tablelayout.java

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/*******************************************************************************
 * Copyright (c) 2000, 2006 IBM Corporation and others.
 * All rights reserved. This program and the accompanying materials
 * are made available under the terms of the Eclipse Public License v1.0
 * which accompanies this distribution, and is available at
 * http://www.eclipse.org/legal/epl-v10.html
 *
 * Contributors:
 *     IBM Corporation - initial API and implementation
 *******************************************************************************/
package org.eclipse.jface.viewers;

import java.util.ArrayList;
import java.util.List;

import org.eclipse.jface.util.Assert;
import org.eclipse.swt.SWT;
import org.eclipse.swt.graphics.Point;
import org.eclipse.swt.widgets.Composite;
import org.eclipse.swt.widgets.Item;
import org.eclipse.swt.widgets.Layout;
import org.eclipse.swt.widgets.Table;
import org.eclipse.swt.widgets.TableColumn;
import org.eclipse.swt.widgets.Tree;
import org.eclipse.swt.widgets.TreeColumn;

/**
 * A layout for a table. Call <code>addColumnData</code> to add columns.
 */
public class TableLayout extends Layout {

	/**
	 * The number of extra pixels taken as horizontal trim by the table column.
	 * To ensure there are N pixels available for the content of the column,
	 * assign N+COLUMN_TRIM for the column width.
	 * 
	 * @since 3.1
	 */
	private static int COLUMN_TRIM = "carbon".equals(SWT.getPlatform()) ? 24 : 3; //$NON-NLS-1$

	/**
	 * The list of column layout data (element type:
	 * <code>ColumnLayoutData</code>).
	 */
	private List columns = new ArrayList();

	/**
	 * Indicates whether <code>layout</code> has yet to be called.
	 */
	private boolean firstTime = true;

	/**
	 * Creates a new table layout.
	 */
	public TableLayout() {
	}

	/**
	 * Adds a new column of data to this table layout.
	 * 
	 * @param data
	 *            the column layout data
	 */
	public void addColumnData(ColumnLayoutData data) {
		columns.add(data);
	}

	/*
	 * (non-Javadoc) Method declared on Layout.
	 */
	public Point computeSize(Composite c, int wHint, int hHint, boolean flush) {
		if (wHint != SWT.DEFAULT && hHint != SWT.DEFAULT) {
			return new Point(wHint, hHint);
		}

		Table table = (Table) c;
		// To avoid recursions.
		table.setLayout(null);
		// Use native layout algorithm
		Point result = table.computeSize(wHint, hHint, flush);
		table.setLayout(this);

		int width = 0;
		int size = columns.size();
		for (int i = 0; i < size; ++i) {
			ColumnLayoutData layoutData = (ColumnLayoutData) columns.get(i);
			if (layoutData instanceof ColumnPixelData) {
				ColumnPixelData col = (ColumnPixelData) layoutData;
				width += col.width;
				if (col.addTrim) {
					width += COLUMN_TRIM;
				}
			} else if (layoutData instanceof ColumnWeightData) {
				ColumnWeightData col = (ColumnWeightData) layoutData;
				width += col.minimumWidth;
			} else {
				Assert.isTrue(false, "Unknown column layout data");//$NON-NLS-1$
			}
		}
		if (width > result.x) {
			result.x = width;
		}
		return result;
	}

	/*
	 * (non-Javadoc) Method declared on Layout.
	 */
	public void layout(Composite c, boolean flush) {
		// Only do initial layout. Trying to maintain proportions when resizing
		// is too hard,
		// causes lots of widget flicker, causes scroll bars to appear and
		// occasionally stick around (on Windows),
		// requires hooking column resizing as well, and may not be what the
		// user wants anyway.
		if (!firstTime) {
			return;
		}

		int width = c.getClientArea().width;

		// XXX: Layout is being called with an invalid value the first time
		// it is being called on Linux. This method resets the
		// Layout to null so we make sure we run it only when
		// the value is OK.
		if (width <= 1) {
			return;
		}

		Item[] tableColumns = getColumns(c);
		int size = Math.min(columns.size(), tableColumns.length);
		int[] widths = new int[size];
		int fixedWidth = 0;
		int numberOfWeightColumns = 0;
		int totalWeight = 0;

		// First calc space occupied by fixed columns
		for (int i = 0; i < size; i++) {
			ColumnLayoutData col = (ColumnLayoutData) columns.get(i);
			if (col instanceof ColumnPixelData) {
				ColumnPixelData cpd = (ColumnPixelData) col;
				int pixels = cpd.width;
				if (cpd.addTrim) {
					pixels += COLUMN_TRIM;
				}
				widths[i] = pixels;
				fixedWidth += pixels;
			} else if (col instanceof ColumnWeightData) {
				ColumnWeightData cw = (ColumnWeightData) col;
				numberOfWeightColumns++;
				// first time, use the weight specified by the column data,
				// otherwise use the actual width as the weight
				// int weight = firstTime ? cw.weight :
				// tableColumns[i].getWidth();
				int weight = cw.weight;
				totalWeight += weight;
			} else {
				Assert.isTrue(false, "Unknown column layout data");//$NON-NLS-1$
			}
		}

		// Do we have columns that have a weight
		if (numberOfWeightColumns > 0) {
			// Now distribute the rest to the columns with weight.
			int rest = width - fixedWidth;
			int totalDistributed = 0;
			for (int i = 0; i < size; ++i) {
				ColumnLayoutData col = (ColumnLayoutData) columns.get(i);
				if (col instanceof ColumnWeightData) {
					ColumnWeightData cw = (ColumnWeightData) col;
					// calculate weight as above
					// int weight = firstTime ? cw.weight :
					// tableColumns[i].getWidth();
					int weight = cw.weight;
					int pixels = totalWeight == 0 ? 0 : weight * rest
							/ totalWeight;
					if (pixels < cw.minimumWidth) {
						pixels = cw.minimumWidth;
					}
					totalDistributed += pixels;
					widths[i] = pixels;
				}
			}

			// Distribute any remaining pixels to columns with weight.
			int diff = rest - totalDistributed;
			for (int i = 0; diff > 0; ++i) {
				if (i == size) {
					i = 0;
				}
				ColumnLayoutData col = (ColumnLayoutData) columns.get(i);
				if (col instanceof ColumnWeightData) {
					++widths[i];
					--diff;
				}
			}
		}

		firstTime = false;

		for (int i = 0; i < size; i++) {
			setWidth(tableColumns[i], widths[i]);
		}
	}

	/**
	 * Set the width of the item.
	 * 
	 * @param item
	 * @param width
	 */
	private void setWidth(Item item, int width) {
		if (item instanceof TreeColumn) {
			((TreeColumn) item).setWidth(width);
		} else {
			((TableColumn) item).setWidth(width);
		}

	}

	/**
	 * Return the columns for the receiver.
	 * 
	 * @param composite
	 * @return Item[]
	 */
	private Item[] getColumns(Composite composite) {
		if (composite instanceof Tree) {
			return ((Tree) composite).getColumns();
		}
		return ((Table) composite).getColumns();
	}
}