Merge pull request #3333 from fonttools/fix-empty-composite-bbox

[glyf] skip empty components when computing bounds of composite glyphs

Lib/fontTools/ttLib/tables/_g_l_y_f.py

@@ -1211,6 +1211,9 @@ class Glyph(object):
                 g.recalcBounds(glyfTable, boundsDone=boundsDone)
                 if boundsDone is not None:
                     boundsDone.add(glyphName)
+            # empty components shouldn't update the bounds of the parent glyph
+            if g.numberOfContours == 0:
+                continue
 
             x, y = compo.x, compo.y
             bounds = updateBounds(bounds, (g.xMin + x, g.yMin + y))

Tests/ttLib/tables/_g_l_y_f_test.py

@@ -562,6 +562,23 @@ class GlyphTest:
         assert glyphSet["percent"].getCompositeMaxpValues(glyphSet)[2] == 2
         assert glyphSet["perthousand"].getCompositeMaxpValues(glyphSet)[2] == 2
 
+    def test_recalcBounds_empty_components(self):
+        glyphSet = {}
+        pen = TTGlyphPen(glyphSet)
+        # empty simple glyph
+        foo = glyphSet["foo"] = pen.glyph()
+        # use the empty 'foo' glyph as a component in 'bar' with some x/y offsets
+        pen.addComponent("foo", (1, 0, 0, 1, -80, 50))
+        bar = glyphSet["bar"] = pen.glyph()
+
+        foo.recalcBounds(glyphSet)
+        bar.recalcBounds(glyphSet)
+
+        # we expect both the empty simple glyph and the composite referencing it
+        # to have empty bounding boxes (0, 0, 0, 0) no matter the component's shift
+        assert (foo.xMin, foo.yMin, foo.xMax, foo.yMax) == (0, 0, 0, 0)
+        assert (bar.xMin, bar.yMin, bar.xMax, bar.yMax) == (0, 0, 0, 0)
+
 
 class GlyphComponentTest:
     def test_toXML_no_transform(self):