-"additions to HTML groups
-syn region htmlItalic start="\\\@<!\*\S\@=" end="\S\@<=\\\@<!\*" keepend oneline
-syn region htmlItalic start="\(^\|\s\)\@<=_\|\\\@<!_\([^_]\+\s\)\@=" end="\S\@<=[^\\]_\|[^\\]_\S\@=" keepend oneline
-syn region htmlBold start="\S\@<=\*\*\|\*\*\S\@=" end="\S\@<=\*\*\|\*\*\S\@=" keepend oneline
-syn region htmlBold start="\S\@<=__\|__\S\@=" end="\S\@<=__\|__\S\@=" keepend oneline
-syn region htmlBoldItalic start="\S\@<=\*\*\*\|\*\*\*\S\@=" end="\S\@<=\*\*\*\|\*\*\*\S\@=" keepend oneline
-syn region htmlBoldItalic start="\S\@<=___\|___\S\@=" end="\S\@<=___\|___\S\@=" keepend oneline
+let s:conceal = ''
+let s:concealends = ''
+if has('conceal') && get(g:, 'vim_markdown_conceal', 1)
+ let s:conceal = ' conceal'
+ let s:concealends = ' concealends'
+endif
+
+" additions to HTML groups
+if get(g:, 'vim_markdown_emphasis_multiline', 1)
+ let s:oneline = ''
+else
+ let s:oneline = ' oneline'
+endif
+execute 'syn region htmlItalic start="\%(^\|\s\)\zs\*\ze[^\\\*\t ]\%(\%([^*]\|\\\*\|\n\)*[^\\\*\t ]\)\?\*\_W" end="[^\\\*\t ]\zs\*\ze\_W" keepend' . s:oneline
+execute 'syn region htmlItalic start="\%(^\|\s\)\zs_\ze[^\\_\t ]" end="[^\\_\t ]\zs_\ze\_W" keepend' . s:oneline
+execute 'syn region htmlBold start="\%(^\|\s\)\*\*\ze\S" end="\S\zs\*\*" keepend' . s:oneline
+execute 'syn region htmlBold start="\%(^\|\s\)\zs__\ze\S" end="\S\zs__" keepend' . s:oneline
+execute 'syn region htmlBoldItalic start="\%(^\|\s\)\zs\*\*\*\ze\S" end="\S\zs\*\*\*" keepend' . s:oneline
+execute 'syn region htmlBoldItalic start="\%(^\|\s\)\zs___\ze\S" end="\S\zs___" keepend' . s:oneline