Harfbuzz tweaks.

Avoid defining any functions/variables beginning with hb_ to avoid
potential namespace clashes.

Clarify language about why the Harfbuzz workarounds are needed.

5 files changed, 88 insertions, 52 deletions

diff --git a/Makethird b/Makethird
index a2de97db..7744072d 100644
--- a/Makethird
+++ b/Makethird
@@ -165,8 +165,8 @@ $(HARFBUZZ_OUT):
 	$(MKDIR_CMD)
 $(HARFBUZZ_OUT)/%.o: $(HARFBUZZ_DIR)/src/%.cc | $(HARFBUZZ_OUT)
 	$(CC_CMD) -DHAVE_OT -DHAVE_UCDN -DHB_NO_MT $(FREETYPE_CFLAGS) \
-		-Dhb_malloc_impl=hb_malloc -Dhb_calloc_impl=hb_calloc \
-		-Dhb_free_impl=hb_free -Dhb_realloc_impl=hb_realloc \
+		-Dhb_malloc_impl=fz_hb_malloc -Dhb_calloc_impl=fz_hb_calloc \
+		-Dhb_free_impl=fz_hb_free -Dhb_realloc_impl=fz_hb_realloc \
 		-fno-rtti -fno-exceptions -fvisibility-inlines-hidden --std=c++0x
 
 HARFBUZZ_CFLAGS := -I$(HARFBUZZ_DIR)/src
diff --git a/include/mupdf/fitz/font.h b/include/mupdf/fitz/font.h
index c47702be..a6e172a1 100644
--- a/include/mupdf/fitz/font.h
+++ b/include/mupdf/fitz/font.h
@@ -606,16 +606,16 @@ void fz_get_glyph_name(fz_context *ctx, fz_font *font, int glyph, char *buf, int
 */
 
 /*
-	hb_lock: Lock against Harfbuzz being called
+	fz_hb_lock: Lock against Harfbuzz being called
 	simultaneously in several threads. This reuses
 	FZ_LOCK_FREETYPE.
 */
-void hb_lock(fz_context *ctx);
+void fz_hb_lock(fz_context *ctx);
 
 /*
-	hb_unlock: Unlock after a Harfbuzz call. This reuses
+	fz_hb_unlock: Unlock after a Harfbuzz call. This reuses
 	FZ_LOCK_FREETYPE.
 */
-void hb_unlock(fz_context *ctx);
+void fz_hb_unlock(fz_context *ctx);
 
