should often be reflected in the translated string, and this requires the intervention of the translator. For this reason, `msgmerge` might mark some entries as being fuzzy.

Also, the translator may decide herself to mark an entry as fuzzy for her own convenience, when she wants to remember that the entry has to be later revisited. So, some commands are more specifically related to fuzzy entry processing.

`f`
  Find the next fuzzy entry.
`M-f`
  Find the previous fuzzy entry.
`TAB`
  Remove the fuzzy attribute of the current entry.

The commands `f` (`po-next-fuzzy`) and `M-f` (`po-previous-fuzzy`) move forwards or backwards, chasing for a fuzzy entry. If none is found, the search is extended and wraps around in the PO file buffer.

The command `TAB` (`po-unfuzzy`) removes the fuzzy attribute associated with an entry, usually leaving it translated. Further, if the variable `po-auto-select-on-unfuzzy` has not the `nil` value, the `TAB` command will automatically chase for another interesting entry to work on. The initial value of `po-auto-select-on-unfuzzy` is `nil`.

The initial value of `po-auto-fuzzy-on-edit` is `nil`. However, if the variable `po-auto-fuzzy-on-edit` is set to `t`, any entry edited through the `RET` command is marked fuzzy, as a way to ensure some kind of double check, later. In this case, the usual paradigm is that an entry becomes fuzzy (if not already) whenever the translator modifies it. If she is satisfied with the translation, she then uses `TAB` to pick another entry to work on, clearing the fuzzy attribute on the same blow. If she is not satisfied yet, she merely uses `SPC` to chase another entry, leaving the entry fuzzy.

The translator may also use the `DEL` command (`po-fade-out-entry`) over any translated entry to mark it as being fuzzy, when she wants to easily leave a trace she wants to later return working at this entry.

Also, when time comes to quit working on a PO file buffer with the `q` command, the translator is asked for confirmation, if fuzzy string still exists.

## Untranslated Entries

When `xgettext` originally creates a PO file, unless told otherwise, it initializes the `msgid` field with the untranslated string, and leaves the `msgstr` string to be empty. Such entries, having an empty translation, are said to be untranslated entries. Later, when the programmer slightly modifies some string right in the program, this change is later reflected in the PO file by the appearance of a new untranslated entry for the modified string.

The usual commands moving from entry to entry consider untranslated entries on the same level as active entries. Untranslated entries are easily recognizable by the fact they end with ``msgstr ""'`.

The work of the translator might be (quite naively) seen as the process of seeking after an untranslated entry, editing a translation for it, and repeating these actions until no untranslated entries remain. Some commands are more specifically related to untranslated entry processing.

`u`
  Find the next untranslated entry.
`M-u`
  Find the previous untranslated entry.
`k`
  Turn the current entry into an untranslated one.

The commands `u` (`po-next-untranslated-entry`) and `M-u` (`po-previous-untransted-entry`) move forwards or backwards, chasing for an untranslated entry. If none is found, the search is extended and wraps around in the PO file buffer.

An entry can be turned back into an untranslated entry by merely emptying its translation, using the command `k` (`po-kill-msgstr`). See section Modifying Translations.

Also, when time comes to quit working on a PO file buffer with the `q` command, the translator is asked for confirmation, if some untranslated string still exists.

## Obsolete Entries

By obsolete PO file entries, we mean those entries which are commented out, usually by `msgmerge` when it found that the translation is not needed anymore by the package being localized.

The usual commands moving from entry to entry consider obsolete entries on the same level as active entries. Obsolete entries are easily recognizable by the fact that all their lines start with `#`, even those lines containing `msgid` or `msgstr`.

Commands exist for emptying the translation or reinitializing it to the original untranslated string. Commands interfacing with the kill ring may force some previously saved text into the translation. The user may interactively edit the translation. All these commands may apply to obsolete entries, carefully leaving the entry obsolete after the fact.

Moreover, some commands are more specifically related to obsolete entry processing.

`o`
  Find the next obsolete entry.
`M-o`
  Find the previous obsolete entry.
`DEL`
  Make an active entry obsolete, or zap out an obsolete entry.

The commands `o` (`po-next-obsolete-entry`) and `M-o` (`po-previous-obsolete-entry`) move forwards or backwards, chasing for an obsolete entry. If none is found, the search is extended and wraps around in the PO file buffer.

PO mode does not provide ways for un-commenting an obsolete entry and making it active, because this would reintroduce an original untranslated string which does not correspond to any marked string in the program sources. This goes with the philosophy of never introducing useless `msgid` values.

