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Java > Open Source Codes > org > eclipse > jdt > ui > text > java > ContentAssistInvocationContext


1 /*******************************************************************************
2  * Copyright (c) 2005, 2006 IBM Corporation and others.
3  * All rights reserved. This program and the accompanying materials
4  * are made available under the terms of the Eclipse Public License v1.0
5  * which accompanies this distribution, and is available at
6  * http://www.eclipse.org/legal/epl-v10.html
7  *
8  * Contributors:
9  * IBM Corporation - initial API and implementation
10  *******************************************************************************/
11 package org.eclipse.jdt.ui.text.java;
12
13 import org.eclipse.core.runtime.Assert;
14
15 import org.eclipse.jface.text.BadLocationException;
16 import org.eclipse.jface.text.IDocument;
17 import org.eclipse.jface.text.ITextViewer;
18
19 /**
20  * Describes the context of an invocation of content assist in a text viewer. The context knows the
21  * document, the invocation offset and can lazily compute the identifier prefix preceding the
22  * invocation offset. It may know the viewer.
23  * <p>
24  * Subclasses may add information to their environment. For example, source code editors may provide
25  * specific context information such as an AST.
26  * </p>
27  * <p>
28  * Clients may instantiate and subclass.
29  * </p>
30  *
31  * @since 3.2
32  */
33 public class ContentAssistInvocationContext {
34     
35     /* state */
36     private final ITextViewer fViewer;
37     private final IDocument fDocument;
38     private final int fOffset;
39     
40     /* cached additional info */
41     private CharSequence JavaDoc fPrefix;
42     
43     /**
44      * Equivalent to
45      * {@linkplain #ContentAssistInvocationContext(ITextViewer, int) ContentAssistInvocationContext(viewer, viewer.getSelectedRange().x)}.
46      *
47      * @param viewer the text viewer that content assist is invoked in
48      */
49     public ContentAssistInvocationContext(ITextViewer viewer) {
50         this(viewer, viewer.getSelectedRange().x);
51     }
52
53     /**
54      * Creates a new context for the given viewer and offset.
55      *
56      * @param viewer the text viewer that content assist is invoked in
57      * @param offset the offset into the viewer's document where content assist is invoked at
58      */
59     public ContentAssistInvocationContext(ITextViewer viewer, int offset) {
60         Assert.isNotNull(viewer);
61         fViewer= viewer;
62         fDocument= null;
63         fOffset= offset;
64     }
65     
66     /**
67      * Creates a new context with no viewer or invocation offset set.
68      */
69     protected ContentAssistInvocationContext() {
70         fDocument= null;
71         fViewer= null;
72         fOffset= -1;
73     }
74     
75     /**
76      * Creates a new context for the given document and offset.
77      *
78      * @param document the document that content assist is invoked in
79      * @param offset the offset into the document where content assist is invoked at
80      */
81     public ContentAssistInvocationContext(IDocument document, int offset) {
82         Assert.isNotNull(document);
83         Assert.isTrue(offset >= 0);
84         fViewer= null;
85         fDocument= document;
86         fOffset= offset;
87     }
88     
89     /**
90      * Returns the invocation offset.
91      *
92      * @return the invocation offset
93      */
94     public final int getInvocationOffset() {
95         return fOffset;
96     }
97     
98     /**
99      * Returns the viewer, <code>null</code> if not available.
100      *
101      * @return the viewer, possibly <code>null</code>
102      */
103     public final ITextViewer getViewer() {
104         return fViewer;
105     }
106     
107     /**
108      * Returns the document that content assist is invoked on, or <code>null</code> if not known.
109      *
110      * @return the document or <code>null</code>
111      */
112     public IDocument getDocument() {
113         if (fDocument == null) {
114             if (fViewer == null)
115                 return null;
116             return fViewer.getDocument();
117         }
118         return fDocument;
119     }
120     
121     /**
122      * Computes the identifier (as specified by {@link Character#isJavaIdentifierPart(char)}) that
123      * immediately precedes the invocation offset.
124      *
125      * @return the prefix preceding the content assist invocation offset, <code>null</code> if
126      * there is no document
127      * @throws BadLocationException if accessing the document fails
128      */
129     public CharSequence JavaDoc computeIdentifierPrefix() throws BadLocationException {
130         if (fPrefix == null) {
131             IDocument document= getDocument();
132             if (document == null)
133                 return null;
134             int end= getInvocationOffset();
135             int start= end;
136             while (--start >= 0) {
137                 if (!Character.isJavaIdentifierPart(document.getChar(start)))
138                     break;
139             }
140             start++;
141             fPrefix= document.get(start, end - start);
142         }
143         
144         return fPrefix;
145     }
146     
147     /**
148      * Invocation contexts are equal if they describe the same context and are of the same type.
149      * This implementation checks for <code>null</code> values and class equality. Subclasses
150      * should extend this method by adding checks for their context relevant fields (but not
151      * necessarily cached values).
152      * <p>
153      * Example:
154      *
155      * <pre>
156      * class MyContext extends ContentAssistInvocationContext {
157      * private final Object fState;
158      * private Object fCachedInfo;
159      *
160      * ...
161      *
162      * public boolean equals(Object obj) {
163      * if (!super.equals(obj))
164      * return false;
165      * MyContext other= (MyContext) obj;
166      * return fState.equals(other.fState);
167      * }
168      * }
169      * </pre>
170      *
171      * </p>
172      * <p>
173      * Subclasses should also extend {@link Object#hashCode()}.
174      * </p>
175      *
176      * @param obj {@inheritDoc}
177      * @return {@inheritDoc}
178      */
179     public boolean equals(Object JavaDoc obj) {
180         if (obj == null)
181             return false;
182         if (!getClass().equals(obj.getClass()))
183             return false;
184         ContentAssistInvocationContext other= (ContentAssistInvocationContext) obj;
185         return (fViewer == null && other.fViewer == null || fViewer != null && fViewer.equals(other.fViewer)) && fOffset == other.fOffset && (fDocument == null && other.fDocument == null || fDocument != null && fDocument.equals(other.fDocument));
186     }
187     
188     /*
189      * @see java.lang.Object#hashCode()
190      */
191     public int hashCode() {
192         return 23459213 << 5 | (fViewer == null ? 0 : fViewer.hashCode() << 3) | fOffset;
193     }
194 }
195
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