Editor API

Overview

# Javadoc

Please see the Javadoc for further details; of greatest interest will be the documentation for `NbDocument`.

# Contents

- Overview
  - Typical use scenario
- Accessing an Open Document
  - Getting the document object for a data object
  - Common operations on resulting document
- Advanced Editor Automation
  - Using guard blocks
  - Using annotations
- Loader Interactions with Guard Blocks
- Implementing a Custom Editor
  - Creating editor kit
  - Creating styled document
  - Handling guards
  - Lines and elements
  - Handling annotations
  - Printing
  - Locking
  - Biases
  - Scrolling to display
  - Presentable actions
  - Undo/redo support
  - Customization
  - Installing

# Editor API

This document describes the NetBeans Editor API, attempting to give a summary of what you need to know about it for different purposes.

The Open APIs only cover certain aspects of working with the editor. For example, you can open documents, modify them, add annotations, register editor kits you built from scratch, and so on. Some more specific capabilities that are frequently requested are not guaranteed by the Open APIs but may be possible using NetBeans modules which may have differing standards of API design, documentation, and compatibility from release to release. Here are some resources that may also be of interest:

- The NetBeans editor module is the typical editor implementation. It is possible to use base classes in this module as a starting point for defining your own editor kits: syntax coloring, code completion, etc. for new languages and file formats. As of this writing, the details of how to add new editor kits from a NetBeans module are virtually undocumented, and compatibility is likely to be broken in future NetBeans releases, so do so at your own risk.

- The lexer module is planned to make creation of new editor kits easier.

## Overview

The Editor API may be used at a first cut for two purposes: accessing editor-related functionality from within the IDE for use by other modules and the core IDE itself; and implementing a custom editor that can be inserted into the IDE as a module, replacing or supplementing the NetBeans-supplied one.

### Typical use scenario

Here is an example sequence of events describing how an editor is used with Java source code and cooperates with the Form Editor.

- The user either opens an existing form, or creates a new form (say for a `JFrame`) from template - in either case, there is a new `.java` file in the user's repository containing Java source, together with a `.form` file.
- A "data object" is created for the form, using the "form" data loader; in this case there is a standard IDE module (installed in the IDE system modules area) for the Form Editor. This module includes the implementation of the Form Editor; but it is invoked only through a loader, which recognizes a `.form` file associated with a `.java` file; when it finds them, it:
  - Creates nodes for the form, including a top-level node, a node for the form itself (with children corresponding to the AWT component structure), and a node for the class (with children corresponding to methods, variables, etc.).
  - Opens the form (`.form`) file in the Form Editor.
  - Asks to open the `.java` file in an editor.
- If the `.java` file was already open in some editor window or pane, then this window/pane is reused and just given focus (i.e. a new `JEditorPane` is created, but using the same `EditorKit` and `StyledDocument`).

  If not, a new `JEditorPane` is asked to create an editor for the Java source content type (typically `text/x-java`). Now, the Form Editor's data loader is an extension of the Java Source data loader; the Java loader specially treats the request to load its content into an editor: it inserts most of the text straight into the `StyledDocument` just as you would expect, but also checks for special comments looking something like `//GEN-BEGIN:` in the source code, which are the markers used to indicate guarded areas in saved source code. When it finds one, rather than inserting the marker into the document, it uses `NbDocument.insertGuarded(...)` to insert the enclosed text area, making it read-only to the user.

- The `JEditorPane` now has a `StyledDocument` suited to Java source code loaded into it. This document may be implemented by the standard NetBeans Editor, or it may be a custom editor. The user may edit non-guarded parts of the document; attempted actions (like typing) that would affect guarded areas are prevented by the editor in use.
- The user may make modifications to the form in the Form Editor. This form is of course linked to the open document, allowing the document to reflect needed code changes. The form editor does not actually need to read the document at all; whenever something is modified on the form, the form editor just replaces an existing guarded block with new, regenerated contents, or it deletes an existing block, or adds a new block just after an existing one. So if the user had foolishly made edits to a guarded area while the source file was on disk, those edits would simply be discarded upon being loaded into the Form Editor.

  Note that the Form Editor directly or indirectly calls `Document.insertString(...)` (or `NbDocument.insertGuarded(...)`) and `Document.remove(...)` to do this work, so it is itself unaffected by guard blocks.

