换行是无法实现的.
   居中可以写一个过程。
   produce Tform1.button1click(sender:objcect);
    var i,j:integer;
        spaces:string;  //空格个数
   begin
     for i:=0 to stringgrid1.colcount-1
       for j:=0 to stringgrid1.rowcount-1
          begin
            with stringgrid1 do
              begin
                spaces:=colwidths[i]-canvas.textwidth(trim(cells[i,j]));
                if spaces>0 then
                   begin
                      spaces:=(spaces div 2) div canvas.font.size
                      if space>=1 then
                          cells[i,j]:=replacespace(space)+cells[i,j]  //replacespace为产生n个空格字串的函数。
                                
                   end;
              end;
          end;
   end;