drag_handler

drag_handler is a dart library to simplify the management of mouse dragging state. An instance of the DragHandler class maintains a set of DOM elements and monitors them for mouse events.

Usage

To use this library in your code :

• add a dependency in your pubspec.yaml :

dependencies: drag_handler: ">=0.1.1 <1.0.0"

* add import in your `dart` code :

    ```dart
import 'package:drag_handler/drag_handler.dart';

• create a DragHandler

var dh = new DragHandler();

* add a target

    ```dart
dh.addTarget(querySelector('#drag-element'));

• listen for drag events

  1. Drag start: when the user mouses down on a DOM element added to the DragHandler and begins to move the mouse.

  dh.onDragStart.listen((DragEvent e) => print('Started dragging on element ${e.element}'));

  2. Drag: each time the user moves the mouse during a drag

  dh.onDrag.listen((DragEvent e) => print('Still dragging ${e.element}'));

  3. Drag out: when the user moves the mouse out of an element in the DragHandler.

  dh.onDragOut.listen((DragEvent e) => print('Started drag on ${e.element}, dragging out of ${e.other}'));

  4. Drag over: when the user moves the mouse into an element in the DragHandler

  dh.onDragOver.listen((DragEvent e) => print('Started drag on ${e.element}, dragging over ${e.other}'));

  5. Drag end: when the user mouses up during a drag

  dh.onDragEnd.listen((DragEvent e) => print('Finished dragging ${e.element}'));

• selectively add targets

  If you want to know if a drag operation enters or leaves an element, but you don't want to watch for drags that start on that element, you can specify those events when adding the target:

dh.addTarget(querySelector("#drag-target"), drag: false, over: true, out: true);

* temporarily disable a DragHandler

    ```dart
dh.enabled = false;

• define conditions in which drags may begin

// don't react to mouse drags when application is loading dh.dragConditions = (DragHandler dh, Element e, MouseEvent me) => application_state == ApplicationState.LOADING;