Single column TableViewer and TableColumnLayout

If you have a single column TableViewer (which is commonly used because ListViewer won't show you the images), the single coloumn won't take the entire space. For example if you run the TableViewer snippet, the output is like this:


To get rid of the other spurious coloum that appears on the right, you have to use the TableColumnLayout. Modifying the code to use that:

public Snippet001TableViewer(Shell shell) {

Composite tableComposite = new Composite(shell, SWT.NONE);
final TableViewer v = new TableViewer(tableComposite);
v.setLabelProvider(new LabelProvider());
v.setContentProvider(new MyContentProvider());
MyModel[] model = createModel();
v.setInput(model);
v.getTable().setLinesVisible(true);

TableColumn singleColumn = new TableColumn(v.getTable(), SWT.NONE);
TableColumnLayout tableColumnLayout = new TableColumnLayout();
tableColumnLayout.setColumnData(singleColumn, new ColumnWeightData(100));
tableComposite.setLayout(tableColumnLayout);

}

Remember, the TableColumnLayout should be applied on the composite that holds the Table. And the composite should contain only the table and nothing else. Here is the result:

Content type Specific File icons

Eclipse 3.4 M6 is out. It has lots of wonderful features like p2 and the installer. But one small change that is going to save a lot of developers time is the content type specific file icons. Earlier if I had to contribute an icon for a specific file, I've to write my own label decorator. Now Eclipse comes with a label decorator that does the same.

All you have to do is to define the content type and associate an editor with that content type. If you were wondering writing an editor is not a trivial task, don't worry, you can reuse the existing ones.

Assume that in my app, I have some files with extension 'config'. They are nothing but normal properties files. I would like to invoke the Properties editor on this extension and give a different icon. Here is how I create a new content type for the extension associated the Properties editor for that.

<extension point="org.eclipse.core.contenttype.contentTypes">
<content-type base-type="org.eclipse.core.runtime.properties"
file-extensions="config"
id="in.cypal.eclipse.myConfig"
name="My Config File"
priority="normal">
</content-type>
</extension>
<extension point="org.eclipse.ui.editors">
<editor class="org.eclipse.jdt.internal.ui.propertiesfileeditor.PropertiesFileEditor"
default="false"
extensions="config"
icon="icons/sample.gif"
id="in.cypal.eclipse.editors.myConfigEditor"
name="My Config Editor">
<contentTypeBinding contentTypeId="in.cypal.eclipse.myConfig">
</contentTypeBinding>
</editor>
</extension>




Content types are not just based on file names/extensions. If you have an xml file, you can use the XMLContentDescriber to find the content type based on the root element; create an editor extension; specify the Text Editor/XML Editor class; associate the content id and add the icon to the editor. You are done. All of this without writing a single line of code!

Wizard as a Dialog

In an RCP application, I had these requirements for a Dialog box:

• OK button should not be enabled until all the mandatory fields are filled
  
• Hints for probably incorrect data (The email id grprakash+eclipse@gmail.com "looks" like a wrong one) These should not stop the user from pressing OK
• Progress bar should be shown for long running operations (clicking OK, "check for user id availability", etc)

I was thinking on how to handle all these in a Dialog and something flashed in my mind - JFace Wizards. All the above requirements can be easily done if I use a Wizard. The Finish button is disabled when we call setPageComplete(false), we can show warnings and still allow the user to finish and by calling setNeedsProgressMonitor() & getContainer().run() we can show the progress bar in the UI as well. But there are two small issues to be handled when we use the wizard.

• The first one is to get rid of the Back and Next buttons. We are lucky here because JFace will not show those buttons if there is only one page in the wizard
  
• The "Finish" looks odd and should be renamed to "OK" or "Submit. This can be done by subclassing the WizardDialog:
  

WizardDialog dialog = new WizardDialog(shell, wizard) {

@Override
protected void createButtonsForButtonBar(Composite parent) {
super.createButtonsForButtonBar(parent);
Button finishButton = getButton(IDialogConstants.FINISH_ID);
finishButton.setText(IDialogConstants.OK_LABEL);
}
};

Now with the util method, I can enable/disable the "OK" button, reflecting the status of the UI items.

Related:
Util method for Wizard Pages
JFace Wizard Guidelines

Eclipse CVS

The CVS Repositories view in Eclipse allows you to paste a CVS URL in the "New Repository Location" Wizard. (If you are on 3.3, you can directly paste on the view without the Wizard) In case you want to browse thru the Eclipse CVS repository, here are the URLs you can copy and paste into the wizard.

