[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

* 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.
3 files changed