Source Code Cross Referenced for SizeCache.java in  » IDE-Eclipse » ui-workbench » org » eclipse » ui » internal » layout » Java Source Code / Java DocumentationJava Source Code and Java Documentation

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Java Source Code / Java Documentation » IDE Eclipse » ui workbench » org.eclipse.ui.internal.layout 
Source Cross Referenced  Class Diagram Java Document (Java Doc) 


001:        /*******************************************************************************
002:         * Copyright (c) 2004, 2006 IBM Corporation and others.
003:         * All rights reserved. This program and the accompanying materials
004:         * are made available under the terms of the Eclipse Public License v1.0
005:         * which accompanies this distribution, and is available at
006:         * http://www.eclipse.org/legal/epl-v10.html
007:         *
008:         * Contributors:
009:         *     IBM Corporation - initial API and implementation
010:         *******************************************************************************/package org.eclipse.ui.internal.layout;
011:
012:        import java.util.List;
013:
014:        import org.eclipse.jface.util.Geometry;
015:        import org.eclipse.swt.SWT;
016:        import org.eclipse.swt.graphics.Point;
017:        import org.eclipse.swt.graphics.Rectangle;
018:        import org.eclipse.swt.widgets.Button;
019:        import org.eclipse.swt.widgets.Combo;
020:        import org.eclipse.swt.widgets.Composite;
021:        import org.eclipse.swt.widgets.Control;
022:        import org.eclipse.swt.widgets.Label;
023:        import org.eclipse.swt.widgets.ProgressBar;
024:        import org.eclipse.swt.widgets.Sash;
025:        import org.eclipse.swt.widgets.Scale;
026:        import org.eclipse.swt.widgets.Slider;
027:        import org.eclipse.swt.widgets.Text;
028:        import org.eclipse.swt.widgets.ToolBar;
029:        import org.eclipse.swt.widgets.Tree;
030:
031:        /**
032:         * Caches the preferred size of an SWT control
033:         * 
034:         * @since 3.0
035:         */
036:        public class SizeCache {
037:            private Control control;
038:
039:            private Point preferredSize;
040:
041:            private Point cachedWidth;
042:
043:            private Point cachedHeight;
044:
045:            /**
046:             * True iff we should recursively flush all children on the next layout
047:             */
048:            private boolean flushChildren;
049:
050:            /**
051:             * True iff changing the height hint does not affect the preferred width and changing
052:             * the width hint does not change the preferred height
053:             */
054:            private boolean independentDimensions = false;
055:
056:            /**
057:             * True iff the preferred height for any hint larger than the preferred width will not
058:             * change the preferred height.
059:             */
060:            private boolean preferredWidthOrLargerIsMinimumHeight = false;
061:
062:            // HACK: these values estimate how much to subtract from the width and height
063:            // hints that get passed into computeSize, in order to produce a result
064:            // that is exactly the desired size. To be removed once bug 46112 is fixed (note:
065:            // bug 46112 is currently flagged as a duplicate, but there is still no workaround).
066:            private int widthAdjustment = 0;
067:
068:            private int heightAdjustment = 0;
069:
070:            // END OF HACK
071:
072:            public SizeCache() {
073:                this (null);
074:            }
075:
076:            /**
077:             * Creates a cache for size computations on the given control
078:             * 
079:             * @param control the control for which sizes will be calculated, 
080:             * or null to always return (0,0) 
081:             */
082:            public SizeCache(Control control) {
083:                setControl(control);
084:            }
085:
086:            /**
087:             * Sets the control whose size is being cached. Does nothing (will not
088:             * even flush the cache) if this is the same control as last time. 
