Technical Q&As

GXPD 10 - QuickDraw GX and DoesPaperFit Message (1-May-95)

Important for all Apple Printing and Graphics Developers:

The information in this Technical Q & A is still relevant up to and including Mac OS 7.6 with QuickDraw GX 1.1.5. Beginning with the release of Mac OS 8.0, however, Apple plans to deliver a system which incorporates QuickDraw GX graphics and typography only. QuickDraw GX printer drivers and GX printing extensions will not be supported in Mac OS 8.0 or in future Mac OS releases. Apple's goal is to simplify the user experience of printing by unifying the Macintosh graphic and printing architectures and standardizing on the classic Printing Manager.

For details on Apple's official announcement, refer to </dev/technotes/gxchange.html>

Q Does QuickDraw GX send the DoesPaperFit message when I'm setting up input-tray dialogs, or is the driver supposed to do this? If GX doesn't, it is possible for users to use completely invalid paper sizes, which can violently crash most raster drivers.

A GX sends the DoesPaperFit message in the default implementation of the Input Trays... dialog to constrain the configuration options, and drivers that perform their own Input Trays... dialog should do the same. A driver should override this message if it needs other than the default logic, which responds that everything fits.

The packing buffer size specified in the 'rpck' resource is set to the expected maximum size needed. Unfortunately, this is far smaller than what's needed when handling larger-than-expected paper sizes. To work around this, you can set the packing buffer size so that it can accommodate the largest paper size the printer can use.

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