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/*
* Copyright 2008 Google Inc.
*
* Licensed under the Apache License, Version 2.0 (the "License"); you may not
* use this file except in compliance with the License. You may obtain a copy of
* the License at
*
* http://www.apache.org/licenses/LICENSE-2.0
*
* Unless required by applicable law or agreed to in writing, software
* distributed under the License is distributed on an "AS IS" BASIS, WITHOUT
* WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied. See the
* License for the specific language governing permissions and limitations under
* the License.
*/
package com.google.gwt.user.rebind.ui;
import com.google.gwt.core.ext.GeneratorContext;
import com.google.gwt.core.ext.TreeLogger;
import com.google.gwt.core.ext.UnableToCompleteException;
import com.google.gwt.dev.util.Util;
import com.google.gwt.dev.util.log.speedtracer.CompilerEventType;
import com.google.gwt.dev.util.log.speedtracer.SpeedTracerLogger;
import java.awt.Graphics2D;
import java.awt.image.BufferedImage;
import java.io.ByteArrayOutputStream;
import java.io.IOException;
import java.io.OutputStream;
import java.net.URL;
import java.util.ArrayList;
import java.util.Collection;
import java.util.Collections;
import java.util.Comparator;
import java.util.HashMap;
import java.util.List;
import java.util.Map;
import javax.imageio.ImageIO;
/**
* Accumulates state for the bundled image.
*/
class ImageBundleBuilder {
/**
* The rectangle at which the original image is placed into the composite
* image.
*/
public static class ImageRect implements HasRect {
private final String name;
private final int height, width;
private final BufferedImage image;
private int left, top;
private boolean hasBeenPositioned;
public ImageRect(String name, BufferedImage image) {
this.name = name;
this.image = image;
this.width = image.getWidth();
this.height = image.getHeight();
}
public int getHeight() {
return height;
}
public int getLeft() {
return left;
}
public String getName() {
return name;
}
public int getTop() {
return top;
}
public int getWidth() {
return width;
}
public boolean hasBeenPositioned() {
return hasBeenPositioned;
}
public void setPosition(int left, int top) {
hasBeenPositioned = true;
this.left = left;
this.top = top;
}
}
/**
* A mockable interface to test the image arrangement algorithms.
*/
interface HasRect {
String getName();
int getHeight();
int getLeft();
int getTop();
int getWidth();
boolean hasBeenPositioned();
void setPosition(int left, int top);
}
/**
* Used to return the size of the resulting image from the method
* {@link ImageBundleBuilder#arrangeImages()}.
*/
private static class Size {
private final int width, height;
Size(int width, int height) {
this.width = width;
this.height = height;
}
}
private static final Comparator decreasingHeightComparator = new Comparator() {
public int compare(HasRect a, HasRect b) {
final int c = b.getHeight() - a.getHeight();
// If we encounter equal heights, use the name to keep things
// deterministic.
return (c != 0) ? c : b.getName().compareTo(a.getName());
}
};
private static final Comparator decreasingWidthComparator = new Comparator() {
public int compare(HasRect a, HasRect b) {
final int c = b.getWidth() - a.getWidth();
// If we encounter equal heights, use the name to keep things
// deterministic.
return (c != 0) ? c : b.getName().compareTo(a.getName());
}
};
/*
* Only PNG is supported right now. In the future, we may be able to infer the
* best output type, and get rid of this constant.
*/
private static final String BUNDLE_FILE_TYPE = "png";
/**
* Arranges the images to try to decrease the overall area of the resulting
* bundle. This uses a strategy that is basically Next-Fit Decreasing Height
* Decreasing Width (NFDHDW). The rectangles to be packed are sorted in
* decreasing order by height. The tallest rectangle is placed at the far
* left. We attempt to stack the remaining rectangles on top of one another to
* construct as many columns as necessary. After finishing each column, we
* also attempt to do some horizontal packing to fill up the space left due to
* widths of rectangles differing in the column.
*/
static Size arrangeImages(Collection rects) {
if (rects.size() == 0) {
return new Size(0, 0);
}
// Create a list of ImageRects ordered by decreasing height used for
// constructing columns.
final ArrayList rectsOrderedByHeight = new ArrayList(
rects);
Collections.sort(rectsOrderedByHeight, decreasingHeightComparator);
// Create a list of ImageRects ordered by decreasing width used for packing
// individual columns.
final ArrayList rectsOrderedByWidth = new ArrayList(rects);
Collections.sort(rectsOrderedByWidth, decreasingWidthComparator);
// Place the first, tallest image as the first column.
final HasRect first = rectsOrderedByHeight.get(0);
first.setPosition(0, 0);
// Setup state for laying things cumulatively.
int curX = first.getWidth();
final int colH = first.getHeight();
for (int i = 1, n = rectsOrderedByHeight.size(); i < n; i++) {
// If this ImageRect has been positioned already, move on.
