Set wrap text style when multiline string encountered

Fixes #10
If a cell contains a multiline string, "wrap text" style option should
automatically be set.

src/Spout/Writer/XLSX/Helper/StyleHelper.php

@@ -71,6 +71,51 @@ class StyleHelper
         return $this->styleIdToStyleMappingTable[$styleId];
     }
 
+    /**
+     * Apply additional styles if the given row needs it.
+     * Typically, set "wrap text" if a cell contains a new line.
+     *
+     * @param \Box\Spout\Writer\Style\Style $style The original style
+     * @param array $dataRow The row the style will be applied to
+     * @return \Box\Spout\Writer\Style\Style The updated style
+     */
+    public function applyExtraStylesIfNeeded($style, $dataRow)
+    {
+        $updatedStyle = $this->applyWrapTextIfCellContainsNewLine($style, $dataRow);
+
+        return $updatedStyle;
+    }
+
+    /**
+     * Set the "wrap text" option if a cell of the given row contains a new line.
+     *
+     * @NOTE: There is a bug on the Mac version of Excel (2011 and below) where new lines
+     *        are ignored even when the "wrap text" option is set. This only occurs with
+     *        inline strings (shared strings do work fine).
+     *        A workaround would be to encode "\n" as "_x000D_" but it does not work
+     *        on the Windows version of Excel...
+     *
+     * @param \Box\Spout\Writer\Style\Style $style The original style
+     * @param array $dataRow The row the style will be applied to
+     * @return \Box\Spout\Writer\Style\Style The eventually updated style
+     */
+    protected function applyWrapTextIfCellContainsNewLine($style, $dataRow)
+    {
+        // if the "wrap text" option is already set, no-op
+        if ($style->shouldWrapText()) {
+            return $style;
+        }
+
+        foreach ($dataRow as $cell) {
+            if (is_string($cell) && strpos($cell, "\n") !== false) {
+                $style->setShouldWrapText();
+                break;
+            }
+        }
+
+        return $style;
+    }
+
     /**
      * Returns the content of the "styles.xml" file, given a list of styles.
      * @return string