However, it is possible to comment out an active entry, so making it obsolete. GNU `gettext` utilities will later react to the disappearance of a translation by using the untranslated string. The command `DEL` (`po-fade-out-entry`) pushes the current entry a little further towards annihilation. If the entry is active (it is a translated entry), then it is first made fuzzy. If it is already fuzzy, then the entry is merely commented out, with confirmation. If the entry is already obsolete, then it is completely deleted from the PO file. It is easy to recycle the translation so deleted into some other PO file entry, usually one which is untranslated. See section Modifying Translations.

Here is a quite interesting problem to solve for later development of PO mode, for those nights you are not sleepy. The idea would be that PO mode might become bright enough, one of these days, to make good guesses at retrieving the most probable candidate, among all obsolete entries, for initializing the translation of a newly appeared string. I think it might be a quite hard problem to do this algorithmically, as we have to develop good and efficient measures of string similarity. Right now, PO mode completely lets the decision to the translator, when the time comes to find the adequate obsolete translation, it merely tries to provide handy tools for helping her to do so.

## Modifying Translations

PO mode prevents direct edition of the PO file, by the usual means Emacs give for altering a buffer's contents. By doing so, it pretends helping the translator to avoid little clerical errors about the overall file format, or the proper quoting of strings, as those errors would be easily made. Other kinds of errors are still possible, but some may be caught and diagnosed by the batch validation process, which the translator may always trigger by the `V` command. For all other errors, the translator has to rely on her own judgment, and also on the linguistic reports submitted to her by the users of the translated package, having the same mother tongue.

When the time comes to create a translation, correct an error diagnosed mechanically or reported by a user, the translators have to resort to using the following commands for modifying the translations.

`RET`
  Interactively edit the translation.
`LFD`
  Reinitialize the translation with the original, untranslated string.
`k`
  Save the translation on the kill ring, and delete it.
`w`
  Save the translation on the kill ring, without deleting it.
`y`
  Replace the translation, taking the new from the kill ring.

The command `RET` (`po-edit-msgstr`) opens a new Emacs window containing a copy of the translation taken from the current PO file entry, all ready for edition, fully modifiable and with the complete extent of GNU Emacs modifying commands. The string is presented to the translator expunged of all quoting marks, and she will modify the unquoted string in this window to heart's content. Once done, the regular Emacs command `M-C-c` (`exit-recursive-edit`) may be used to return the edited translation into the PO file, replacing the original translation. The keys `C-c C-c` are bound so they have the same effect as `M-C-c`.

If the translator becomes unsatisfied with her translation to the extent she prefers keeping the translation which was existent prior to the `RET` command, she may use the standard Emacs command `C-]` (`abort-recursive-edit`) to merely get rid of edition, while preserving the original translation. The keys `C-c C-k` are bound so they have the same effect as `C-]`. Another way would be for her to exit normally with `C-c C-c`, then type `U` once for undoing the whole effect of last edition.

Functions found on `po-subedit-mode-hook`, if any, are executed after the string has been inserted in the edit buffer and before recursive edit is entered.

While editing her translation, the translator should pay attention to not inserting unwanted ``RET`` (carriage returns) characters at the end of the translated string if those are not meant to be there, or to removing such characters when they are required. Since these characters are not visible in the editing buffer, they are easily introduced by mistake. To help her, ``RET`` automatically puts the character `<` at the end of the string being edited, but this `<` is not really part of the string. On exiting the editing window with `C-c C-c`, PO mode automatically removes such `<` and all whitespace added after it. If the translator adds characters after the terminating `<`, it looses its delimiting property and integrally becomes part of the string. If she removes the delimiting `<`, then the edited string is taken as is, with all trailing newlines, even if invisible. Also, if the translated string ought to end itself with a genuine `<`, then the delimiting `<` may not be removed; so the string should appear, in the editing window, as ending with two `<` in a row.

When a translation (or a comment) is being edited, the translator may move the cursor back into the PO file buffer and freely move to other entries, browsing at will. The edited entry will be recovered as soon as the edit ceases, because it is this entry only which is being modified. If, with an edition still opened, the translator wanders in the PO file buffer, she cannot modify any other entry. If she tries to, PO mode will react by suggesting that she abort the current edit, or else, by inviting her to finish the current edit prior to any other modification.

The command `LFD` (`po-msgid-to-msgstr`) initializes, or reinitializes the translation with the original string. This command is normally used when the translator wants to redo a fresh translation of the original string, disregarding any previous work.

It is possible to arrange so, whenever editing an untranslated entry, the `LFD` command be automatically executed. If you set `po-auto-edit-with-msgid` to `t`, the translation gets initialised with the original string, in case none exist already. The default value for `po-auto-edit-with-msgid` is `nil`.

