Describe the bug

Currently, there are three possible sources for the Dock icon on macOS in the order of precedence:

1. An explicitly set icon via
   -Xdock:icon=/path/to/icon.icns
   which calls
   NSApp setApplicationIconImage

2. An implicitly set icon via
   org.eclipse.swt.widgets.Decorations.setImage(Image)
   org.eclipse.swt.widgets.Decorations.setImages(Image[])
   which in passed down to the Dock also via
   NSApp setApplicationIconImage

3. An implicitly set icon in a Bundled.app distrubution via
   CFBundleIconName / CFBundleIconFile in the Info.plist file

1 and 2 use legacy API NSApp setApplicationIconImage which only supports a single fixed NSImage, i.e. there is no support for dark/light mode and or modern look & feel such as Liquid Glass.

Only 3 (app bundle) supports dynamic icons.

The problem is that 2) currently overwrites whatever 3) has set. On top of that, the Decorations are typically cross-platform, so in fact this will prevents using a macOS-specific icon at all.

We want to prefer 3) over 2), i.e. only pass down the decorations whenever we are not an app bundle with a declared image.

Similar coding also exists in the JVM, where the dock icon is only set if we are not in an app bundle that specifies an icon:

https://github.com/openjdk/jdk21u/blob/8c322f5953ae161d793213f92d13a1f53d995883/src/java.desktop/macosx/native/libosxapp/NSApplicationAWT.m#L280-L290

To Reproduce

Build an RCP product as a macOS Product.App, which defines a macOS-specific icon in the .product configuration and also launches a branded RCP product.

When the product launches, it shortly shows the icon defined in the Product.app/Info.plist file.

As soon as SWT initializes it overwrites the icon with whatever platform-agnostic icon is set in the product branding.

Expected behavior

The icon specified in the Product.App should be shown in the Dock.

Screenshots

During launcher:

After SWT initialization:

Environment:

1. Select the platform(s) on which the behavior is seen:

• • All OS
• • Windows
• • Linux
• • macOS

Workaround (or) Additional context

Specifying -Xdock:icon=/path/to/static/image.icns prevents SWT from changing the Dock image, but this is legacy API and does not support modern / dynamic icon features