001 /* GridLayout.java -- Grid-based layout engine
002 Copyright (C) 1999, 2000, 2002, 2004 Free Software Foundation
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 java.awt;
040
041 import java.io.Serializable;
042
043 /** This class implements a grid-based layout scheme. Components are
044 * all given the same size and are laid out from left to right and top
045 * to bottom. A GridLayout is configured with a number of rows and a
046 * number of columns. If both are specified, then the number of
047 * columns is ignored and is derived from the number of rows and the
048 * total number of components. If either is zero then that dimension
049 * is computed based on the actual size of the container. An
050 * exception is thrown if an attempt is made to set both the number of
051 * rows and the number of columns to 0. This class also supports
052 * horizontal and vertical gaps; these are used as spacing between
053 * cells.
054 *
055 * @author Tom Tromey (tromey@redhat.com)
056 * @author Aaron M. Renn (arenn@urbanophile.com)
057 */
058 public class GridLayout implements LayoutManager, Serializable
059 {
060 static final long serialVersionUID = -7411804673224730901L;
061
062 /** Add a new component to the layout. This particular implementation
063 * does nothing.
064 * @param name The name of the component to add.
065 * @param comp The component to add.
066 */
067 public void addLayoutComponent (String name, Component comp)
068 {
069 // Nothing.
070 }
071
072 /** Return the number of columns in this layout. */
073 public int getColumns ()
074 {
075 return cols;
076 }
077
078 /** Return the horizontal gap. */
079 public int getHgap ()
080 {
081 return hgap;
082 }
083
084 /** Return the number of rows in this layout. */
085 public int getRows ()
086 {
087 return rows;
088 }
089
090 /** Return the vertical gap. */
091 public int getVgap ()
092 {
093 return vgap;
094 }
095
096 /** Create a new <code>GridLayout</code> with one row and any number
097 * of columns. Both gaps are set to 0.
098 */
099 public GridLayout ()
100 {
101 this (1, 0, 0, 0);
102 }
103
104 /** Create a new <code>GridLayout</code> with the specified number
105 * of rows and columns. Both gaps are set to 0. Note that the row
106 * and column settings cannot both be zero. If both the row and
107 * column values are non-zero, the rows value takes precedence.
108 * @param rows Number of rows
109 * @param cols Number of columns
110 * @exception IllegalArgumentException If rows and columns are both
111 * 0, or if either are negative
112 */
113 public GridLayout (int rows, int cols)
114 {
115 this (rows, cols, 0, 0);
116 }
117
118 /** Create a new GridLayout with the specified number of rows and
119 * columns and the specified gaps.
120 * Note that the row and column settings cannot both be
121 * zero. If both the row and column values are non-zero, the rows value
122 * takes precedence.
123 * @param rows Number of rows
124 * @param cols Number of columns
125 * @param hgap The horizontal gap
126 * @param vgap The vertical gap
127 * @exception IllegalArgumentException If rows and columns are both
128 * 0, if either are negative, or if either gap is negative
129 */
130 public GridLayout (int rows, int cols, int hgap, int vgap)
131 {
132 if (rows < 0)
133 throw new IllegalArgumentException ("number of rows cannot be negative");
134 if (cols < 0)
135 throw new IllegalArgumentException ("number of columns cannot be negative");
136 if (rows == 0 && cols == 0)
137 throw new IllegalArgumentException ("both rows and columns cannot be 0");
138 if (hgap < 0)
139 throw new IllegalArgumentException ("horizontal gap must be nonnegative");
140 if (vgap < 0)
141 throw new IllegalArgumentException ("vertical gap must be nonnegative");
142 this.rows = rows;
143 this.cols = cols;
144 this.hgap = hgap;
145 this.vgap = vgap;
146 }
147
148 /** Lay out the container's components based on current settings.
149 * The free space in the container is divided evenly into the specified
150 * number of rows and columns in this object.
151 * @param parent The container to lay out
152 */
153 public void layoutContainer (Container parent)
154 {
155 synchronized (parent.getTreeLock ())
156 {
157 int num = parent.ncomponents;
158
159 // There's no point, and handling this would mean adding special
160 // cases.
161 if (num == 0)
162 return;
163
164 // This is more efficient than calling getComponents().
165 Component[] comps = parent.component;
166
167 int real_rows = rows;
168 int real_cols = cols;
169 if (real_rows == 0)
170 real_rows = (num + real_cols - 1) / real_cols;
171 else
172 real_cols = (num + real_rows - 1) / real_rows;
173
174 // We might have less than a single row. In this case we expand
175 // to fill.
176 if (num < real_cols)
177 real_cols = num;
178
179 Dimension d = parent.getSize ();
180 Insets ins = parent.getInsets ();
181
182 // Compute width and height of each cell in the grid.