if (rectsOrderedByHeight.get(i).hasBeenPositioned()) {
continue;
}
int colW = 0;
int curY = 0;
final ArrayList rectsInColumn = new ArrayList();
for (int j = i; j < n; j++) {
final HasRect current = rectsOrderedByHeight.get(j);
// Look for rects that have not been positioned with a small enough
// height to go in this column.
if (!current.hasBeenPositioned()
&& (curY + current.getHeight()) <= colH) {
// Set the horizontal position here, the top field will be set in
// arrangeColumn after we've collected a full set of ImageRects.
current.setPosition(curX, 0);
colW = Math.max(colW, current.getWidth());
curY += current.getHeight();
// Keep the ImageRects in this column in decreasing order by width.
final int pos = Collections.binarySearch(rectsInColumn, current,
decreasingWidthComparator);
assert pos < 0;
rectsInColumn.add(-1 - pos, current);
}
}
// Having selected a set of ImageRects that fill out this column vertical,
// now we'll scan the remaining ImageRects to try to fit some in the
// horizontal gaps.
if (!rectsInColumn.isEmpty()) {
arrangeColumn(rectsInColumn, rectsOrderedByWidth);
}
// We're done with that column, so move the horizontal accumulator by the
// width of the column we just finished.
curX += colW;
}
return new Size(curX, colH);
}
/**
* Companion method to {@link #arrangeImages()}. This method does a best
* effort horizontal packing of a column after it was packed vertically. This
* is the Decreasing Width part of Next-Fit Decreasing Height Decreasing
* Width. The basic strategy is to sort the remaining rectangles by decreasing
* width and try to fit them to the left of each of the rectangles we've
* already picked for this column.
*
* @param rectsInColumn the ImageRects that were already selected for this
* column
* @param remainingRectsOrderedByWidth the sub list of ImageRects that may not
* have been positioned yet
*/
private static void arrangeColumn(List rectsInColumn,
List remainingRectsOrderedByWidth) {
final HasRect first = rectsInColumn.get(0);
final int columnWidth = first.getWidth();
int curY = first.getHeight();
// Skip this first ImageRect because it is guaranteed to consume the full
// width of the column.
for (int i = 1, m = rectsInColumn.size(); i < m; i++) {
final HasRect r = rectsInColumn.get(i);
// The ImageRect was previously positioned horizontally, now set the top
// field.
r.setPosition(r.getLeft(), curY);
int curX = r.getWidth();
// Search for ImageRects that are shorter than the left most ImageRect and
// narrow enough to fit in the column.
for (int j = 0, n = remainingRectsOrderedByWidth.size(); j < n; j++) {
final HasRect current = remainingRectsOrderedByWidth.get(j);
if (!current.hasBeenPositioned()
&& (curX + current.getWidth()) <= columnWidth
&& (current.getHeight() <= r.getHeight())) {
current.setPosition(r.getLeft() + curX, r.getTop());
curX += current.getWidth();
}
}
// Update the vertical accumulator so we'll know where to place the next
// ImageRect.
curY += r.getHeight();
}
}
private final Map imageNameToImageRectMap = new HashMap();
/**
* Assimilates the image associated with a particular image method into the
* master composite. If the method names an image that has already been
* assimilated, the existing image rectangle is reused.
*
* @param logger a hierarchical logger which logs to the hosted console
* @param imageName the name of an image that can be found on the classpath
* @throws UnableToCompleteException if the image with name
* imageName cannot be added to the master composite
* image
*/
public void assimilate(TreeLogger logger, String imageName)
throws UnableToCompleteException {
/*
* Decide whether or not we need to add to the composite image. Either way,
* we associated it with the rectangle of the specified image as it exists
* within the composite image. Note that the coordinates of the rectangle
* aren't computed until the composite is written.
*/
ImageRect rect = getMapping(imageName);
if (rect == null) {
// Assimilate the image into the composite.
rect = addImage(logger, imageName);
// Map the URL to its image so that even if the same URL is used more than
// once, we only include the referenced image once in the bundled image.
putMapping(imageName, rect);
}
}
public ImageRect getMapping(String imageName) {
return imageNameToImageRectMap.get(imageName);
}
public String writeBundledImage(TreeLogger logger, GeneratorContext context)
throws UnableToCompleteException {
// Create the bundled image from all of the constituent images.
BufferedImage bundledImage = drawBundledImage();
// Write the bundled image into a byte array, so that we can compute
// its strong name.
byte[] imageBytes;
try {
ByteArrayOutputStream byteOutputStream = new ByteArrayOutputStream();
boolean writerAvailable = ImageIO.write(bundledImage, BUNDLE_FILE_TYPE,
byteOutputStream);
if (!writerAvailable) {
logger.log(TreeLogger.ERROR, "No " + BUNDLE_FILE_TYPE
+ " writer available");
throw new UnableToCompleteException();
}
imageBytes = byteOutputStream.toByteArray();
} catch (IOException e) {
logger.log(TreeLogger.ERROR,
"An error occurred while trying to write the image bundle.", e);
throw new UnableToCompleteException();
}
// Compute the file name. The strong name is generated from the bytes of
// the bundled image. The '.cache' part indicates that it can be
// permanently cached.
