Default row style should only apply to existing cells

src/Spout/Writer/XLSX/Manager/Style/StyleManager.php

@@ -204,8 +204,8 @@ EOD;
 
         foreach ($registeredStyles as $style) {
             $styleId = $style->getId();
-            $fillId = $this->styleRegistry->getFillIdForStyleId($styleId);
-            $borderId = $this->styleRegistry->getBorderIdForStyleId($styleId);
+            $fillId = $this->getFillIdForStyleId($styleId);
+            $borderId = $this->getBorderIdForStyleId($styleId);
 
             $content .= '<xf numFmtId="0" fontId="' . $styleId . '" fillId="' . $fillId . '" borderId="' . $borderId . '" xfId="0"';
 
@@ -229,6 +229,38 @@ EOD;
         return $content;
     }
 
+    /**
+     * Returns the fill ID associated to the given style ID.
+     * For the default style, we don't a fill.
+     *
+     * @param int $styleId
+     * @return int
+     */
+    private function getFillIdForStyleId($styleId)
+    {
+        // For the default style (ID = 0), we don't want to override the fill.
+        // Otherwise all cells of the spreadsheet will have a background color.
+        $isDefaultStyle = ($styleId === 0);
+
+        return $isDefaultStyle ? 0 : ($this->styleRegistry->getFillIdForStyleId($styleId) ?: 0);
+    }
+
+    /**
+     * Returns the fill ID associated to the given style ID.
+     * For the default style, we don't a border.
+     *
+     * @param int $styleId
+     * @return int
+     */
+    private function getBorderIdForStyleId($styleId)
+    {
+        // For the default style (ID = 0), we don't want to override the border.
+        // Otherwise all cells of the spreadsheet will have a border.
+        $isDefaultStyle = ($styleId === 0);
+
+        return $isDefaultStyle ? 0 : ($this->styleRegistry->getBorderIdForStyleId($styleId) ?: 0);
+    }
+
     /**
      * Returns the content of the "<cellStyles>" section.
      *