dataBinding.ts

/* --------------------------------------------------------------------------------------------
 * Copyright (c) Microsoft Corporation. All Rights Reserved.
 * See 'LICENSE' in the project root for license information.
 * ------------------------------------------------------------------------------------------ */
import * as vscode from 'vscode';
import { Deferral } from './utils';

export class DataBinding<T> {
    private valueChanged = new vscode.EventEmitter<T>();
    private isActive: boolean = true;
    private deferral?: Deferral;

    /**
     * Bind an event to a value so that a data model can automatically update the UI when values change.
     * Since values can change quickly and cause UI to flicker, an optional delay/trigger combination can
     * be specified to prevent UI elements from appearing/disappearing too quickly.
     * @param value The initial value in the binding.
     * @param delay An optional delay (in milliseconds) for firing the value changed event.
     * @param delayValueTrigger The value that triggers an event delay.
     */
    constructor(private value: T, private delay: number = 0, private delayValueTrigger?: T) {
        this.isActive = true;
    }

    public get Value(): T {
        return this.value;
    }

    public set Value(value: T) {
        if (value !== this.value) {
            if (this.delay === 0 || value !== this.delayValueTrigger) {
                this.value = value;
                this.valueChanged.fire(this.value);
            } else {
                if (this.deferral) {
                    this.deferral.cancel();
                }
                this.deferral = new Deferral(() => {
                    this.value = value;
                    this.valueChanged.fire(this.value);
                }, this.delay);
            }
        } else if (this.deferral) {
            this.deferral.cancel();
            this.deferral = undefined;
        }
    }

    public setValueIfActive(value: T): void {
        if (value !== this.value) {
            this.value = value;
            if (this.isActive) {
                this.valueChanged.fire(this.value);
            }
        }
    }

    public get ValueChanged(): vscode.Event<T> {
        return this.valueChanged.event;
    }

    public activate(): void {
        this.isActive = true;
        this.valueChanged.fire(this.value);
    }

    public deactivate(): void {
        this.isActive = false;
    }

    public dispose(): void {
        this.deactivate();
        this.valueChanged.dispose();
    }
}