 #endif
diff --git a/platform/win32/libthirdparty.vcproj b/platform/win32/libthirdparty.vcproj
index 7192841d..49e07c3e 100644
--- a/platform/win32/libthirdparty.vcproj
+++ b/platform/win32/libthirdparty.vcproj
@@ -43,7 +43,7 @@
 				Name="VCCLCompilerTool"
 				Optimization="0"
 				AdditionalIncludeDirectories="..\..\thirdparty\lcms2\include;..\..\scripts\freetype;..\..\scripts\libjpeg;..\..\thirdparty\jbig2dec;..\..\thirdparty\libjpeg;..\..\thirdparty\openjpeg\src\lib\openjp2;..\..\thirdparty\zlib;..\..\thirdparty\freetype\include;..\..\thirdparty\freetype\include\freetype;..\..\include\"
-				PreprocessorDefinitions="WIN32;_DEBUG;_CRT_SECURE_NO_WARNINGS;FT2_BUILD_LIBRARY;OPJ_STATIC;USE_JPIP=1;FT_CONFIG_MODULES_H=\"slimftmodules.h\";FT_CONFIG_OPTIONS_H=\"slimftoptions.h\";verbose=-1;JBIG_EXTERNAL_MEMENTO_H=\"memento.h\";HAVE_OT;HAVE_UCDN;HB_NO_MT;hb_malloc_impl=hb_malloc;hb_calloc_impl=hb_calloc;hb_realloc_impl=hb_realloc;hb_free_impl=hb_free"
+				PreprocessorDefinitions="WIN32;_DEBUG;_CRT_SECURE_NO_WARNINGS;FT2_BUILD_LIBRARY;OPJ_STATIC;USE_JPIP=1;FT_CONFIG_MODULES_H=\"slimftmodules.h\";FT_CONFIG_OPTIONS_H=\"slimftoptions.h\";verbose=-1;JBIG_EXTERNAL_MEMENTO_H=\"memento.h\";HAVE_OT;HAVE_UCDN;HB_NO_MT;hb_malloc_impl=fz_hb_malloc;hb_calloc_impl=fz_hb_calloc;hb_realloc_impl=fz_hb_realloc;hb_free_impl=fz_hb_free"
 				MinimalRebuild="true"
 				BasicRuntimeChecks="3"
 				RuntimeLibrary="1"
@@ -105,7 +105,7 @@
 				Name="VCCLCompilerTool"
 				Optimization="0"
 				AdditionalIncludeDirectories="..\..\scripts\freetype;..\..\scripts\libjpeg;..\..\thirdparty\jbig2dec;..\..\thirdparty\libjpeg;..\..\thirdparty\openjpeg\src\lib\openjp2;..\..\thirdparty\zlib;..\..\thirdparty\freetype\include;..\..\thirdparty\freetype\include\freetype;..\..\include\"
-				PreprocessorDefinitions="WIN64;_DEBUG;_CRT_SECURE_NO_WARNINGS;FT2_BUILD_LIBRARY;OPJ_STATIC;USE_JPIP=1;FT_CONFIG_MODULES_H=\"slimftmodules.h\";FT_CONFIG_OPTIONS_H=\"slimftoptions.h\";verbose=-1;HAVE_OT;HAVE_UCDN;HB_NO_MT;hb_malloc_impl=hb_malloc;hb_calloc_impl=hb_calloc;hb_realloc_impl=hb_realloc;hb_free_impl=hb_free"
+				PreprocessorDefinitions="WIN64;_DEBUG;_CRT_SECURE_NO_WARNINGS;FT2_BUILD_LIBRARY;OPJ_STATIC;USE_JPIP=1;FT_CONFIG_MODULES_H=\"slimftmodules.h\";FT_CONFIG_OPTIONS_H=\"slimftoptions.h\";verbose=-1;HAVE_OT;HAVE_UCDN;HB_NO_MT;hb_malloc_impl=fz_hb_malloc;hb_calloc_impl=fz_hb_calloc;hb_realloc_impl=fz_hb_realloc;hb_free_impl=fz_hb_free"
