How to align image to center of table cell (SWT Table)

Question

I develop Eclipse RCP application and got a problem with a Table. We have some data in database in boolean format and users wants to see that field using

Answer 1

You might also want to have a look at this blog entry: TableViewers and Nativelooking Checkboxes.

Answer 2

You may add PaintListener to your table and when it will paint selected column (column 5 in my case), check the size of row and align the image by yourself..

testTable.addListener(SWT.PaintItem, new Listener() {

    @Override
    public void handleEvent(Event event) {
        // Am I on collumn I need..?
        if(event.index == 5) {
            Image tmpImage = IMAGE_TEST_PASS;
            int tmpWidth = 0;
            int tmpHeight = 0;
            int tmpX = 0;
            int tmpY = 0;

            tmpWidth = testTable.getColumn(event.index).getWidth();
            tmpHeight = ((TableItem)event.item).getBounds().height;

            tmpX = tmpImage.getBounds().width;
            tmpX = (tmpWidth / 2 - tmpX / 2);
            tmpY = tmpImage.getBounds().height;
            tmpY = (tmpHeight / 2 - tmpY / 2);
            if(tmpX <= 0) tmpX = event.x;
            else tmpX += event.x;
            if(tmpY <= 0) tmpY = event.y;
            else tmpY += event.y;
            event.gc.drawImage(tmpImage, tmpX, tmpY);
        }
    }
});

Answer 3

Here is the example using OwnerDrawLabelProvider: http://bingjava.appspot.com/snippet.jsp?id=3221

I combined it with Tonny's link to TableViewers and Nativelooking Checkboxes and created handy abstract CenteredCheckboxLabelProvider class

import org.eclipse.jface.resource.JFaceResources;
import org.eclipse.jface.viewers.ColumnViewer;
import org.eclipse.jface.viewers.OwnerDrawLabelProvider;
import org.eclipse.swt.SWT;
import org.eclipse.swt.graphics.GC;
import org.eclipse.swt.graphics.Image;
import org.eclipse.swt.graphics.Point;
import org.eclipse.swt.graphics.Rectangle;
import org.eclipse.swt.widgets.Button;
import org.eclipse.swt.widgets.Event;
import org.eclipse.swt.widgets.Shell;
import org.eclipse.swt.widgets.TableItem;

public abstract class CenteredCheckboxLabelProvider extends OwnerDrawLabelProvider {
    private static final String CHECKED_KEY = "CHECKED";
    private static final String UNCHECK_KEY = "UNCHECKED";

    public CenteredCheckboxLabelProvider(ColumnViewer viewer) {
        if (JFaceResources.getImageRegistry().getDescriptor(CHECKED_KEY) == null) {
            JFaceResources.getImageRegistry().put(UNCHECK_KEY, makeShot(viewer.getControl().getShell(), false));
            JFaceResources.getImageRegistry().put(CHECKED_KEY, makeShot(viewer.getControl().getShell(), true));
        }
    }

    private Image makeShot(Shell shell, boolean type) {
        Shell s = new Shell(shell, SWT.NO_TRIM);
        Button b = new Button(s, SWT.CHECK);
        b.setSelection(type);
        Point bsize = b.computeSize(SWT.DEFAULT, SWT.DEFAULT);
        b.setSize(bsize);
        b.setLocation(0, 0);
        s.setSize(bsize);
        s.open();

        GC gc = new GC(b);
        Image image = new Image(shell.getDisplay(), bsize.x, bsize.y);
        gc.copyArea(image, 0, 0);
        gc.dispose();

        s.close();

        return image;
    }

    public Image getImage(Object element) {
        if (isChecked(element)) {
            return JFaceResources.getImageRegistry().get(CHECKED_KEY);
        } else {
            return JFaceResources.getImageRegistry().get(UNCHECK_KEY);
        }
    }

    @Override
    protected void measure(Event event, Object element) {
    }

    @Override
    protected void paint(Event event, Object element) {
        Image img = getImage(element);

        if (img != null) {
            Rectangle bounds = ((TableItem) event.item).getBounds(event.index);
            Rectangle imgBounds = img.getBounds();
            bounds.width /= 2;
            bounds.width -= imgBounds.width / 2;
            bounds.height /= 2;
            bounds.height -= imgBounds.height / 2;

            int x = bounds.width > 0 ? bounds.x + bounds.width : bounds.x;
            int y = bounds.height > 0 ? bounds.y + bounds.height : bounds.y;

            event.gc.drawImage(img, x, y);
        }
    }

    protected abstract boolean isChecked(Object element);
}

Answer 4

Sorceror's solution came in handy. I've adapted it to a custom IStyledLabelProvider to be used within a DelegatingStyledCellLabelProvider:

public class MutedLabelProvider extends LabelProvider implements IStyledLabelProvider {

  public MutedLabelProvider(Tree containerTree, int columnIndex) {
    registerIconListener(containerTree, columnIndex);
  }

  @Override
  public StyledString getStyledText(Object element) {
    return new StyledString();
  }

  private void registerIconListener(Tree containerTree, int columnIndex) {
    containerTree.addListener(SWT.PaintItem, new Listener() {
      @Override
      public void handleEvent(Event event) {
        if (event.index == columnIndex) {
          TreeItem treeItem = (TreeItem) event.item;
          Object data = treeItem.getData();
          Image tmpImage = getImageFromData(data);
          if (tmpImage != null) {
            int tmpWidth = 0;
            int tmpHeight = 0;
            int tmpX = 0;
            int tmpY = 0;
            tmpWidth = containerTree.getColumn(event.index).getWidth();
            tmpHeight = treeItem.getBounds().height;
            tmpX = tmpImage.getBounds().width;
            tmpX = (tmpWidth / 2 - tmpX / 2);
            tmpY = tmpImage.getBounds().height;
            tmpY = (tmpHeight / 2 - tmpY / 2);
            if (tmpX <= 0) tmpX = event.x;
            else tmpX += event.x;
            if (tmpY <= 0) tmpY = event.y;
            else tmpY += event.y;
            event.gc.drawImage(tmpImage, tmpX, tmpY);
          }
        }
      }
    });
  }

  private Image getImageFromData(Object element) {
    if (element != null && element instanceof IMarker) {
      IMarker marker = (IMarker) element;
      boolean isItTrue = marker.getAttribute("MyBooleanAttr", false);
      if (isItTrue) {
        // TODO return here the image you want for true state
        return JFaceResources.getImageRegistry().get("MyImageForTrue");
      } else {
        // TODO return here the image you want for false state
        // Alternatively, you can return null for no image
        return null;
      }
    } else {
      return null;
    }
  }

}

Note that I'm using IMarker as data for elements, and a TreeViewer (so I'm receiving TreeItems), but your data might differ, and your viewer might be a TableViewer; you just have to make your own adjustments.