From 28d5193ba3b2e5e83ed6a8024a8d3b814603b981 Mon Sep 17 00:00:00 2001
From: Kovid Goyal <kovid@kovidgoyal.net>
Date: Fri, 9 Jul 2010 14:15:20 -0600
Subject: [PATCH] MOBI Output: Partial support for nested superscript and
 subscripts. Fixes #6132 (nested subscript conversion-----epub to mobi)

---
 src/calibre/ebooks/mobi/mobiml.py | 15 +++++++++++++--
 1 file changed, 13 insertions(+), 2 deletions(-)

diff --git a/src/calibre/ebooks/mobi/mobiml.py b/src/calibre/ebooks/mobi/mobiml.py
index bfa8758c85..231ad51eee 100644
--- a/src/calibre/ebooks/mobi/mobiml.py
+++ b/src/calibre/ebooks/mobi/mobiml.py
@@ -58,6 +58,7 @@ class FormatState(object):
         self.fsize = 3
         self.ids = set()
         self.valign = 'baseline'
+        self.nest = False
         self.italic = False
         self.bold = False
         self.strikethrough = False
@@ -233,9 +234,17 @@ class MobiMLizer(object):
                 inline = etree.SubElement(inline, XHTML('a'), href=href)
                 bstate.anchor = inline
             if valign == 'super':
-                inline = etree.SubElement(inline, XHTML('sup'))
+                parent = inline
+                if istate.nest and bstate.inline is not None:
+                    parent = bstate.inline
+                    istate.nest = False
+                inline = etree.SubElement(parent, XHTML('sup'))
             elif valign == 'sub':
-                inline = etree.SubElement(inline, XHTML('sub'))
+                parent = inline
+                if istate.nest and bstate.inline is not None:
+                    parent = bstate.inline
+                    istate.nest = False
+                inline = etree.SubElement(parent, XHTML('sub'))
             elif fsize != 3:
                 inline = etree.SubElement(inline, XHTML('font'),
                                           size=str(fsize))
@@ -343,8 +352,10 @@ class MobiMLizer(object):
             istate.family = 'serif'
         valign = style['vertical-align']
         if valign in ('super', 'text-top') or asfloat(valign) > 0:
+            istate.nest = istate.valign in ('sub', 'super')
             istate.valign = 'super'
         elif valign == 'sub'  or asfloat(valign) < 0:
+            istate.nest = istate.valign in ('sub', 'super')
             istate.valign = 'sub'
         else:
             istate.valign = 'baseline'