Creating a Sketch NSPanel

panel.js

export function runPanel() {
	let threadDictionary = NSThread.mainThread().threadDictionary()
	let identifier = "co.yourIdentifier"

	// If there is already a panel, prevent the plugin from running again
	if (threadDictionary[identifier]) return
	threadDictionary.panelOpen = true
	setupPanel(threadDictionary, identifier)
}

function setupPanel(threadDictionary, identifier) {
	var panelWidth = 500
	var panelHeight = 300
	let panel = NSPanel.alloc().init()
	panel.setFrame_display(NSMakeRect(0, 0, panelWidth, panelHeight), true)
	panel.setStyleMask(NSTexturedBackgroundWindowMask | NSTitledWindowMask | NSClosableWindowMask | NSFullSizeContentViewWindowMask | NSWindowStyleMaskResizable)
	panel.setBackgroundColor(NSColor.whiteColor());
	panel.title = "SVGO UI"
	
	panel.center()
	panel.makeKeyAndOrderFront(null)
	panel.setLevel(NSFloatingWindowLevel)
	panel.minSize = NSMakeSize(panelWidth, panelHeight)
	
	COScript.currentCOScript().setShouldKeepAround_(true)
	
	panel.standardWindowButton(NSWindowMiniaturizeButton).setHidden(true)
	panel.standardWindowButton(NSWindowZoomButton).setHidden(true)
	
	var vibrancy = NSVisualEffectView.alloc().initWithFrame(NSMakeRect(0, 0, panelWidth, panelHeight))
	vibrancy.setAppearance(NSAppearance.appearanceNamed(NSAppearanceNameVibrantLight))
	vibrancy.setBlendingMode(NSVisualEffectBlendingModeBehindWindow)
	panel.contentView().addSubview(vibrancy)
	fitSubviewToView(vibrancy,panel.contentView(), [0.0,0.0,0.0,0.0])
	
	threadDictionary[identifier] = panel;
	
	var closeButton = panel.standardWindowButton(NSWindowCloseButton)
	closeButton.setCOSJSTargetFunction(function(sender) {
		panel.close()

		//Remove the reference to the panel
		threadDictionary.removeObjectForKey(identifier)
		threadDictionary.panelOpen = false

		//Stop this script
		COScript.currentCOScript().setShouldKeepAround_(false)
	})
}

function fitSubviewToView(subview, view, constants) {
    subview.setTranslatesAutoresizingMaskIntoConstraints(false)

    addEdgeConstraint(NSLayoutAttributeLeft, subview, view, constants[0])
    addEdgeConstraint(NSLayoutAttributeTop, subview, view, constants[1])
    addEdgeConstraint(NSLayoutAttributeRight, subview, view, constants[2])
    addEdgeConstraint(NSLayoutAttributeBottom, subview, view, constants[3])
}

function addEdgeConstraint(layoutAttribute, subview, view, constant) {
    view.addConstraint(
        NSLayoutConstraint.constraintWithItem_attribute_relatedBy_toItem_attribute_multiplier_constant(
                subview,
                layoutAttribute,
                NSLayoutRelationEqual,
                view,
                layoutAttribute,
                1.0,
                constant
            )
        )
}