001    /* BasicHTML.java -- Provides HTML support to ComponentUI implementations
002       Copyright (C) 2006 Free Software Foundation, Inc.
003    
004    This file is part of GNU Classpath.
005    
006    GNU Classpath is free software; you can redistribute it and/or modify
007    it under the terms of the GNU General Public License as published by
008    the Free Software Foundation; either version 2, or (at your option)
009    any later version.
010    
011    GNU Classpath is distributed in the hope that it will be useful, but
012    WITHOUT ANY WARRANTY; without even the implied warranty of
013    MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
014    General Public License for more details.
015    
016    You should have received a copy of the GNU General Public License
017    along with GNU Classpath; see the file COPYING.  If not, write to the
018    Free Software Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA
019    02110-1301 USA.
020    
021    Linking this library statically or dynamically with other modules is
022    making a combined work based on this library.  Thus, the terms and
023    conditions of the GNU General Public License cover the whole
024    combination.
025    
026    As a special exception, the copyright holders of this library give you
027    permission to link this library with independent modules to produce an
028    executable, regardless of the license terms of these independent
029    modules, and to copy and distribute the resulting executable under
030    terms of your choice, provided that you also meet, for each linked
031    independent module, the terms and conditions of the license of that
032    module.  An independent module is a module which is not derived from
033    or based on this library.  If you modify this library, you may extend
034    this exception to your version of the library, but you are not
035    obligated to do so.  If you do not wish to do so, delete this
036    exception statement from your version. */
037    
038    
039    package javax.swing.plaf.basic;
040    
041    import java.awt.Container;
042    import java.awt.Graphics;
043    import java.awt.Rectangle;
044    import java.awt.Shape;
045    import java.io.IOException;
046    import java.io.StringReader;
047    
048    import javax.swing.JComponent;
049    import javax.swing.SwingConstants;
050    import javax.swing.event.DocumentEvent;
051    import javax.swing.text.AttributeSet;
052    import javax.swing.text.BadLocationException;
053    import javax.swing.text.Document;
054    import javax.swing.text.EditorKit;
055    import javax.swing.text.Element;
056    import javax.swing.text.Position;
057    import javax.swing.text.View;
058    import javax.swing.text.ViewFactory;
059    import javax.swing.text.html.HTMLDocument;
060    import javax.swing.text.html.HTMLEditorKit;
061    
062    /**
063     * Provides support for HTML rendering to {@link javax.swing.plaf.ComponentUI}
064     * implementations.
065     *
066     * @author Roman Kennke (kennke@aicas.com)
067     */
068    public class BasicHTML
069    {
070    
071      /**
072       * This class serves as the root view for HTML rendering components.
073       * Its purpose and implementation is similar to the BasicTextUI.RootView
074       * class, only that is implements some stuff differently due to the nature
075       * of not beeing inside a JTextComponent.
076       *
077       * @author Roman Kennke (kennke@aicas.com)
078       */
079      private static class HTMLRootView extends View
080      {
081        /**
082         * The real root view.
083         */
084        private View view;
085    
086        /**
087         * The component on which to render the view.
088         */
089        private JComponent component;
090    
091        /**
092         * The EditorKit.
093         */
094        private EditorKit editorKit;
095    
096        /**
097         * The document to use.
098         */
099        private Document document;
100    
101        /**
102         * Creates a new RootView.
103         */
104        public HTMLRootView(JComponent c, View view, EditorKit kit, Document doc)
105        {
106          super(null);
107          component = c;
108          editorKit = kit;
109          document = doc;
110          setView(view);
111          setSize(view.getPreferredSpan(X_AXIS), view.getPreferredSpan(Y_AXIS));
112        }
113    
114        /**
115         * Returns the ViewFactory for this RootView. If the current EditorKit
116         * provides a ViewFactory, this is used. Otherwise the TextUI itself
117         * is returned as a ViewFactory.
118         *
119         * @return the ViewFactory for this RootView
120         */
121        public ViewFactory getViewFactory()
122        {
123          return editorKit.getViewFactory();
124        }
125    
126        /**
127         * Indicates that the preferences of one of the child view has changed.
128         * This calls revalidate on the text component.
129         *
130         * @param v the child view which's preference has changed
131         * @param width <code>true</code> if the width preference has changed
132         * @param height <code>true</code> if the height preference has changed
133         */
134        public void preferenceChanged(View v, boolean width, boolean height)
135        {
136          component.revalidate();
137        }
138    
139        /**
140         * Sets the real root view.
141         *
142         * @param v the root view to set
143         */
144        public void setView(View v)
145        {
146          if (view != null)
147            view.setParent(null);
148    
149          if (v != null)
150            v.setParent(this);
151    
152          view = v;
153        }
154    
155        /**
156         * Overridden to forward to real view.