- The user may explore the Java parse hierarchy as presented in the Explorer when expanding the class node for the form; from here, methods, variables, and so on in the code may be seen as attributed objects. If the user modifies one of these attributes, or uses a more complex JavaBean view of the class, the document is asked to make the corresponding update in the source; but in this case, the guarded attribute is checked, since the user should not be able to arbitrarily rename or otherwise affect members used by the Form Editor without its consent! The IDE actions implementing such modifications will use `NbDocument.WriteLockable.runAtomicAsUser(...)` to make sure that the guard blocks are properly honored.
- When the user is done with the form, he may close it; then he will be prompted to save to disk. If a save action is performed, the Java Data Object is responsible for looking for guard blocks in the editor and converting these back into comments like `//GEN-BEGIN:` before the text is written to file.

## Accessing an Open Document

Starting from other APIs, it is not difficult to make use of the Editor API to get access to an editor window displaying a particular file.

### Getting the document object for a data object

Here is an example of how to find a file by name stored in some filesystem in the Repository; get its data object (assuming you do not already have its data object, or a node representing the data object); and get the Swing document to edit it, opening a new Editor window with that document if necessary. Naturally this example is somewhat long, because it demonstrates how to do all of this from scratch. Also, exception handling is not illustrated here.

    File f = new File("/home/me/sources/my/pkg/MyFile.java");
    FileObject fo = FileUtil.fromFile(f)[0];
    DataObject d = DataObject.find(fo);
    EditorCookie ec = (EditorCookie)d.getCookie(EditorCookie.class);
    ec.open();
    StyledDocument doc = ec.openDocument();

### Common operations on resulting document

You can check such things as whether or not the file is modified in the Editor:

    if (ec.isModified()) ...

Then see what the current contents of line 26 are (zero-based):

    int start=NbDocument.findLineOffset(doc, 25);
    int end=NbDocument.findLineOffset(doc, 26);
    String contents=doc.getText(start, end-start);

And display this line in the Editor window:

    ec.getLineSet().getCurrent(25).show(Line.SHOW_TRY_SHOW);

Now insert a new line here after it:

    final BadLocationException[] exc = new BadLocationException[] {null};
    NbDocument.runAtomicAsUser(doc, new Runnable() {
        public void run() {
            try {
                doc.insertString(NbDocument.findLineOffset(doc, 26),
                                 "// New text.\n",
                                 SimpleAttributeSet.EMPTY);
            } catch (BadLocationException e) {
                exc[0] = e;
            }
        }
    });
    if (exc[0] != null) throw exc[0];

All done! Prompt to save the file, and close the editor window:

    ec.close();

## Advanced Editor Automation

For advanced modules on a level with the Form Editor or the Compiler and Debugger, it is necessary to take more complete control over the actions and content of an editor.

### Using guard blocks

Manipulating guarded blocks should not be very difficult, if your application requires it. They are used by the FormEditor, but any module which needs to prevent the user from editing certain portions of a text document (typically because they will be mechanically recreated by other means), can do so.

- To create a guard block over an existing area of text, you may use `NbDocument.markGuarded(...)`; the guard block may subsequently be removed using `NbDocument.unmarkGuarded(...)`.

  Typically you will want to remember the positions of the guard blocks you added using a position, so that user edits in the vicinity of the guard block will be taken into consideration. You may create such a position using `NbDocument.createPosition(...)`, and retrieve its current offset when needed using `Position.getOffset()`.

- To insert a new guarded block of text, you may use `NbDocument.insertGuarded(...)`.
- To change the contents of part of the document, without regard to the presence of guard blocks (this assumes you know what you are doing and what the guard blocks are being used for), you may use the standard Swing `Document.insertString(...)` and `Document.remove(...)`. You probably want to use `NbDocument.runAtomic(...)` to prevent errors in threaded code.

  To do the same sort of thing while preventing yourself from accidentally touching a guard block, i.e. if your module was not the creator of the guard block (or you are not even sure if there any in the document), please use `NbDocument.runAtomicAsUser(...)` instead.

### Using annotations

In order to provide richer interactions between the editor and other modules, the APIs provide for a system of annotations which are used for things like debugger breakpoints, erroneous lines, and so on. From an API perspective, anyone can create annotations and attach them to a document; the editor implementation should attempt to display these annotations as it sees fit, taking hints from the annotation provider.

