Reproduce crash on Windows? (#37)

Keep a reference to the data blob to avoid HB looking at GC-ed memory. This avoids bad gids and crashes in some environments if the user code doesn't hold on to the blob itself.

src/uharfbuzz/_harfbuzz.pyx

@@ -264,10 +264,12 @@ cdef hb_blob_t* _reference_table_func(
 cdef class Face:
     cdef hb_face_t* _hb_face
     cdef object _reference_table_func
+    cdef object _blob
 
     def __cinit__(self, bytes blob, int index=0):
         cdef hb_blob_t* hb_blob
         if blob is not None:
+            self._blob = blob
             hb_blob = hb_blob_create(
                 blob, len(blob), HB_MEMORY_MODE_READONLY, NULL, NULL)
             self._hb_face = hb_face_create(hb_blob, index)

tests/test_uharfbuzz.py

@@ -4,7 +4,7 @@
 
 
 TESTDATA = Path(__file__).parent / "data"
-ADOBE_BLANK_TTF = (TESTDATA / "AdobeBlank.subset.ttf").read_bytes()
+ADOBE_BLANK_TTF_PATH = TESTDATA / "AdobeBlank.subset.ttf"
 
 
 @pytest.fixture
@@ -22,7 +22,7 @@ def blankfont():
         {gid=8, name="u1F4A9", code=0x1F4A9},  # PILE OF POO
     ]
     """
-    face = hb.Face(ADOBE_BLANK_TTF)
+    face = hb.Face(ADOBE_BLANK_TTF_PATH.read_bytes())
     font = hb.Font(face)
     upem = face.upem
     font.scale = (upem, upem)