In fact, whether it is best to start a translation with an empty string, or rather with a copy of the original string, is a matter of taste or habit. Sometimes, the source language and the target language are so different that is simply best to start writing on an empty page. At other times, the source and target languages are so close that it would be a waste to retype a number of words already being written in the original string. A translator may also like having the original string right under her eyes, as she will progressively overwrite the original text with the translation, even if this requires some extra editing work to get rid of the original.

The command `k` (`po-kill-msgstr`) merely empties the translation string, so turning the entry into an untranslated one. But while doing so, its previous contents is put apart in a special place, known as the kill ring. The command `w` (`po-kill-ring-save-msgstr`) has also the effect of taking a copy of the translation onto the kill ring, but it otherwise leaves the entry alone, and does not remove the translation from the entry. Both commands use exactly the Emacs kill ring, which is shared between buffers, and which is well known already to GNU Emacs lovers.

The translator may use `k` or `w` many times in the course of her work, as the kill ring may hold several saved translations. From the kill ring, strings may later be reinserted in various Emacs buffers. In particular, the kill ring may be used for moving translation strings between different entries of a single PO file buffer, or if the translator is handling many such buffers at once, even between PO files.

To facilitate exchanges with buffers which are not in PO mode, the translation string put on the kill ring by the `k` command is fully unquoted before being saved: external quotes are removed, multi-lines strings are concatenated, and backslashed escaped sequences are turned into their corresponding characters. In the special case of obsolete entries, the translation is also uncommented prior to saving.

The command `y` (`po-yank-msgstr`) completely replaces the translation of the current entry by a string taken from the kill ring. Following GNU Emacs terminology, we then say that the replacement string is yanked into the PO file buffer. See section `Yanking' in The Emacs Editor. The first time `y` is used, the translation receives the value of the most recent addition to the kill ring. If `y` is typed once again, immediately, without intervening keystrokes, the translation just inserted is taken away and replaced by the second most recent addition to the kill ring. By repeating `y` many times in a row, the translator may travel along the kill ring for saved strings, until she finds the string she really wanted.

When a string is yanked into a PO file entry, it is fully and automatically requoted for complying with the format PO files should have. Further, if the entry is obsolete, PO mode then appropriately push the inserted string inside comments. Once again, translators should not burden themselves with quoting considerations besides, of course, the necessity of the translated string itself respective to the program using it.

Note that `k` or `w` are not the only commands pushing strings on the kill ring, as almost any PO mode command replacing translation strings (or the translator comments) automatically save the old string on the kill ring. The main exceptions to this general rule are the yanking commands themselves.

To better illustrate the operation of killing and yanking, let's use an actual example, taken from a common situation. When the programmer slightly modifies some string right in the program, his change is later reflected in the PO file by the appearance of a new untranslated entry for the modified string, and the fact that the entry translating the original or unmodified string becomes obsolete. In many cases, the translator might spare herself some work by retrieving the unmodified translation from the obsolete entry, then initializing the untranslated entry `msgstr` field with this retrieved translation. Once this done, the obsolete entry is not wanted anymore, and may be safely deleted.

When the translator finds an untranslated entry and suspects that a slight variant of the translation exists, she immediately uses `m` to mark the current entry location, then starts chasing obsolete entries with `o`, hoping to find some translation corresponding to the unmodified string. Once found, she uses the `DEL` command for deleting the obsolete entry, knowing that `DEL` also kills the translation, that is, pushes the translation on the kill ring. Then, `r` returns to the initial untranslated entry, `y` then yanks the saved translation right into the `msgstr` field. The translator is then free to use ``RET`` for fine tuning the translation contents, and maybe to later use `u`, then `m` again, for going on with the next untranslated string.

When some sequence of keys has to be typed over and over again, the translator may find it useful to become better acquainted with the GNU Emacs capability of learning these sequences and playing them back under request. See section `Keyboard Macros' in The Emacs Editor.

## Modifying Comments

Any translation work done seriously will raise many linguistic difficulties, for which decisions have to be made, and the choices further documented. These documents may be saved within the PO file in form of translator comments, which the translator is free to create, delete, or modify at will. These comments may be useful to herself when she returns to this PO file after a while.

Comments not having whitespace after the initial ``#'`, for example, those beginning with ``#.'` or ``#:'`, are not translator comments, they are exclusively created by other `gettext` tools. So, the commands below will never alter such system added comments, they are not meant for the translator to modify. See section The Format of PO Files.

The following commands are somewhat similar to those modifying translations, so the general indications given for those apply here. See section Modifying Translations.

