Commit 4eff854c27728aa21751af2c4f3c5f0afe83ebd1
2015-01-14T20:06:19
* docs/CHANGES: Updated, using a description from Behdad.
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diff --git a/ChangeLog b/ChangeLog
index 0ae7f74..f68af52 100644
--- a/ChangeLog
+++ b/ChangeLog
@@ -1,3 +1,7 @@
+2015-01-14 Werner Lemberg <wl@gnu.org>
+
+ * docs/CHANGES: Updated, using a description from Behdad.
+
2015-01-14 Behdad Esfahbod <behdad@behdad.org>
* src/autofit/afmodule.c (af_autofitter_done): Fix compiler warning.
diff --git a/docs/CHANGES b/docs/CHANGES
index bbc3110..1d2d339 100644
--- a/docs/CHANGES
+++ b/docs/CHANGES
@@ -1,4 +1,29 @@
+CHANGES BETWEEN 2.5.5 and 2.5.6
+
+ II. IMPORTANT CHANGES
+
+ - Behdad Esfahbod contributed code for improved thread-safety,
+ which results in the following model.
+
+ * An `FT_Face' object can only be safely used from one thread at
+ a time.
+
+ * An `FT_Library' object can now be used without modification
+ from multiple threads at the same time.
+
+ * `FT_Face' creation and destruction with the same `FT_Library'
+ object can only be done from one thread at a time.
+
+ One can use a single `FT_Library' object across threads as long
+ as a mutex lock is used around `FT_New_Face' and `FT_Done_Face'.
+ Any calls to `FT_Load_Glyph' and similar API are safe and do not
+ need the lock to be held as long as the same `FT_Face' is not
+ used from multiple threads at the same time.
+
+
+======================================================================
+
CHANGES BETWEEN 2.5.4 and 2.5.5
I. IMPORTANT BUG FIXES
diff --git a/include/freetype.h b/include/freetype.h
index 27fd44b..1022719 100644
--- a/include/freetype.h
+++ b/include/freetype.h
@@ -394,8 +394,11 @@ FT_BEGIN_HEADER
/* It also embeds a memory manager (see @FT_Memory), as well as a */
/* scan-line converter object (see @FT_Raster). */
/* */
- /* In multi-threaded applications, make sure that the same FT_Library */
- /* object or any of its children doesn't get accessed in parallel. */
+ /* In multi-threaded applications it is easiest to use one */
+ /* `FT_Library' object per thread. In case this is too cumbersome, */
+ /* a single `FT_Library' object across threads is possible also */
+ /* (since FreeType version 2.5.6), as long as a mutex lock is used */
+ /* around @FT_New_Face and @FT_Done_Face. */
/* */
/* <Note> */
/* Library objects are normally created by @FT_Init_FreeType, and */
@@ -477,6 +480,14 @@ FT_BEGIN_HEADER
/* */
/* Use @FT_Done_Face to destroy it (along with its slot and sizes). */
/* */
+ /* An `FT_Face' object can only be safely used from one thread at a */
+ /* time. Similarly, creation and destruction of `FT_Face' with the */
+ /* same @FT_Library object can only be done from one thread at a */
+ /* time. On the other hand, functions like @FT_Load_Glyph and its */
+ /* siblings are thread-safe and do not need the lock to be held as */
+ /* long as the same `FT_Face' object is not used from multiple */
+ /* threads at the same time. */
+ /* */
/* <Also> */
/* See @FT_FaceRec for the publicly accessible fields of a given face */
/* object. */
@@ -1769,8 +1780,8 @@ FT_BEGIN_HEADER
/* use @FT_New_Library instead, followed by a call to */
/* @FT_Add_Default_Modules (or a series of calls to @FT_Add_Module). */
/* */
- /* For multi-threading applications each thread should have its own */
- /* FT_Library object. */
+ /* See the documentation of @FT_Library and @FT_Face for */
+ /* multi-threading issues. */
/* */
/* If you need reference-counting (cf. @FT_Reference_Library), use */
/* @FT_New_Library and @FT_Done_Library. */