doc sprmPShd documentation.

sprmPShd (0xC64D) is a SHDOperand value that specifies
the background shading for the paragraph. The SDHOperand
structure is an operand that is used by several Sprm structures
to specify the background shading to be applied.

ShdAuto is a special value for Shd that specifies that no shading
is applied and is defined as 0xFF000000 / 0x0000

ShdNil is a special value for Shd. If ShdNil is used in a Table Style
definition, ShdNil is ignored and the shading of the cell is not affected.
If ShdNil is applied outside of a Table Style, ShdNil
specifies that no shading is applied. ShdNil is defined as 0xFFFFFFFF

Change-Id: I66ec3cbccae60eb658ee00cb01b22cfae36482d0
Reviewed-on: https://gerrit.libreoffice.org/64184
Tested-by: Jenkins
Reviewed-by: Justin Luth <justin_luth@sil.org>

sw/source/filter/ww8/ww8atr.cxx

@@ -4195,19 +4195,16 @@ void WW8AttributeOutput::FormatBackground( const SvxBrushItem& rBrush )
     if ( !m_rWW8Export.m_bOutPageDescs )
     {
         WW8_SHD aSHD;
-
         WW8Export::TransBrush( rBrush.GetColor(), aSHD );
-        // sprmPShd
+
         m_rWW8Export.InsUInt16( NS_sprm::sprmPShd80 );
         m_rWW8Export.InsUInt16( aSHD.GetValue() );
 
-        // Quite a few unknowns, some might be transparency or something
-        // of that nature...
-        m_rWW8Export.InsUInt16( 0xC64D );
-        m_rWW8Export.pO->push_back( 10 );
-        m_rWW8Export.InsUInt32( 0xFF000000 );
-        m_rWW8Export.InsUInt32( SuitableBGColor( rBrush.GetColor() ) );
-        m_rWW8Export.InsUInt16( 0x0000 );
+        m_rWW8Export.InsUInt16( NS_sprm::sprmPShd );
+        m_rWW8Export.pO->push_back( 10 ); //size of operand: MUST be 10
+        m_rWW8Export.InsUInt32( 0xFF000000 ); //cvFore: Foreground BGR = cvAuto
+        m_rWW8Export.InsUInt32( SuitableBGColor( rBrush.GetColor() ) ); //cvBack
+        m_rWW8Export.InsUInt16( 0x0000 ); //iPat: specifies the pattern used for shading = clear/100% background
     }
 }