[skrifa] empty glyphs have phantom points too (#1283)

Fixes a small oversight: we explicitly didn't account for phantom point memory for empty glyphs. Just removes the explicit check and adds a test to ensure it works.

skrifa/src/outline/glyf/mod.rs

@@ -150,13 +150,10 @@ impl<'a> Outlines<'a> {
             ..Default::default()
         };
         let glyph = self.loca.get_glyf(glyph_id, &self.glyf)?;
-        if glyph.is_none() {
-            return Ok(outline);
-        }
-        self.outline_rec(glyph.as_ref().unwrap(), &mut outline, 0, 0)?;
-        if outline.points != 0 {
-            outline.points += PHANTOM_POINT_COUNT;
+        if let Some(glyph) = glyph.as_ref() {
+            self.outline_rec(glyph, &mut outline, 0, 0)?;
         }
+        outline.points += PHANTOM_POINT_COUNT;
         outline.max_stack = self.max_stack_elements as usize;
         outline.cvt_count = self.cvt_len as usize;
         outline.storage_count = self.max_storage as usize;
@@ -1320,17 +1317,30 @@ mod tests {
         let gid = font.charmap().map(' ').unwrap();
         let outline = outlines.outline(gid).unwrap();
         // Make sure this is an empty outline since that's what we're testing
-        assert_eq!(outline.points, 0);
-        let scaler = FreeTypeScaler::unhinted(&outlines, &outline, &mut [], ppem, &coords).unwrap();
+        assert!(outline.glyph.is_none());
+        let mut buf = [0u8; 128];
+        let scaler =
+            FreeTypeScaler::unhinted(&outlines, &outline, &mut buf, ppem, &coords).unwrap();
         let scaled = scaler.scale(&outline.glyph, gid).unwrap();
         let advance_hvar = scaled.adjusted_advance_width();
         // Set HVAR table to None to force loading metrics from gvar
         outlines.common.hvar = None;
-        let scaler = FreeTypeScaler::unhinted(&outlines, &outline, &mut [], ppem, &coords).unwrap();
+        let scaler =
+            FreeTypeScaler::unhinted(&outlines, &outline, &mut buf, ppem, &coords).unwrap();
         let scaled = scaler.scale(&outline.glyph, gid).unwrap();
         let advance_gvar = scaled.adjusted_advance_width();
         // Make sure we have an advance and that the two are the same
         assert!(advance_hvar != F26Dot6::ZERO);
         assert_eq!(advance_hvar, advance_gvar);
     }
+
+    #[test]
+    fn empty_glyphs_have_phantom_points_too() {
+        let font = FontRef::new(font_test_data::HVAR_WITH_TRUNCATED_ADVANCE_INDEX_MAP).unwrap();
+        let outlines = Outlines::new(&OutlinesCommon::new(&font).unwrap()).unwrap();
+        let gid = font.charmap().map(' ').unwrap();
+        let outline = outlines.outline(gid).unwrap();
+        assert!(outline.glyph.is_none());
+        assert_eq!(outline.points, PHANTOM_POINT_COUNT);
+    }
 }