 				MinimalRebuild="true"
 				BasicRuntimeChecks="3"
 				RuntimeLibrary="1"
@@ -168,7 +168,7 @@
 				Optimization="2"
 				EnableIntrinsicFunctions="true"
 				AdditionalIncludeDirectories="..\..\thirdparty\lcms2\include;..\..\scripts\freetype;..\..\scripts\libjpeg;..\..\thirdparty\jbig2dec;..\..\thirdparty\libjpeg;..\..\thirdparty\openjpeg\src\lib\openjp2;..\..\thirdparty\zlib;..\..\thirdparty\freetype\include;..\..\thirdparty\freetype\include\freetype;..\..\include\"
-				PreprocessorDefinitions="WIN32;NDEBUG;_CRT_SECURE_NO_WARNINGS;FT2_BUILD_LIBRARY;OPJ_STATIC;USE_JPIP=1;FT_CONFIG_MODULES_H=\"slimftmodules.h\";FT_CONFIG_OPTIONS_H=\"slimftoptions.h\";verbose=-1;JBIG_EXTERNAL_MEMENTO_H=\"memento.h\";HAVE_OT;HAVE_UCDN;HB_NO_MT;hb_malloc_impl=hb_malloc;hb_calloc_impl=hb_calloc;hb_realloc_impl=hb_realloc;hb_free_impl=hb_free"
+				PreprocessorDefinitions="WIN32;NDEBUG;_CRT_SECURE_NO_WARNINGS;FT2_BUILD_LIBRARY;OPJ_STATIC;USE_JPIP=1;FT_CONFIG_MODULES_H=\"slimftmodules.h\";FT_CONFIG_OPTIONS_H=\"slimftoptions.h\";verbose=-1;JBIG_EXTERNAL_MEMENTO_H=\"memento.h\";HAVE_OT;HAVE_UCDN;HB_NO_MT;hb_malloc_impl=fz_hb_malloc;hb_calloc_impl=fz_hb_calloc;hb_realloc_impl=fz_hb_realloc;hb_free_impl=fz_hb_free"
 				RuntimeLibrary="0"
 				EnableFunctionLevelLinking="true"
 				WarningLevel="3"
@@ -231,7 +231,7 @@
 				Optimization="2"
 				EnableIntrinsicFunctions="true"
 				AdditionalIncludeDirectories="..\..\scripts\freetype;..\..\scripts\libjpeg;..\..\thirdparty\jbig2dec;..\..\thirdparty\libjpeg;..\..\thirdparty\openjpeg\src\lib\openjp2;..\..\thirdparty\zlib;..\..\thirdparty\freetype\include;..\..\thirdparty\freetype\include\freetype;..\..\include\"
-				PreprocessorDefinitions="WIN64;NDEBUG;_CRT_SECURE_NO_WARNINGS;FT2_BUILD_LIBRARY;OPJ_STATIC;USE_JPIP=1;FT_CONFIG_MODULES_H=\"slimftmodules.h\";FT_CONFIG_OPTIONS_H=\"slimftoptions.h\";verbose=-1;HAVE_OT;HAVE_UCDN;HB_NO_MT;hb_malloc_impl=hb_malloc;hb_calloc_impl=hb_calloc;hb_realloc_impl=hb_realloc;hb_free_impl=hb_free"
+				PreprocessorDefinitions="WIN64;NDEBUG;_CRT_SECURE_NO_WARNINGS;FT2_BUILD_LIBRARY;OPJ_STATIC;USE_JPIP=1;FT_CONFIG_MODULES_H=\"slimftmodules.h\";FT_CONFIG_OPTIONS_H=\"slimftoptions.h\";verbose=-1;HAVE_OT;HAVE_UCDN;HB_NO_MT;hb_malloc_impl=fz_hb_malloc;hb_calloc_impl=fz_hb_calloc;hb_realloc_impl=fz_hb_realloc;hb_free_impl=fz_hb_free"
 				RuntimeLibrary="0"
