001/* BasicHTML.java -- Provides HTML support to ComponentUI implementations
002   Copyright (C) 2006 Free Software Foundation, Inc.
003
004This file is part of GNU Classpath.
005
006GNU Classpath is free software; you can redistribute it and/or modify
007it under the terms of the GNU General Public License as published by
008the Free Software Foundation; either version 2, or (at your option)
009any later version.
010
011GNU Classpath is distributed in the hope that it will be useful, but
012WITHOUT ANY WARRANTY; without even the implied warranty of
013MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
014General Public License for more details.
015
016You should have received a copy of the GNU General Public License
017along with GNU Classpath; see the file COPYING.  If not, write to the
018Free Software Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA
01902110-1301 USA.
020
021Linking this library statically or dynamically with other modules is
022making a combined work based on this library.  Thus, the terms and
023conditions of the GNU General Public License cover the whole
024combination.
025
026As a special exception, the copyright holders of this library give you
027permission to link this library with independent modules to produce an
028executable, regardless of the license terms of these independent
029modules, and to copy and distribute the resulting executable under
030terms of your choice, provided that you also meet, for each linked
031independent module, the terms and conditions of the license of that
032module.  An independent module is a module which is not derived from
033or based on this library.  If you modify this library, you may extend
034this exception to your version of the library, but you are not
035obligated to do so.  If you do not wish to do so, delete this
036exception statement from your version. */
037
038
039package javax.swing.plaf.basic;
040
041import java.awt.Container;
042import java.awt.Graphics;
043import java.awt.Rectangle;
044import java.awt.Shape;
045import java.io.IOException;
046import java.io.StringReader;
047
048import javax.swing.JComponent;
049import javax.swing.SwingConstants;
050import javax.swing.event.DocumentEvent;
051import javax.swing.text.AttributeSet;
052import javax.swing.text.BadLocationException;
053import javax.swing.text.Document;
054import javax.swing.text.EditorKit;
055import javax.swing.text.Element;
056import javax.swing.text.Position;
057import javax.swing.text.View;
058import javax.swing.text.ViewFactory;
059import javax.swing.text.html.HTMLDocument;
060import 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 */
068public 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}