pattern()
Produces an SVG "pattern" element.
Syntax
pattern(
   id STRING,
   x DECIMAL,
   y DECIMAL,
   width DECIMAL,
   height DECIMAL,
   patternUnits STRING,
   patternContentUnits STRING,
   patternTransform STRING,
   preserveAspectRatio STRING )
  RETURNS om.DomNode
- id is the SVG object identifier.
 - x defines the X coordinate where the patterm starts.
 - y defines the Y coordinate where the patterm starts.
 - width defines the width of the pattern.
 - height defines the height of the pattern.
 - patternUnits defines the patternUnits attribute.
 - patternContentUnits defines the patternContentUnits attribute.
 - patternTransform defines the patternTransform attribute.
 - preserveAspectRatio is the aspect ratio to preserve.
 
Usage
This function creates a "pattern" SVG DOM element from the parameters.
The resulting DOM can be used in a "defs" element created with the defs() function, to
produce pattern definitions.
Example
DEFINE pattern, n om.DomNode
...
LET pattern = fglsvgcanvas.pattern( "pattern1", 0,0,20,20, "userSpaceOnUse",
                                    NULL, "rotate(45)", NULL )
CALL pattern.appendChild( n:=fglsvgcanvas.rect(0,0,1000,10,NULL,NULL) )
CALL n.setAttribute(SVGATT_STYLE, 'stroke:none; fill:blue;' )
CALL pattern.appendChild( n:=fglsvgcanvas.rect(0,10,1000,10,NULL,NULL) )
CALL n.setAttribute(SVGATT_STYLE, 'stroke:none; fill:navy;' )