删除SWT TreeItem图像缩进

Question

I am trying to build an SWT Tree that has icons at the top level but not at the next level.

Is there any way to avoid the blank space which seems to have been left for the image which I'm not using? I tried using the following code snippets but neither did what I wanted.

SWT.MeasureItem:

tree.addListener(SWT.MeasureItem, new Listener()
{
  @Override
  public void handleEvent(Event event)
  {
    TreeItem item = (TreeItem)event.item;
    Image image = item.getImage();
    if (image == null)
    {
      event.x -= 40;
    }
  }
});

SWT.PaintItem:

tree.addListener(SWT.PaintItem, new Listener()
{
  @Override
  public void handleEvent(Event event) {
    TreeItem item = (TreeItem)event.item;
    Image image = item.getImage();
    if (image == null)
    {
      event.x -= 40;
    }
  }
});

In both cases I was just hoping that the text could be drawn a bit further to the left.

Answer 1

This behavior comes from the native controls and is OS-specific (AFAIR, on Macs you won't see this problem). Alas, no easy fix but add some generic icon (or not adding icons at all).

Answer 2

I have done some more investigation myself. As per Eugene's answer this seems to be native behaviour. There are a couple of things worth noting.

If no items in the Tree have an icon then no space is left for icons. However, even a single item with an icon will cause all items to leave space for icons.

A hacky solution can be implemented as follows:

• Use no icons so that the native control leaves no icon space
• For items where you want an icon prefix some spaces to the text eg " " + text
• Add a PaintItem listener that draws the icon you want into the space left by the text

This probably doesn't work well across platforms and across system fonts so I've just decided to live with having icons.