17. The host's concerns
Contents of ATD 0.1
What a description leaves to the host is only (FR-022): rendering (pixels, fonts and their rasterizing, images), gestures (the pointer and keys a host maps to the intents a description names), text measurement (beyond the text metric a description declares), file dialogs, opening links (beyond open's rules), and the host's undo stack (beyond each transaction's one step). An item of a companion that is one of these is traced as hostConcern with its reason (section 2.5); a description states nothing else about them.