<style>
    div { margin: 8px 0; }
    span { -webkit-text-emphasis: 'x'; }
    .flipped { -webkit-writing-mode: horizontal-bt; }
</style>
<body style="font-family: ahem; font-size: 32px; -webkit-font-smoothing: none;">
    <!-- emphasis under, should not be suppressed by ruby -->
    <div>
        1 <ruby><rb>23 <span style="-webkit-text-emphasis-position: under;">45</span></rb><rt>678</rt></ruby>
    </div>
    <!-- emphasis over, but no lines in ruby text, should not inhibit emphasis -->
    <div>
        1 <ruby><rb>23 <span style="-webkit-text-emphasis-position: over;">45</span></rb><rt> </rt></ruby>
    </div>
    <!-- emphasis over should be suppressed by ruby -->
    <div>
        1 <ruby><rb>23 <span style="-webkit-text-emphasis-position: over; -webkit-text-emphasis-color: red;">45</span></rb><rt>678</rt></ruby>
    </div>

    <!-- emphasis under, should not be suppressed by ruby -->
    <div class="flipped">
        1 <ruby><rb>23 <span style="-webkit-text-emphasis-position: under;">45</span></rb><rt>678</rt></ruby>
    </div>
    <!-- emphasis over, but no lines in ruby text, should not inhibit emphasis -->
    <div class="flipped">
        1 <ruby><rb>23 <span style="-webkit-text-emphasis-position: over;">45</span></rb><rt> </rt></ruby>
    </div>
    <!-- emphasis over should be suppressed by ruby -->
    <div class="flipped">
        1 <ruby><rb>23 <span style="-webkit-text-emphasis-position: over; -webkit-text-emphasis-color: red;">45</span></rb><rt>678</rt></ruby>
    </div>

</body>