JxBrowser supports two rendering modes: lightweight and heavyweight.


By default, heavyweight rendering mode is enabled, so when you create Browser instance using the following code, it creates a new Browser instance configured to use heavyweight rendering mode: 

Browser browser = new Browser();

To create a new Browser instance with specified rendering mode use the following way: 

// Creates Browser instance with enabled lightweight rendering mode
Browser browser = new Browser(BrowserType.LIGHTWEIGHT);

// Creates Browser instance with enabled heavyweight rendering mode
Browser browser = new Browser(BrowserType.HEAVYWEIGHT);

The differences between lightweight and heavyweight rendering modes and recommendations about what rendering mode you should use in your application you can find below:


Lightweight (off-screen)

In lightweight rendering mode Chromium engine renders web page off-screen using CPU. Images that represent different parts of loaded web page are stored in shared memory. JxBrowser reads the images from the shared memory and displays them using standard Java Swing/JavaFX 2D Graphics API.


To interact with displayed web page we listen to mouse and keyboard events using Java Events API, convert them to appropriate Chromium mouse/keyboard events, and send them to Chromium engine. With this approach we receive a pure lightweight solution.


This rendering mode works great if you need a true lightweight Swing/JavaFX component that allows displaying modern HTML5/JavaScript/CSS web pages in your Java application. You can make this lightweight component semitransparent, display other components on top of it, put it into JLayeredPane or JInternalFrame, get notifications about mouse and keyboard events, etc.


Headless environment

In case you need to use JxBrowser in a headless Linux environment, we recommend that you use the Lightweight rendering mode.


There are two main reasons for that:

  1. The Heavyweight (GPU-accelerated) rendering mode running in a headless environment via xvfb is useless because GPU acceleration in xvfb is disabled.
  2. Very often in such environment the JxBrowser functionality that allows getting screenshots of the loaded web-pages is used. That functionality is available in the Lightweight rendering mode only.


Limitations

  • Heavy animation on loaded web page cause high CPU and memory usage. It happens because Chromium engine needs to render a lot of images and save them into allocated shared memory.
  • In lightweight mode only Chromium plugins that supports windowless mode can be displayed. Since rendering is done off-screen, Flash player or other plugin must support windowless (off-screen) rendering as well. If plugin doesn't support off-screen rendering, it will not be displayed in lightweight mode.
  • Mouse/keyboard/touch events are processes on Java side and forwarded to Chromium engine. Right now Java doesn't provide fully functional touch events support, so in lightweight rendering mode JxBrowser doesn't support some touch gestures. Same limitation is true for Drag&Drop functionality. In lightweight rendering mode, drag and drop is processed using Java API, so it doesn't work exactly as in Google Chrome. Drag&Drop supports only predefined set of flavours.


Heavyweight (GPU-accelerated)

In the heavyweight rendering mode, which is default mode in JxBrowser, we embed a native window into your Java application window and configure Chromium engine to render content into this native window using GPU.


User interaction with displayed web page is done by Chromium engine. Chromium receives and processes mouse/keyboard/touch events using platform specific native functionality. It brings a better support of mouse/keyboard/touch events compared to lightweight rendering mode where JxBrowser has to process Java events and forward them to Chromium engine.


Heavyweight (GPU-accelerated) rendering mode works much faster compared to lightweight rendering mode. Rendering performance is the same as in Google Chrome. You can display full screen video or HTML5 animation with 60fps. Compared to lightweight rendering mode, CPU and memory usage is much smaller, because web page's content is rendered via GPU.


So, if rendering performance is very important for your application, then we recommend that you use default heavyweight rendering mode.


Limitations

Lightweight and heavyweight mixing

Java Swing/JavaFX toolkits allows building UI based on lightweight components. When we embed a native window into Java frame it can lead to a well-known issue with mixing heavyweight and lightweight components. It's not recommended that you put heavyweight BrowserView component into JLayeredPane or JInternalFrame, or mix it with the lightweight components (e.g. trying to display a lightweight component over heavyweight BrowserView).


Layered windows in JavaFX applications

Configuring the stage with the StageStyle.TRANSPARENT style adds the WS_EX_LAYERED window style flag to JavaFX window. This flag is used to create a layered window. The layered window represents an off-screen window that draws its content off-screen. If we embed another window (it happens when heavyweight rendering mode is used in JxBrowser) into a layered window, its content will not be painted because of window types conflict.


Browser disposal in JavaFX

Disposing Browser instance in the incorrect thread in JavaFX may lead to a deadlock on the native side. The Browser instances must be disposed on different threads depending on the operating system. In Linux and macOS the Browser.dispose() method must be called on the UI thread, while on Windows Browser must be disposed on the non-UI thread. For example:

Platform.runLater(new Runnable() {
    @Override
    public void run() {
        browser.dispose();
    }
});
Linux and MacOS 
new Thread(new Runnable() {
    @Override
    public void run() {
        browser.dispose();
    }
}).start();
Windows