This post is from the Activity iPhone Duo UIKit Q&A.
We have a mature Objective-C/UIKit PDF editor. Its editing UI uses two custom toolbar views that we build and lay out ourselves, so they aren't UINavigationBar or UIToolbar items:
- a tool-selection bar (annotate, edit, sign and so on), and
- a tools bar that shows the tools for the selected mode, with contextual options.
They hold custom controls, selection state and popovers that can't be expressed as bar button items, so moving to UINavigationBar or UIToolbar isn't realistic for us. Right now we swap between a compact and a regular toolbar layout on size-class changes (traitCollectionDidChange:), and handle geometry in viewWillTransitionToSize:withTransitionCoordinator:.
Questions:
- Posture changes: When the device folds or unfolds, what's the recommended way for custom toolbar views to adapt? Should we rely on size-class and size transitions only, or is there a posture signal we should observe?
- Fold region: How should custom bars avoid the fold? Is it exposed through safe areas or a layout guide, or should we split a bar across both halves?
- Placement: In a partially folded (tabletop) posture, is there guidance on moving tool bars to the lower half, the way the system does for its own bars?
- Workarounds: If the system bar behavior for fold postures isn't available to custom views, what have others done? For example, hosting our custom views inside system bars, or mirroring system bar positioning manually.
Suggestions or pointers to docs, sample code or WWDC sessions would be much appreciated. Thanks!