String bundleFileName = Util.computeStrongName(imageBytes) + ".cache."
+ BUNDLE_FILE_TYPE;
// Try and write the file to disk. If a file with bundleFileName already
// exists, then the file will not be written.
OutputStream outStream = context.tryCreateResource(logger, bundleFileName);
if (outStream != null) {
try {
// Write the image bytes from the byte array to the pending stream.
outStream.write(imageBytes);
// Commit the stream.
context.commitResource(logger, outStream);
} catch (IOException e) {
logger.log(TreeLogger.ERROR, "Failed while writing", e);
throw new UnableToCompleteException();
}
} else {
logger.log(TreeLogger.TRACE,
"Generated image bundle file already exists; no need to rewrite it.",
null);
}
return bundleFileName;
}
private ImageRect addImage(TreeLogger logger, String imageName)
throws UnableToCompleteException {
logger = logger.branch(TreeLogger.TRACE,
"Adding image '" + imageName + "'", null);
// Fetch the image.
try {
// Could turn this lookup logic into an externally-supplied policy for
// increased generality.
URL imageUrl = getClass().getClassLoader().getResource(imageName);
if (imageUrl == null) {
// This should never happen, because this check is done right after
// the image name is retrieved from the metadata or the method name.
// If there is a failure in obtaining the resource, it will happen
// before this point.
logger.log(TreeLogger.ERROR,
"Resource not found on classpath (is the name specified as "
+ "ClassLoader.getResource() would expect?)", null);
throw new UnableToCompleteException();
}
BufferedImage image;
// Load the image
try {
image = ImageIO.read(imageUrl);
} catch (IllegalArgumentException iex) {
if (imageName.toLowerCase().endsWith("png")
&& iex.getMessage() != null
&& iex.getStackTrace()[0].getClassName().equals(
"javax.imageio.ImageTypeSpecifier$Indexed")) {
logger.log(
TreeLogger.ERROR,
"Unable to read image. The image may not be in valid PNG format. "
+ "This problem may also be due to a bug in versions of the "
+ "JRE prior to 1.6. See "
+ "http://bugs.sun.com/bugdatabase/view_bug.do?bug_id=5098176 "
+ "for more information. If this bug is the cause of the "
+ "error, try resaving the image using a different image "
+ "program, or upgrade to a newer JRE.", null);
throw new UnableToCompleteException();
} else {
throw iex;
}
}
if (image == null) {
logger.log(TreeLogger.ERROR, "Unrecognized image file format", null);
throw new UnableToCompleteException();
}
return new ImageRect(imageName, image);
} catch (IOException e) {
logger.log(TreeLogger.ERROR, "Unable to read image resource", null);
throw new UnableToCompleteException();
}
}
/**
* This method creates the bundled image through the composition of the other
* images.
*
* In this particular implementation, we use NFDHDW (see
* {@link #arrangeImages()}) to get an approximate optimal image packing.
*
* The most important aspect of drawing the bundled image is that it be drawn
* in a deterministic way. The drawing of the image should not rely on
* implementation details of the Generator system which may be subject to
* change.
*/
private BufferedImage drawBundledImage() {
// There is no need to impose any order here, because arrangeImages
// will position the ImageRects in a deterministic fashion, even though
// we might paint them in a non-deterministic order.
Collection imageRects = imageNameToImageRectMap.values();
// Arrange images and determine the size of the resulting bundle.
final Size size = arrangeImages(imageRects);
// Create the bundled image.
BufferedImage bundledImage = new BufferedImage(size.width, size.height,
BufferedImage.TYPE_INT_ARGB_PRE);
SpeedTracerLogger.Event createGraphicsEvent =
SpeedTracerLogger.start(CompilerEventType.GRAPHICS_INIT,
"java.awt.headless", System.getProperty("java.awt.headless"));
Graphics2D g2d = bundledImage.createGraphics();
createGraphicsEvent.end();
for (ImageRect imageRect : imageRects) {
// We do not need to pass in an ImageObserver, because we are working
// with BufferedImages. ImageObservers only need to be used when
// the image to be drawn is being loaded asynchronously. See
// http://java.sun.com/docs/books/tutorial/2d/images/drawimage.html
// for more information.
g2d.drawImage(imageRect.image, imageRect.left, imageRect.top, null);
}
g2d.dispose();
return bundledImage;
}
private void putMapping(String imageName, ImageRect rect) {
imageNameToImageRectMap.put(imageName, rect);
}
}
