Editors and Views

The primary focus of The RCP Company is the development of plug-ins for the Eclipse platform. A majority of plug-ins for Eclipse are concerned with editors and views where other plug-ins are used to extend the basic functionality of existing plug-ins - e.g. for a specific editor or view.

The plug-ins will be usable in any product that is based on the Eclipse platform, including IBM Rational Developer, BEA WebLogic Workshop, Genuitec MyEclipse and numerous other products. Read more…).

Editors and view are very central elements to the Eclipse platform and the development of these can be relative easy to rather complex depending on the wanted functionality.

Editors

To a large extend, editors are the main feature of the Eclipse platform. Most of the complexity of the Eclipse platform centers on the functionality of editors. Most editors are pure text editors and an editor usually corresponds to a specific content type (e.g. Java, XML or properties). This is not a requirement though. An editor can be purely graphical or property-sheet like or it can handle a number of files at a time. One such example is the plugin.xml editor of PDE.

New editors are typically constructed for internal languages that are important in the development environment.

For a non-trivial language there are a clear relationship between the functionality of the editor and the increased productivity. The typical Eclipse editor plug-in has a number of functions.

Syntax-based coloring

This is the ability to color the different parts of the text of an editor according to the syntactical meaning. E.g. strings, comments and keywords are each colored using a different color. The level of syntax-based coloring that can be performed depends on the language.

Syntax parsing along with reporting of problems (in the Problems view).

The text of the editor is parsed with a very forgiving parser that builds an abstract syntax tree (AST) as the result. This AST is essential for most of the functionality listed below. As a by product any syntax errors are registered in the Eclipse platform so they show up in the existing "Problems" view.

Semantics analysis of the AST

When the text of an editor has been completely parsed, the resulting AST can be analyzed further to find semantics errors. This can be as simple as undefined names but also complex issues with constants of wrong type or other issues involving more than one statement of the text.

Semantics-based coloring

This is an extension of the syntax-based coloring, where the coloring of specific tokens (e.g. identifiers) is based on the actual use of the token (e.g. whether it is a class, a variable, a method, etc).

Outline view

Most non-trivial languages have a concept of nesting – e.g. in Java the individual method declarations are enclosed in classes and in SQL the individual attributes are in table definitions. The actual nesting in an editor can be presented in the "Outline" view. Even for languages without nesting, the Outline view can be used to navigate the editor in a easy manner. Outline views can be extended in various manners to include filtering and sorting of the items in the view.

Folding based on syntax

The nesting information used for the Outline view can also be used to support folding in the editor. This way it is possible to hide specific sections of the text and by this ease the understanding of the rest of the text. Folding can also including comments and strings if these take up a larger part of the text.

Hover help

Hover help is the help that shows up when the pointer hovers above a token with some associated help. The help can be any relevant string, but often is a comment that is specified in connection with the definition of the token. Hover help often also includes information about any relevant problems that are detected at this point in the editor.

Templates

The use of templates can enhance the productivity a lot when the text contains many sections that are very similar. It is possible for the user to create new templates as needed. Templates can include substitutions, including substitutions based on the specific position where the template is inserted - e.g. the name of the class in Java.

Quick fixes

Many errors found during the syntax parsing and the subsequent semantics checks are due to minor and trivial errors and can easily be fixed semi-automatically. Trivial examples are many spelling errors (e.g. missing letters in keywords) and missing punctuation, but also many cases with missing declarations of names, constants of wrong type and similar global issues.

Content Assist

Content Assist is an extension to the quick fixes where no error needs to be present. This is primary used to assist the user in choosing the correct changes to the text of the editor.

Refactoring

The refactoring support is a safe way to make changes to an existing (correct) text. A trivial example is to change an identifier across multiple files (possibly even for different languages). More complex examples can be to exact certain parts of the text to external files or changes to the signature of classes or functions.

Content Sensitive Search

The Eclipse platform has a built-in text search command that can search for a specific string in any number of files. This command can be enhanced to only search specific types of information - e.g. only class names or method names.

Preference Pages

All of the above functionality can be handled in a number of ways and in some cases it is beneficial to allow the user to customize the exact behavior. This is done via preference pages. Properly formatted preference pages allow the user to search for specific options across all preference pages. 

The functionality of an editor is divided into the simple functionality and the more complex functionality depending on whether it is necessary to parse the text or not.

Views

Views in Eclipse are used to display non-modal information. Most views are either tied into a specific type of editor and shows information about the active editor or the views show global information pertaining to the complete Eclipse platform or some running tasks.

The following is some of the more important views from the Eclipse platform that all can be extended.

Problems

Shows the found problems. The view includes some very advanced filtering capabilities to limit the shown problems.

Outline

Shows an outline of the current active editor (usually) in terms of the nested structure of the language of the editor - e.g. classes, methods and fields for Java.

Search

Shows the results of the current set of active searches. Again, can filtering be used to limit the found occurrences.

Tasks

Shows the identified tasks in the currently opened projects. As before, can filtering be used to limit the shown items.

The RCP Company has a lot of experience in building new views and extending the existing views of the Eclipse platform. 

Plug-ins are also used to integrate 3^rd party applications into the Eclipse platform. Normally this is just a special case of the above. Read more…

Relevant Courses

If you need to make an editor or a view please have a look at our courses: RC0604 - Development of Eclipse Plug-ins and RC0605 - Advanced Eclipse Plug-in Development.