Add HarfBuzz font backend for MS-Windows

* src/w32uniscribe.c [HAVE_HARFBUZZ]: Include math.h and
hb.h.
(bswap_32): Define for GCC 4.3.0 and later; else include
<byteswap.h> from Gnulib.
(struct uniscribe_font_info): Extend for HarfBuzz; 'cache' is
now a 'void *' (all users changed).
[HAVE_HARFBUZZ]: Define typedefs for HarfBuzz functions to be
loaded dynamically from the HarfBuzz DLL.  Define macros to
call those functions via function pointers.
(uniscribe_open) [HAVE_HARFBUZZ]: Use the HarfBuzz font driver
if the type of the font entity is 'harfbuzz'.
(uniscribe_close) [HAVE_HARFBUZZ]: For fonts using the
HarfBuzz backend, call hb_font_destroy to free memory used for
the cached hb_font data.
(uniscribe_shape): Fix assignment of character codepoints to
glyphs from a single cluster.
(w32hb_list, w32hb_match, free_cb, w32hb_get_font_table)
(w32hb_get_font, w32hb_encode_char, w32hb_begin_font)
(w32uni_combining, w32uni_general, w32uni_mirroring)
(get_hb_unicode_funcs, w32hb_shape)
(w32hb_combining_capability, load_harfbuzz_funcs)
[HAVE_HARFBUZZ]: New functions.
(syms_of_w32uniscribe_for_pdumper) [HAVE_HARFBUZZ]: Load the
HarfBuzz DLL and register the HarfBuzz backend with its
functions.
* src/w32font.c (syms_of_w32font) <Qharfbuzz>: New DEFSYM.
* src/w32fns.c (Fx_create_frame, w32_create_tip_frame)
[HAVE_HARFBUZZ]: Register the harfbuzz font backend.
* src/lisp.h (get_unicode_property): Declare prototype.
* src/font.h (harfbuzz_font_driver) [HAVE_NTGUI]: Declare.
* src/chartab.c (get_unicode_property): New function, body
taken from get-unicode-property-internal.
(Fget_unicode_property_internal): Call get_unicode_property
after validating input.

* doc/lispref/frames.texi (Font and Color Parameters):
* doc/emacs/msdos.texi (Windows Fonts): Document support for
HarfBuzz text shaping on MS-Windows.

* configure.ac (HAVE_HARFBUZZ): Move out of the X-specific
part, and consider HarfBuzz also for HAVE_W32 systems.
Require HarfBuzz v1.2.3 for w32.

2 files changed, 37 insertions, 27 deletions

diff --git a/doc/emacs/msdos.texi b/doc/emacs/msdos.texi
index 9fc4b6262fb..27a7cd80968 100644
--- a/doc/emacs/msdos.texi
+++ b/doc/emacs/msdos.texi
@@ -985,21 +985,28 @@ fontconfig library used in modern Free desktops:
   The old XLFD based format is also supported for backwards compatibility.
 