157         */
158        public void setSize(float w, float h)
159        {
160          view.setSize(w, h);
161        }
162    
163        /**
164         * Returns the real root view, regardless of the index.
165         *
166         * @param index not used here
167         *
168         * @return the real root view, regardless of the index.
169         */
170        public View getView(int index)
171        {
172          return view;
173        }
174    
175        /**
176         * Returns <code>1</code> since the RootView always contains one
177         * child, that is the real root of the View hierarchy.
178         *
179         * @return <code>1</code> since the RootView always contains one
180         *         child, that is the real root of the View hierarchy
181         */
182        public int getViewCount()
183        {
184          int count = 0;
185          if (view != null)
186            count = 1;
187          return count;
188        }
189    
190        /**
191         * Returns the <code>Container</code> that contains this view. This
192         * normally will be the text component that is managed by this TextUI.
193         *
194         * @return the <code>Container</code> that contains this view
195         */
196        public Container getContainer()
197        {
198          return component;
199        }
200    
201        /**
202         * Returns the preferred span along the specified <code>axis</code>.
203         * This is delegated to the real root view.
204         *
205         * @param axis the axis for which the preferred span is queried
206         *
207         * @return the preferred span along the axis
208         */
209        public float getPreferredSpan(int axis)
210        {
211          if (view != null)
212            return view.getPreferredSpan(axis);
213    
214          return Integer.MAX_VALUE;
215        }
216    
217        /**
218         * Paints the view. This is delegated to the real root view.
219         *
220         * @param g the <code>Graphics</code> context to paint to
221         * @param s the allocation for the View
222         */
223        public void paint(Graphics g, Shape s)
224        {
225          if (view != null)
226            {
227              Rectangle b = s.getBounds();
228              view.setSize(b.width, b.height);
229              view.paint(g, s);
230            }
231        }
232    
233    
234        /**
235         * Maps a position in the document into the coordinate space of the View.
236         * The output rectangle usually reflects the font height but has a width
237         * of zero.
238         *
239         * This is delegated to the real root view.
240         *
241         * @param position the position of the character in the model
242         * @param a the area that is occupied by the view
243         * @param bias either {@link Position.Bias#Forward} or
244         *        {@link Position.Bias#Backward} depending on the preferred
245         *        direction bias. If <code>null</code> this defaults to
246         *        <code>Position.Bias.Forward</code>
247         *
248         * @return a rectangle that gives the location of the document position
249         *         inside the view coordinate space
250         *
251         * @throws BadLocationException if <code>pos</code> is invalid
252         * @throws IllegalArgumentException if b is not one of the above listed
253         *         valid values
254         */
255        public Shape modelToView(int position, Shape a, Position.Bias bias)
256          throws BadLocationException
257        {
258          return view.modelToView(position, a, bias);
259        }
260    
261        /**
262         * Maps coordinates from the <code>View</code>'s space into a position
263         * in the document model.
264         *
265         * @param x the x coordinate in the view space
266         * @param y the y coordinate in the view space
267         * @param a the allocation of this <code>View</code>
268         * @param b the bias to use
269         *
270         * @return the position in the document that corresponds to the screen
271         *         coordinates <code>x, y</code>
272         */
273        public int viewToModel(float x, float y, Shape a, Position.Bias[] b)
274        {
275          return view.viewToModel(x, y, a, b);
276        }
277    
278        /**
279         * Notification about text insertions. These are forwarded to the
280         * real root view.
281         *
282         * @param ev the DocumentEvent describing the change
283         * @param shape the current allocation of the view's display
284         * @param vf the ViewFactory to use for creating new Views
285         */
286        public void insertUpdate(DocumentEvent ev, Shape shape, ViewFactory vf)
287        {
288          view.insertUpdate(ev, shape, vf);
289        }
290    
291        /**
292         * Notification about text removals. These are forwarded to the
293         * real root view.
294         *
295         * @param ev the DocumentEvent describing the change
296         * @param shape the current allocation of the view's display
297         * @param vf the ViewFactory to use for creating new Views
298         */
299        public void removeUpdate(DocumentEvent ev, Shape shape, ViewFactory vf)
300        {
301          view.removeUpdate(ev, shape, vf);
302        }
303    
304        /**
305         * Notification about text changes. These are forwarded to the
306         * real root view.
307         *
308         * @param ev the DocumentEvent describing the change
309         * @param shape the current allocation of the view's display
310         * @param vf the ViewFactory to use for creating new Views
311         */
312        public void changedUpdate(DocumentEvent ev, Shape shape, ViewFactory vf)
313        {
314          view.changedUpdate(ev, shape, vf);
315        }
316    
317        /**
318         * Returns the document position that is (visually) nearest to the given
319         * document position <code>pos</code> in the given direction <code>d</code>.
