Python i18n API. Many thanks to Campbell and Brecht for the reviews and suggestions!

This commit adds:
* A new bpy.app.translations module giving some info about locales/translation stuff (current active locale, all locales currently known by blender, all translation contexts currently defined, etc.).

* The ability for addons to feature translations, using the (un)register functions of above module.

* Also cleans up "translate py string when storing into RNA prop" by removing "PROP_TRANSLATE" string's subtype, and adding a PROP_STRING_PY_TRANSLATE flag instead (this way it is no more exposed to python...).

Addon translations work with py dictionaries: each addon features a dict {lang: {(context, message): translation, ...}, ...}, which is registered when the addon is enabled (and unregistered when disabled). 

Then, when a key (context, message) is not found in regular mo catalog, a cache dict for current locale is built from all registered addon translations, and key is searched in it.

Note: currently addons writers have to do all the work by hand, will add something (probably extend "edit translation" addon) to automate messages extraction from addons soon(ish)! To get a look to expected behavior from addons, have a look at render_copy_settings/__init__.py and render_copy_settings/translations.py (rather stupid example currently, but...). Once we have a complete process, I'll also update relevant wiki pages.

5 files changed, 138 insertions, 7 deletions

diff --git a/source/blender/blenfont/BLF_translation.h b/source/blender/blenfont/BLF_translation.h
index 0832907d1d9..59f66cae727 100644
--- a/source/blender/blenfont/BLF_translation.h
+++ b/source/blender/blenfont/BLF_translation.h
@@ -51,6 +51,13 @@ void BLF_lang_set(const char *);
 /* Get the current locale (short code, e.g. es_ES). */
 const char *BLF_lang_get(void);
 
+/* Get locale's elements (if relevant pointer is not NULL and element actually exists, e.g. if there is no variant,
+ * *variant and *language_variant will always be NULL).
+ * Non-null elements are always MEM_mallocN'ed, it's the caller's responsibility to free them. 
+ */
+void BLF_locale_explode(const char *locale, char **language, char **country, char **variant,
+                        char **language_country, char **language_variant);
+
 /* Get EnumPropertyItem's for translations menu. */
 struct EnumPropertyItem *BLF_RNA_lang_enum_properties(void);
 
@@ -143,4 +150,54 @@ const char *BLF_translate_do_tooltip(const char *msgctxt, const char *msgid);
 #define BLF_I18NCONTEXT_ID_MOVIECLIP            "MovieClip"
 #define BLF_I18NCONTEXT_ID_MASK                 "Mask"
 
