Docx writer: fix sizing for images.

Setting size to a percent now scales image to percent of
page width. Previously a percent width or height would
just provide a maximum bound rather than scaling.

Closes #11838.

src/Text/Pandoc/Writers/Docx/OpenXML.hs

@@ -995,10 +995,23 @@ inlineToOpenXML' opts (Image attr@(imgident, _, _) alt (src, title)) = do
         (xpt,ypt) = desiredSizeInPoints opts attr
                (either (const def) id (imageSize opts img))
         -- 12700 emu = 1 pt
-        pageWidthPt = case dimension Width attr of
-                        Just (Percent a) -> pageWidth * floor (a * 127)
-                        _                -> pageWidth * 12700
-        (xemu,yemu) = fitToPage (xpt * 12700, ypt * 12700) pageWidthPt
+        pageWidthPt = fromIntegral pageWidth
+        pageWidthEmu = pageWidth * 12700
+        (xpt', ypt') =
+          case (dimension Width attr, dimension Height attr) of
+                 (Just (Percent a), Just (Percent b))
+                   -> ((a / 100.0) * pageWidthPt, (b / 100.0) * pageWidthPt)
+                      -- note, should use pageHeightPt but we don't have this
+                      -- information.
+                 (Just (Percent a), _)
+                   -> ((a / 100.0) * pageWidthPt,
+                       (a / 100.0) * pageWidthPt * (ypt / xpt))
+                 (_, Just (Percent b))
+                   -> ((b / 100.0) * pageWidthPt * (xpt / ypt),
+                       (b / 100.0) * pageWidthPt)
+                 (_, _) -> (xpt, ypt)
+        (xemu,yemu) = fitToPage (xpt' * 12700,
+                                 ypt' * 12700) pageWidthEmu
         cNvPicPr = mknode "pic:cNvPicPr" [] $
                          mknode "a:picLocks" [("noChangeArrowheads","1")
                                              ,("noChangeAspect","1")] ()

src/Text/Pandoc/Writers/Docx/Types.hs

@@ -87,7 +87,7 @@ data WriterEnv = WriterEnv
   , envInNote         :: Bool
   , envChangesAuthor  :: Text
   , envChangesDate    :: Text
-  , envPrintWidth     :: Integer
+  , envPrintWidth     :: Integer  -- in points
   , envLang           :: Maybe Text
   , envSectPr         :: Maybe Element
   }

src/Text/Pandoc/Writers/OOXML.hs

@@ -89,8 +89,8 @@ isElem ns prefix name element =
 
 type NameSpaces = [(Text, Text)]
 
--- | Scales the image to fit the page
--- sizes are passed in emu
+-- | Scales the image to fit the page if it would overflow.
+-- Sizes are passed in emu.
 fitToPage :: (Double, Double) -> Integer -> (Integer, Integer)
 fitToPage (x, y) pageWidth
   -- Fixes width to the page width and scales the height