Implement issue 36 (#38)

* added post table format 2.0, so we have glyph names

* implement a issue #36: adding font.get_glyph_name(gid) method

* also expose hb_font_glyph_to_string() via font.glyph_to_string()

src/uharfbuzz/_harfbuzz.pyx

@@ -374,6 +374,23 @@ cdef class Font:
         finally:
             free(hb_variations)
 
+    def get_glyph_name(self, gid: int):
+        cdef char name[64]
+        cdef bytes packed
+        success = hb_font_get_glyph_name(self._hb_font, gid, name, 64)
+        if success:
+            packed = name
+            return packed.decode()
+        else:
+            return None
+
+    def glyph_to_string(self, gid: int):
+        cdef char name[64]
+        cdef bytes packed
+        hb_font_glyph_to_string(self._hb_font, gid, name, 64)
+        packed = name
+        return packed.decode()
+
 
 cdef hb_position_t _glyph_h_advance_func(hb_font_t* font, void* font_data,
                                          hb_codepoint_t glyph,

src/uharfbuzz/charfbuzz.pxd

@@ -212,6 +212,16 @@ cdef extern from "hb.h":
         hb_font_t* font,
         const hb_variation_t* variations,
         unsigned int variations_length)
+    hb_bool_t hb_font_get_glyph_name(
+        hb_font_t* font,
+        hb_codepoint_t glyph,
+        char* name,
+        unsigned int size)
+    void hb_font_glyph_to_string(
+        hb_font_t* font,
+        hb_codepoint_t glyph,
+        char* name,
+        unsigned int size)
     void hb_font_destroy(hb_font_t* font)
 
     # hb-shape.h

tests/test_uharfbuzz.py

@@ -112,6 +112,32 @@ def test_gid_and_cluster_no_features(self, blankfont, string, expected):
         infos = [(g.codepoint, g.cluster) for g in buf.glyph_infos]
         assert infos == expected
 
+    @pytest.mark.parametrize(
+        "string, expected",
+        [
+            ("abcde", ["a", "b", "c", "d", "e"]),
+            ("abçde", ["a", "b", "ccedilla", "d", "e"]),
+            ("aбcde", ["a", "uni0431", "c", "d", "e"]),
+            ("abc💩e", ["a", "b", "c", "u1F4A9", "e"]),
+        ],
+        ids=["ascii", "latin1", "ucs2", "ucs4"],
+    )
+    def test_glyh_name_no_features(self, blankfont, string, expected):
+        buf = hb.Buffer()
+        buf.add_str(string)
+        buf.guess_segment_properties()
+        hb.shape(blankfont, buf)
+        # font.get_glyph_name() returns None if the font does not contain glyph names
+        # or if the glyph ID does not exist.
+        glyph_names = [blankfont.get_glyph_name(g.codepoint) for g in buf.glyph_infos]
+        assert glyph_names == expected
+        assert blankfont.get_glyph_name(1000) is None
+        # font.glyph_to_string() return "gidN" if the font does not contain glyph names
+        # or if the glyph ID does not exist.
+        glyph_names = [blankfont.glyph_to_string(g.codepoint) for g in buf.glyph_infos]
+        assert glyph_names == expected
+        assert blankfont.glyph_to_string(1000) == 'gid1000'
+
 
 class TestCallbacks:
     def test_nominal_glyph_func(self, blankfont):