 				EnableFunctionLevelLinking="true"
 				WarningLevel="3"
@@ -291,7 +291,7 @@
 				Name="VCCLCompilerTool"
 				Optimization="0"
 				AdditionalIncludeDirectories="..\..\thirdparty\lcms2\include;..\..\scripts\freetype;..\..\scripts\libjpeg;..\..\thirdparty\jbig2dec;..\..\thirdparty\libjpeg;..\..\thirdparty\openjpeg\src\lib\openjp2;..\..\thirdparty\zlib;..\..\thirdparty\freetype\include;..\..\thirdparty\freetype\include\freetype;..\..\include\"
-				PreprocessorDefinitions="WIN32;_DEBUG;_CRT_SECURE_NO_WARNINGS;FT2_BUILD_LIBRARY;OPJ_STATIC;USE_JPIP=1;FT_CONFIG_MODULES_H=\"slimftmodules.h\";FT_CONFIG_OPTIONS_H=\"slimftoptions.h\";MEMENTO=1;verbose=-1;JBIG_EXTERNAL_MEMENTO_H=\"memento.h\";HAVE_OT;HAVE_UCDN;HB_NO_MT;hb_malloc_impl=hb_malloc;hb_calloc_impl=hb_calloc;hb_realloc_impl=hb_realloc;hb_free_impl=hb_free"
+				PreprocessorDefinitions="WIN32;_DEBUG;_CRT_SECURE_NO_WARNINGS;FT2_BUILD_LIBRARY;OPJ_STATIC;USE_JPIP=1;FT_CONFIG_MODULES_H=\"slimftmodules.h\";FT_CONFIG_OPTIONS_H=\"slimftoptions.h\";MEMENTO=1;verbose=-1;JBIG_EXTERNAL_MEMENTO_H=\"memento.h\";HAVE_OT;HAVE_UCDN;HB_NO_MT;hb_malloc_impl=fz_hb_malloc;hb_calloc_impl=fz_hb_calloc;hb_realloc_impl=fz_hb_realloc;hb_free_impl=fz_hb_free"
 				MinimalRebuild="true"
 				BasicRuntimeChecks="3"
 				RuntimeLibrary="1"
@@ -353,7 +353,7 @@
 				Name="VCCLCompilerTool"
 				Optimization="0"
 				AdditionalIncludeDirectories="..\..\scripts\freetype;..\..\scripts\libjpeg;..\..\thirdparty\jbig2dec;..\..\thirdparty\libjpeg;..\..\thirdparty\openjpeg\src\lib\openjp2;..\..\thirdparty\zlib;..\..\thirdparty\freetype\include;..\..\thirdparty\freetype\include\freetype;..\..\include\"
-				PreprocessorDefinitions="WIN64;_DEBUG;_CRT_SECURE_NO_WARNINGS;FT2_BUILD_LIBRARY;OPJ_STATIC;USE_JPIP=1;FT_CONFIG_MODULES_H=\"slimftmodules.h\";FT_CONFIG_OPTIONS_H=\"slimftoptions.h\";MEMENTO=1;verbose=-1;HAVE_OT;HAVE_UCDN;HB_NO_MT;hb_malloc_impl=hb_malloc;hb_calloc_impl=hb_calloc;hb_realloc_impl=hb_realloc;hb_free_impl=hb_free"
+				PreprocessorDefinitions="WIN64;_DEBUG;_CRT_SECURE_NO_WARNINGS;FT2_BUILD_LIBRARY;OPJ_STATIC;USE_JPIP=1;FT_CONFIG_MODULES_H=\"slimftmodules.h\";FT_CONFIG_OPTIONS_H=\"slimftoptions.h\";MEMENTO=1;verbose=-1;HAVE_OT;HAVE_UCDN;HB_NO_MT;hb_malloc_impl=fz_hb_malloc;hb_calloc_impl=fz_hb_calloc;hb_realloc_impl=fz_hb_realloc;hb_free_impl=fz_hb_free"
 				MinimalRebuild="true"
 				BasicRuntimeChecks="3"
 				RuntimeLibrary="1"
