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

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

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.