320         *
321         * @param pos the document position
322         * @param b the bias for <code>pos</code>
323         * @param a the allocation for the view
324         * @param d the direction, must be either {@link SwingConstants#NORTH},
325         *        {@link SwingConstants#SOUTH}, {@link SwingConstants#WEST} or
326         *        {@link SwingConstants#EAST}
327         * @param biasRet an array of {@link Position.Bias} that can hold at least
328         *        one element, which is filled with the bias of the return position
329         *        on method exit
330         *
331         * @return the document position that is (visually) nearest to the given
332         *         document position <code>pos</code> in the given direction
333         *         <code>d</code>
334         *
335         * @throws BadLocationException if <code>pos</code> is not a valid offset in
336         *         the document model
337         */
338        public int getNextVisualPositionFrom(int pos, Position.Bias b, Shape a,
339                                             int d, Position.Bias[] biasRet)
340          throws BadLocationException
341        {
342          return view.getNextVisualPositionFrom(pos, b, a, d, biasRet);
343        }
344    
345        public int getStartOffset()
346        {
347          return 0;
348        }
349    
350        public int getEndOffset()
351        {
352          return getDocument().getLength();
353        }
354    
355        public Document getDocument()
356        {
357          return document;
358        }
359    
360        /**
361         * Overridden to return null, as a RootView has no attributes on its own.
362         */
363        public AttributeSet getAttributes()
364        {
365          return null;
366        }
367    
368        /**
369         * Overridden to provide an element for the view.
370         */
371        public Element getElement()
372        {
373          return view.getElement();
374        }
375      }
376    
377      /**
378       * The key that is used to store a HTML view in a JComponent's client
379       * properties.
380       */
381      public static final String propertyKey = "html";
382    
383      /**
384       * The key that is used to store the document base in a JComponent's client
385       * properties. The document base is used to resolve relative references
386       * in HTML.
387       */
388      public static final String documentBaseKey = "html.base";
389    
390      /**
391       * Creates a new instance of BasicHTML. This should not be necessary since
392       * all methods in this class are static.
393       */
394      public BasicHTML()
395      {
396        // Nothing to do here.
397      }
398    
399      /**
400       * Creates a {@link View} instance that can be used by the component
401       * <code>c</code> to render the HTML string <code>html</code>.
402       *
403       * @param c the component that needs to render the HTML string
404       * @param html the HTML string to be rendered
405       *
406       * @return a view that can render the HTML string
407       */
408      public static View createHTMLView(JComponent c, String html)
409      {
410        // TODO: This might be wrong. Lets see if it turns out good when
411        // the javax.swing.text.html package is in a good shape.
412        HTMLDocument doc = new HTMLDocument();
413        HTMLEditorKit kit = new HTMLEditorKit();
414        StringReader reader = new StringReader(html);
415        try
416          {
417            kit.read(reader, doc, 0);
418          }
419        catch (IOException ex)
420          {
421            AssertionError err = new AssertionError("unexpected IOException");
422            err.initCause(ex);
423            throw err;
424          }
425        catch (BadLocationException ex)
426          {
427            AssertionError err =
428              new AssertionError("unexpected BadLocationException");
429            err.initCause(ex);
430            throw err;
431          }
432        ViewFactory vf = kit.getViewFactory();
433        Element root = doc.getDefaultRootElement();
434        View view = vf.create(root);
435        HTMLRootView rootView = new HTMLRootView(c, view, kit, doc);
436        return rootView;
437      }
438    
439      /**
440       * Returns <code>true</code> if <code>s</code> is HTML, <code>false</code>
441       * otherwise.
442       *
443       * @param s the string to test
444       *
445       * @return <code>true</code> if <code>s</code> is HTML, <code>false</code>
446       *         otherwise
447       */
448      public static boolean isHTMLString(String s)
449      {
450        // We consider a string to be HTML if it contains both the '<' and '>'
451        // character at least once.
452        return (s != null) && s.contains("<") && s.contains(">");
453      }
454    
455      /**
456       * Stores a HTML renderer in <code>c</code>'s client property if
457       * <code>text</code> is HTML, otherwise it clears the corresponding client
458       * property. This is useful for {@link javax.swing.plaf.ComponentUI}
459       * implementations that are shared between it's components.
460       *
461       * @param c the component to update the renderer for
462       * @param text the string to be rendered
463       */
464      public static void updateRenderer(JComponent c, String text)
465      {
466        if (isHTMLString(text))
467          c.putClientProperty(propertyKey, createHTMLView(c, text));
468        else
469          c.putClientProperty(propertyKey, null);
470      }
471    }