@@ -414,7 +414,7 @@
 				Name="VCCLCompilerTool"
 				Optimization="0"
 				AdditionalIncludeDirectories="..\..\thirdparty\lcms2\include;..\..\scripts\freetype;..\..\scripts\libjpeg;..\..\thirdparty\jbig2dec;..\..\thirdparty\libjpeg;..\..\thirdparty\openjpeg\src\lib\openjp2;..\..\thirdparty\zlib;..\..\thirdparty\freetype\include;..\..\thirdparty\freetype\include\freetype;..\..\include\"
-				PreprocessorDefinitions="WIN32;_DEBUG;_CRT_SECURE_NO_WARNINGS;FT2_BUILD_LIBRARY;OPJ_STATIC;USE_JPIP=1;FT_CONFIG_MODULES_H=\"slimftmodules.h\";FT_CONFIG_OPTIONS_H=\"slimftoptions.h\";verbose=-1;JBIG_EXTERNAL_MEMENTO_H=\"memento.h\";HAVE_OT;HAVE_UCDN;HB_NO_MT;hb_malloc_impl=hb_malloc;hb_calloc_impl=hb_calloc;hb_realloc_impl=hb_realloc;hb_free_impl=hb_free"
+				PreprocessorDefinitions="WIN32;_DEBUG;_CRT_SECURE_NO_WARNINGS;FT2_BUILD_LIBRARY;OPJ_STATIC;USE_JPIP=1;FT_CONFIG_MODULES_H=\"slimftmodules.h\";FT_CONFIG_OPTIONS_H=\"slimftoptions.h\";verbose=-1;JBIG_EXTERNAL_MEMENTO_H=\"memento.h\";HAVE_OT;HAVE_UCDN;HB_NO_MT;hb_malloc_impl=fz_hb_malloc;hb_calloc_impl=fz_hb_calloc;hb_realloc_impl=fz_hb_realloc;hb_free_impl=fz_hb_free"
 				MinimalRebuild="true"
 				BasicRuntimeChecks="3"
 				RuntimeLibrary="3"
@@ -476,7 +476,7 @@
 				Name="VCCLCompilerTool"
 				Optimization="0"
 				AdditionalIncludeDirectories="..\..\scripts\freetype;..\..\scripts\libjpeg;..\..\thirdparty\jbig2dec;..\..\thirdparty\libjpeg;..\..\thirdparty\openjpeg\src\lib\openjp2;..\..\thirdparty\zlib;..\..\thirdparty\freetype\include;..\..\thirdparty\freetype\include\freetype;..\..\include\"
-				PreprocessorDefinitions="WIN64;_DEBUG;_CRT_SECURE_NO_WARNINGS;FT2_BUILD_LIBRARY;OPJ_STATIC;USE_JPIP=1;FT_CONFIG_MODULES_H=\"slimftmodules.h\";FT_CONFIG_OPTIONS_H=\"slimftoptions.h\";verbose=-1;HAVE_OT;HAVE_UCDN;HB_NO_MT;hb_malloc_impl=hb_malloc;hb_calloc_impl=hb_calloc;hb_realloc_impl=hb_realloc;hb_free_impl=hb_free"
+				PreprocessorDefinitions="WIN64;_DEBUG;_CRT_SECURE_NO_WARNINGS;FT2_BUILD_LIBRARY;OPJ_STATIC;USE_JPIP=1;FT_CONFIG_MODULES_H=\"slimftmodules.h\";FT_CONFIG_OPTIONS_H=\"slimftoptions.h\";verbose=-1;HAVE_OT;HAVE_UCDN;HB_NO_MT;hb_malloc_impl=fz_hb_malloc;hb_calloc_impl=fz_hb_calloc;hb_realloc_impl=fz_hb_realloc;hb_free_impl=fz_hb_free"
 				MinimalRebuild="true"
 				BasicRuntimeChecks="3"
 				RuntimeLibrary="3"
@@ -539,7 +539,7 @@
 				Optimization="2"
 				EnableIntrinsicFunctions="true"
