Canvas event handling

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The Canvas event handling system is heavily inspired by the DOM Event Model. If you have already worked with events in HTML and JavaScript most concepts of the Canvas event system should be already familiar to you.

Listen for events

To receive events callback function can be added to elements on a Canvas as well as to the Canvas itself:

canvas.addEventListener("<type>", <func>);
canvas_element.addEventListener("<type>", <func>);

For each placement of a Canvas handling events can be enabled or disabled. A Canvas placed in a PUI widget or as standalone GUI window receive events by default, whereas Canvases placed onto the aircraft model or in the scenery do not receive any events by default.

For standalone GUI windows setting capture-events to 0 or 1 enables or disables handling of events respectively. For a Canvas placed onto a 3d model setting capture-events inside the placement can be used to activate event handling:

var dlg = canvas.Window.new([152,74]);

# Disable event handling for this window. Events will pass through
# and can reach any window or also object covered by the window.
dlg.setBool("capture-events", 0);

# Place the canvas onto the PFD and enable receiving events
my_canvas.addPlacement({"node": "PFD-Screen", "capture-events": 1});

Event classes

var Event = {
  # Name of event type [read-only]
  type: <typename>,

  # Target element [read-only]
  target: <target-element>,

  # Stop further propagation of event (stop
  # bubbling up to its parents)
  stopPropagation: func()
};

var MouseEvent = {
  parents: [Event],

  # Position in screen coordinates [read-only]
  screenX: <screen-x>,
  screenY: <screen-y>,

  # Position in window/canvas coordinates [read-only]
  clientX: <client-x>,
  clientY: <client-y>,

  # Distance to position of previous event [read-only]
  deltaX: <delta-x>,
  deltaY: <delta-y>,

  # Current click count (number of clicks within a certain
  # time limit. max. 3) [read-only]
  click_count: <click-count>
};

Event types

Type	Description	DOM equivalent event	Notes
mousedown	Mouse button pressed	mousedown
mouseup	Mouse button released	mouseup
click	mousedown + mouseup have been triggered for this element without moving more than a certain maximum distance	click
dblclick	Two click events have been triggered for this element without moving more than a certain maximum distance and time limit	dblclick
drag	The mouse has been moved with a button down. After dragging has started above an element, all consecutive drag events are send to this element even if the mouse leaves its area
wheel	Mouse wheel rotated (see deltaY for direction)	wheel
mouseover	TODO	mouseover
mouseout	TODO	mouseout
mouseleave	TODO	mouseleave