Java Magazine - May/June 2012

//java architect /

Java SE 7: Shaped and Translucent Windows Deep Dive

COMMUNITY

Enhance your applications in new and interesting ways.

JOSH MARINACCI

JAVA IN ACTION PHOTOGRAPH BY CHRIS PIETSCH/GETTY IMAGES

One of the best new features of Java SE 7 is official support for shaped and transparent windows. While shaped windows have long been possible using various tricks and hacks, operating systems have started to support this feature natively in recent years. Updates to Java SE 6 exposed this native functionality through private APIs, but starting with Java SE 7, it is now an official part of Java SE.

With shaped and transparent windows, you can enhance your applications in ways that simply weren’t possible before. This article takes you on a deep dive into the technology and shows you some advanced ways to enhance your applications with it. If you would like to code along with me, download the full project source code.

I will assume that you are already familiar with the shaped and translucent window concept and API. If not, Oracle has a great tutorial on the topic. The Java SE 7 API exposes three kinds of window effects: shaped windows, transparent windows, and windows with a full alpha channel. I won’t cover the first two types because I have found their usefulness to be limited, and the most common use cases are already covered in the standard tutorials. Instead, I will focus on the third kind: windows with a full alpha channel.

ing effects, such as fuzzy edges, translucent overlays, windows with holes in them, and cool pop-down menus.

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Background

Working with a per-pixel alpha channel is more powerful than shaped and transparent windows because you can control the transparency of each pixel independently. A shaped window is simply a nonrectangular window. All visible pixels are still 100 percent opaque, but the window might be circular or some other funky shape. Translucent windows set a single transparency value for the entire window, which can be useful if you want to fade the window all at once, but it’s not useful for much beyond that. The per-pixel alpha channel is where the real magic is.

About Screen

Let’s start off with something simple: an “about” screen with fuzzy edges. This could be the screen that a user sees when selecting the About menu item from the system menu of your application. First, I will create a Swing component that draws some text on top of a translucent gradient. The code is pretty straightforward Java 2-D code, which fills a rectangle with a gradient and then draws text on top, as shown in Listing 1.