Fix Broken Font Preview (reported over IRC by kopias, thanks).

Broken by font wrap commit rBf2341f829654c4dc97, there was actually two things here:
* Using non-initialized color (which lead to transparent drawing...), we need to use new
  `blf_draw_buffer__start/end` helpers here too, made them shared internally.
* Using `draw_str_i18n_nbr` as `draw_str[i]` length, ugh! That's the number of utf8 glyphs of
  translated string, not the length of untranslated string!

This fix must be backported to final 2.76.

3 files changed, 9 insertions, 3 deletions

diff --git a/source/blender/blenfont/intern/blf.c b/source/blender/blenfont/intern/blf.c
index a97187657b8..61b847fd3a3 100644
--- a/source/blender/blenfont/intern/blf.c
+++ b/source/blender/blenfont/intern/blf.c
@@ -908,7 +908,7 @@ void BLF_buffer_col(int fontid, float r, float g, float b, float a)
 }
 
 
-static void blf_draw_buffer__start(FontBLF *font)
+void blf_draw_buffer__start(FontBLF *font)
 {
 	FontBufInfoBLF *buf_info = &font->buf_info;
 
@@ -925,7 +925,7 @@ static void blf_draw_buffer__start(FontBLF *font)
 		srgb_to_linearrgb_v4(buf_info->col_float, buf_info->col_init);
 	}
 }
-static void blf_draw_buffer__end(void) {}
+void blf_draw_buffer__end(void) {}
 
 void BLF_draw_buffer_ex(
         int fontid, const char *str, size_t len,
diff --git a/source/blender/blenfont/intern/blf_internal.h b/source/blender/blenfont/intern/blf_internal.h
index 55bc61e0e43..d9d758ce548 100644
--- a/source/blender/blenfont/intern/blf_internal.h
+++ b/source/blender/blenfont/intern/blf_internal.h
@@ -47,6 +47,9 @@ char *blf_dir_metrics_search(const char *filename);
 int blf_font_init(void);
 void blf_font_exit(void);
 
+void blf_draw_buffer__start(struct FontBLF *font);
+void blf_draw_buffer__end(void);
+
 struct FontBLF *blf_font_new(const char *name, const char *filename);
 struct FontBLF *blf_font_new_from_mem(const char *name, const unsigned char *mem, int mem_size);
 void blf_font_attach_from_mem(struct FontBLF *font, const unsigned char *mem, int mem_size);
diff --git a/source/blender/blenfont/intern/blf_thumbs.c b/source/blender/blenfont/intern/blf_thumbs.c
index 76479593b54..133168fccf2 100644
--- a/source/blender/blenfont/intern/blf_thumbs.c
+++ b/source/blender/blenfont/intern/blf_thumbs.c
@@ -89,6 +89,8 @@ void BLF_thumb_preview(
 
 	font_size_curr = font_size;
 
+	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 size_t draw_str_i18n_len = strlen(draw_str_i18n);
@@ -110,12 +112,13 @@ void BLF_thumb_preview(
 		if (blf_font_count_missing_chars(
 		        font, draw_str_i18n, draw_str_i18n_len, &draw_str_i18n_nbr) > (draw_str_i18n_nbr / 2))
 		{
-			blf_font_draw_buffer(font, draw_str[i], (size_t)draw_str_i18n_nbr, NULL);
+			blf_font_draw_buffer(font, draw_str[i], strlen(draw_str[i]), NULL);
 		}
 		else {
 			blf_font_draw_buffer(font, draw_str_i18n, draw_str_i18n_len, NULL);
 		}
 	}
 
+	blf_draw_buffer__end();
 	blf_font_free(font);
 }