HTML: prevent gratuitious emojification on iOS.

iOS chooses to render a number of Unicode entities,
including '↩', as big colorful emoji.  This can be
defeated by appending Unicode
VARIATION SELECTOR-15'/'VARIATION SELECTOR-16'.
So we now append this character when escaping
strings, for both '↩' and '↔'.

If other characters prove problematic, they can
simply be added to needsVariationSelector.

Closes #5469.

1 files changed, 10 insertions, 1 deletions

diff --git a/src/Text/Pandoc/Writers/HTML.hs b/src/Text/Pandoc/Writers/HTML.hs
index 2a8835263..3cd9a0892 100644
--- a/src/Text/Pandoc/Writers/HTML.hs
+++ b/src/Text/Pandoc/Writers/HTML.hs
@@ -108,11 +108,20 @@ defaultWriterState = WriterState {stNotes= [], stMath = False, stQuotes = False,
 strToHtml :: String -> Html
 strToHtml ('\'':xs) = preEscapedString "\'" `mappend` strToHtml xs
 strToHtml ('"' :xs) = preEscapedString "\"" `mappend` strToHtml xs
-strToHtml xs@(_:_)  = case break (\c -> c == '\'' || c == '"') xs of
+strToHtml (x:xs) | needsVariationSelector x
+                    = preEscapedString [x, '\xFE0E'] `mappend` strToHtml xs
+strToHtml xs@(_:_)  = case break (\c -> c == '\'' || c == '"' ||
+                                        needsVariationSelector c) xs of
                            (_ ,[]) -> toHtml xs
                            (ys,zs) -> toHtml ys `mappend` strToHtml zs
 strToHtml [] = ""
 
+-- See #5469: this prevents iOS from substituting emojis.
+needsVariationSelector :: Char -> Bool
+needsVariationSelector '↩' = True
+needsVariationSelector '↔' = True
+needsVariationSelector _   = False
+
 -- | Hard linebreak.
 nl :: WriterOptions -> Html
 nl opts = if writerWrapText opts == WrapNone