>From: ###@###.### (Doug Stein)
This does not look like form output to me.


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Category: AWT

Priority: CRITICAL! (Low/Medium/High/Critical)

JDK version: JDK-1_0-win32-x86.exe

Platforms: Windows 95 [Version 4.00.950]
Windows NT version 3.51

Synopsis
--------

The locations of AWT components are reported incorrectly on Windows.


Description
-----------

This bug occurs on Windows95 and WindowsNT.

The "location" method of the Component class returns the location of
a component relative to its parent. On Windows this location is not
always correct.

I did some experimentation to figure out what was going on. The
"reshape" method takes an x, y, width, and height. I subclassed a
component and overrode reshape to keep track of the current location
of the component. I discovered that the x and y values reported by
the "location" method do not always match the x and y values given in
the most recent call to "reshape"!


Test Case
---------

- Compile and run location.java:

javac location.java
java location

- Resize the window several times.

On Motif, you get the correct output for the x and y values:

LOCATIONS
x=5 y=25 w=274 h=242
x=10 y=10 w=254 h=222
x=10 y=10 w=234 h=202
x=10 y=10 w=214 h=182
x=10 y=10 w=194 h=162
x=10 y=10 w=174 h=142
x=10 y=10 w=154 h=122
x=10 y=10 w=134 h=102
x=10 y=10 w=114 h=82
x=10 y=10 w=94 h=62
x=10 y=10 w=74 h=42

However, on Windows, you get something like this:

LOCATIONS
x=4 y=23 w=268 h=244
x=14 y=33 w=248 h=224
x=24 y=43 w=228 h=204
x=34 y=53 w=208 h=184
x=44 y=63 w=188 h=164
x=54 y=73 w=168 h=144
x=64 y=83 w=148 h=124
x=74 y=93 w=128 h=104
x=84 y=103 w=108 h=84
x=94 y=113 w=88 h=64
x=104 y=123 w=68 h=44

You may also see a mixture of correct and incorrect values:

LOCATIONS
x=4 y=23 w=217 h=392
x=10 y=10 w=197 h=372
x=10 y=10 w=177 h=352
x=10 y=10 w=157 h=332
x=10 y=10 w=137 h=312
x=10 y=10 w=117 h=292
x=64 y=83 w=97 h=272
x=74 y=93 w=77 h=252
x=84 y=103 w=57 h=232
x=10 y=10 w=37 h=212
x=10 y=10 w=17 h=192

Normally, I get a lot more incorrect locations than correct locations.
However, when I redirect the output of the test program to a file, I
get more correct positions than incorrect positions. This indicates a
race condition of some sort.


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import java.awt.*;

class BorderPanel extends Panel {
  private static final int borderWidth = 10;

  public Dimension minimumSize() {
    Dimension d;

    if (countComponents() > 0) {
      Component comp = getComponent(0);
      d = comp.minimumSize();
    }
    else {
      d = new Dimension(0, 0);
    }

    d.width += 2*borderWidth;
    d.height += 2*borderWidth;

    return d;
  }

  public Dimension preferredSize() {
    return minimumSize();
  }

  public void layout() {
    Dimension d = size();
    Component components[] = getComponents();

    for (int i=0; i<components.length; i++) {
      if (i==0) {
components[i].reshape(borderWidth, borderWidth,
d.width - 2*borderWidth,
d.height - 2*borderWidth);
      }
      else {
components[i].reshape(-1, -1, 0, 0);
      }
    }
  }

  public void paint(Graphics g) {
    Dimension d = size();
    g.drawRect(0, 0, d.width-1, d.height-1);
    g.drawRect(1, 1, d.width-3, d.height-3);
  }
}

public class location extends Frame {
  private int validateCount;

  public static void main(String argv[]) {
    new location();
  }

  public location() {
    Button button = new Button("Button");
    Panel p = new BorderPanel();
    createNestedPanels(button, p, 10);
    add("Center", p);

    show();
    resize(preferredSize());
    validate();
  }

  public void createNestedPanels(Component c, Panel parent, int num) {
    if (num == 0)
      parent.add(c);
    else {
      Panel bp = new BorderPanel();
      parent.add(bp);
      createNestedPanels(c, bp, num-1);
    }
  }

  public synchronized void validate() {
    boolean valid = isValid();
    super.validate();

    System.out.println("validate " + validateCount++);
    if (!valid)
      printLocations();
  }

  public void printLocations() {
    Point p;
    Dimension d;
    Panel panel;
    Component c = getComponent(0);

    System.out.println("LOCATIONS");
    while (c instanceof Panel) {
      panel = (Panel)c;
      p = panel.location();
      d = panel.size();

      System.out.println("x=" + p.x + "\\ty=" + p.y +
"\\tw=" + d.width + "\\th=" + d.height);
      c = panel.getComponent(0);
    }
    System.out.println("");
  }
}