`#`
  Interactively edit the translator comments.
`K`
  Save the translator comments on the kill ring, and delete it.
`W`
  Save the translator comments on the kill ring, without deleting it.
`Y`
  Replace the translator comments, taking the new from the kill ring.

These commands parallel PO mode commands for modifying the translation strings, and behave much the same way as they do, except that they handle this part of PO file comments meant for translator usage, rather than the translation strings. So, if the descriptions given below are slightly succinct, it is because the full details have already been given. See section Modifying Translations.

The command `#` (`po-edit-comment`) opens a new Emacs window containing a copy of the translator comments on the current PO file entry. If there are no such comments, PO mode understands that the translator wants to add a comment to the entry, and she is presented with an empty screen. Comment marks (`#`) and the space following them are automatically removed before edition, and reinstated after. For translator comments pertaining to obsolete entries, the uncommenting and recommenting operations are done twice. Once in the editing window, the keys `C-c C-c` allow the translator to tell she is finished with editing the comment.

Functions found on `po-subedit-mode-hook`, if any, are executed after the string has been inserted in the edit buffer and before recursive edit is entered.

The command `K` (`po-kill-comment`) get rid of all translator comments, while saving those comments on the kill ring. The command `W` (`po-kill-ring-save-comment`) takes a copy of the translator comments on the kill ring, but leaves them undisturbed in the current entry. The command `Y` (`po-yank-comment`) completely replaces the translator comments by a string taken at the front of the kill ring. When this command is immediately repeated, the comments just inserted are withdrawn, and replaced by other strings taken along the kill ring.

On the kill ring, all strings have the same nature. There is no distinction between translation strings and translator comments strings. So, for example, let's presume the translator has just finished editing a translation, and wants to create a new translator comment to document why the previous translation was not good, just to remember what was the problem. Foreseeing that she will do that in her documentation, the translator may want to quote the previous translation in her translator comments. To do so, she may initialize the translator comments with the previous translation, still at the head of the kill ring. Because editing already pushed the previous translation on the kill ring, she merely has to type `M-w` prior to `#`, and the previous translation will be right there, all ready for being introduced by some explanatory text.

On the other hand, presume there are some translator comments already and that the translator wants to add to those comments, instead of wholly replacing them. Then, she should edit the comment right away with `#`. Once inside the editing window, she can use the regular GNU Emacs commands `C-y` (`yank`) and `M-y` (`yank-pop`) to get the previous translation where she likes.

## Consulting Auxiliary PO Files

PO mode is able to help the knowledgeable translator, being fluent in many languages, at taking advantage of translations already achieved in other languages she just happens to know. It provides these other language translations as additional context for her own work. Moreover, it has features to ease the production of translations for many languages at once, for translators preferring to work in this way.

An auxiliary PO file is an existing PO file meant for the same package the translator is working on, but targeted to a different mother tongue language. Commands exist for declaring and handling auxiliary PO files, and also for showing contexts for the entry under work.

Here are the auxiliary file commands available in PO mode.

`a`
  Seek auxiliary files for another translation for the same entry.
`M-a`
  Switch to a particular auxiliary file.
`A`
  Declare this PO file as an auxiliary file.
`M-A`
  Remove this PO file from the list of auxiliary files.

Command `A` (`po-consider-as-auxiliary`) adds the current PO file to the list of auxiliary files, while command `M-A` (`po-ignore-as-auxiliary` just removes it.

The command `a` (`po-cycle-auxiliary`) seeks all auxiliary PO files, round-robin, searching for a translated entry in some other language having an `msgid` field identical as the one for the current entry. The found PO file, if any, takes the place of the current PO file in the display (its window gets on top). Before doing so, the current PO file is also made into an auxiliary file, if not already. So, `a` in this newly displayed PO file will seek another PO file, and so on, so repeating `a` will eventually yield back the original PO file.

The command `M-a` (`po-select-auxiliary`) asks the translator for her choice of a particular auxiliary file, with completion, and then switches to that selected PO file. The command also checks if the selected file has an `msgid` field identical as the one for the current entry, and if yes, this entry becomes current. Otherwise, the cursor of the selected file is left undisturbed.

For all this to work fully, auxiliary PO files will have to be normalized, in that way that `msgid` fields should be written exactly the same way. It is possible to write `msgid` fields in various ways for representing the same string, different writing would break the proper behaviour of the auxiliary file commands of PO mode. This is not expected to be much a problem in practice, as most existing PO files have their `msgid` entries written by the same GNU `gettext` tools.

However, PO files initially created by PO mode itself, while marking strings in source files, are normalised differently. So are PO files resulting of the the ``M-x normalize'` command. Until these discrepancies between PO mode and other GNU `gettext` tools get fully resolved, the translator should stay aware of normalisation issues.

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