Using annotations on a document need not be difficult. Everything you need to do is to define the visual appearance of your annotation and to provide a class which will represent it programmatically. For example, if you are writing a module which interacts with an open document containing some sort of program code, and the user has made a syntax error in the code which you were able to detect and want to point out, you may want to mark the line or part of the line as "erroneous". To achieve this you must:

1. Describe the appearance of your annotation. This is the so-called annotation type which consist of attributes like colors and so on. After you have defined the annotation type you will be able to create document annotations which will reference this annotation type. Definition of an annotation type involves creation of an XML file with the format specified by a standard DTD. This XML file must be registered in your module installation layer in the folder `Editors/AnnotationTypes`. Here is an example XML file `Editors/AnnotationTypes/org-nb-modules-foo-some-annotation.xml` (the file name within this folder is arbitrary but should be distinctive to prevent collisions between modules):

       <?xml version="1.0" encoding="UTF-8"?>
       <!DOCTYPE type PUBLIC
                 "-//NetBeans//DTD annotation type 1.0//EN"
                 "http://www.netbeans.org/dtds/annotation-type-1_0.dtd">
       <type name="org-nb-modules-foo-some-annotation"
             description_key="LBL_some-annotation"
             localizing_bundle="org.nb.modules.foo.Bundle"
             visible="true"
             glyph="nbresloc:/org/nb/modules/foo/some-annotation-glyph.gif"
             highlight="#FFFF00"
             type="line"/>

   As you can see the definition of the annotation type consists of the highlight color; the glyph icon which could be shown in the left margin of the editing area - the glyph gutter; the localized name; and so on. For more details about each field in the DTD see below.

2. Extend the `Annotation` abstract class and define your own annotation. You must specify the type - which matches the code name given in the XML description - and a short description, which can form tool-tip text for the annotation. For example:

       public final class SomeAnnotation extends Annotation {
           private final String error;
           public SomeAnnotation(String error) {
               this.error = error;
           }
           public String getAnnotationType() {
               return "org-nb-modules-foo-some-annotation";
           }
           public String getShortDescription() {
               // Localize this with NbBundle:
               return "The error was: " + error;
           }
       }

   Note that you can return the tooltip text asynchronously, on demand, or dynamically: you may return `null` for no tooltip, and you may later return a new or changed tooltip - just use:

       firePropertyChange(PROP_SHORT_DESCRIPTION, null, null);

   to inform the editor of the change. The tooltip should be refreshed on-screen.
3. Finally, attach an annotation instance you make to some `Annotatable` object. Normally this will be a `Line` representing a whole line of text, or a `Line.Part` representing a section of a line. For example:

       // Given error output like: "pkg/Name.java:123: You made a mistake"
       FileObject fileWithError = fs.findResource("pkg/Name.java");
       DataObject objWithError = DataObject.find(fileWithError);
       LineCookie cookie = (LineCookie)objWithError.getCookie(LineCookie.class);
       Line.Set lineSet = cookie.getLineSet();
       final Line line = lineSet.getOriginal(123);
       final Annotation ann = new SomeAnnotation("You made a mistake");
       ann.attach(line);

4. In this example the user may correct the erroneous line, or at least do something to it - in this case we assume that the annotation is no longer needed, and should be removed. It is a simple call to do this; of course you need to know when it is appropriate, so for example:

       line.addPropertyChangeListener(new PropertyChangeListener() {
           public void propertyChange(PropertyChangeEvent ev) {
               String type = ev.getPropertyName();
               if (type == null || type == Annotatable.PROP_TEXT) {
                   // User edited the line, assume error should be cleared.
                   ann.detach();
                   line.removePropertyChangeListener(this);
               }
           }
       });

It is possible that there might be more than one annotation on the same line. In this case it depends on the capabilities of the editor how the annotations will be displayed. The simplest scenario is that only one annotation is visible at time and the user can cycle through them. If this is the case it may be helpful to force the editor to move your annotation in front of any others:

    ann.moveToFront();

The IDE presents GUI settings to the user in which it is possible to customize the attributes of annotation types - for example, foreground and background color. Remember however that some editor implementations may find it difficult or impossible to accurately display all of these settings (for example display of arbitrary glyphs may be infeasible).

