Java tutorial
/******************************************************************************* * Copyright (c) 2000, 2018 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.swt.layout; import org.eclipse.swt.*; import org.eclipse.swt.graphics.*; import org.eclipse.swt.widgets.*; /** * Instances of this class are used to define the attachments * of a control in a <code>FormLayout</code>. * <p> * To set a <code>FormData</code> object into a control, you use the * <code>setLayoutData ()</code> method. To define attachments for the * <code>FormData</code>, set the fields directly, like this: * </p> * <pre> * FormData data = new FormData(); * data.left = new FormAttachment(0,5); * data.right = new FormAttachment(100,-5); * button.setLayoutData(formData); * </pre> * <p> * <code>FormData</code> contains the <code>FormAttachments</code> for * each edge of the control that the <code>FormLayout</code> uses to * determine the size and position of the control. <code>FormData</code> * objects also allow you to set the width and height of controls within * a <code>FormLayout</code>. * </p> * * @see FormLayout * @see FormAttachment * @see <a href="http://www.eclipse.org/swt/">Sample code and further information</a> * * @since 2.0 */ public final class FormData { /** * width specifies the preferred width in points. This value * is the wHint passed into Control.computeSize(int, int, boolean) * to determine the preferred size of the control. * * The default value is SWT.DEFAULT. * * @see Control#computeSize(int, int, boolean) */ public int width = SWT.DEFAULT; /** * height specifies the preferred height in points. This value * is the hHint passed into Control.computeSize(int, int, boolean) * to determine the preferred size of the control. * * The default value is SWT.DEFAULT. * * @see Control#computeSize(int, int, boolean) */ public int height = SWT.DEFAULT; /** * left specifies the attachment of the left side of * the control. */ public FormAttachment left; /** * right specifies the attachment of the right side of * the control. */ public FormAttachment right; /** * top specifies the attachment of the top of the control. */ public FormAttachment top; /** * bottom specifies the attachment of the bottom of the * control. */ public FormAttachment bottom; int cacheWidth = -1, cacheHeight = -1; int defaultWhint, defaultHhint, defaultWidth = -1, defaultHeight = -1; int currentWhint, currentHhint, currentWidth = -1, currentHeight = -1; FormAttachment cacheLeft, cacheRight, cacheTop, cacheBottom; boolean isVisited, needed; /** * Constructs a new instance of FormData using * default values. */ public FormData() { } /** * Constructs a new instance of FormData according to the parameters. * A value of SWT.DEFAULT indicates that no minimum width or * no minimum height is specified. * * @param width a minimum width for the control * @param height a minimum height for the control */ public FormData(int width, int height) { this.width = width; this.height = height; } void computeSize(Control control, int wHint, int hHint, boolean flushCache) { if (cacheWidth != -1 && cacheHeight != -1) return; if (wHint == this.width && hHint == this.height) { if (defaultWidth == -1 || defaultHeight == -1 || wHint != defaultWhint || hHint != defaultHhint) { Point size = control.computeSize(wHint, hHint, flushCache); defaultWhint = wHint; defaultHhint = hHint; defaultWidth = size.x; defaultHeight = size.y; } cacheWidth = defaultWidth; cacheHeight = defaultHeight; return; } if (currentWidth == -1 || currentHeight == -1 || wHint != currentWhint || hHint != currentHhint) { Point size = control.computeSize(wHint, hHint, flushCache); currentWhint = wHint; currentHhint = hHint; currentWidth = size.x; currentHeight = size.y; } cacheWidth = currentWidth; cacheHeight = currentHeight; } void flushCache() { cacheWidth = cacheHeight = -1; defaultHeight = defaultWidth = -1; currentHeight = currentWidth = -1; } int getWidth(Control control, boolean flushCache) { needed = true; computeSize(control, width, height, flushCache); return cacheWidth; } int getHeight(Control control, boolean flushCache) { computeSize(control, width, height, flushCache); return cacheHeight; } FormAttachment getBottomAttachment(Control control, int spacing, boolean flushCache) { if (cacheBottom != null) return cacheBottom; if (isVisited) return cacheBottom = new FormAttachment(0, getHeight(control, flushCache)); if (bottom == null) { if (top == null) return cacheBottom = new FormAttachment(0, getHeight(control, flushCache)); return cacheBottom = getTopAttachment(control, spacing, flushCache) .plus(getHeight(control, flushCache)); } Control bottomControl = bottom.control; if (bottomControl != null) { if (bottomControl.isDisposed()) { bottom.control = bottomControl = null; } else { if (bottomControl.getParent() != control.getParent()) { bottomControl = null; } } } if (bottomControl == null) return cacheBottom = bottom; isVisited = true; FormData bottomData = (FormData) bottomControl.getLayoutData(); FormAttachment bottomAttachment = bottomData.getBottomAttachment(bottomControl, spacing, flushCache); switch (bottom.alignment) { case SWT.BOTTOM: cacheBottom = bottomAttachment.plus(bottom.offset); break; case SWT.CENTER: { FormAttachment topAttachment = bottomData.getTopAttachment(bottomControl, spacing, flushCache); FormAttachment bottomHeight = bottomAttachment.minus(topAttachment); cacheBottom = bottomAttachment.minus(bottomHeight.minus(getHeight(control, flushCache)).divide(2)); break; } default: { FormAttachment topAttachment = bottomData.getTopAttachment(bottomControl, spacing, flushCache); cacheBottom = topAttachment.plus(bottom.offset - spacing); break; } } isVisited = false; return cacheBottom; } FormAttachment getLeftAttachment(Control control, int spacing, boolean flushCache) { if (cacheLeft != null) return cacheLeft; if (isVisited) return cacheLeft = new FormAttachment(0, 0); if (left == null) { if (right == null) return cacheLeft = new FormAttachment(0, 0); return cacheLeft = getRightAttachment(control, spacing, flushCache) .minus(getWidth(control, flushCache)); } Control leftControl = left.control; if (leftControl != null) { if (leftControl.isDisposed()) { left.control = leftControl = null; } else { if (leftControl.getParent() != control.getParent()) { leftControl = null; } } } if (leftControl == null) return cacheLeft = left; isVisited = true; FormData leftData = (FormData) leftControl.getLayoutData(); FormAttachment leftAttachment = leftData.getLeftAttachment(leftControl, spacing, flushCache); switch (left.alignment) { case SWT.LEFT: cacheLeft = leftAttachment.plus(left.offset); break; case SWT.CENTER: { FormAttachment rightAttachment = leftData.getRightAttachment(leftControl, spacing, flushCache); FormAttachment leftWidth = rightAttachment.minus(leftAttachment); cacheLeft = leftAttachment.plus(leftWidth.minus(getWidth(control, flushCache)).divide(2)); break; } default: { FormAttachment rightAttachment = leftData.getRightAttachment(leftControl, spacing, flushCache); cacheLeft = rightAttachment.plus(left.offset + spacing); } } isVisited = false; return cacheLeft; } String getName() { String string = getClass().getName(); int index = string.lastIndexOf('.'); if (index == -1) return string; return string.substring(index + 1, string.length()); } FormAttachment getRightAttachment(Control control, int spacing, boolean flushCache) { if (cacheRight != null) return cacheRight; if (isVisited) return cacheRight = new FormAttachment(0, getWidth(control, flushCache)); if (right == null) { if (left == null) return cacheRight = new FormAttachment(0, getWidth(control, flushCache)); return cacheRight = getLeftAttachment(control, spacing, flushCache).plus(getWidth(control, flushCache)); } Control rightControl = right.control; if (rightControl != null) { if (rightControl.isDisposed()) { right.control = rightControl = null; } else { if (rightControl.getParent() != control.getParent()) { rightControl = null; } } } if (rightControl == null) return cacheRight = right; isVisited = true; FormData rightData = (FormData) rightControl.getLayoutData(); FormAttachment rightAttachment = rightData.getRightAttachment(rightControl, spacing, flushCache); switch (right.alignment) { case SWT.RIGHT: cacheRight = rightAttachment.plus(right.offset); break; case SWT.CENTER: { FormAttachment leftAttachment = rightData.getLeftAttachment(rightControl, spacing, flushCache); FormAttachment rightWidth = rightAttachment.minus(leftAttachment); cacheRight = rightAttachment.minus(rightWidth.minus(getWidth(control, flushCache)).divide(2)); break; } default: { FormAttachment leftAttachment = rightData.getLeftAttachment(rightControl, spacing, flushCache); cacheRight = leftAttachment.plus(right.offset - spacing); break; } } isVisited = false; return cacheRight; } FormAttachment getTopAttachment(Control control, int spacing, boolean flushCache) { if (cacheTop != null) return cacheTop; if (isVisited) return cacheTop = new FormAttachment(0, 0); if (top == null) { if (bottom == null) return cacheTop = new FormAttachment(0, 0); return cacheTop = getBottomAttachment(control, spacing, flushCache) .minus(getHeight(control, flushCache)); } Control topControl = top.control; if (topControl != null) { if (topControl.isDisposed()) { top.control = topControl = null; } else { if (topControl.getParent() != control.getParent()) { topControl = null; } } } if (topControl == null) return cacheTop = top; isVisited = true; FormData topData = (FormData) topControl.getLayoutData(); FormAttachment topAttachment = topData.getTopAttachment(topControl, spacing, flushCache); switch (top.alignment) { case SWT.TOP: cacheTop = topAttachment.plus(top.offset); break; case SWT.CENTER: { FormAttachment bottomAttachment = topData.getBottomAttachment(topControl, spacing, flushCache); FormAttachment topHeight = bottomAttachment.minus(topAttachment); cacheTop = topAttachment.plus(topHeight.minus(getHeight(control, flushCache)).divide(2)); break; } default: { FormAttachment bottomAttachment = topData.getBottomAttachment(topControl, spacing, flushCache); cacheTop = bottomAttachment.plus(top.offset + spacing); break; } } isVisited = false; return cacheTop; } /** * Returns a string containing a concise, human-readable * description of the receiver. * * @return a string representation of the FormData object */ @Override public String toString() { String string = getName() + " {"; if (width != SWT.DEFAULT) string += "width=" + width + " "; if (height != SWT.DEFAULT) string += "height=" + height + " "; if (left != null) string += "left=" + left + " "; if (right != null) string += "right=" + right + " "; if (top != null) string += "top=" + top + " "; if (bottom != null) string += "bottom=" + bottom + " "; string = string.trim(); string += "}"; return string; } }