Duplexing in HqnImpose2

This page applies to Harlequin v13.1r0 and later; both Harlequin Core and Harlequin MultiRIP.

HqnImpose2 contains code to allow it to support duplexing capabilities. The following keys should be configured as desired:

`/Duplex`	Boolean. Should pages be duplexed or not. Default: `false`.
`/Tumble`	Boolean. If pages are duplexed, how should the back of the sheet be positioned relative to the front. Default: `false`.
`/RedBookTumble`	Boolean. The Red Book is very clear about how tumbling should be applied, but most common printer drivers (including Adobe’s) simplify it to “short edge binding” or “long edge binding”, which produces different results where the `PageSize` requested by a job is wider than it is tall. If `RedBookTumble` is set to `true`, the Red Book definition is used; otherwise the more common long/short edge binding is used. Default: `false`.
`/HardwareTumble`	Procedure. When printing on both sides of the paper, every printer effectively flips the page in one direction or the other. This procedure should be defined so as to return `true` if the printer flips the page on an axis parallel to the fast scan direction,; it is `false` if the axis of the flip is parallel with the slow scan direction. If the printer has two writing heads, the value returned should indicate the relationship between those heads. The default procedure returns `true` for portrait pages, `false` for landscape ones.
`/IsBack`	Procedure. This procedure should return `true` if the back of a sheet is currently being processed, or `false` if the front is being processed. The default is that odd numbered sheets return `false`, even numbered sheets return `true`.

If the page device keys Duplex and Tumble are set and the Imposition keys of the same name (in HqnImpose2) are not set, in Imposition the RIP sets Tumble to RedBookTumble. If the page device keys Duplex and Tumble and the Imposition keys of the same name are set, the RIP honors the Imposition keys and ignores the page device keys.