089:             * 
090:             * @param newControl the control whose size is being cached, or null to always return (0,0)
091:             */
092:            public void setControl(Control newControl) {
093:                if (newControl != control) {
094:                    control = newControl;
095:                    if (control == null) {
096:                        independentDimensions = true;
097:                        preferredWidthOrLargerIsMinimumHeight = false;
098:                        widthAdjustment = 0;
099:                        heightAdjustment = 0;
100:                    } else {
101:                        independentDimensions = independentLengthAndWidth(control);
102:                        preferredWidthOrLargerIsMinimumHeight = isPreferredWidthMaximum(control);
103:                        computeHintOffset(control);
104:                        flush();
105:                    }
106:                }
107:            }
108:
109:            /**
110:             * Returns the control whose size is being cached
111:             * 
112:             * @return the control whose size is being cached, or null if this cache always returns (0,0)
113:             */
114:            public Control getControl() {
115:                return control;
116:            }
117:
118:            /**
119:             * Flush the cache (should be called if the control's contents may have changed since the
120:             * last query)
121:             */
122:            public void flush() {
123:                flush(true);
124:            }
125:
126:            public void flush(boolean recursive) {
127:                preferredSize = null;
128:                cachedWidth = null;
129:                cachedHeight = null;
130:                this .flushChildren = recursive;
131:            }
132:
133:            private Point getPreferredSize() {
134:                if (preferredSize == null) {
135:                    preferredSize = computeSize(control, SWT.DEFAULT,
136:                            SWT.DEFAULT);
137:                }
138:
139:                return preferredSize;
140:            }
141:
142:            /**
143:             * Computes the preferred size of the control.
144:             *  
145:             * @param widthHint the known width of the control (pixels) or SWT.DEFAULT if unknown
146:             * @param heightHint the known height of the control (pixels) or SWT.DEFAULT if unknown
147:             * @return the preferred size of the control
148:             */
149:            public Point computeSize(int widthHint, int heightHint) {
150:                if (control == null) {
151:                    return new Point(0, 0);
152:                }
153:
154:                // If both dimensions were supplied in the input, return them verbatim
155:                if (widthHint != SWT.DEFAULT && heightHint != SWT.DEFAULT) {
156:                    return new Point(widthHint, heightHint);
157:                }
158:
159:                // No hints given -- find the preferred size
160:                if (widthHint == SWT.DEFAULT && heightHint == SWT.DEFAULT) {
161:                    return Geometry.copy(getPreferredSize());
162:                }
163:
164:                // If the length and width are independent, compute the preferred size
165:                // and adjust whatever dimension was supplied in the input
166:                if (independentDimensions) {
167:                    Point result = Geometry.copy(getPreferredSize());
168:
169:                    if (widthHint != SWT.DEFAULT) {
170:                        result.x = widthHint;
171:                    }
172:
173:                    if (heightHint != SWT.DEFAULT) {
174:                        result.y = heightHint;
175:                    }
176:
177:                    return result;
178:                }
179:
180:                // Computing a height
181:                if (heightHint == SWT.DEFAULT) {
182:                    // If we know the control's preferred size
183:                    if (preferredSize != null) {
184:                        // If the given width is the preferred width, then return the preferred size
185:                        if (widthHint == preferredSize.x) {
186:                            return Geometry.copy(preferredSize);
187:                        }
188:                    }
189:
190:                    // If we have a cached height measurement
191:                    if (cachedHeight != null) {
192:                        // If this was measured with the same width hint
193:                        if (cachedHeight.x == widthHint) {
194:                            return Geometry.copy(cachedHeight);
195:                        }
196:                    }
197:
198:                    // If this is a control where any hint larger than the
199:                    // preferred width results in the minimum height, determine if
200:                    // we can compute the result based on the preferred height
201:                    if (preferredWidthOrLargerIsMinimumHeight) {
202:                        // Computed the preferred size (if we don't already know it)
203:                        getPreferredSize();
204:
205:                        // If the width hint is larger than the preferred width, then
206:                        // we can compute the result from the preferred width
207:                        if (widthHint >= preferredSize.x) {
208:                            Point result = Geometry.copy(preferredSize);
209:                            result.x = widthHint;
210:                            return result;
211:                        }
212:                    }
213:
214:                    // Else we can't find an existing size in the cache, so recompute
215:                    // it from scratch.
216:                    cachedHeight = computeSize(control, widthHint, heightHint);
217:
218:                    return Geometry.copy(cachedHeight);
219:                }
220:
221:                // Computing a width
222:                if (widthHint == SWT.DEFAULT) {
223:                    // If we know the control's preferred size
224:                    if (preferredSize != null) {
225:                        // If the given height is the preferred height, then return the preferred size
226:                        if (heightHint == preferredSize.y) {
227:                            return Geometry.copy(preferredSize);
228:                        }
229:                    }
230:
231:                    // If we have a cached width measurement
232:                    if (cachedWidth != null) {
233:                        // If this was measured with the same height hint
234:                        if (cachedWidth.y == heightHint) {
235:                            return Geometry.copy(cachedWidth);
236:                        }
237:                    }
238:
239:                    cachedWidth = computeSize(control, widthHint, heightHint);
240:
241:                    return Geometry.copy(cachedWidth);
242:                }
243:
244:                return computeSize(control, widthHint, heightHint);
245:            }
246:
247:            /**
248:             * Compute the control's size, and ensure that non-default hints are returned verbatim
249:             * (this tries to compensate for SWT's hints, which aren't really the outer width of the
250:             * control).
