Accept valid source actions in drop target events

[duncanmcqueen]

Split from #57.

Problem and fix

The constructors of DropTargetDragEvent and DropTargetDropEvent test the source actions with ~(actions ^ mask) != 0. This test is true for all values except ~mask. Thus both constructors throw IllegalArgumentException for all valid actions, for example ACTION_COPY_OR_MOVE, and a drop target never gets an event.

Now the constructors reject only bits that are not in the mask: (actions & ~mask) != 0. I found this bug when I wrote an AWT toolkit for Haiku, which supplies drag and drop peers.

How to reproduce

javac DropEventActions.java
java DropEventActions

DropEventActions.java

import java.awt.*;
import java.awt.dnd.*;

/**
 * DropTargetDragEvent and DropTargetDropEvent must accept valid source
 * actions, and reject bits that are not actions.
 */
public class DropEventActions
{
  static boolean failed;

  static void check(String what, boolean ok, String detail)
  {
    System.out.println((ok ? "PASS " : "FAIL ") + what + ": " + detail);
    failed |= !ok;
  }

  public static void main(String[] args)
  {
    DropTarget dt = new DropTarget(new Canvas(), new DropTargetAdapter()
      {
        public void drop(DropTargetDropEvent e) {}
      });
    DropTargetContext dtc = dt.getDropTargetContext();
    Point p = new Point(1, 1);
    int copy = DnDConstants.ACTION_COPY;
    int copyOrMove = DnDConstants.ACTION_COPY_OR_MOVE;
    try
      {
        new DropTargetDragEvent(dtc, p, copy, copyOrMove);
        check("new DropTargetDragEvent(ACTION_COPY_OR_MOVE)", true, "accepted");
      }
    catch (IllegalArgumentException e)
      {
        check("new DropTargetDragEvent(ACTION_COPY_OR_MOVE)", false, e.toString());
      }
    try
      {
        new DropTargetDropEvent(dtc, p, copy, copyOrMove);
        check("new DropTargetDropEvent(ACTION_COPY_OR_MOVE)", true, "accepted");
      }
    catch (IllegalArgumentException e)
      {
        check("new DropTargetDropEvent(ACTION_COPY_OR_MOVE)", false, e.toString());
      }
    try
      {
        new DropTargetDragEvent(dtc, p, copy, 0x100);
        check("new DropTargetDragEvent(0x100)", false, "accepted an invalid action");
      }
    catch (IllegalArgumentException e)
      {
        check("new DropTargetDragEvent(0x100)", true, "rejected");
      }
    System.exit(failed ? 1 : 0);
  }
}

Results

Linux x86_64, ingelabs/classpath master (0406074), JamVM master, javac from JDK 8, autoconf 2.73, automake 1.19, the configure options of the CI Linux job, out-of-tree build. "Before" is master. "After" is master with this commit.

Before:
FAIL new DropTargetDragEvent(ACTION_COPY_OR_MOVE): java.lang.IllegalArgumentException
FAIL new DropTargetDropEvent(ACTION_COPY_OR_MOVE): java.lang.IllegalArgumentException
PASS new DropTargetDragEvent(0x100): rejected

After:
PASS new DropTargetDragEvent(ACTION_COPY_OR_MOVE): accepted
PASS new DropTargetDropEvent(ACTION_COPY_OR_MOVE): accepted
PASS new DropTargetDragEvent(0x100): rejected

JDK 8 (1.8.0_504) gives the "After" result.

Platforms

Not specific to Haiku. The problem is in java.awt.dnd and occurs with all toolkits. I reproduced it on Linux.

AI assistance

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