 @cindex font backend selection (MS-Windows)
-  Emacs 23 and later supports a number of font backends.  Currently,
-the @code{gdi} and @code{uniscribe} backends are supported on Windows.
-The @code{gdi} font backend is available on all versions of Windows,
-and supports all fonts that are natively supported by Windows.  The
-@code{uniscribe} font backend is available on Windows 2000 and later,
-and supports TrueType and OpenType fonts.  Some languages requiring
-complex layout can only be properly supported by the Uniscribe
-backend.  By default, both backends are enabled if supported, with
-@code{uniscribe} taking priority over @code{gdi}.  To override that
-and use the GDI backend even if Uniscribe is available, invoke Emacs
-with the @kbd{-xrm Emacs.fontBackend:gdi} command-line argument, or
-add a @code{Emacs.fontBackend} resource with the value @code{gdi} in
-the Registry under either the
-@samp{HKEY_CURRENT_USER\SOFTWARE\GNU\Emacs} or the
-@samp{HKEY_LOCAL_MACHINE\SOFTWARE\GNU\Emacs} key (@pxref{Resources}).
+  Emacs on MS-Windows supports a number of font backends.  Currently,
+the @code{gdi}, @code{uniscribe}, and @code{harfbuzz} backends are
+available.  The @code{gdi} font backend is available on all versions
+of Windows, and supports all fonts that are natively supported by
+Windows.  The @code{uniscribe} font backend is available on Windows
+2000 and later, and supports TrueType and OpenType fonts.  The
+@code{harfbuzz} font backend is available if Emacs was built with
+HarfBuzz support, and if the HarfBuzz DLL is installed on your system;
+like @code{uniscribe}, this backend supports only TrueType and
+OpenType fonts.  Some languages requiring complex layout can only be
+properly supported by the Uniscribe or HarfBuzz backends.  By default,
+all backends are enabled if supported, with @code{harfbuzz} taking
+priority over @code{uniscribe}, and @code{uniscribe} taking priority
+over @code{gdi}.  To override that and use the GDI backend even if
+Uniscribe is available, invoke Emacs with the @kbd{-xrm
+Emacs.fontBackend:gdi} command-line argument, or add a
+@code{Emacs.fontBackend} resource with the value @code{gdi} in the
+Registry under either the @samp{HKEY_CURRENT_USER\SOFTWARE\GNU\Emacs}
+or the @samp{HKEY_LOCAL_MACHINE\SOFTWARE\GNU\Emacs} key
+(@pxref{Resources}).  Similarly, to use the Uniscribe backend even if
+HarfBuzz is available, use @kbd{-xrm Emacs.fontBackend:uniscribe} on
+the command line that invokes Emacs.
 
 @cindex font properties (MS Windows)
 @noindent
diff --git a/doc/lispref/frames.texi b/doc/lispref/frames.texi
index c94b4e67aed..336075a1ca2 100644
--- a/doc/lispref/frames.texi
+++ b/doc/lispref/frames.texi
@@ -2278,18 +2278,21 @@ variable do not take effect immediately, only when you specify the
 @vindex font-backend@r{, a frame parameter}
 @item font-backend
 A list of symbols, specifying the @dfn{font backends} to use for
-drawing fonts in the frame, in order of priority.  On X, there are
-currently three available font backends if Emacs was built without the
-Cairo drawing: @code{x} (the X core font driver), @code{xft} (the Xft
-font driver), and @code{xfthb} (the Xft font driver with HarfBuzz text
-shaping).  If built with the Cairo drawing, then there are two
-available font backends: @code{ftcr} (the FreeType font driver on
-Cairo) and @code{ftcrhb} (the FreeType font driver on Cairo with
-HarfBuzz text shaping).  On MS-Windows, there are currently two
-available font backends: @code{gdi} and @code{uniscribe}
-(@pxref{Windows Fonts,,, emacs, The GNU Emacs Manual}).  On other
-systems, there is only one available font backend, so it does not make
-sense to modify this frame parameter.
+drawing characters on the frame, in order of priority.  In Emacs built
+without Cairo drawing on X, there are currently three available font
+backends: @code{x} (the X core font driver), @code{xft} (the Xft font
+driver), and @code{xfthb} (the Xft font driver with HarfBuzz text
+shaping).  If built with the Cairo drawing, there are two available
+font backends on X: @code{ftcr} (the FreeType font driver on Cairo)
+and @code{ftcrhb} (the FreeType font driver on Cairo with HarfBuzz
+text shaping).  On MS-Windows, there are currently three available
+font backends: @code{gdi} (the core MS-Windows font driver),
+@code{uniscribe} (font driver for OTF and TTF fonts with text shaping
+by the Uniscribe engine), and @code{harfbuzz} (font driver for OTF and
+TTF fonts with HarfBuzz text shaping) (@pxref{Windows Fonts,,, emacs,
+The GNU Emacs Manual}).  On other systems, there is only one available
+font backend, so it does not make sense to modify this frame
+parameter.
 
 @vindex background-mode@r{, a frame parameter}
 @item background-mode