#### Detailed description of annotation XML files

Attributes of the `<type>` element are:

`name`
  Unique non-localized name of the annotation type. Should match the result of `Annotation.getAnnotationType()`.
`description_key`
  Bundle key for the localized name of the annotation type. This name is shown in annotation settings as the name of the annotation type.
`localizing_bundle`
  Name of the bundle (dot-separated and sans extension or locale suffix) which contains the localized annotation name under the `description_key`.
`visible`
  Whether the annotation type is visible or not.
`glyph`
  URL of the glyph icon. Typically this would use the `nbresloc` protocol to access module resources and automatically localize them. A 16x16 GIF is common.
`highlight`
  RGB value of the highlight color.
`foreground`
  RGB value of the foreground color. If the color is not specified, the line's normal text color is inherited.
`type`
  Style of annotation. Currently two styles are permitted: `line` (full-line annotation) and `linepart` (may be applied to a column range within a line).
`actions`
  The name of a subfolder (rooted from `Editors/AnnotationTypes/`) in which actions for this annotation type may be specified. The editor may present these actions to the user when the annotation glyph is right-clicked, for example. The actions may be defined by listing instances:

      <folder name="YourAnnotationTypeActions">
        <file name="org-foo-BarAction.instance"/>
      </folder>

`severity`
  Severity of this annotation. Allowed values are `error`, `warning`, `ok` and `none`. Annotations with severity other then `none` will be shown in the Error Stripe using default color or color specified in `custom_sidebar_color`. Default value is `none`.
`custom_sidebar_color`
  A color which should be used when showing this annotation in the Error Stripe. Specify this color if the default color derived from the `severity` is not feasible. Note that this setting has no effect if `severity` is set to `none`.
`browseable`
  Whether this annotation should be "browseable" using action like Show Next Error. Valid values are `true` and `false`, default is `false`.
`priority`
  Priority of this annotation with respect to other annotations with the same severity. Valid values are integer numbers. Default is 0.

The annotation `<type>` may also contain the `<combinations>` element - a definition of annotation combinations. If two or more annotations from the same module (or otherwise mutually known) are on the same line it might make sense to combine them into one annotation visually. For example, if a debugger module attached a breakpoint to a line and the current program counter reached the same line, it is more pleasant to show a combination of these two annotations rather than two separate annotations. This can be accomplished using a combination definition. A combined annotation type is otherwise normal (it may have a glyph icon and colors), but it also contains the definition of annotation types which are subsumed by this type. For example the combination of program counter with breakpoint could be defined as follows:

    <combinations tiptext_key="PC_BREAKPOINT_COMBINATION_TOOLTIP_TEXT">
      <combine annotationtype="NameOfTheBreakpointAnnotationType"/>
      <combine annotationtype="NameOfTheCurrentPCAnnotationType"/>
    </combinations>

It is the responsibility of the editor to display combinations where the criteria for combinations as defined in available annotation types are met.

Attributes of the `<combinations>` element are:

`tiptext_key`
  Bundle key for the localized tooltip text of the combining annotation. The same bundle is used as was specified in `description_key` on `<type>`. Since multiple annotation types are being combined, each of which might have its own tooltip, the combined annotation has just a static tooltip which might explain that several annotations are combined in it.
`order`
  If necessary, the order in which the combinations should be processed can be specified. This might be useful for more complicated combinations. If the value is not specified, the combination is added to the end of the list.
`min_optionals`
  This is related to the attribute `optional` of the `<combine/>` element. The combination is defined as a list of annotation types to be combined. To make creation of the combination more flexible, some annotation types can be optional (`optional` attribute on `<combine/>`). `min_optionals` is then used to specify the minimum number of optional annotation types which must be found to make the combination valid. For example, you may have have a conditional breakpoint and disabled breakpoint and wish to combine either of them with the current program counter. You can define it as follows:

      <combinations tiptext_key="COMBINATION_TOOLTIP_TEXT" min_optionals="1">
        <combine annotationtype="debugger-disabledbreakpoint" optional="true"/>
        <combine annotationtype="debugger-conditionalbreakpoint" optional="true"/>
        <combine annotationtype="debugger-currentpc"/>
      </combinations>

  This way you specify that both breakpoints are optional, but that at least one must be found to make the combination succeed.

