7 posts
Compose's drag-and-drop moves ClipData between sources and targets, including across apps. Reordering a list is a different problem with a different solution, and conflating them is why reorder implementations get complicated.
Compose's focus system handles keyboard, D-pad and accessibility navigation. The APIs are small, but modifier order matters, and a form with no focus handling is unusable on any device without a touchscreen.
NestedScrollConnection gives parents four chances to consume scroll deltas around a child. Choosing the wrong one is why collapsing headers collapse late, and why same-axis nesting misbehaves.
Multi-touch gestures produce pan, zoom and rotation simultaneously. The centroid — the point between the fingers — is what makes the transform feel anchored, and ignoring it is the most common photo-viewer bug.
Hand-rolled swipe gestures compare a distance threshold and ignore velocity, which is why a fast flick feels wrong. AnchoredDraggableState models discrete positions and settles between them using both distance and speed.
Modifier.clickable adds accessibility semantics, focus, keyboard activation, ripple and a minimum touch target on top of tap detection. Reaching for detectTapGestures instead silently drops all of it.
pointerInput gives you a coroutine scope over raw pointer events. Understanding that gestures are suspending loops rather than callbacks explains the whole API, including why the key parameter matters more than it looks.
