Name: bk70084 Date: 05/22/98


I'm reading over the awt source in jdk1.1.6 and came across this
oddity:

public abstract class Container extends Component {
   ...
    public void update(Graphics g) {
        if (isShowing()) {
            if (! (peer instanceof java.awt.peer.LightweightPeer)) {
                g.setColor(getBackground());
                g.fillRect(0, 0, width, height);
                g.setColor(getForeground());
            }
            super.update(g);
        }
    }
  ...
}

public abstract class Component ... {
   ...

    public void update(Graphics g) {
        if (! (peer instanceof java.awt.peer.LightweightPeer)) {
            g.setColor(getBackground());
            g.fillRect(0, 0, width, height);
            g.setColor(getForeground());
        }
        paint(g);
    }
    ...
}

So, the default case is to fill in the background twice.
I guess that this is not a big problem because folks usually
completely overide update in subclasses of Container. Still,
it's probably something to look at.

-glenn

-----End Original Message-----


The following is a snipet from JDK 1.2b3 code:


public class Container extends Component {
    . . .
    public void update(Graphics g) {
        if (isShowing()) {
            if (! (peer instanceof java.awt.peer.LightweightPeer)) {
                g.clearRect(0, 0, width, height);
            }
            super.update(g); // By default, Component.update() calls paint()
        }
    }
    . . .
}


public abstract class Component implements ImageObserver, MenuContainer,
    Serializable
{
    . . .
    public void update(Graphics g) {
  if (! (peer instanceof java.awt.peer.LightweightPeer)) {
      g.clearRect(0, 0, width, height);
  }
  paint(g);
    }
    . . .
}

It seems you do the same double-clear-background thing here. But this seems slightly worse since
the foreground and background colors are never set for lightweight components (as the comment on
Component.update(Graphics g ) claims).
(Review ID: 30058)
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