 				AdditionalIncludeDirectories="..\..\thirdparty\lcms2\include;..\..\scripts\freetype;..\..\scripts\libjpeg;..\..\thirdparty\jbig2dec;..\..\thirdparty\libjpeg;..\..\thirdparty\openjpeg\src\lib\openjp2;..\..\thirdparty\zlib;..\..\thirdparty\freetype\include;..\..\thirdparty\freetype\include\freetype;..\..\include\"
-				PreprocessorDefinitions="WIN32;NDEBUG;_CRT_SECURE_NO_WARNINGS;FT2_BUILD_LIBRARY;OPJ_STATIC;USE_JPIP=1;FT_CONFIG_MODULES_H=\"slimftmodules.h\";FT_CONFIG_OPTIONS_H=\"slimftoptions.h\";verbose=-1;JBIG_EXTERNAL_MEMENTO_H=\"memento.h\";HAVE_OT;HAVE_UCDN;HB_NO_MT;hb_malloc_impl=hb_malloc;hb_calloc_impl=hb_calloc;hb_realloc_impl=hb_realloc;hb_free_impl=hb_free"
+				PreprocessorDefinitions="WIN32;NDEBUG;_CRT_SECURE_NO_WARNINGS;FT2_BUILD_LIBRARY;OPJ_STATIC;USE_JPIP=1;FT_CONFIG_MODULES_H=\"slimftmodules.h\";FT_CONFIG_OPTIONS_H=\"slimftoptions.h\";verbose=-1;JBIG_EXTERNAL_MEMENTO_H=\"memento.h\";HAVE_OT;HAVE_UCDN;HB_NO_MT;hb_malloc_impl=fz_hb_malloc;hb_calloc_impl=fz_hb_calloc;hb_realloc_impl=fz_hb_realloc;hb_free_impl=fz_hb_free"
 				RuntimeLibrary="2"
 				EnableFunctionLevelLinking="true"
 				WarningLevel="3"
@@ -602,7 +602,7 @@
 				Optimization="2"
 				EnableIntrinsicFunctions="true"
 				AdditionalIncludeDirectories="..\..\scripts\freetype;..\..\scripts\libjpeg;..\..\thirdparty\jbig2dec;..\..\thirdparty\libjpeg;..\..\thirdparty\openjpeg\src\lib\openjp2;..\..\thirdparty\zlib;..\..\thirdparty\freetype\include;..\..\thirdparty\freetype\include\freetype;..\..\include\"
-				PreprocessorDefinitions="WIN64;NDEBUG;_CRT_SECURE_NO_WARNINGS;FT2_BUILD_LIBRARY;OPJ_STATIC;USE_JPIP=1;FT_CONFIG_MODULES_H=\"slimftmodules.h\";FT_CONFIG_OPTIONS_H=\"slimftoptions.h\";verbose=-1;HAVE_OT;HAVE_UCDN;HB_NO_MT;hb_malloc_impl=hb_malloc;hb_calloc_impl=hb_calloc;hb_realloc_impl=hb_realloc;hb_free_impl=hb_free"
+				PreprocessorDefinitions="WIN64;NDEBUG;_CRT_SECURE_NO_WARNINGS;FT2_BUILD_LIBRARY;OPJ_STATIC;USE_JPIP=1;FT_CONFIG_MODULES_H=\"slimftmodules.h\";FT_CONFIG_OPTIONS_H=\"slimftoptions.h\";verbose=-1;HAVE_OT;HAVE_UCDN;HB_NO_MT;hb_malloc_impl=fz_hb_malloc;hb_calloc_impl=fz_hb_calloc;hb_realloc_impl=fz_hb_realloc;hb_free_impl=fz_hb_free"
 				RuntimeLibrary="2"
 				EnableFunctionLevelLinking="true"
 				WarningLevel="3"
diff --git a/source/fitz/harfbuzz.c b/source/fitz/harfbuzz.c
index 80451278..be70cdd6 100644
--- a/source/fitz/harfbuzz.c
+++ b/source/fitz/harfbuzz.c
@@ -9,14 +9,31 @@
 
