Attachment 211906 Details for Bug 373010 – Example program

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Example program

StyledCellLabelProviderLeaksElementOfLastMeasure.java (text/plain), 4.34 KB, created by Eleanor Joslin

on 2012-03-01 13:57:10 EST

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Filename:

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Creator: Eleanor Joslin

Created: 2012-03-01 13:57:10 EST

Size: 4.34 KB

patch

obsolete

>package com.corefiling.eclipse.ui.bugs;
>
>import java.lang.ref.WeakReference;
>
>import org.eclipse.jface.dialogs.MessageDialog;
>import org.eclipse.jface.viewers.ArrayContentProvider;
>import org.eclipse.jface.viewers.CellLabelProvider;
>import org.eclipse.jface.viewers.StyledCellLabelProvider;
>import org.eclipse.jface.viewers.TableViewer;
>import org.eclipse.jface.viewers.TableViewerColumn;
>import org.eclipse.jface.viewers.ViewerCell;
>import org.eclipse.swt.SWT;
>import org.eclipse.swt.events.SelectionAdapter;
>import org.eclipse.swt.events.SelectionEvent;
>import org.eclipse.swt.layout.GridData;
>import org.eclipse.swt.layout.GridLayout;
>import org.eclipse.swt.widgets.Button;
>import org.eclipse.swt.widgets.Composite;
>import org.eclipse.swt.widgets.Display;
>import org.eclipse.swt.widgets.Shell;
>
>
>/**
> * Shows how a {@link StyledCellLabelProvider} leaks its elementOfLastMeasure field.
> *
> * Initially the table contains one element.  When the "Remove Row" button is pressed,
> * the table is emptied and refreshed, a {@link System#gc()} is performed, and the
> * program checks whether it still holds a weak reference to the element, indicating
> * that it has leaked.  The {@link StyledCellLabelProvider} does leak the element.
> *
> * If you change {@link #USE_STYLED_CELL_LABEL_PROVIDER} to <code>false</code> and
> * run the program again, it uses a plain {@link CellLabelProvider} instead and there
> * is no leak.
> */
>public class StyledCellLabelProviderLeaksElementOfLastMeasure {
>
>  private static final boolean USE_STYLED_CELL_LABEL_PROVIDER = true;
>
>  private WeakReference<?> _lastElementUpdated = new WeakReference<Object>(null);
>
>  private Shell _shell;
>  private TableViewer _tableViewer;
>
>  public void run() {
>    Display display = new Display();
>    _shell = new Shell(display);
>    _shell.setLayout(new GridLayout(1, false));
>
>    Composite composite = new Composite(_shell, SWT.NONE);
>    composite.setLayoutData(new GridData(SWT.FILL, SWT.FILL, true, true));
>    composite.setLayout(new GridLayout(1, false));
>
>    _tableViewer = new TableViewer(composite, SWT.NONE);
>    GridData layoutData = new GridData(SWT.FILL, SWT.FILL, true, true);
>    layoutData.heightHint = 400;
>    layoutData.widthHint = 600;
>    _tableViewer.getTable().setLayoutData(layoutData);
>
>    TableViewerColumn column = new TableViewerColumn(_tableViewer, SWT.BORDER);
>    column.getColumn().setWidth(600);
>    column.setLabelProvider(createLabelProvider());
>    _tableViewer.setContentProvider(new ArrayContentProvider());
>    _tableViewer.setInput(new Object[] {new Object()});
>    _tableViewer.refresh();
>
>    final Button button = new Button(composite, SWT.PUSH);
>    button.setLayoutData(new GridData(SWT.BEGINNING, SWT.CENTER, false, false));
>    button.setText("Remove Row");
>    button.addSelectionListener(new SelectionAdapter() {
>      @Override
>      public void widgetSelected(final SelectionEvent e) {
>        clearTableAndReportLeak();
>        button.setEnabled(false);
>      }
>    });
>
>    _shell.pack();
>    _shell.open();
>    while (!_shell.isDisposed()) {
>      if (!display.readAndDispatch()) {
>        display.sleep();
>      }
>    }
>    display.dispose();
>  }
>
>  private CellLabelProvider createLabelProvider() {
>    if (USE_STYLED_CELL_LABEL_PROVIDER) {
>      return new StyledCellLabelProvider() {
>        @Override
>        public void update(final ViewerCell cell) {
>          updateCellAndCacheElementWeakly(cell);
>          super.update(cell);
>        }
>      };
>    }
>    else {
>      return new CellLabelProvider() {
>        @Override
>        public void update(final ViewerCell cell) {
>          updateCellAndCacheElementWeakly(cell);
>        }
>      };
>    }
>  }
>
>  private void updateCellAndCacheElementWeakly(final ViewerCell cell) {
>    cell.setText(cell.getElement().toString());
>    _lastElementUpdated = new WeakReference<Object>(cell.getElement());
>  }
>
>  private void clearTableAndReportLeak() {
>    _tableViewer.setInput(new Object[0]);
>    System.gc();
>    Object possiblyLeakedElement = _lastElementUpdated.get();
>    if (possiblyLeakedElement != null) {
>      MessageDialog.openError(_shell, "Table Element Leaked", "This element was leaked: " + possiblyLeakedElement);
>    }
>    else {
>      MessageDialog.openInformation(_shell, "No Leak", "No element was leaked from the table.");
>    }
>  }
>
>  public static void main(final String[] args) {
>    new StyledCellLabelProviderLeaksElementOfLastMeasure().run();
>  }
>
>}

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Attachments on bug 373010: 211906