Function lilv_sys::lilv_plugin_get_port_by_designation

pub unsafe extern "C" fn lilv_plugin_get_port_by_designation(
    plugin: *const LilvPlugin, 
    port_class: *const LilvNode, 
    designation: *const LilvNode
) -> *const LilvPort

Get a port on plugin by its lv2:designation.

The designation of a port describes the meaning, assignment, allocation or role of the port, e.g. "left channel" or "gain". If found, the port with matching port_class and designation is be returned, otherwise NULL is returned. The port_class can be used to distinguish the input and output ports for a particular designation. If port_class is NULL, any port with the given designation will be returned.