Platform, SWT, JFace, Equinox, JDT, launcher, UI, update, search, debug, team, etc) are available here:
:pserver:anonymous@dev.eclipse.org:/cvsroot/eclipse
Mylyn, GEF, CDT, COBOL, VE:
:pserver:anonymous@dev.eclipse.org:/cvsroot/tools
AspectJ, Nebula, EPP:
:pserver:anonymous@dev.eclipse.org:/cvsroot/technology
EMF, GMF, MDT:
:pserver:anonymous@dev.eclipse.org:/cvsroot/modeling
WTP:
:pserver:anonymous@dev.eclipse.org:/cvsroot/webtools
Data Tools:
:pserver:anonymous@dev.eclipse.org:/cvsroot/datatools


If you want to browse thru the CVS, you can use the web based viewer also: http://dev.eclipse.org/viewcvs/
More info on connecting to Eclipse CVS: http://wiki.eclipse.org/index.php/CVS_Howto

Related:
Searching Eclipse Sources

Handy util method for WizardPages

Consider this familiar New Java class wizard.


It has to keep track of the status of the source folder, package, enclosing type, name, ... When ever there is a change in these fields, the WizardPage's status has to be updated. The algorithm goes like this: find the most severe status and update the wizard page with that status. This is a very common operation can be applied to any WizardPage. So I've written a helper method which I usually use it in almost all of the WizardPage I create. Let me know if it can be improved

public static void applyStatus(WizardPage page, IStatus[] statuses) {

IStatus severeStatus = statuses[0];
for (IStatus status : statuses) {
severeStatus = severeStatus.getSeverity() >= status.getSeverity() ? severeStatus : status;
}

String message = severeStatus.getMessage();
switch (severeStatus.getSeverity()) {
case IStatus.OK:
page.setMessage(null, IMessageProvider.NONE);
page.setErrorMessage(null);
break;
case IStatus.WARNING:
page.setMessage(message, IMessageProvider.WARNING);
page.setErrorMessage(null);
break;
case IStatus.INFO:
page.setMessage(message, IMessageProvider.INFORMATION);
page.setErrorMessage(null);
break;
default:
if (message.length() == 0) {
message = null;
}
page.setMessage(null);
page.setErrorMessage(message);
break;
}
}

How to add TrayItem in Eclipse RCP application?

In an application like Yahoo Messenger or Skype, you don't want to quit the application when the main window is closed. Most of these applications will move themselves to System Tray when the main window is closed and clicking on the Tray icon would bring back the window. Lets try to see how to do it in an Eclipse RCP Application.

When the window is closed, the WorkbenchWindowAdvisor.preWindowShellClose() method is called. If this returns false, then the close request will not be honored. So all we need to do is to override this method; create a TrayItem; hide the window and return false.


trayItem = new TrayItem(Display.getDefault().getSystemTray(), SWT.NONE);
trayItem.setText("My RCP App");
trayItem.setImage(getAppIcon());
trayItem.addSelectionListener(getSelectionListener());
getWindowConfigurer().getWindow().getShell().setVisible(false);
return false;

In the SelectionListener, we can add code to bring up the window:

Shell workbenchWindowShell = getWindowConfigurer().getWindow().getShell();
workbenchWindowShell.setVisible(true);
workbenchWindowShell.setActive();
workbenchWindowShell.setFocus();
workbenchWindowShell.setMinimized(false);
trayItem.dispose();

Simple :-)

How to add a status bar in an RCP app?

If you are writing an RCP application, you may want to add a status message in the status bar. Adding it is very simple.

By all chance, you already have a class extending org.eclipse.ui.application.ActionBarAdvisor in your RCP app (If not, Google around to find out how to add one to your RCP app). Just override the fillStatusLine method.

private StatusLineContributionItem statusItem;

@Override
protected void fillStatusLine(IStatusLineManager statusLine) {

statusItem = new StatusLineContributionItem("LoggedInStatus");
statusItem.setText("Logged in");
statusLine.add(statusItem);
}

Thats it :-)



Note 1: You can add any number of status items
Note 2: In Eclipse 3.3, the class StatusLineContributionItem is in org.eclipse.ui.internal.util package. This has been moved to org.eclipse.jface.action package in Eclipse 3.4

JFace Wizard Guidelines

During Eclipse Plugin Developement training, I always end JFace Wizards session with these guidelines:

1. Wizards should be aimed for minimal user interaction
2. Wizard pages can be filled with meaningful defaults
3. When a Wizard is shown it should not contain any errors. They should appear only after a user interaction
4. Present Errors/Warnings in the tab order of the fields
   
5. When a task is split into steps, a wizard page can model a step and shouldn't be doing more things
6. Don't create pages that needs scrolling. In general if a wizard's height is greater than its width, probably it needs a review
7. Total number of Wizard pages should be ~ 5

Once when I finished explaining them, one smart guy said: "Have you ever looked at the New Java Project Wizard?". True. The first page of that wizard doesn't comply with the Guideline #6. These points are not official standards, mere guidelines by me, but still I think they are good. So what is the problem with the New Java Project Wizard and how can it be better?

The options in the first page falls into three categories:

1. Resource: Project name, location & working sets
2. Compiler: Source folders
3. Runtime: JRE & Execution env.

Ideally the first page should just give the resource related options and the others can be pushed to second page/elsewhere. Since the second page allows the user to configure the JRE, source & binary folder, I guess we are not loosing any functionality if we get rid of those options. If the first page is cleaned up to have only resource related options, this is how it would look like:




in contrast to the current: