[macOS Sonoma] Control.setBackgroundImage - image is upside down and flipped

[Phillipus]

Describe the bug
Background images on SWT controls are inverted.

This was reported here but I've opened a dedicated issue as it's not to do with the splash screen but rather Control#setBackgroundImage.

To Reproduce

import org.eclipse.swt.graphics.Image;
import org.eclipse.swt.layout.FillLayout;
import org.eclipse.swt.widgets.Display;
import org.eclipse.swt.widgets.Shell;

public class ImageTest {

    public static void main(String[] args) {
        Display display = new Display();
        Shell shell = new Shell(display);
        shell.setText("Image Test");
        shell.setLayout(new FillLayout());
        
        Image image = new Image(display, ImageTest.class.getResourceAsStream("splash.png"));
        shell.setBackgroundImage(image);
        
        shell.setSize(image.getBounds().width, image.getBounds().height);
        shell.open();
        
        while(!shell.isDisposed()) {
            if(!display.readAndDispatch()) display.sleep();
        }

        display.dispose();
    }
}

Use this image for testing (rename to splash.png), or your own image if you prefer:

Expected behavior
The image should display the right way.

Screenshots
Run the snippet and see this:

Environment:

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

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

2. Additional OS info (e.g. OS version, Linux Desktop, etc)
   macOS Sonoma 14
   Mac Mini M1

3. JRE/JDK version
   Temurin 17

[Phillipus]

In the case of displaying the splash screen when launching Eclipse or an RCP app, the image initially appears correctly but is inverted after a second or two. AFAICS, this is because the initial display of the splash is done natively in the org.eclipse.equinox.launcher.Main class which calls the org.eclipse.equinox.launcher.JNIBridge method showSplash which then calls the native _show_splash method. Presumably whatever is happening in _show_splash works OK.

But then the trail goes to org.eclipse.ui.internal.Workbench and the method createSplashWrapper. Here is where the Shell's background is set at line 786:

splashShell.setBackgroundImage(background);

Then spinEventQueueToUpdateSplash(display) is called by Workbench#createAndRunWorkbench to dispatch messages which updates the splash Shell. This is where the underlying ObjC message from calling setBackgroundImage is dispatched and the image is painted inverted.

Control#setBackgroundImage only sets the Image object and requests an update. Painting the background image is done in Control#fillBackground. The line that actually draws the background image is at line 1323:

NSColor.colorWithPatternImage(image.handle).setFill();

The code for this call is in org.eclipse.swt.internal.cocoa.NSColor:

public static NSColor colorWithPatternImage(NSImage image) {
    long result = OS.objc_msgSend(OS.class_NSColor, OS.sel_colorWithPatternImage_, image != null ? image.id : 0);
    return result != 0 ? new NSColor(result) : null;
}

And another at line 1345:

NSBezierPath.fillRect(rect);

So, there's either a bug in Apple's code or something has changed and a workaround is needed in SWT code.

I can't do any more than offer this analysis, so please feel free to help. :-)

[Phillipus]

The same problem with using a Pattern with image:

import org.eclipse.swt.graphics.Image;
import org.eclipse.swt.graphics.Pattern;
import org.eclipse.swt.layout.GridLayout;
import org.eclipse.swt.widgets.Display;
import org.eclipse.swt.widgets.Shell;

public class ImageTestWithPattern {

    public static void main(String[] args) {
        Display display = new Display();
        Shell shell = new Shell(display);
        shell.setText("Image Test with Pattern");
        shell.setLayout(new GridLayout());
        
        Image image = new Image(display, ImageTestWithPattern.class.getResourceAsStream("splash.png"));
        shell.setSize(image.getBounds().width, image.getBounds().height);
        
        Pattern pattern = new Pattern(display, image);
        
        shell.addPaintListener(e -> {
            e.gc.setBackgroundPattern(pattern);
            e.gc.fillRectangle(0, 0, shell.getSize().x, shell.getSize().y);
        });
        
        shell.open();
        
        while(!shell.isDisposed()) {
            if(!display.readAndDispatch()) display.sleep();
        }

        display.dispose();
    }
}

[Phillipus]

This will be in macOS Sonoma final as the behaviour exists in the Release Candidate.

[Phillipus]

A self-contained snippet:

import org.eclipse.swt.graphics.Color;
import org.eclipse.swt.graphics.GC;
import org.eclipse.swt.graphics.Image;
import org.eclipse.swt.layout.GridLayout;
import org.eclipse.swt.widgets.Display;
import org.eclipse.swt.widgets.Shell;

public class ImageTest {

    public static void main(String[] args) {
        Display display = new Display();
        Shell shell = new Shell(display);
        shell.setText("Image Test");
        shell.setLayout(new GridLayout());
        
        shell.setSize(200, 200);
        
        Image image = new Image(Display.getDefault(), 200, 200);
        GC gc = new GC(image);
        gc.setForeground(new Color(null, 0, 0, 0));
        gc.drawText("Hello World", 50, 100);
        gc.dispose();
        
        shell.setBackgroundImage(image);

        shell.open();
        
        while(!shell.isDisposed()) {
            if(!display.readAndDispatch()) display.sleep();
        }

        display.dispose();
    }
}

[TIBCOeddie]

I'm hoping this can be addressed asap; it will hold up our adoption of this latest release

[Phillipus]

I'm hoping this can be addressed asap; it will hold up our adoption of this latest release

I've documented my analysis of the problem in the previous comments, but I don't know if this is an Apple bug (I have reported it) or something that needs to change in SWT. It needs someone else to answer that.