| /******************************************************************************* |
| * Copyright (c) 2004, 2015 IBM Corporation and others. |
| * |
| * This program and the accompanying materials |
| * are made available under the terms of the Eclipse Public License 2.0 |
| * which accompanies this distribution, and is available at |
| * https://www.eclipse.org/legal/epl-2.0/ |
| * |
| * SPDX-License-Identifier: EPL-2.0 |
| * |
| * Contributors: |
| * IBM Corporation - initial API and implementation |
| *******************************************************************************/ |
| package org.eclipse.ui; |
| |
| |
| /** |
| * Interface implemented by objects that are capable of computing a preferred |
| * size. |
| * |
| * @since 3.1 |
| */ |
| public interface ISizeProvider { |
| |
| /** |
| * Constant used to indicate infinite size. This is equal to Integer.MAX_VALUE, ensuring |
| * that it is greater than any other integer. |
| */ |
| int INFINITE = Integer.MAX_VALUE; |
| |
| /** |
| * Returns a bitwise combination of flags indicating how and when computePreferredSize should |
| * be used. When called with horizontal=true, this indicates the usage of computePreferredSize(true,...) |
| * for computing widths. When called with horizontal=false, this indicates the usage of computeSize(false,...) |
| * for computing heights. These flags are used for optimization. Each flag gives the part more control |
| * over its preferred size but slows down the layout algorithm. Parts should return the minimum set |
| * of flags necessary to specify their constraints. |
| * <p> |
| * If the return value of this function ever changes, the part must call <code>flushLayout</code> before |
| * the changes will take effect. |
| * </p> |
| * |
| * <ul> |
| * <li>SWT.MAX: The part has a maximum size that will be returned by computePreferredSize(horizontal, |
| * INFINITE, someWidth, INFINITE)</li> |
| * <li>SWT.MIN: The part has a minimum size that will be returned by computePreferredSize(horizontal, |
| * INFINITE, someWidth, 0)</li> |
| * <li>SWT.WRAP: Indicates that computePreferredSize makes use of the availablePerpendicular argument. If this |
| * flag is not specified, then the third argument to computePreferredSize will always be set to |
| * INFINITE. The perpendicular size is expensive to compute, and it is usually only used |
| * for wrapping parts. |
| * <li>SWT.FILL: The part may not return the preferred size verbatim when computePreferredSize is |
| * is given a value between the minimum and maximum sizes. This is commonly used if the part |
| * wants to use a set of predetermined sizes instead of using the workbench-provided size. |
| * For example, computePreferredSize(horizontal, availableSpace, someWidth, |
| * preferredSize) may return the nearest predetermined size. Note that this flag should |
| * be used sparingly. It can prevent layout caching and cause the workbench layout algorithm |
| * to degrade to exponential worst-case runtime. If this flag is omitted, then |
| * computePreferredSize may be used to compute the minimum and maximum sizes, but not for |
| * anything in between.</li> |
| * </ul> |
| * |
| * @param width a value of true or false determines whether the return value applies when computing |
| * widths or heights respectively. That is, getSizeFlags(true) will be used when calling |
| * computePreferredSize(true,...) |
| * @return any bitwise combination of SWT.MAX, SWT.MIN, SWT.WRAP, and SWT.FILL |
| */ |
| int getSizeFlags(boolean width); |
| |
| /** |
| * <p> |
| * Returns the best size for this part, given the available width and height |
| * and the workbench's preferred size for the part. Parts can overload this |
| * to enforce a minimum size, maximum size, or a quantized set of preferred |
| * sizes. If width == true, this method computes a width in pixels. If width |
| * == false, this method computes a height. availableParallel and |
| * availablePerpendicular contain the space available, and preferredParallel |
| * contains the preferred result. |
| * </p> |
| * |
| * <p> |
| * This method returns an answer that is less than or equal to |
| * availableParallel and as close to preferredParallel as possible. Return |
| * values larger than availableParallel will be truncated. |
| * </p> |
| * |
| * <p> |
| * Most presentations will define a minimum size at all times, and a maximum |
| * size that only applies when maximized. |
| * </p> |
| * |
| * <p> |
| * The getSizeFlags method controls how frequently this method will be |
| * called and what information will be available when it is. Any subclass |
| * that specializes this method should also specialize getSizeFlags. |
| * computePreferredSize(width, INFINITE, someSize, 0) returns the minimum |
| * size of the control (if any). computePreferredSize(width, INFINITE, |
| * someSize, INFINITE) returns the maximum size of the control. |
| * </p> |
| * |
| * <p> |
| * Examples: |
| * <ul> |
| * <li>To maintain a constant size of 100x300 pixels: {return width ? 100 : |
| * 300}, getSizeFlags(boolean) must return SWT.MIN | SWT.MAX</li> |
| * <li>To grow without constraints: {return preferredResult;}, |
| * getSizeFlags(boolean) must return 0.</li> |
| * <li>To enforce a width that is always a multiple of 100 pixels, to a |
| * minimum of 100 pixels: <code> |
| * { |
| * if (width && preferredResult != INFINITE) { |
| * int result = preferredResult - ((preferredResult + 50) % 100) + 50; |
| * result = Math.max(100, Math.min(result, availableParallel - (availableParallel % 100))); |
| * |
| * return result; |
| * } |
| * return preferredResult; |
| * } |
| * </code> In this case, getSizeFlags(boolean width) must return (width ? |
| * SWT.FILL | SWT.MIN: 0) |
| * </ul> |
| * <li>To maintain a minimum area of 100000 pixels: <code> |
| * {return availablePerpendicular < 100 ? 1000 : 100000 / availablePerpendicular;} |
| * </code> getSizeFlags(boolean width) must return SWT.WRAP | SWT.MIN;</li> |
| * </p> |
| * |
| * @param width |
| * indicates whether a width (if <code>true</code>) or a height |
| * (if <code>false</code>) is being computed |
| * @param availableParallel |
| * available space. This is a width (pixels) if width == true, |
| * and a height (pixels) if width == false. A return value larger |
| * than this will be ignored. |
| * @param availablePerpendicular |
| * available space perpendicular to the direction being measured |
| * or INFINITE if unbounded (pixels). This is a height if width |
| * == true, or a height if width == false. Implementations will |
| * generally ignore this argument unless they contain wrapping |
| * widgets. Note this argument will only contain meaningful |
| * information if the part returns the SWT.WRAP flag from |
| * getSizeFlags(width) |
| * @param preferredResult |
| * preferred size of the control (pixels, <= availableParallel). |
| * Set to INFINITE if unknown or unbounded. |
| * @return returns the preferred size of the control (pixels). This is a |
| * width if width == true or a height if width == false. Callers are |
| * responsible for rounding down the return value if it is larger |
| * than availableParallel. If availableParallel is INFINITE, then a |
| * return value of INFINITE is permitted, indicating that the |
| * preferred size of the control is unbounded. |
| * |
| * @see ISizeProvider#getSizeFlags(boolean) |
| */ |
| int computePreferredSize(boolean width, int availableParallel, int availablePerpendicular, int preferredResult); |
| } |
