test assertions trigger
I've added a number of reasonable-looking assertions about extents to test-layout (to improve test coverage), but it turns out that they trigger in some cases. For example:
width=200,ellipsize=end
<span font='LiberationSans 100'><span font='LiberationSerif'>Text</span>Text</span>
gives
$ ./build/tests/test-layout test
**
ERROR:../tests/test-layout.c:488:test_file: assertion failed (line_height <= height): (163840 <= 156263)
Bail out! ERROR:../tests/test-layout.c:488:test_file: assertion failed (line_height <= height): (163840 <= 156263)
This needs investigation