[woff2] Avoid too many calls to `FT_REALLOC'.

We do this by using `totalSfntSize' as an initial reference, and
extending the buffer when required.  This reduces rendering time
considerably.

* include/freetype/internal/wofftypes.h (WOFF2_HeaderRec): Add
`totalSfntSize', rename `total_sfnt_size' to `actual_sfnt_size'.

* src/sfnt/sfwoff2.c (write_buf): Add parameter `dst_size' to keep
track of and update total size of stream.

(WRITE_SFNT_BUF, WRITE_SFNT_BUF_AT): Modify macros accordingly.

(pad4, store_loca, reconstruct_glyf, reconstruct_hmtx,
reconstruct_font): Update parameters to accept `sfnt_size'.

(woff2_open_font): Add variable `sfnt_size'.  Use WOFF2 header field
`totalSfntSize' as initial reference (if value makes sense) and
allocate `totalSfntSize' bytes for the sfnt stream.  `write_buf'
handles reallocation if and when required.  Also resize the stream
to `actual_sfnt_size' after reconstruction.

1 files changed, 2 insertions, 1 deletions

diff --git a/include/freetype/internal/wofftypes.h b/include/freetype/internal/wofftypes.h
index efadb7743..9c827e32c 100644
--- a/include/freetype/internal/wofftypes.h
+++ b/include/freetype/internal/wofftypes.h
@@ -165,6 +165,7 @@ FT_BEGIN_HEADER
     FT_ULong   flavor;
     FT_ULong   length;
     FT_UShort  num_tables;
+    FT_ULong   totalSfntSize;
     FT_ULong   totalCompressedSize;
     FT_ULong   metaOffset;
     FT_ULong   metaLength;
@@ -176,7 +177,7 @@ FT_BEGIN_HEADER
     FT_ULong   compressed_offset;
     FT_ULong   header_version;
     FT_UShort  num_fonts;
-    FT_ULong   total_sfnt_size;
+    FT_ULong   actual_sfnt_size;
 
     WOFF2_TtcFont  ttc_fonts;