SWT and blinking

Question

I need the ability to have a blinking (red, maybe more colors) background for rows in a TableViewer/TreeViewer. What are the best options?

There may be more than one row blinking, the blinking MUST be synchron and I need two blinking modes, fast and slow.

Answer 1

Have you tried implementing a Thread which will periodically update the backgroundcolor of the blinking rows and requests a redraw of the view?

Answer 2

You should have a construction that resembles something like this:

LinkedList<Row> rows = new LinkedList<Row>();
Thread blinker = null;

public void start() {
    blinker = new Thread() {
        public void run() {
            while(!this.interrupted()) {
                try {
                    synchronized (rows) {
                        for (Row row : rows) {
                            row.setForegroundColor(color1);
                        }
                    }
                    Thread.sleep(500);
                    synchronized (rows) {
                        for (Row row : rows) {
                            row.setForegroundColor(color2);
                        }
                    }
                    Thread.sleep(500);
                } catch (InterruptException e) {
                    break;
                }
            }
        }
    };
    blinker.start();
}

public void stop() {
    if (blinker != null) {
        blinker.interrupt();
    }
}

public void add(Row row) {
    synchronized (rows) {
        if (!rows.contains(row)) {
            rows.add(row);
        }
    }
}

public void remove(Row row) {
    synchronized (rows) {
        rows.remove(row);
    }
}

When the Shell displays, it should call start(). When it disposes, call stop().

Note that I haven't actually tested this; it's some Javaish pseudocode. If you can't set the row color with the suggested setForegroundColor() above, you could perhaps introduce a widget and define a paint() event.

Answer 3

Howdy, this is a fast hack that shows the idea, improvable in many ways. I show the three classes doing the job. If you want I can provide an exported source plugin ready to install into your eclipse workbench tomorrow. Here are the core classes:

import java.util.TimerTask;

import org.eclipse.jface.resource.ColorDescriptor;
import org.eclipse.jface.viewers.IColorProvider;
import org.eclipse.jface.viewers.ITableLabelProvider;
import org.eclipse.jface.viewers.LabelProvider;
import org.eclipse.jface.viewers.TableViewer;
import org.eclipse.swt.graphics.Color;
import org.eclipse.swt.graphics.Image;
import org.eclipse.swt.graphics.RGB;
import org.eclipse.ui.PlatformUI;

public class Blinker extends LabelProvider implements ITableLabelProvider, IColorProvider  {

    private final TableViewer viewer;


    public Blinker(TableViewer viewer){
     this.viewer = viewer;
    }

    // this is just a lousy way to store blink_on/blink_off...
    private byte state; 

    // there must be a better way to get a color...
    final static Color red = ColorDescriptor.createFrom(new RGB(255,0,0)).createColor(PlatformUI.getWorkbench().getDisplay());
    final static Color green = ColorDescriptor.createFrom(new RGB(0,255,0)).createColor(PlatformUI.getWorkbench().getDisplay());


    private final TimerTask task = new TimerTask(){
     @Override
     public void run() {
      state++;
      PlatformUI.getWorkbench().getDisplay().asyncExec(new Runnable(){
       public void run() {
        viewer.refresh();
       }
      });
     }
    };

    private Timer t;

    synchronized byte getState(){
     return state;
    }

    @Override
    public Image getColumnImage(Object element, int columnIndex) {
     return null;
    }

    @Override
    public String getColumnText(Object element, int columnIndex) {
     return ((Element) element).text;
    }

    @Override
    public Color getBackground(Object object) {
     Element element = (Element) object;
     if (element.isBlinking()){
      return getState() % 2 == 0 ? Blinker.red : Blinker.green;
     } else {
      return Blinker.green;
     }
    }

    @Override
    public Color getForeground(Object element) {
     return null;
    }


    public void start() {
     t = new Timer();
     t.schedule(task, 200, 1000);
    }

    public void stop() {
     t.cancel();
     t = null;
        }

}

This is a sample model class. Blink state is stored within the object, but you might want to improve this by using some sort of Adapter:

package com.example.blinker;

public class Element {

    private boolean blinking;
    public final String text;


    public Element(String string, boolean b) {
     this.text = string;
     this.blinking = b;
    }


    public synchronized boolean isBlinking(){
     return blinking;
    }


    public synchronized void setBlinking(boolean b){
     this.blinking = b;
    }


    public static final Element[] sampledata = new Element[] {
     new Element("Merkur", false),
     new Element("Venus", true),
     new Element("Erde", false),
     new Element("Mars", true),
     new Element("Jupiter", false),
     new Element("Saturn", true),
     new Element("Uranus", false),
     new Element("Neptun", true),
     new Element("Pluto", false),
    };

}

And finally a TableViewer embedded in a View, making use of the two above:

package com.example.blinker.views;

import org.eclipse.jface.viewers.IStructuredContentProvider;
import org.eclipse.jface.viewers.TableViewer;
import org.eclipse.jface.viewers.Viewer;
import org.eclipse.swt.SWT;
import org.eclipse.swt.widgets.Composite;
import org.eclipse.ui.part.ViewPart;

import com.example.blinker.Blinker;
import com.example.blinker.Element;

public class SampleView extends ViewPart {

    public static final String ID = "com.example.blinker.views.SampleView";

    private TableViewer viewer;
    private Blinker blinker;

    class ViewContentProvider implements IStructuredContentProvider {
     public void inputChanged(Viewer v, Object oldInput, Object newInput) {}
     public void dispose() {}
     public Object[] getElements(Object parent) {
      return Element.sampledata;
     }
    }

    public void createPartControl(Composite parent) {
     viewer = new TableViewer(parent, SWT.MULTI | SWT.H_SCROLL | SWT.V_SCROLL);
     viewer.setContentProvider(new ViewContentProvider());
     blinker = new Blinker(viewer);
     viewer.setLabelProvider(blinker);
     viewer.setInput(new Object());
     blinker.start();
    }

    public void setFocus() {
     viewer.getControl().setFocus();
    }

    public void dispose() {
     blinker.stop();
    }
}

Answer 4

I would do something similar to this. Update the elements that you need to change the colors for at a regular interval. At each update toggle the colors depending on how you want them to flash.

void scheduleColorChange(final Color colors[], final int startIndex, final int changeInterval)
{
  getDisplay().timerExec(changeInterval, new Runnable()
  {
    public void run()
    {
      Object[] elements = getColorChangingElements();
      setColorsForFlashingElements(elements, colors[index%colors.length]);
      getViewer().update(elements);
      scheduleColorChange(colors, startIndex+1, changeInterval)
    }
 });

}

and the have you label provider implement IColorProvider.