The `<combinations>` element can contain only `<combine/>` elements (one for each annotation type) and they can have these attributes:

`annotationtype`
  Name of the annotation which is subsumed by this combination; matches `name` on `<type>`.
`absorb_all`
  Whether all occurrences of this annotation type should be absorbed by this combination or only one. This might be useful in case there are for example multiple breakpoints on the same line.
`optional`
  Whether this annotation type is optional for the combination or not.
`min`
  Minimum count of annotations of this annotation type which must be on the line for the combination to match with this type. This can be used to define combinations such as collapsed multiple breakpoints.

## Loader Interactions with Guard Blocks

The NetBeans-supplied data object for Java source code automatically sets up guard blocks in the source documents it opens, if they contain the magic tokens in comments which delimit guard blocks on disk. So, if you are working with Java sources, you need do nothing special to load and save guarded documents; you may set guard blocks on them in memory, and this will be retained; or you may add the special tokens to them on disk, triggering guard block creation when the file is opened.

If you would like to add something akin to guard blocks to a custom file type handled by your module, you will need to insert the appropriate hooks. The best thing to do is to subclass `EditorSupport`, and use this subclass to implement cookies such as `EditorCookie`. Now just provide appropriate implementations of `CloneableEditorSupport.loadFromStreamToKit(...)` (to interpret special markings in the saved file and convert them into document attributes); and `CloneableEditorSupport.saveFromKitToStream(...)` (to translate these attributes back into ASCII markings).

## Implementing a Custom Editor

It is possible to integrate a custom editor (presumably for textual content types) into the IDE, in place of the default editor. The basic requirement is that it conform to the Swing EditorKit conventions. The Swing Text system is rather complex, so if you are not familiar with it you should look at Using the Swing Text Package.

Beyond being a generic EditorKit, there are two significant pieces of functionality used by the IDE which the editor should support if at all possible:

- Be able to mark IDE-supplied blocks of text as read-only, and prevent the user from editing or removing these blocks.
- Be able to mark certain lines of the document (or parts of lines) with IDE-supplied annotations, e.g. background color, gutter glyphs, or as much as feasible, and change these display markings upon request.

### Creating editor kit

You should not need to do anything special to create the editor kit beyond what is normally required by Swing.

### Creating styled document

You will need to create an implementation of `javax.swing.text.StyledDocument` to hold the content of the buffer being edited.

Actually, you could get away with a plain `Document` if you really wanted, but you would be unable to support guard blocks and would have a harder time supporting annotations and line numbering; while this would probably suffice for an editor that was not to be used on Java source code, in general it is very much recommended that `StyledDocument` be used instead.

### Handling guards

This is really the central problem in creating a compliant editor. If you want to completely skip this step, it is possible to return a plain `Document` from the registered editor kit; however this will not support guards (or IDE attributes either), and so if the user edits what should have been a guarded block, they may cause errors in the code, and their edits may be overwritten by the IDE. If you implement `StyledDocument`, it is assumed you are handling guard blocks, but again it is up to you to actually do so correctly - the IDE cannot determine this.

There is very little to the way the IDE indicates guarding. Essentially, it is just a character attribute, `NbDocument.GUARDED`, which will be set to `Boolean.TRUE` for guarded characters, and `Boolean.FALSE` (or unset) for others; it is typically placed on the document by means of the `NbDocument.markGuarded(...)` and `NbDocument.unmarkGuarded(...)` methods, which just call `StyledDocument.setCharacterAttributes(...)`. Very likely you will want to override this method, calling its superclass method but first checking to see if the attribute setting mentions `GUARDED`, whether setting it to `TRUE` or `FALSE`, and if so keeping track in another data structure of which ranges of characters are currently guarded or not; or you might already have a good way of keeping track of attributes in general and would rather just query this attribute when it is needed. If overriding `setCharacterAttributes` for this purpose, also remember to check the attributes on `insertString`, etc.

Note that currently guarded areas always consist of entire lines or sets of lines, so if you make this assumption your editor will be acceptable - but please handle sub-line granularity of guard blocks if you can do so easily, in case this situation changes. Along the same lines, you should make sure that users may only insert a newline immediately before a guarded block, and not any other character, for otherwise a half-guarded line would be created.

It is important to understand that the guarded attribute applies only to user modifications, i.e. those undertaken in the context of a user-initiated Swing action, or by `NbDocument.runAtomicAsUser(...)`. Internal IDE code may freely insert or remove text (typically using `NbDocument.insertGuarded(...)` and `Document.remove(...)`). For example, this would be done by the Form Editor component while adding a new event handler. The editor implementation should permit such programmatic inserts and removes, while corresponding user actions must be forbidden.

