RFR: 8276849: Refresh the window icon on graphics configuration changes

[Emmanuel Bourg]

On Sun, 31 Oct 2021 08:21:58 GMT, Emmanuel Bourg <duke at openjdk.java.net> wrote:

> When a list of icons is set on a window, the most appropiate icon is selected depending on the graphics configuration. But if the graphics configuration changes (because the window is moved to a different screen, or because the DPI settings of the screen is changed), the frame icon isn't updated.
> 
> Here is an example illustrating the issue:
> 
>     public static void main(String[] args) throws Exception {
>         SwingUtilities.invokeLater(() -> {
>             JFrame frame = new JFrame("Window Icon Test");
>             frame.setDefaultCloseOperation(WindowConstants.DISPOSE_ON_CLOSE);
>             frame.setSize(400, 300);
>             frame.setVisible(true);
> 
>             List<Image> images = new ArrayList<>();
>             for (int size = 16; size <= 32; size++) {
>                 // create an image displaying the size used
>                 BufferedImage image = new BufferedImage(size, size, BufferedImage.TYPE_INT_ARGB);
>                 Graphics2D g = image.createGraphics();
>                 g.setFont(new Font("dialog", Font.BOLD, 12));
>                 g.setColor(Color.BLACK);
>                 g.drawString(String.valueOf(size), 0, size - (size - g.getFont().getSize()) / 2);
>                 images.add(image);
>             }
> 
>             frame.setIconImages(images);
>         });
>     }
> 
> On Windows if the screen scaling is set to 100% the 16x16 icon is picked from the list. If the scaling of the screen is set to 150% while the application is running, the 16x16 icon is upscaled and looks blurry.
> 
> A way to work around this issue is to listen for graphics configuration changes with:
> 
>     frame.addPropertyChangeListener("graphicsConfiguration", event -> frame.setIconImages(frame.getIconImages()));
> 
> 
> Ideally this should be done automatically by the JDK. Maybe the `WindowPeer` could call `updateIconImages()` when `updateGraphicsData()` or `displayChanged()` is invoked?

1. Run the test code on a screen with DPI scaling set to 100%, the frame icon displayed should be "16"

![image](https://user-images.githubusercontent.com/54304/148357766-541ebc0d-343a-4135-a2a6-d4a57e60f446.png)

2. Change the DPI scaling of the screen (or move the frame to a secondary screen with a different scaling), the frame icon should change ("20" at 125%, "24" at 150%)

![image](https://user-images.githubusercontent.com/54304/148357980-457068b0-cdd0-43e7-b4dc-6d7c10c78b68.png)

-------------

PR: https://git.openjdk.java.net/jdk/pull/6180