pptx: Fix list level numbering

In PowerPoint, the content of a top-level list is at the same level as
the content of a top-level paragraph – the only difference is that a
list style has been applied.

At the moment, the pptx writer increments the paragraph level on each
list, turning what should be top-level lists into second-level lists.

This commit changes that logic, only incrementing the paragraph level on
continuation paragraphs of lists.

- Fixes https://github.com/jgm/pandoc/issues/4828
- Fixes https://github.com/jgm/pandoc/issues/4663

pandoc.cabal

@@ -429,6 +429,8 @@ extra-source-files:
                  test/pptx/inline-formatting/*.pptx
                  test/pptx/lists/input.native
                  test/pptx/lists/*.pptx
+                 test/pptx/list-level/input.native
+                 test/pptx/list-level/*.pptx
                  test/pptx/raw-ooxml/input.native
                  test/pptx/raw-ooxml/*.pptx
                  test/pptx/remove-empty-slides/input.native

src/Text/Pandoc/Writers/Powerpoint/Presentation.hs

@@ -500,27 +500,23 @@ blockToParagraphs (Header _ (ident, _, _) ils) = do
 blockToParagraphs (BulletList blksLst) = do
   pProps <- asks envParaProps
   incremental <- listShouldBeIncremental
-  let lvl = pPropLevel pProps
   local (\env -> env{ envInList = True
-                    , envParaProps = pProps{ pPropLevel = lvl + 1
-                                           , pPropBullet = Just Bullet
+                    , envParaProps = pProps{ pPropBullet = Just Bullet
                                            , pPropMarginLeft = Nothing
                                            , pPropIndent = Nothing
                                            , pPropIncremental = incremental
                                            }}) $
-    concatMapM multiParBullet blksLst
+    concatMapM multiParList blksLst
 blockToParagraphs (OrderedList listAttr blksLst) = do
   pProps <- asks envParaProps
   incremental <- listShouldBeIncremental
-  let lvl = pPropLevel pProps
   local (\env -> env{ envInList = True
-                    , envParaProps = pProps{ pPropLevel = lvl + 1
-                                           , pPropBullet = Just (AutoNumbering listAttr)
+                    , envParaProps = pProps{ pPropBullet = Just (AutoNumbering listAttr)
                                            , pPropMarginLeft = Nothing
                                            , pPropIndent = Nothing
                                            , pPropIncremental = incremental
                                            }}) $
-    concatMapM multiParBullet blksLst
+    concatMapM multiParList blksLst
 blockToParagraphs (DefinitionList entries) = do
   incremental <- listShouldBeIncremental
   let go :: ([Inline], [[Block]]) -> Pres [Paragraph]
@@ -545,14 +541,21 @@ blockToParagraphs blk = do
   addLogMessage $ BlockNotRendered blk
   return []
 
--- Make sure the bullet env gets turned off after the first para.
-multiParBullet :: [Block] -> Pres [Paragraph]
-multiParBullet [] = return []
-multiParBullet (b:bs) = do
+-- | Make sure the bullet env gets turned off after the first paragraph, and
+-- indent any continuation paragraphs.
+multiParList :: [Block] -> Pres [Paragraph]
+multiParList [] = return []
+multiParList (b:bs) = do
   pProps <- asks envParaProps
   p <- blockToParagraphs b
-  ps <- local (\env -> env{envParaProps = pProps{pPropBullet = Nothing}}) $
-    concatMapM blockToParagraphs bs
+  let level = pPropLevel pProps
+  ps <- local (\env -> env
+                { envParaProps = pProps
+                  { pPropBullet = Nothing
+                  , pPropLevel = level + 1
+                  }
+                })
+        $ concatMapM blockToParagraphs bs
   return $ p ++ ps
 
 cellToParagraphs :: Alignment -> SimpleCell -> Pres [Paragraph]

test/Tests/Writers/Powerpoint.hs

@@ -66,6 +66,10 @@ tests = let
                      def
                      "pptx/start-numbering-at/input.native"
                      "pptx/start-numbering-at/output.pptx"
+                   , pptxTests "List continuation paragraph indentation"
+                     def
+                     "pptx/list-level/input.native"
+                     "pptx/list-level/output.pptx"
                    , pptxTests "tables"
                      def
                      "pptx/tables/input.native"

test/pptx/list-level/input.native

@@ -0,0 +1,20 @@
+[Header 1 ("slide",[],[]) [Str "Slide"]
+,BulletList
+ [[Para [Str "Top-level"]
+  ,Para [Str "With",Space,Str "continuation",Space,Str "paragraph"]]
+ ,[Para [Str "Then:"]
+  ,BulletList
+   [[Plain [Str "nested"]]
+   ,[Plain [Str "list"]]
+   ,[Plain [Str "items"]]]]]
+,Header 1 ("slide-1",[],[]) [Str "Slide"]
+,Para [Str "Paragraph."]
+,OrderedList (1,Decimal,Period)
+ [[Para [Str "Top-level"]
+  ,Para [Str "Continuation"]
+  ,OrderedList (1,Decimal,Period)
+   [[Para [Str "Sub-list"]
+    ,Para [Str "With",Space,Str "Continuation"]]
+   ,[Para [Str "(still",Space,Str "sub-list)"]]]]
+ ,[Para [Str "(back",Space,Str "to",Space,Str "top-level)"]]]
+,Para [Str "Paragraph."]]