It is preferable, though optional, for the editor to visually mark guarded areas, say with a special background color. It is your responsibility to choose a color or another appearance for this purpose, however. Possibly the IDE will specify a `StyleConstants.ColorConstants.Background` attribute describing which color will actually be used, and make this color settable in a control panel, but assume that you need to colorize based on this attribute yourself.

#### The recommended way to handle guards

It is highly recommended that all of the Swing actions (such as those returned by `EditorKit.getActions()`) applicable to your editor kit be reviewed for the possibility that they might attempt to change the content of the document (so, not only character inserts but search-and-replace, block paste, etc.). Any that do perform some kind of mutation should be reimplemented (or a wrapper written for them) so that they check to make sure that a guarded block is not being violated.

Even better, whenever possible an action should be disabled when it can easily be determined in advance that it would be in violation if performed at that time. As an example, if the user moves the caret into the middle of a guarded block, it would be much preferable for the editor to disable "Paste" (say, on a right-click context menu) for the time being, rather than permitting a Paste action to be invoked but then displaying an error dialog or beeping!

#### The cheap way to handle guards

If you think the recommended path is too much work, you can try a cheaper trick - but this is not recommended, and we do not guarantee that it is even possible to do satisfactorily. This applies only to people who are trying to adapt an existing `StyledDocument`, such as Swing's `DefaultStyledDocument`, which already has a full implementation of important things but no recognition of guard blocks.

The idea is to first get a list of all actions which might involve buffer modification - or, to be conservative, just all actions. For each of these, create a new action which calls the original `actionPerformed`, but "dynamically binds" some special flag stored with the document to true - dynamic binding here means that it should be restored (turned back off) in a `finally` block, and also that its value should be specific to the executing thread (and its children, perhaps). This flag indicates that operations are currently being performed from a user action.

Override the `insertString(...)` and `remove` methods. They should check the flag just mentioned. If it is turned off, just call the superclass method normally. If it is turned on, check whether the requested insertion or removal is affecting a guarded area (insertion within, or removal within or overlapping). If not, again call the superclass method. If there is an attempted violation, you might do one or more of the following:

- Not perform the insertion/removal, and just silently return.
- Throw a `javax.swing.text.BadLocationException` and see what happens. Since the original action cannot ignore this exception (since `actionPerformed` does not have any throws), it must do something - currently, it seems the Swing actions simply beep.
- Try to run a beep action to alert the user (using `Toolkit.beep()`). This would probably need to be done with `SwingUtilities.invokeLater(...)`.

Now bind all invocation objects (such as keymaps) to the new "wrapper" actions. Note that just returning them from the editor kit may not suffice.

If you go to the trouble of identifying specifically which actions could cause a violation, and under what circumstances they would or would not do so, then you could make specific wrappers that could disable actions, or safely invoke them only when possible, calling the original action if all is well - this is just one way to do the recommended implementation.

#### Testing guard blocks

If you are not able to test live in the IDE, try doing something like this:

`SimpleAttributeSet sas=new SimpleAttributeSet();
sas.addAttribute(NbDocument.GUARDED, Boolean.TRUE);
doc.setCharacterAttributes(0, 100, sas, false);`

Now verify that modification attempts in this block are disabled.

### Lines and elements

You should make sure that lines in the editor are separated by exactly one text character - a newline. The APIs may rely on this to count character positions during parsing, so that this functionality may be efficient.

Furthermore you should ensure that the default root element of the document has child elements corresponding to all text lines; and if using `StyledDocument`, that "paragraph" elements again correspond to text lines. Proper use of elements corresponding to lines will enable the APIs to accurately translate between buffer offsets and line numbers. It is fine to have additional element structures not corresponding to lines so long as the two conditions above are met.

### Handling annotations

An editor must do two things to support annotations:

- Implement the `NbDocument.Annotatable` interface.
- Implement parsing of annotation type XML files.

#### `NbDocument.Annotatable`

This interface has two methods. One adds an annotation to the document:

    public void addAnnotation(Position startPos, int length, Annotation annotation);

The method is called with a `Position` in the document; the length of the annotation (if the annotation is of the whole-line type, the length will be `-1`); and the annotation instance. Now it is the responsibility of editor to collect all annotations for the document and to display them properly. It may be helpful to take advantage of `StyledDocument` for changing the style of the line (or part of the line). As for the glyph icon, it is fully up to the editor how to represent it (if at all). The NetBeans standard editor displays it in the left gutter.

