Why does the ToolController's getPriority return 0 for my tool? - autodesk-forge

Question

According to a prior SO answer, you can implement getPriority for a forge viewer Tool. And according to another SO answer extending the ToolInterface does not work. Hence, me not extending the ToolInterface implementing my Tool like so:
class MyCustomExtension extends Autodesk.Viewing.Extension {
constructor(viewer, options) {
super(viewer, options);
this.theiaUtil = new TheiaUtil(this);
}
getPriority() {
console.log("Theia#getPriority called! ", (this.getPriority && this.getPriority() || 0));
return 100000;
}
...
}
My tool's priority is returned as 0 in the ToolController, although it shouldn't:
function getPriority(tool)
{
return tool.getPriority instanceof Function && tool.getPriority() || 0;
}
I don't know why this function returns 0 as tool.getPriority instanceof Function returns true if I call MyCustomExtension.getPriority myself.

Answer 1

Note that ToolInterface is implemented like so:
function ToolInterface()
{
this.names = [ "unnamed" ];
this.getNames = function() { return this.names; };
this.getName = function() { return this.names[0]; };
this.getPriority = function() { return 0; };
this.register = function() {};
this.deregister = function() {};
this.activate = function(name, viewerApi) {};
this.deactivate = function(name) {};
this.update = function(highResTimestamp) { return false; };
this.handleSingleClick = function( event, button ) { return false; };
this.handleDoubleClick = function( event, button ) { return false; };
this.handleSingleTap = function( event ) { return false; };
this.handleDoubleTap = function( event ) { return false; };
// ...
}
Because of that, simply extending the ToolInterface class won't work because all these properties and functions added to the instance in the constructor will take precedence over your actual class methods. This is also likely the reason why you're seeing the priority value returned as zero - when you call myTool.getPriority(), you are not actually calling your getPriority method, but rather the default function which was assigned to this.getPriority in ToolInterface's constructor.
To work around this issue I would recommend explicitly deleting the corresponding fields in your class' constructor (something I explain in my blog post on implementing custom Forge Viewer tools):
class DrawTool extends Autodesk.Viewing.ToolInterface {
constructor() {
super();
this.names = ['box-drawing-tool', 'sphere-drawing-tool'];
// Hack: delete functions defined *on the instance* of the tool.
// We want the tool controller to call our class methods instead.
delete this.register;
delete this.deregister;
delete this.activate;
delete this.deactivate;
delete this.getPriority;
delete this.handleMouseMove;
delete this.handleButtonDown;
delete this.handleButtonUp;
delete this.handleSingleClick;
}
register() {
console.log('DrawTool registered.');
}
deregister() {
console.log('DrawTool unregistered.');
}
activate(name, viewer) {
console.log('DrawTool activated.');
}
deactivate(name) {
console.log('DrawTool deactivated.');
}
getPriority() {
return 42; // Or feel free to use any number higher than 0 (which is the priority of all the default viewer tools)
}
// ...
}

Answer 2

TL;DR: Activate the tool in button click event from a toolbar button instead of the extension's load method.
class MyExtension extends Autodesk.Viewing.Extension {
...
onToolbarCreated(toolbar) {
const MyToolName = 'My.Tool.Name'
let button = new Autodesk.Viewing.UI.Button('my-tool-button');
button.onClick = (e) => {
const controller = this.viewer.toolController;
if (controller.isToolActivated(MyToolName)) {
controller.deactivateTool(MyToolName);
button.setState(Autodesk.Viewing.UI.Button.State.INACTIVE);
} else {
controller.activateTool(MyToolName);
button.setState(Autodesk.Viewing.UI.Button.State.ACTIVE);
}
};
}
...
}
I activated the tool instantly after registering it in the Extension's load method. Petr Broz's github repo from his blog post loads the tool from a button in the toolbar. So I moved the activation of the tool to a button click in the toolbar which worked for me.