tts:textEmphasis before/after not working properly #154
Description
tts:textEmphasis with horizontal text will always produce the boutens on the top of the text for single lined bottom positioned horizontal text, regardless of if before or after is used.
Example IMSC 1.1:
<?xml version="1.0" encoding="utf-8" ?>
<tt xml:lang="ja" ttp:contentProfiles="http://www.w3.org/ns/ttml/profile/imsc1.1/text" xmlns="http://www.w3.org/ns/ttml" xmlns:tts="http://www.w3.org/ns/ttml#styling" xmlns:ttm="http://www.w3.org/ns/ttml#metadata" xmlns:ttp="http://www.w3.org/ns/ttml#parameter" ttp:timeBase="media" ttp:frameRate="24" ttp:frameRateMultiplier="1000 1001" ttp:displayAspectRatio="16 9">
<head>
<styling>
<style xml:id="default" tts:color="white" tts:backgroundColor="transparent" tts:fontFamily="proportionalSansSerif" tts:fontSize="80%" tts:fontWeight="normal" tts:fontStyle="normal"/>
</styling>
<layout>
<region xml:id="Region_Bottom" tts:backgroundColor="transparent" tts:showBackground="whenActive" tts:origin="10% 10%" tts:extent="80% 80%" tts:textAlign="center" tts:displayAlign="after" tts:luminanceGain="4.0"/>
</layout>
</head>
<body>
<div>
<p begin="00f" end="10f" style="default" region="Region_Bottom">
<span tts:textEmphasis="filled circle before">花</span>
<span tts:textEmphasis="filled dot before">よ</span>
<span tts:textEmphasis="filled sesame before">り</span>
<span tts:textEmphasis="open circle before">だ</span>
<span tts:textEmphasis="open dot before">ん</span>
<span tts:textEmphasis="open sesame before">ご</span>
<br/>
<span tts:textEmphasis="filled circle after">花</span>
<span tts:textEmphasis="filled dot after">よ</span>
<span tts:textEmphasis="filled sesame after">り</span>
<span tts:textEmphasis="open circle after">だ</span>
<span tts:textEmphasis="open dot after">ん</span>
<span tts:textEmphasis="open sesame after">ご</span>
</p>
<p begin="10f" end="20f" style="default" region="Region_Bottom">
<span tts:textEmphasis="filled circle before">花</span>
<span tts:textEmphasis="filled dot before">よ</span>
<span tts:textEmphasis="filled sesame before">り</span>
<span tts:textEmphasis="open circle before">だ</span>
<span tts:textEmphasis="open dot before">ん</span>
<span tts:textEmphasis="open sesame before">ご</span>
</p>
<p begin="20f" end="30f" style="default" region="Region_Bottom">
<span tts:textEmphasis="filled circle after">花</span>
<span tts:textEmphasis="filled dot after">よ</span>
<span tts:textEmphasis="filled sesame after">り</span>
<span tts:textEmphasis="open circle after">だ</span>
<span tts:textEmphasis="open dot after">ん</span>
<span tts:textEmphasis="open sesame after">ご</span>
</p>
</div>
</body>
</tt>