The second method removed an annotation previously added:

    public void removeAnnotation(Annotation annotation);

This method will be called when the annotation is programmatically detached, or the document is about to be closed.

The editor should combine annotation types where requested if this behavior is supported.

#### Annotation type XML files

As for visual attributes of annotations, the editor should parse the XML files in the `Editors/AnnotationTypes/` directory. The NetBeans standard editor can serve as a source of examples for how to do this. In the future there may be shared parsing support.

### Printing

If you want your editor to support printing of its contents from the IDE, you might just provide no special support. In this case, printing should be able to work with plain text. If you have a styled document, it is possible that the IDE will be able to run through the entire contents of the document; for each paragraph, retrieve its `Style`, and for each character, its attribute set; and then attempt to convert these (Swing) formatting specifications into (AWT) attributed character descriptions, for purposes of printing.

However, this process could be rather slow; is not terribly exact; and may not be implemented. To better support printing, it is desirable for the `StyledDocument` to implement `org.openide.text.NbDocument.Printable`, which will allow it to specify exactly how it wants to be printed. The method `NbDocument.Printable.createPrintIterators(...)` should return a list of `java.text.AttributedCharacterIterator`s, providing attributes taken from `java.awt.font.TextAttribute`.

Also, if your document supports either `java.awt.print.Printable` or `java.awt.print.Pageable`, then these interfaces will be used to perform the printing directly. You should only need to do this if attributed characters do not satisfactorily capture everything that you are interested in printing - for example, if your editor is working on HTML and it is desired to print embedded images.

### Locking

It is desirable for your `StyledDocument` implementation to be able to lock the document against write access, as this will make certain operations (performed by the IDE, not in response to user events) more reliable and safer. In order to do this, please implement `org.openide.text.NbDocument.WriteLockable` and its `runAtomic(...)` method. The `Runnable` passed in this way should be executed with all other write actions (and reads) disabled, i.e. blocked.

If you are extending `javax.swing.text.AbstractDocument`, please note that just enclosing the `Runnable` block in calls to `writeLock()` and `writeUnlock()` will not do the trick - these calls do take out exclusive locks, however they specifically do not nest. This means that you cannot lock and then enter a runnable this way, because any modifications attempted within the runnable will throw an illegal state exception. Also, the locking methods are final and cannot be advised to nest. So you must find some other way to implement this, e.g. your own locks.

You must also implement `NbDocument.WriteLockable.runAtomicAsUser(...)`, which is very similar but is invoked on behalf of user actions unrelated to whatever component created the guard blocks - e.g., this would be used to rename a method from the Explorer, in which case the rename ought to check that the renamed method is not guarded due to being used by the Form Editor. Thus, it should attempt to make modifications requested by the `Runnable`, locking out other modifications, but ensure that guard blocks are not violated. Any attempted violation should be prevented (or rolled back at the end of the runnable), and after the end of the runnable an appropriate exception should be thrown.

Note that while both methods in this interface ought to provide a transactional interface if at all possible - i.e., either succeed at executing the entire `Runnable`, or fail and leave the document untouched - the transactional aspect is much more important to implement properly for `runAtomicAsUser`. This is because it is quite possible for an innocent user action (e.g. attempting to rename a JavaBean property) to interfere with a guard block, and the document should not be left half-modified after such a mistake. On the other hand, a failure in the block of `runAtomic` is more likely to be an bug in some IDE module, and not the user's fault; so perfect recovery is of course less important, as the bug should be fixed anyway.

There is currently no default convenience implementation of `runAtomicAsUser`, as any implementation may well be closely tied to how guard blocks are implemented in that particular editor - e.g. in Emacs there will be a quite idiosyncratic implementation.

### Biases

Please consider implementing `org.openide.text.NbDocument.PositionBiasable` and its `createPosition(...)` method, to create a position marker which not only moves freely with insertions and deletions in nearby text, but also specifies the direction the marker will move to when text is inserted at that position.

If this is not done, the IDE creates its own replacement.

### Scrolling to display

The IDE sometimes asks the editor to scroll the display so that a given line will be displayed. You should not need to do anything special to support this; `Caret.setDot()` will be called and ought to perform the scrolling appropriately.