183 int tw = d.width - ins.left - ins.right;
184 tw = (tw - (real_cols - 1) * hgap) / real_cols;
185 int th = d.height - ins.top - ins.bottom;
186 th = (th - (real_rows - 1) * vgap) / real_rows;
187
188 // If the cells are too small, still try to do something.
189 if (tw < 0)
190 tw = 1;
191 if (th < 0)
192 th = 1;
193
194 int x = ins.left;
195 int y = ins.top;
196 int i = 0;
197 int recount = 0;
198
199 while (i < num)
200 {
201 comps[i].setBounds (x, y, tw, th);
202
203 ++i;
204 ++recount;
205 if (recount == real_cols)
206 {
207 recount = 0;
208 y += vgap + th;
209 x = ins.left;
210 }
211 else
212 x += hgap + tw;
213 }
214 }
215 }
216
217 /** Get the minimum layout size of the container.
218 * @param cont The parent container
219 */
220 public Dimension minimumLayoutSize (Container cont)
221 {
222 return getSize (cont, true);
223 }
224
225 /** Get the preferred layout size of the container.
226 * @param cont The parent container
227 */
228 public Dimension preferredLayoutSize (Container cont)
229 {
230 return getSize (cont, false);
231 }
232
233 /** Remove the indicated component from this layout manager.
234 * This particular implementation does nothing.
235 * @param comp The component to remove
236 */
237 public void removeLayoutComponent (Component comp)
238 {
239 // Nothing.
240 }
241
242 /** Set the number of columns.
243 * @param newCols
244 * @exception IllegalArgumentException If the number of columns is
245 * negative, or if the number of columns is zero and the number
246 * of rows is already 0.
247 */
248 public void setColumns (int newCols)
249 {
250 if (newCols < 0)
251 throw new IllegalArgumentException ("number of columns cannot be negative");
252 if (newCols == 0 && rows == 0)
253 throw new IllegalArgumentException ("number of rows is already 0");
254 this.cols = newCols;
255 }
256
257 /** Set the horizontal gap. An Exception is not thrown if hgap < 0.
258 * @param hgap The horizontal gap
259 */
260 public void setHgap (int hgap)
261 {
262 this.hgap = hgap;
263 }
264
265 /** Set the number of rows
266 * @param newRows
267 * @exception IllegalArgumentException If the number of rows is
268 * negative, or if the number of rows is zero and the number
269 * of columns is already 0.
270 */
271 public void setRows (int newRows)
272 {
273 if (newRows < 0)
274 throw new IllegalArgumentException ("number of rows cannot be negative");
275 if (newRows == 0 && cols == 0)
276 throw new IllegalArgumentException ("number of columns is already 0");
277 this.rows = newRows;
278 }
279
280 /** Set the vertical gap. An Exception is not thrown if vgap < 0.
281 * @param vgap The vertical gap
282 */
283 public void setVgap (int vgap)
284 {
285 this.vgap = vgap;
286 }
287
288 /** Return String description of this object. */
289 public String toString ()
290 {
291 return (getClass ().getName () + "["
292 + "hgap=" + hgap + ",vgap=" + vgap
293 + ",rows=" + rows + ",cols=" + cols
294 + "]");
295 }
296
297 // This method is used to compute the various sizes.
298 private Dimension getSize (Container parent, boolean is_min)
299 {
300 synchronized (parent.getTreeLock ())
301 {
302 int w = 0, h = 0, num = parent.ncomponents;
303 // This is more efficient than calling getComponents().
304 Component[] comps = parent.component;
305
306 for (int i = 0; i < num; ++i)
307 {
308 Dimension d;
309
310 if (is_min)
311 d = comps[i].getMinimumSize ();
312 else
313 d = comps[i].getPreferredSize ();
314
315 w = Math.max (d.width, w);
316 h = Math.max (d.height, h);
317 }
318
319 int real_rows = rows;
320 int real_cols = cols;
321 if (real_rows == 0)
322 real_rows = (num + real_cols - 1) / real_cols;
323 else
324 real_cols = (num + real_rows - 1) / real_rows;
325
326 Insets ins = parent.getInsets ();
327 // We subtract out an extra gap here because the gaps are only
328 // between cells.
329 w = ins.left + ins.right + real_cols * (w + hgap) - hgap;
330 h = ins.top + ins.bottom + real_rows * (h + vgap) - vgap;
331 return new Dimension (w, h);
332 }
333 }
334
335 /**
336 * @serial The number of columns in the grid.
337 */
338 private int cols;
339
340 /**
341 * @serial The number of rows in the grid.
342 */
343 private int rows;
344
345 /**
346 * @serial The horizontal gap between columns
347 */
348 private int hgap;
349
350 /**
351 * @serial The vertical gap between rows
352 */
353 private int vgap;
354 }