 #include <assert.h>
 
-/* Harfbuzz has some major design flaws.
+/* Harfbuzz has some major design flaws (for our usage
+ * at least).
  *
- * It is utterly thread unsafe. It uses statics to hold
- * structures in, meaning that if it is ever called from
- * more than one thread at a time, access to such
- * structures can race. We work around this by imposing
- * a lock on our calls to harfbuzz (we reuse the freetype
- * lock).
+ * By default it uses malloc and free as the underlying
+ * allocators. Thus in its default form we cannot get
+ * a record (much less control) over how much allocation
+ * is done.
+ *
+ * Harfbuzz does allow build options to control where
+ * malloc and free go - in particular we point them at
+ * fz_hb_malloc and fz_hb_free in our implementation.
+ * Unfortunately, this has problems too.
+ *
+ * Firstly, there is no mechanism for getting a context
+ * through the call. Most other libraries allow us to
+ * pass a "void *" value in, and have it passed through
+ * to arrive unchanged at the allocator functions.
+ *
+ * Without this rudimentary functionality, we are forced
+ * to serialise all access to Harfbuzz.
+ *
+ * By taking a mutex around all calls to Harfbuzz, we
+ * can use a static of our own to get a fz_context safely
+ * through to the allocators. This obviously costs us
+ * performance in the multi-threaded case.
  *
  * This does not protect us against the possibility of
  * other people calling harfbuzz; for instance, if we
@@ -30,9 +47,9 @@
  *
  * In order to ensure that allocations throughout mupdf
  * are done consistently, we get harfbuzz to call our
- * own hb_malloc/realloc/calloc/free functions that
+ * own fz_hb_malloc/realloc/calloc/free functions that
  * call down to fz_malloc/realloc/calloc/free. These
- * require context variables, so we get our hb_lock
+ * require context variables, so we get our fz_hb_lock
  * and unlock to set these. Any attempt to call through
  * without setting these will be detected.
  *
@@ -40,12 +57,31 @@
  * handlers are shared between all the fz_contexts in
  * use at a time.
  *
- * Finally, harfbuzz stores various malloced structures
- * in statics. These can either be left to leak on
- * closedown, or (if HAVE_ATEXIT is defined), they will
- * be freed using various 'atexit' callbacks. Unfortunately
- * this won't reset the fz_context value, so the allocators
- * can't free them correctly.
+ * Secondly, Harfbuzz allocates some 'internal' memory
+ * on the first call, and leaves this linked from static
+ * variables. By default, this data is never freed back.
+ * This means it is impossible to clear the library back
+ * to a default state. Memory debugging will always show
+ * Harfbuzz as having leaked a set amount of memory.
+ *
+ * There is a mechanism in Harfbuzz for freeing these
+ * blocks - that of building with HAVE_ATEXIT. This
+ * causes the blocks to be freed back on exit, but a)
+ * this doesn't reset the fz_context value, so we can't
+ * free them correctly, and b) any fz_context value it
+ * did keep would already have been closed down due to
+ * the program exit.
+ *
+ * In addition, because of these everlasting blocks, we
+ * cannot safely call Harfbuzz after we close down any
+ * allocator that Harfbuzz has been using (because
+ * Harfbuzz may still be holding pointers to data within
+ * that allocators managed space).
+ *
+ * There is nothing we can do about the leaking blocks
+ * except to add some hacks to our memory debugging
+ * library to allow it to suppress the blocks that
+ * harfbuzz leaks.
  *
  * Consequently, we leave them to leak, and warn Memento
  * about this.
@@ -64,33 +100,33 @@
  * problems that for now, we'll just forbid it.
  */
 
-static fz_context *hb_secret = NULL;
+static fz_context *fz_hb_secret = NULL;
 
 static void set_hb_context(fz_context *ctx)
 {
-	hb_secret = ctx;
+	fz_hb_secret = ctx;
 }
 
 static fz_context *get_hb_context(void)
 {
-	return hb_secret;
+	return fz_hb_secret;
 }
 
-void hb_lock(fz_context *ctx)
+void fz_hb_lock(fz_context *ctx)
 {
 	fz_lock(ctx, FZ_LOCK_FREETYPE);
 
 	set_hb_context(ctx);
 }
 
-void hb_unlock(fz_context *ctx)
+void fz_hb_unlock(fz_context *ctx)
 {
 	set_hb_context(NULL);
 
 	fz_unlock(ctx, FZ_LOCK_FREETYPE);
 }
 
-void *hb_malloc(size_t size)
+void *fz_hb_malloc(size_t size)
 {
 	fz_context *ctx = get_hb_context();
 
@@ -99,7 +135,7 @@ void *hb_malloc(size_t size)
 	return fz_malloc_no_throw(ctx, size);
 }
 
-void *hb_calloc(size_t n, size_t size)
+void *fz_hb_calloc(size_t n, size_t size)
 {
 	fz_context *ctx = get_hb_context();
 
@@ -108,7 +144,7 @@ void *hb_calloc(size_t n, size_t size)
 	return fz_calloc_no_throw(ctx, n, size);
 }
 