-#endif /* __BLF_TRANSLATION_H__ */
+/* Helper for bpy.app.i18n object... */
+typedef struct
+{
+	const char *c_id;
+	const char *py_id;
+	const char *value;
+} BLF_i18n_contexts_descriptor;
+
+#define BLF_I18NCONTEXTS_ITEM(ctxt_id, py_id) {#ctxt_id, py_id, ctxt_id}
+
+#define BLF_I18NCONTEXTS_DESC {                                                                                         \
+	BLF_I18NCONTEXTS_ITEM(BLF_I18NCONTEXT_DEFAULT, "default"),                                                         \
+	BLF_I18NCONTEXTS_ITEM(BLF_I18NCONTEXT_OPERATOR_DEFAULT, "operator_default"),                                       \
+	BLF_I18NCONTEXTS_ITEM(BLF_I18NCONTEXT_ID_ACTION, "id_action"),                                                     \
+	BLF_I18NCONTEXTS_ITEM(BLF_I18NCONTEXT_ID_ARMATURE, "id_armature"),                                                 \
+	BLF_I18NCONTEXTS_ITEM(BLF_I18NCONTEXT_ID_BRUSH, "id_brush"),                                                       \
+	BLF_I18NCONTEXTS_ITEM(BLF_I18NCONTEXT_ID_CAMERA, "id_camera"),                                                     \
+	BLF_I18NCONTEXTS_ITEM(BLF_I18NCONTEXT_ID_CURVE, "id_curve"),                                                       \
+	BLF_I18NCONTEXTS_ITEM(BLF_I18NCONTEXT_ID_GPENCIL, "id_gpencil"),                                                   \
+	BLF_I18NCONTEXTS_ITEM(BLF_I18NCONTEXT_ID_GROUP, "id_group"),                                                       \
+	BLF_I18NCONTEXTS_ITEM(BLF_I18NCONTEXT_ID_ID, "id_id"),                                                             \
+	BLF_I18NCONTEXTS_ITEM(BLF_I18NCONTEXT_ID_IMAGE, "id_image"),                                                       \
+	/*BLF_I18NCONTEXTS_ITEM(BLF_I18NCONTEXT_ID_IPO, "id_ipo"),*/                                                       \
+	BLF_I18NCONTEXTS_ITEM(BLF_I18NCONTEXT_ID_SHAPEKEY, "id_shapekey"),                                                 \
+	BLF_I18NCONTEXTS_ITEM(BLF_I18NCONTEXT_ID_LAMP, "id_lamp"),                                                         \
+	BLF_I18NCONTEXTS_ITEM(BLF_I18NCONTEXT_ID_LIBRARY, "id_library"),                                                   \
+	BLF_I18NCONTEXTS_ITEM(BLF_I18NCONTEXT_ID_LATTICE, "id_lattice"),                                                   \
+	BLF_I18NCONTEXTS_ITEM(BLF_I18NCONTEXT_ID_MATERIAL, "id_material"),                                                 \
+	BLF_I18NCONTEXTS_ITEM(BLF_I18NCONTEXT_ID_METABALL, "id_metaball"),                                                 \
+	BLF_I18NCONTEXTS_ITEM(BLF_I18NCONTEXT_ID_MESH, "id_mesh"),                                                         \
+	BLF_I18NCONTEXTS_ITEM(BLF_I18NCONTEXT_ID_NODETREE, "id_nodetree"),                                                 \
+	BLF_I18NCONTEXTS_ITEM(BLF_I18NCONTEXT_ID_OBJECT, "id_object"),                                                     \
+	BLF_I18NCONTEXTS_ITEM(BLF_I18NCONTEXT_ID_PARTICLESETTINGS, "id_particlesettings"),                                 \
+	BLF_I18NCONTEXTS_ITEM(BLF_I18NCONTEXT_ID_SCENE, "id_scene"),                                                       \
+	BLF_I18NCONTEXTS_ITEM(BLF_I18NCONTEXT_ID_SCREEN, "id_screen"),                                                     \
+	BLF_I18NCONTEXTS_ITEM(BLF_I18NCONTEXT_ID_SEQUENCE, "id_sequence"),                                                 \
+	BLF_I18NCONTEXTS_ITEM(BLF_I18NCONTEXT_ID_SPEAKER, "id_speaker"),                                                   \
+	BLF_I18NCONTEXTS_ITEM(BLF_I18NCONTEXT_ID_SOUND, "id_sound"),                                                       \
+	BLF_I18NCONTEXTS_ITEM(BLF_I18NCONTEXT_ID_TEXTURE, "id_texture"),                                                   \
+	BLF_I18NCONTEXTS_ITEM(BLF_I18NCONTEXT_ID_TEXT, "id_text"),                                                         \
+	BLF_I18NCONTEXTS_ITEM(BLF_I18NCONTEXT_ID_VFONT, "id_vfont"),                                                       \
+	BLF_I18NCONTEXTS_ITEM(BLF_I18NCONTEXT_ID_WORLD, "id_world"),                                                       \
+	BLF_I18NCONTEXTS_ITEM(BLF_I18NCONTEXT_ID_WINDOWMANAGER, "id_windowmanager"),                                       \
+	BLF_I18NCONTEXTS_ITEM(BLF_I18NCONTEXT_ID_MOVIECLIP, "id_movieclip"),                                               \
+	BLF_I18NCONTEXTS_ITEM(BLF_I18NCONTEXT_ID_MASK, "id_mask"),                                                         \
+	{NULL, NULL, NULL}                                                                                                 \
+}
+
+//#undef _BLF_I18NCONTEXTS_ITEM
+
+#endif /* __BLF_TRANSLATION_H__ */
\ No newline at end of file
diff --git a/source/blender/blenfont/CMakeLists.txt b/source/blender/blenfont/CMakeLists.txt
index 90baef14a74..7bb80c34323 100644
--- a/source/blender/blenfont/CMakeLists.txt
+++ b/source/blender/blenfont/CMakeLists.txt
@@ -29,6 +29,7 @@ set(INC
 	../editors/include
 	../makesdna
 	../makesrna
+	../python
 	../imbuf
 	../../../intern/guardedalloc
 	../../../intern/locale
diff --git a/source/blender/blenfont/SConscript b/source/blender/blenfont/SConscript
index a6ea724a51f..d1ef181f75c 100644
--- a/source/blender/blenfont/SConscript
+++ b/source/blender/blenfont/SConscript
@@ -31,7 +31,7 @@ Import ('env')
 sources = env.Glob('intern/*.c')
 
 incs = '. intern  #/intern/guardedalloc #/intern/locale ../blenkernel ../blenlib ../blenloader'
-incs += ' ../makesdna ../makesrna ../imbuf ../editors/include'
+incs += ' ../makesdna ../makesrna ../python ../imbuf ../editors/include'
 incs += ' #/extern/glew/include'
 incs += ' ' + env['BF_FREETYPE_INC']
 
diff --git a/source/blender/blenfont/intern/blf_lang.c b/source/blender/blenfont/intern/blf_lang.c
index 9086799f984..ab29fae1a58 100644
--- a/source/blender/blenfont/intern/blf_lang.c
+++ b/source/blender/blenfont/intern/blf_lang.c
@@ -60,7 +60,7 @@ static EnumPropertyItem *locales_menu = NULL;
 static int num_locales_menu = 0;
 
