Canvas Map API: Difference between revisions

Add this to the "Nasal/open" tag of your XML dialog and customize it for your dialog:

  ## "prologue" currently required by the canvas-generic-map  

       var dialog_name ="airports"; #TODO: use substr() and cmdarg() to get this dynamically

Add this to the "Nasal/close" tag to clean up all resources automatically:

map.cleanup_listeners();  

</syntaxhighlight>

This is what the tower.draw file looks like:

var draw_tower = func (group, apt,lod) {

       var group = group.createChild("group", "tower");

The airport.draw file demonstrates how to create OpenVG paths procedurally. But you can just as well load the vector image from an SVG file. For an example, please refer to navaid.draw, which is shown below:

var draw_navaid = func (group, navaid, lod) {

       var symbols = {

For example, the various airport-specific "layers" all use the same "AirportModel" to be found in airport.model. In the future, other models can be found in *.model files. For a simple example of how to populate the model, just refer to the file "navaid.model", which is shown here:

var NavaidModel = {};

  NavaidModel.new = func make(LayerModel, NavaidModel);

Also, the LayerModel class is currently just an extremely simple wrapper, all of its fields/methods are directly available to you:

##

# A layer model is just a wrapper for a vector with elements

Now, to actually make a new layer known to the system, we need to add another file that registers the layer. For an example of how to do this, please see navaids.layer:

var NavLayer =  {};

  NavLayer.new = func(group,name) {

Currently, it is also necessary to edit $FG_ROOT/Nasal/canvas/map.nas in order to add your new *.model, *.draw and *.layer files to a vector of files that are explicitly loaded at the end of the file, search for three global variables named DRAWABLES, MODELS and LAYERS:

var DRAWABLES = ["navaid.draw",  "parking.draw",  "runways.draw",  "taxiways.draw",  "tower.draw"];

load_modules(DRAWABLES);