-void *hb_realloc(void *ptr, size_t size)
+void *fz_hb_realloc(void *ptr, size_t size)
 {
 	fz_context *ctx = get_hb_context();
 
@@ -117,7 +153,7 @@ void *hb_realloc(void *ptr, size_t size)
 	return fz_resize_array_no_throw(ctx, ptr, 1, size);
 }
 
-void hb_free(void *ptr)
+void fz_hb_free(void *ptr)
 {
 	fz_context *ctx = get_hb_context();
 
diff --git a/source/html/html-layout.c b/source/html/html-layout.c
index 488f6f38..cb101394 100644
--- a/source/html/html-layout.c
+++ b/source/html/html-layout.c
@@ -885,9 +885,9 @@ static void init_string_walker(fz_context *ctx, string_walker *walker, hb_buffer
 static void
 destroy_hb_shaper_data(fz_context *ctx, void *handle)
 {
-	hb_lock(ctx);
+	fz_hb_lock(ctx);
 	hb_font_destroy(handle);
-	hb_unlock(ctx);
+	fz_hb_unlock(ctx);
 }
 
 static int walk_string(string_walker *walker)
@@ -927,7 +927,7 @@ static int walk_string(string_walker *walker)
 	if (walker->script <= 3 && !walker->rtl && !fz_font_flags(walker->font)->has_opentype)
 		quickshape = 1;
 
-	hb_lock(ctx);
+	fz_hb_lock(ctx);
 	fz_try(ctx)
 	{
 		face = fz_font_ft_face(ctx, walker->font);
@@ -971,7 +971,7 @@ static int walk_string(string_walker *walker)
 	}
 	fz_always(ctx)
 	{
-		hb_unlock(ctx);
+		fz_hb_unlock(ctx);
 	}
 	fz_catch(ctx)
 	{
@@ -1891,11 +1891,11 @@ fz_draw_html(fz_context *ctx, fz_device *dev, const fz_matrix *ctm, fz_html *htm
 
 	fz_pre_translate(&local_ctm, html->page_margin[L], html->page_margin[T]);
 
-	hb_lock(ctx);
+	fz_hb_lock(ctx);
 	fz_try(ctx)
 	{
 		hb_buf = hb_buffer_create();
-		hb_unlock(ctx);
+		fz_hb_unlock(ctx);
 		unlocked = 1;
 
 		for (box = html->root->down; box; box = box->next)
@@ -1904,9 +1904,9 @@ fz_draw_html(fz_context *ctx, fz_device *dev, const fz_matrix *ctm, fz_html *htm
 	fz_always(ctx)
 	{
 		if (unlocked)
-			hb_lock(ctx);
+			fz_hb_lock(ctx);
 		hb_buffer_destroy(hb_buf);
-		hb_unlock(ctx);
+		fz_hb_unlock(ctx);
 	}
 	fz_catch(ctx)
 	{
@@ -2471,13 +2471,13 @@ fz_layout_html(fz_context *ctx, fz_html *html, float w, float h, float em)
 	html->page_w = w - html->page_margin[L] - html->page_margin[R];
 	html->page_h = h - html->page_margin[T] - html->page_margin[B];
 
-	hb_lock(ctx);
+	fz_hb_lock(ctx);
 
 	fz_try(ctx)
 	{
 		hb_buf = hb_buffer_create();
 		unlocked = 1;
-		hb_unlock(ctx);
+		fz_hb_unlock(ctx);
 
 		box->em = em;
 		box->w = html->page_w;
@@ -2492,9 +2492,9 @@ fz_layout_html(fz_context *ctx, fz_html *html, float w, float h, float em)
 	fz_always(ctx)
 	{
 		if (unlocked)
-			hb_lock(ctx);
+			fz_hb_lock(ctx);
 		hb_buffer_destroy(hb_buf);
-		hb_unlock(ctx);
+		fz_hb_unlock(ctx);
 	}
 	fz_catch(ctx)
 	{