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Interaction

Flot offers support for both mouse and touch interactions by using navigate, touch and touchNavigate plugins.

navigate plugin

This plugin is adding zoom, pan, smartPan, recenter and activate capabilities to flot.

It is listening for the following events:

  • click
  • dblclick
  • dragstart
  • drag
  • dragend
  • mousewheel

For pan, dragstart, drag and dragend events are used which are triggered by the deprecated version 1.6 of jquery.event.drag.js. To perform a zoom operation, the mouse wheel can be used which is done by using mousewheel event generated by jquery.mousewheel.js version 3.0.6. These files are included inside lib folder and should be replaced by the npm latest releases of those packages.

The touch interactions are using only a part of the functionalities:

  • zoom
  • pan
  • recenter
  • activate

Any of the functions can be used by the mouse, touch or any other event handler.

touch plugin

This plugin is responsible only for transforming the low level touchstart, touchmove and touchend events into higher level events like:

  • panstart
  • pandrag
  • panend
  • pinchstart
  • pinchdrag
  • pinchend
  • doubletap
  • longtap
  • tap

This plugin is using the bindEvents hook of flot to add the event listenters for the low level events and, after interpreting them, will dispach the higher level events to the same event holder.

It's up to the other plugins to listen for these events and take any actions if necessary. Also they have the possibility to stop the propagation to prevent other plugins for handling the same event. For example, the pan events are normally handled by the touchNavigate plugin, but in some cases the user might want to interact with other elements like cursors or markes which are on top of the plot. In this case panning is not appropriate so other event handler specific to those elements should intercept these events first and stop their propagation before they get to the touchNavigate plugin.

Having a single place where the low level events are interpreted removes the burden of implementing the same logic in multiple places. Some of the things this plugin is doing in order to extract the gestures or the user intentions:

  • doesn't emit some pan or pinch events unless the user moved its finger(s) a minimum distance
  • doesn't emit the double tap event unless both taps are near and fast enough
  • deals with accidental multiple touches when panning

touchNavigate plugin

Similar to the touch plugin, the touchNavigate is using the same bindEvents hook to add its own listeners to the event holder of the flot, but it will listen for the high level events only emitted by the touch plugin.

When a pan or pinch is started the plugin will determine what exactly is being "touched": the entire plot or just one of the axes. After determining the element that the user wants to interact with then this plugin will call one of the zoom, pan or recenter of the navigate plugin.