Fix T67620: Font preview translations malfunction in Blender 2.8

We cannot reliably use translations API from non-main threads.

Now storing translated strings in a static cache, with basic mechanism
to update it on language change.

Reviewers: brecht, campbellbarton

Differential Revision: https://developer.blender.org/D5350

2 files changed, 3 insertions, 1 deletions

diff --git a/source/blender/blenfont/BLF_api.h b/source/blender/blenfont/BLF_api.h
index 448bb0d621a..bf0aa96df84 100644
--- a/source/blender/blenfont/BLF_api.h
+++ b/source/blender/blenfont/BLF_api.h
@@ -223,6 +223,7 @@ void BLF_dir_free(char **dirs, int count) ATTR_NONNULL();
 /* blf_thumbs.c */
 void BLF_thumb_preview(const char *filename,
                        const char **draw_str,
+                       const char **i18n_draw_str,
                        const unsigned char draw_str_lines,
                        const float font_color[4],
                        const int font_size,
diff --git a/source/blender/blenfont/intern/blf_thumbs.c b/source/blender/blenfont/intern/blf_thumbs.c
index 802f97fc5f5..d6710b91539 100644
--- a/source/blender/blenfont/intern/blf_thumbs.c
+++ b/source/blender/blenfont/intern/blf_thumbs.c
@@ -50,6 +50,7 @@
  */
 void BLF_thumb_preview(const char *filename,
                        const char **draw_str,
+                       const char **i18n_draw_str,
                        const unsigned char draw_str_lines,
                        const float font_color[4],
                        const int font_size,
@@ -90,7 +91,7 @@ void BLF_thumb_preview(const char *filename,
   blf_draw_buffer__start(font);
 
   for (i = 0; i < draw_str_lines; i++) {
-    const char *draw_str_i18n = BLT_translate_do(BLT_I18NCONTEXT_DEFAULT, draw_str[i]);
+    const char *draw_str_i18n = i18n_draw_str[i] != NULL ? i18n_draw_str[i] : draw_str[i];
     const size_t draw_str_i18n_len = strlen(draw_str_i18n);
     int draw_str_i18n_nbr = 0;