(v13) Opening a channel in an input plugin

This page applies to Harlequin v13.1r0 and later; and to Harlequin MultiRIP but not Harlequin Core

When the RIP learns that there is a job waiting to be processed on a particular channel, it attempts to open the channel for reading and writing. It does this with two D_IP_CHANNEL_OPEN calls. (See (v13) D_IP_CHANNEL_OPEN ).

The first call attempts to open the channel for reading. It usually succeeds, since the plugin has already indicated that input data is ready.

The second call attempts to open the channel for writing. The plugin might not wish to give the RIP permission to write to the channel, depending on the class of the channel. (Font queries, for example, require that the RIP have permission to write to the channel: the interpreter sends data back to the source about the font presented to it.)

If the second D_IP_CHANNEL_OPEN request fails, the RIP assumes that it is not required to write to the channel. If the job produces any output, it is sent to the monitor window.