Thumbnails: Add translations to font preview.

Not much to say, this is pretty straightforward.
We just have to add current locale to thumbnails 'signature', so that
previews get re-generated when we change locale...

Tested with Japanese and French.

Btw, I do not really understand why using BLF in ImBuf is badlevel... :/

source/blender/blenfont/intern/blf_thumbs.c

@@ -45,6 +45,7 @@
 #include "blf_internal_types.h"
 
 #include "BLF_api.h"
+#include "BLF_translation.h"
 
 #include "BLI_strict_flags.h"
 
@@ -97,7 +98,7 @@ void BLF_thumb_preview(
 
 		font->pos[1] -= font->glyph_cache->ascender * 1.1f;
 
-		blf_font_buffer(font, draw_str[i]);
+		blf_font_buffer(font, BLF_translate_do(BLF_I18NCONTEXT_DEFAULT, draw_str[i]));
 	}
 
 	blf_font_free(font);

source/blender/imbuf/IMB_thumbs.h

@@ -82,6 +82,7 @@ void   IMB_thumb_overlay_blend(unsigned int *thumb, int width, int height, float
 
 /* special function for previewing fonts */
 ImBuf *IMB_thumb_load_font(const char *filename, unsigned int x, unsigned int y);
+const char *IMB_thumb_load_font_get_language(void);
 
 #ifdef __cplusplus
 }

source/blender/imbuf/intern/thumbs.c

@@ -483,18 +483,22 @@ void IMB_thumb_delete(const char *path, ThumbSize size)
 
 
 /* create the thumb if necessary and manage failed and old thumbs */
-ImBuf *IMB_thumb_manage(const char *path, ThumbSize size, ThumbSource source)
+ImBuf *IMB_thumb_manage(const char *org_path, ThumbSize size, ThumbSource source)
 {
 	char thumb_path[FILE_MAX];
 	char thumb_name[40];
 	char uri[URI_MAX];
 	const char *file_path;
+	const char *path;
 	char path_buff[FILE_MAX];
 	BLI_stat_t st;
 	ImBuf *img = NULL;
 
-	file_path = path;
-	UNUSED_VARS(path_buff);
+	path = file_path = org_path;
+	if (source == THB_SOURCE_FONT) {
+		BLI_snprintf(path_buff, sizeof(path_buff), "%s.%s", org_path, IMB_thumb_load_font_get_language());
+		path = path_buff;
+	}
 
 	if (BLI_stat(file_path, &st) == -1) {
 		return NULL;

source/blender/imbuf/intern/thumbs_font.c

@@ -34,18 +34,19 @@
 
 /* XXX, bad level call */
 #include "../../blenfont/BLF_api.h"
+#include "../../blenfont/BLF_translation.h"  /* 'N_' macro and BLF_lang_get()... */
 
 
 struct ImBuf *IMB_thumb_load_font(const char *filename, unsigned int x, unsigned int y)
 {
 	const int font_size = y / 4;
 	const char *thumb_str[] = {
-	    "AaBbCc",
+	    N_("AaBbCc"),
 
-	    "The quick",
-	    "brown fox",
-	    "jumps over",
-	    "the lazy dog",
+	    N_("The quick"),
+	    N_("brown fox"),
+	    N_("jumps over"),
+	    N_("the lazy dog"),
 	};
 
 	struct ImBuf *ibuf;
@@ -71,3 +72,7 @@ struct ImBuf *IMB_thumb_load_font(const char *filename, unsigned int x, unsigned
 	return ibuf;
 }
 
+const char *IMB_thumb_load_font_get_language(void)
+{
+	return BLF_lang_get();
+}