onPanStart

onPanStart is a callback function used in gesture recognition libraries, particularly in mobile development and frameworks like React Native. It is invoked when a user initiates a panning gesture. A panning gesture, often referred to as a drag, involves the user touching the screen with one or more fingers and then moving them across the surface without lifting them.

The onPanStart callback is typically triggered at the very beginning of such a gesture, meaning as soon as the system detects that a touch has been made and movement has begun. This event handler receives an event object that contains information about the gesture's initial state. This information usually includes the starting coordinates (x and y positions) of the touch event on the screen.

Developers utilize onPanStart to set up the initial state for more complex interactions. For example, it can be used to record the starting position of an element that is about to be dragged, to enable visual feedback such as highlighting the element being interacted with, or to prepare for subsequent gesture events like onPanMove and onPanEnd. By knowing the starting point, subsequent calculations for movement and final position can be more accurate, leading to a smoother and more responsive user experience. It’s a fundamental part of implementing draggable components or any UI element that responds to swipe or drag motions.