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Updating Existing PO Files

Invoking the tupdate Program

tupdate --help
tupdate --version
tupdate new old

File new is the last created PO file (generally by xgettext). It need not contain any translations. File old is the PO file including the old translations which will be taken over to the newly created file as long as they still match.

When English messages change in the programs, this is reflected in the PO file as extracted by xgettext. In large messages, that can be hard to detect, and will obviously result in an incomplete translation. One of the virtues of tupdate is that it detects such changes, saving the previous translation into a PO file comment, so marking the entry as obsolete, and giving the modified string with an empty translation, that is, marking the entry as untranslated.

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.

Find the next untranslated entry.
Find the previous untranslated entry.
Turn the current entry into an untranslated one.

The commands e (po-next-empty-entry) and M-e (po-previous-empty) 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.

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 tupdate 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.

Find the next obsolete entry.
Find the previous obsolete entry.
Make an active entry obsolete, or zap out an obsolete entry.

The commands M-n (po-next-obsolete-entry) and M-p (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. The commands M-SPC and M-DEL are synonymous to M-n and M-p, respectively.

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 z (po-fade-out-entry) pushes the current entry a little further towards annihilation. If the entry is active, then the entry is merely commented out. 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 catched 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 a error diagnosed mechanically or reported by a user, the translator have to resort to using the following commands for modifying the translations.

Interactively edit the translation.
Reinitialize the translation with the original, untranslated string.
Save the translation on the kill ring, and delete it.
Save the translation on the kill ring, without deleting it.
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 regular Emacs command C-] (abort-recursive-edit) to merely get rid of edition, while preserving the original translation. 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.

While editing her translation, the translator should pay attention at not inserting unwanted RET (carriage returns) characters at the end of the translated string if those are not meant to be there, or removing such characters when they are required. Since these characters are not visible in the editing buffer, they are easily to introduce 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, and browsing at will. The edited entry will be recovered as soon as the edit ceases, because this 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 aborts the current edit, or else, by inviting her to finish the current edit prior to any other modification.

The command TAB (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.

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 mother tongue 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 M-SPC, hoping to find some translation corresponding to the unmodified string. Once found, she uses the z command for deleting the obsolete entry, knowing that z also kills the translation, that is, pushes the translation on the kill ring. Then, l 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 e, 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 comfortable to become more 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. Memory forgets!

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

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

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

The command M-RET (po-edit-comment) opens a new Emacs window containing a copy of the translator comments the current PO file entry. If there is no such comments, PO mode understands that the translator wants to add a comment to the entry, and she is presented 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. The command # also has the same effect as M-RET, and might be easier to type. Once in the editing window, the keys C-c C-c allow the translator to tell she is finished with editing the comment.

The command M-k (po-kill-comment) get rid of all translator comments, while saving those comments on the kill ring. The command M-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 M-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 comments for documenting 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 will want to quote the previous translation in her translator comments. For doing 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 just 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) for getting the previous translation where she likes.

Consulting Auxiliary PO Files

An incoming feature of PO mode should help the knowledgeable translator to take advantage of translations already achieved in other languages she just happens to know, by providing these other language translation as additional context for her own work. Each PO file existing for the same package the translator is working on, but targeted to a different mother tongue language, is called an auxiliary PO file. Commands will exist for declaring and handling auxiliary PO files, and also for showing contexts for the entry under work. For this to work fully, all auxiliary PO files will have to be normalized.

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