### Presentable actions

It is desirable for the editor to present actions to the user that may be invoked on the document and may be accessed in various ways. For example, if your editor provides an action for reindenting a section of text, it is best if this action can be integrated into the rest of the IDE consistently: a "Reindent" item under the "Edit" menu on the main toolbar, active when your editor has focus; a button with an icon representing reindentation placed onto the IDE's toolbar; a context menu item within the editor pane named "Reindent"; a keyboard shortcut `Ctrl-R`; etc.

While it might be possible to add some of these things manually into the IDE's action containers (like the "Main Window" entry in the Environment, visible in the Explorer), this is discouraged as that makes it more difficult for the IDE to manage actions added by various modules.

Instead, you should use the Actions API to add `CallbackSystemAction`s (e.g.) to your module.

#### Default toolbar

Although it is best to use the Actions API to specify in your module's manifest file which actions to install where in the IDE, the IDE may also create a toolbar attached to the editor window which will reflect all displayable actions supported by your editor, automatically. This may be better for less-commonly used actions which it would be inappropriate to install into the main control window.

You do not need to do much to support this editor toolbar: in the `getActions()` method of your editor kit, if there are any actions which are also `SystemAction`s implementing `Presenter.Toolbar`, then this interface will be used to get a `java.awt.Component` which will be displayed in the editor toolbar. You are free to make this component be whatever you like, e.g. a button to run some routine, or a checkbox to toggle an option; just add the appropriate event listeners to it.

#### Standard actions

A few basic editing commands you do not need to explicitly present to the IDE; this will be done for you automatically. The IDE tests whether an editor kit provides (from its `EditorKit.getActions()` method) any actions with certain names. Default instances of these are also available in the `DefaultEditorKit` class, but your actions will be recognized based on a call to `getValue(Action.NAME)`:

Name | Static field in `DefaultEditorKit`
--- | ---
`copy-to-clipboard` | `copyAction`
`cut-to-clipboard` | `cutAction`
`paste-from-clipboard` | `pasteAction`

There are a few more which unfortunately do not exist in the `DefaultEditorKit`, and therefore have no standard names. The following may be used:

Name | Description
--- | ---
`find` | Pop up dialog to find a string in the text.
`replace` | Pop up dialog to find & replace a string in the text.
`goto` | Pop up dialog to go to some place in the text, e.g. a specific line number.
`delete` | Delete the selection, without affecting clipboard.
`undo` | Undo action. See package `javax.swing.undo` for help. Currently not specially supported by the IDE, except to call your action.
`redo` | Redo action. Ditto.

The corresponding items in the IDE's "Edit" menu, and other standard invocations such as from the system toolbar, will automatically invoke these actions on your document, if you supply them. You should use `Action.isEnabled()` to indicate whether your action is ready, and thus whether or not the corresponding UI elements in the IDE should be grayed out.

### Undo/redo support

It is desirable for your document's user-level edit actions to implement `UndoableEdit`, so that the IDE can smoothly provide Undo/Redo support for the editor from the standard places (e.g. in the Edit menu). Note that `AbstractDocument`, for example, already provides this support.

### Customization

This API does not provide any special mechanism for allowing the user to customize aspects of the editor's operation from the IDE; if you want to do this, please use the Options API.

### Installing

It should be straightforward to install the new editor into the IDE - you will make a JAR file containing a manifest with attributes recognized by the IDE as constituting an IDE module, and just call `javax.swing.JEditorPane.registerEditorKitForContentType(...)`, and the IDE should subsequently use it.

#### Implementing a module with editor support

It is possible that there will be special support in the Modules API for registering editors. Although doing it manually in the module's `installed()` method is not difficult, properly the module should also restore the original editor kit for each content type upon an uninstall, and ideally there would be a user-visible control panel permitting selection of the editor for each content type from among those claiming to support it.

This is not likely to be done unless it turns out to be popular to have multiple editors installed, and conflicts become a problem.

In the meantime, please refer to the Modules API for instructions on creating a module to contain your editor.

#### Registering unusual MIME types

If your editor has support for an unusual MIME type that is not currently recognized, you may wish to use the MIME resolution infrastructure in the Filesystems API to help your files be recognized. Additionally, `CloneableEditorSupport.setMIMEType(String)` may be used to control the MIME type of an editor kit regardless of the type of the underlying file.

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