[scaled-font] Hold reference to original font face

As noted by Carl during his LCA talk, caching of toy fonts was broken
because we create the scaled font using the implementation font face and
lose the reference to the containing font face that is cached by the toy
font face create routines. So the toy fonts were not being preserved for
the duration of the holdover scaled fonts and we recreated a new font
face, new scaled font and new glyph caches every time we needed a font.

src/cairo-ft-font.c

@@ -444,6 +444,7 @@ _cairo_ft_unscaled_font_create_internal (cairo_bool_t from_face,
     if (unlikely (status))
 	goto UNWIND_UNSCALED_MALLOC;
 
+    assert (unscaled->base.hash_entry.hash == key.base.hash_entry.hash);
     status = _cairo_hash_table_insert (font_map->hash_table,
 				       &unscaled->base.hash_entry);
     if (unlikely (status))
@@ -484,7 +485,6 @@ _cairo_ft_unscaled_font_create_for_pattern (FcPattern *pattern)
 
 DONE:
     return _cairo_ft_unscaled_font_create_internal (font_face != NULL, filename, id, font_face);
-
 }
 
 static cairo_ft_unscaled_font_t *

src/cairo-scaled-font-private.h

@@ -84,6 +84,8 @@ struct _cairo_scaled_font {
     cairo_reference_count_t ref_count;
     cairo_user_data_array_t user_data;
 
+    cairo_font_face_t *original_font_face; /* may be NULL */
+
     /* hash key members */
     cairo_font_face_t *font_face; /* may be NULL */
     cairo_matrix_t font_matrix;	  /* font space => user space */

src/cairo-scaled-font.c

@@ -206,6 +206,7 @@ static const cairo_scaled_font_t _cairo_scaled_font_nil = {
     CAIRO_STATUS_NO_MEMORY,	/* status */
     CAIRO_REFERENCE_COUNT_INVALID,	/* ref_count */
     { 0, 0, 0, NULL },		/* user_data */
+    NULL,			/* original_font_face */
     NULL,			/* font_face */
     { 1., 0., 0., 1., 0, 0},	/* font_matrix */
     { 1., 0., 0., 1., 0, 0},	/* ctm */
@@ -706,14 +707,17 @@ _cairo_scaled_font_keys_equal (const void *abstract_key_a, const void *abstract_
     const cairo_scaled_font_t *key_a = abstract_key_a;
     const cairo_scaled_font_t *key_b = abstract_key_b;
 
-    return (key_a->font_face == key_b->font_face &&
+    if (key_a->hash_entry.hash != key_b->hash_entry.hash)
+	return FALSE;
+
+    return key_a->font_face == key_b->font_face &&
 	    memcmp ((unsigned char *)(&key_a->font_matrix.xx),
 		    (unsigned char *)(&key_b->font_matrix.xx),
 		    sizeof(cairo_matrix_t)) == 0 &&
 	    memcmp ((unsigned char *)(&key_a->ctm.xx),
 		    (unsigned char *)(&key_b->ctm.xx),
 		    sizeof(cairo_matrix_t)) == 0 &&
-	    cairo_font_options_equal (&key_a->options, &key_b->options));
+	    cairo_font_options_equal (&key_a->options, &key_b->options);
 }
 
 /*
@@ -863,8 +867,8 @@ _cairo_scaled_font_fini_internal (cairo_scaled_font_t *scaled_font)
 
     _cairo_scaled_glyph_page_cache_remove_scaled_font (scaled_font);
 
-    if (scaled_font->font_face != NULL)
-	cairo_font_face_destroy (scaled_font->font_face);
+    cairo_font_face_destroy (scaled_font->font_face);
+    cairo_font_face_destroy (scaled_font->original_font_face);
 
     CAIRO_MUTEX_FINI (scaled_font->mutex);
 
@@ -916,6 +920,7 @@ cairo_scaled_font_create (cairo_font_face_t          *font_face,
 {
     cairo_status_t status;
     cairo_scaled_font_map_t *font_map;
+    cairo_font_face_t *original_font_face = font_face;
     cairo_scaled_font_t key, *old = NULL, *scaled_font = NULL;
     double det;
 
@@ -1051,6 +1056,10 @@ cairo_scaled_font_create (cairo_font_face_t          *font_face,
 	return scaled_font;
     }
 
+    scaled_font->original_font_face =
+	cairo_font_face_reference (original_font_face);
+
+    assert (scaled_font->hash_entry.hash == key.hash_entry.hash);
     status = _cairo_hash_table_insert (font_map->hash_table,
 				       &scaled_font->hash_entry);
     if (likely (status == CAIRO_STATUS_SUCCESS)) {

src/cairo-toy-font-face.c

@@ -325,6 +325,7 @@ cairo_toy_font_face_create (const char          *family,
     if (unlikely (status))
 	goto UNWIND_FONT_FACE_MALLOC;
 
+    assert (font_face->base.hash_entry.hash == key.base.hash_entry.hash);
     status = _cairo_hash_table_insert (hash_table, &font_face->base.hash_entry);
     if (unlikely (status))
 	goto UNWIND_FONT_FACE_INIT;