RST writer: Improve spacing for tables with no width information.

If a simple table would be too wide, we use a grid table.
The code for generating grid tables has been adjusted to
give more intelligent column widths when widths aren't
given. (This also affects the markdown writer.)

Closes #5899.

2 files changed, 26 insertions, 6 deletions

diff --git a/src/Text/Pandoc/Writers/RST.hs b/src/Text/Pandoc/Writers/RST.hs
index 4a3b1b066..dc732b0e6 100644
--- a/src/Text/Pandoc/Writers/RST.hs
+++ b/src/Text/Pandoc/Writers/RST.hs
@@ -296,7 +296,13 @@ blockToRST (Table caption aligns widths headers rows) = do
   opts <- gets stOptions
   let isSimple = all (== 0) widths
   tbl <- if isSimple
-            then simpleTable opts blocksToDoc headers rows
+            then do
+              tbl' <- simpleTable opts blocksToDoc headers rows
+              if offset tbl' > writerColumns opts
+                 then gridTable opts blocksToDoc (all null headers)
+                      (map (const AlignDefault) aligns) widths
+                      headers rows
+                 else return tbl'
             else gridTable opts blocksToDoc (all null headers)
                   (map (const AlignDefault) aligns) widths
                   headers rows
diff --git a/src/Text/Pandoc/Writers/Shared.hs b/src/Text/Pandoc/Writers/Shared.hs
index 39035832f..0161db506 100644
--- a/src/Text/Pandoc/Writers/Shared.hs
+++ b/src/Text/Pandoc/Writers/Shared.hs
@@ -229,8 +229,7 @@ gridTable opts blocksToDoc headless aligns widths headers rows = do
   -- handleGivenWidths wraps the given blocks in order for them to fit
   -- in cells with given widths. the returned content can be
   -- concatenated with borders and frames
-  let handleGivenWidths widths' = do
-        let widthsInChars' = officialWidthsInChars widths'
+  let handleGivenWidthsInChars widthsInChars' = do
         -- replace page width (in columns) in the options with a
         -- given width if smaller (adjusting by two)
         let useWidth w = opts{writerColumns = min (w - 2) (writerColumns opts)}
@@ -241,6 +240,8 @@ gridTable opts blocksToDoc headless aligns widths headers rows = do
              (\cs -> zipWithM blocksToDoc columnOptions cs)
              rows
         return (widthsInChars', rawHeaders', rawRows')
+  let handleGivenWidths widths' = handleGivenWidthsInChars
+                                     (officialWidthsInChars widths')
   -- handleFullWidths tries to wrap cells to the page width or even
   -- more in cases where `--wrap=none`. thus the content here is left
   -- as wide as possible
@@ -262,9 +263,22 @@ gridTable opts blocksToDoc headless aligns widths headers rows = do
   let handleZeroWidths widths' = do
         (widthsInChars', rawHeaders', rawRows') <- handleFullWidths widths'
         if foldl' (+) 0 widthsInChars' > writerColumns opts
-           then -- use even widths
-                handleGivenWidths
-                  (replicate numcols (1.0 / fromIntegral numcols) :: [Double])
+           then do -- use even widths except for thin columns
+             let evenCols  = max 5
+                              (((writerColumns opts - 1) `div` numcols) - 3)
+             let (numToExpand, colsToExpand) =
+                   foldr (\w (n, tot) -> if w < evenCols
+                                            then (n, tot + (evenCols - w))
+                                            else (n + 1, tot))
+                                   (0,0) widthsInChars'
+             let expandAllowance = colsToExpand `div` numToExpand
+             let newWidthsInChars = map (\w -> if w < evenCols
+                                                  then w
+                                                  else min
+                                                       (evenCols + expandAllowance)
+                                                       w)
+                                        widthsInChars'
+             handleGivenWidthsInChars newWidthsInChars
            else return (widthsInChars', rawHeaders', rawRows')
   -- render the contents of header and row cells differently depending
   -- on command line options, widths given in this specific table, and