 #define ULANGUAGE ((U.language >= 0 && U.language < num_locales) ? U.language : 0)
-#define LOCALE(_id) (locales ? locales[_id] : "")
+#define LOCALE(_id) (locales ? locales[(_id)] : "")
 
 static void free_locales(void)
 {
@@ -113,7 +113,7 @@ static void fill_locales(void)
 	}
 	num_locales_menu++; /* The "closing" void item... */
 
-	/* And now, buil locales and locale_menu! */
+	/* And now, build locales and locale_menu! */
 	locales_menu = MEM_callocN(num_locales_menu * sizeof(EnumPropertyItem), __func__);
 	line = lines;
 	/* Do not allocate locales with zero-sized mem, as LOCALE macro uses NULL locales as invalid marker! */
@@ -234,10 +234,15 @@ void BLF_lang_set(const char *str)
 	}
 }
 
+/* Get the current locale (short code, e.g. es_ES). */
 const char *BLF_lang_get(void)
 {
-	int uilang = ULANGUAGE;
-	return LOCALE(uilang);
+	const char *locale = LOCALE(ULANGUAGE);
+	if (locale[0] == '\0') {
+		/* Default locale, we have to find which one we are actually using! */
+		locale = bl_locale_get();
+	}
+	return locale;
 }
 
 #undef LOCALE
@@ -245,6 +250,11 @@ const char *BLF_lang_get(void)
 
 #else /* ! WITH_INTERNATIONAL */
 
+EnumPropertyItem *BLF_RNA_lang_enum_properties(void)
+{
+	return NULL;
+}
+
 void BLF_lang_init(void)
 {
 	return;
@@ -266,3 +276,56 @@ const char *BLF_lang_get(void)
 }
 
 #endif /* WITH_INTERNATIONAL */
+
+
+/* Get locale's elements (if relevant pointer is not NULL and element actually exists, e.g. if there is no variant,
+ * *variant and *language_variant will always be NULL).
+ * Non-null elements are always MEM_mallocN'ed, it's the caller's responsibility to free them.
+ * NOTE: Keep that one always available, you never know, may become useful even in no-WITH_INTERNATIONAL context...
+ */
+void BLF_locale_explode(const char *locale, char **language, char **country, char **variant,
+                        char **language_country, char **language_variant)
+{
+	char *m1, *m2, *_t = NULL;
+
+	m1 = strchr(locale, '_');
+	m2 = strchr(locale, '@');
+
+	if (language || language_variant) {
+		if (m1 || m2) {
+			_t = m1 ? BLI_strdupn(locale, m1 - locale) : BLI_strdupn(locale, m2 - locale);
+			if (language)
+				*language = _t;
+		}
+		else if (language) {
+			*language = NULL;
+		}
+	}
+	if (country) {
+		if (m1)
+			*country = m2 ? BLI_strdupn(m1 + 1, m2 - (m1 + 1)) : BLI_strdup(m1 + 1);
+		else
+			*country = NULL;
+	}
+	if (variant) {
+		if (m2)
+			*variant = BLI_strdup(m2 + 1);
+		else
+			*variant = NULL;
+	}
+	if (language_country) {
+		if (m2)
+			*language_country = BLI_strdupn(locale, m2 - locale);
+		else
+			*language_country = NULL;
+	}
+	if (language_variant) {
+		if (m2)
+			*language_variant = m1 ? BLI_strdupcat(_t, m2 + 1) : BLI_strdup(locale);
+		else
+			*language_variant = NULL;
+	}
+	if (_t && !language) {
+		MEM_freeN(_t);
+	}
+}
\ No newline at end of file
diff --git a/source/blender/blenfont/intern/blf_translation.c b/source/blender/blenfont/intern/blf_translation.c
index 5d4b631688a..3aaa61d55f2 100644
--- a/source/blender/blenfont/intern/blf_translation.c
+++ b/source/blender/blenfont/intern/blf_translation.c
@@ -47,6 +47,8 @@
 
 #include "DNA_userdef_types.h" /* For user settings. */
 
+#include "BPY_extern.h"
+
 static const char unifont_filename[] = "droidsans.ttf.gz";
 static unsigned char *unifont_ttf = NULL;
 static int unifont_size = 0;
@@ -84,7 +86,15 @@ const char *BLF_pgettext(const char *msgctxt, const char *msgid)
 {
 #ifdef WITH_INTERNATIONAL
 	if (msgid && msgid[0]) {
-		return bl_locale_pgettext(msgctxt, msgid);
+		const char *ret = bl_locale_pgettext(msgctxt, msgid);
+		/* We assume if the returned string is the same (memory level) as the msgid, no translation was found,
+		 * and we can try py scripts' ones!
+		 */
+		if (ret == msgid) {
+			ret = BPY_app_translations_py_pgettext(msgctxt, msgid);
+		}
+
+		return ret;
 	}
 	return "";
 #else