[GTK] Control.setBackgroundImage is ignored on ToolBar

[vogella]

On GTK a background image set on a ToolBar is never painted; the bar shows the GTK theme's toolbar colour. The same image on a Composite or Label paints fine.

Snippet

import org.eclipse.swt.*;
import org.eclipse.swt.graphics.*;
import org.eclipse.swt.layout.*;
import org.eclipse.swt.widgets.*;

public class ToolBarBackgroundImage {

      public static void main(String[] args) {
              Display display = new Display();
              Shell shell = new Shell(display);
              shell.setText("ToolBar background image");
              shell.setLayout(new GridLayout(1, false));

              Image image = new Image(display, 10, 40);
              GC gc = new GC(image);
              gc.setBackground(display.getSystemColor(SWT.COLOR_MAGENTA));
              gc.fillRectangle(0, 0, 10, 40);
              gc.dispose();

              new Label(shell, SWT.NONE).setText("ToolBar: image is not painted");
              ToolBar bar = new ToolBar(shell, SWT.FLAT);
              bar.setLayoutData(new GridData(200, 40));
              new ToolItem(bar, SWT.PUSH).setText("Item");
              bar.setBackgroundImage(image);

              new Label(shell, SWT.NONE).setText("Composite: image is painted");
              Composite composite = new Composite(shell, SWT.NONE);
              composite.setLayoutData(new GridData(200, 40));
              composite.setBackgroundImage(image);

              shell.setSize(400, 250);
              shell.open();
              while (!shell.isDisposed()) {
                      if (!display.readAndDispatch()) display.sleep();
              }
              image.dispose();
              display.dispose();
      }
}

Expected on GTK: the composite is magenta, the tool bar is not.