JFace Viewer钢结构焦点的自定义工具提示

Question

Another bug in JFace? I implemented a custom tooltip using standard mechanisms: a CellLabelProvider implementing the method getToolTipText() .

Everything seems fine, but it isnt't.

I got a view and an editor, both showing tables with these custom tooltips. If you have focused the editor and hover over its cells, you see its tooltips. Correct. If you hover over the view's table's cells, you see their tooltips. Correct.

BUT: if you happen to move the mouse inside the tooptip and move out again, the focus shifts from the editor to the view (and vice versa)!!

I don't see how this is meant to be like it is. It is very distracting indeed.

Did anybody ever see this? If not, try it, please!

To reproduce, take this snippet, which is taken from JFaceSnippets 3.11 :

package org.eclipse.jface.snippets.viewers;

import org.eclipse.jface.viewers.CellLabelProvider;
import org.eclipse.jface.viewers.ColumnViewerToolTipSupport;
import org.eclipse.jface.viewers.IStructuredContentProvider;
import org.eclipse.jface.viewers.TableViewer;
import org.eclipse.jface.viewers.TableViewerColumn;
import org.eclipse.jface.viewers.Viewer;
import org.eclipse.jface.viewers.ViewerCell;
import org.eclipse.jface.window.ToolTip;
import org.eclipse.swt.SWT;
import org.eclipse.swt.layout.FillLayout;
import org.eclipse.swt.widgets.Display;
import org.eclipse.swt.widgets.Shell;
import org.eclipse.swt.widgets.Text;

/**
 * Explore New API: JFace custom tooltips drawing.
 * 
 * @author Tom Schindl <tom.schindl@bestsolution.at>
 * @since 3.3
 */
public class Snippet011CustomTooltips {
    private static class MyContentProvider implements IStructuredContentProvider {
        @Override
        public Object[] getElements( final Object inputElement ) {
            return new String[] { "one", "two", "three", "four", "five", "six", "seven", "eight", "nine", "ten" };
        }

        @Override
        public void dispose() {
        }

        @Override
        public void inputChanged( final Viewer viewer, final Object oldInput, final Object newInput ) {
        }
    }

    /**
     * @param args
     */
    public static void main( final String[] args ) {
        final Display display = new Display();
        final Shell shell = new Shell( display );
        shell.setLayout( new FillLayout( SWT.VERTICAL ) );

        final Text t = new Text( shell, SWT.MULTI );
        t.setText( "1) Make sure focus is somewhere here. See the blinking caret!\n"
                + "2) Now get a tooltip displayed in the table by hovering there with the mouse cursor\n"
                + "3a) If you move the cursor INSIDE the tooltip just shortly and out again, the input focus will be stolen from this text field\n"
                + "3b) If you DO NOT move the cursor INSIDE the tooltip, input focus will remain with the text edit field\n\n"
                + "=> to me, this is a bug!" );

        final TableViewer v = new TableViewer( shell, SWT.FULL_SELECTION );
        v.getTable().setLinesVisible( true );
        v.getTable().setHeaderVisible( true );
        v.setContentProvider( new MyContentProvider() );
        ColumnViewerToolTipSupport.enableFor( v, ToolTip.NO_RECREATE );

        final CellLabelProvider labelProvider = new CellLabelProvider() {
            @Override
            public String getToolTipText( final Object element ) {
                return "Tooltip (" + element + ") - if you move HERE, the table will grab input focus!";
            }

            @Override
            public void update( final ViewerCell cell ) {
                cell.setText( cell.getElement().toString() );
            }
        };

        final TableViewerColumn column = new TableViewerColumn( v, SWT.NONE );
        column.setLabelProvider( labelProvider );
        column.getColumn().setText( "Table" );
        column.getColumn().setWidth( 100 );

        v.setInput( "" );

        shell.setSize( 800, 400 );
        shell.open();

        while( !shell.isDisposed() ) {
            if( !display.readAndDispatch() ) {
                display.sleep();
            }
        }

        display.dispose();
    }

}

Answer 1

I agree with you that this behavior is very odd, and I'd also call it a bug. Moving the focus to the underlying table simply because the tool tip label has been disposed makes no sort of obvious sense.

The problem is caused by the ColumnViewerToolTipSupport.afterHideToolTip() method:

protected void afterHideToolTip(Event event) {
    super.afterHideToolTip(event);

    // Clear the restored value else this could be a source of a leak
    setData(VIEWER_CELL_KEY, null);
    if (event != null && event.widget != viewer.getControl()) {
        viewer.getControl().setFocus();
    }
}

If you don't mouse into the tool tip, and simply move away from the cell you're hovering over, the event passed to afterHideToolTip() is null, and the setFocus() call is not made.

If you do mouse into the tool tip, and then away, the event passed to afterHideToolTip() is apparently generated by the tool tip's label itself as it dies.

Fiddling around with the few parameters at our disposal had no effect on the behavior: having useNativeToolTips() return true, passing RECREATE instead of NO_RECREATE ...

You can't even subclass ColumnViewerToolTipSupport and override afterHideToolTipEvent() , removing that mysterious setFocus() call, because the table viewer reference ColumnViewerToolTipSupport.viewer has private access.

The only course of action I can see is to file a bug and see if you can get some advice from the JFace devs. I'd be very interested to learn what the thinking is behind that setFocus() call.