Returns the fraction or shift value of a stroke resource.

If the auto phase flag is set, the value is a fraction, otherwise the value is a shift distance.

• Shift is an offset of the stroke pattern in units relative to the

start of the line or line segment.

• Fraction is an offset of the stroke pattern in a percent of the pattern

length relative to the start of the line or line segment.

• The value is ignored if the center stretch phase mode is on.