251:             * 
252:             * @param control
253:             * @param widthHint
254:             * @param heightHint
255:             * @return
256:             */
257:            private Point computeSize(Control control, int widthHint,
258:                    int heightHint) {
259:                int adjustedWidthHint = widthHint == SWT.DEFAULT ? SWT.DEFAULT
260:                        : Math.max(0, widthHint - widthAdjustment);
261:                int adjustedHeightHint = heightHint == SWT.DEFAULT ? SWT.DEFAULT
262:                        : Math.max(0, heightHint - heightAdjustment);
263:
264:                Point result = control.computeSize(adjustedWidthHint,
265:                        adjustedHeightHint, flushChildren);
266:                flushChildren = false;
267:
268:                // If the amounts we subtracted off the widthHint and heightHint didn't do the trick, then
269:                // manually adjust the result to ensure that a non-default hint will return that result verbatim.
270:
271:                if (widthHint != SWT.DEFAULT) {
272:                    result.x = widthHint;
273:                }
274:
275:                if (heightHint != SWT.DEFAULT) {
276:                    result.y = heightHint;
277:                }
278:
279:                return result;
280:            }
281:
282:            /**
283:             * Returns true if the preferred length of the given control is 
284:             * independent of the width and visa-versa. If this returns true,
285:             * then changing the widthHint argument to control.computeSize will
286:             * never change the resulting height and changing the heightHint
287:             * will never change the resulting width. Returns false if unknown.
288:             * <p>
289:             * This information can be used to improve caching. Incorrectly returning
290:             * a value of false may decrease performance, but incorrectly returning 
291:             * a value of true will generate incorrect layouts... so always return
292:             * false if unsure.
293:             * </p>
294:             * 
295:             * @param control
296:             * @return
297:             */
298:            static boolean independentLengthAndWidth(Control control) {
299:                if (control == null) {
300:                    return true;
301:                }
302:
303:                if (control instanceof  Button || control instanceof  ProgressBar
304:                        || control instanceof  Sash || control instanceof  Scale
305:                        || control instanceof  Slider || control instanceof  List
306:                        || control instanceof  Combo || control instanceof  Tree) {
307:                    return true;
308:                }
309:
310:                if (control instanceof  Label || control instanceof  Text) {
311:                    return (control.getStyle() & SWT.WRAP) == 0;
312:                }
313:
314:                // Unless we're certain that the control has this property, we should
315:                // return false.
316:
317:                return false;
318:            }
319:
320:            /**
321:             * Try to figure out how much we need to subtract from the hints that we
322:             * pass into the given control's computeSize(...) method. This tries to
323:             * compensate for bug 46112. To be removed once SWT provides an "official"
324:             * way to compute one dimension of a control's size given the other known
325:             * dimension.
326:             * 
327:             * @param control
328:             */
329:            private void computeHintOffset(Control control) {
330:                if (control instanceof  Composite) {
331:                    // For composites, subtract off the trim size
332:                    Composite composite = (Composite) control;
333:                    Rectangle trim = composite.computeTrim(0, 0, 0, 0);
334:
335:                    widthAdjustment = trim.width;
336:                    heightAdjustment = trim.height;
337:                } else {
338:                    // For non-composites, subtract off 2 * the border size
339:                    widthAdjustment = control.getBorderWidth() * 2;
340:                    heightAdjustment = widthAdjustment;
341:                }
342:            }
343:
344:            /**
345:             * Returns true only if the control will return a constant height for any
346:             * width hint larger than the preferred width. Returns false if there is
347:             * any situation in which the control does not have this property.
348:             * 
349:             * <p>
350:             * Note: this method is only important for wrapping controls, and it can
351:             * safely return false for anything else. AFAIK, all SWT controls have this
352:             * property, but to be safe they will only be added to the list once the
353:             * property has been confirmed.
354:             * </p> 
355:             * 
356:             * @param control
357:             * @return
358:             */
359:            private static boolean isPreferredWidthMaximum(Control control) {
360:                return (control instanceof  ToolBar
361:                //|| control instanceof CoolBar
362:                || control instanceof  Label);
363:            }
364:
365:        }
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