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Issue#550: double buffer pattern (#1024)

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* Basic implementation

* implement double buffer

* add unit test

* add unit test

* Add Readme

* Change local value declaration to var

* Remove unused fields
This commit is contained in:
Azureyjt
2019-10-20 23:55:36 +08:00
committed by Ilkka Seppälä
parent 82f9a6c232
commit 2217fbc5ff
11 changed files with 623 additions and 0 deletions
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85
double-buffer/src/main/java/com/iluwatar/doublebuffer/App.java Normal file
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/**
* The MIT License
* Copyright (c) 2014-2016 Ilkka Seppälä
* <p>
* Permission is hereby granted, free of charge, to any person obtaining a copy
* of this software and associated documentation files (the "Software"), to deal
* in the Software without restriction, including without limitation the rights
* to use, copy, modify, merge, publish, distribute, sublicense, and/or sell
* copies of the Software, and to permit persons to whom the Software is
* furnished to do so, subject to the following conditions:
* <p>
* The above copyright notice and this permission notice shall be included in
* all copies or substantial portions of the Software.
* <p>
* THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
* IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
* FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
* AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
* LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
* OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN
* THE SOFTWARE.
*/
package com.iluwatar.doublebuffer;
import org.apache.commons.lang3.tuple.MutablePair;
import org.apache.commons.lang3.tuple.Pair;
import org.slf4j.Logger;
import org.slf4j.LoggerFactory;
import java.util.ArrayList;
import java.util.List;
/**
* Double buffering is a term used to describe a device that has two buffers.
* The usage of multiple buffers increases the overall throughput of a device
* and helps prevents bottlenecks. This example shows using double buffer pattern
* on graphics. It is used to show one image or frame while a separate frame
* is being buffered to be shown next. This method makes animations and games
* look more realistic than the same done in a single buffer mode.
*/
public class App {
private static final Logger LOGGER = LoggerFactory.getLogger(App.class);
/**
* Program main entry point.
* @param args runtime arguments
*/
public static void main(String[] args) {
var scene = new Scene();
List<Pair<Integer, Integer>> drawPixels = new ArrayList<>();
Pair<Integer, Integer> pixel1 = new MutablePair<>(1, 1);
Pair<Integer, Integer> pixel2 = new MutablePair<>(5, 6);
Pair<Integer, Integer> pixel3 = new MutablePair<>(3, 2);
drawPixels.add(pixel1);
drawPixels.add(pixel2);
drawPixels.add(pixel3);
scene.draw(drawPixels);
var buffer1 = scene.getBuffer();
printBlackPixelCoordinate(buffer1);
drawPixels.clear();
Pair<Integer, Integer> pixel4 = new MutablePair<>(3, 7);
Pair<Integer, Integer> pixel5 = new MutablePair<>(6, 1);
drawPixels.add(pixel4);
drawPixels.add(pixel5);
scene.draw(drawPixels);
Buffer buffer2 = scene.getBuffer();
printBlackPixelCoordinate(buffer2);
}
private static void printBlackPixelCoordinate(Buffer buffer) {
var log = "Black Pixels: ";
Pixel[] pixels = buffer.getPixels();
for (var i = 0; i < pixels.length; ++i) {
if (pixels[i] == Pixel.BLACK) {
var y = i / FrameBuffer.WIDTH;
var x = i % FrameBuffer.WIDTH;
log += " (" + x + ", " + y + ")";
}
}
LOGGER.info(log);
}
}

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double-buffer/src/main/java/com/iluwatar/doublebuffer/Buffer.java Normal file
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/**
* The MIT License
* Copyright (c) 2014-2016 Ilkka Seppälä
* <p>
* Permission is hereby granted, free of charge, to any person obtaining a copy
* of this software and associated documentation files (the "Software"), to deal
* in the Software without restriction, including without limitation the rights
* to use, copy, modify, merge, publish, distribute, sublicense, and/or sell
* copies of the Software, and to permit persons to whom the Software is
* furnished to do so, subject to the following conditions:
* <p>
* The above copyright notice and this permission notice shall be included in
* all copies or substantial portions of the Software.
* <p>
* THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
* IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
* FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
* AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
* LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
* OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN
* THE SOFTWARE.
*/
package com.iluwatar.doublebuffer;
/**
* Buffer interface.
*/
public interface Buffer {
/**
* Clear the pixel in (x, y).
* @param x X coordinate
* @param y Y coordinate
*/
void clear(int x, int y);
/**
* Draw the pixel in (x, y).
* @param x X coordinate
* @param y Y coordinate
*/
void draw(int x, int y);
/**
* Clear all the pixels.
*/
void clearAll();
/**
* Get all the pixels.
* @return pixel list
*/
Pixel[] getPixels();
}

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double-buffer/src/main/java/com/iluwatar/doublebuffer/FrameBuffer.java Normal file
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/**
* The MIT License
* Copyright (c) 2014-2016 Ilkka Seppälä
* <p>
* Permission is hereby granted, free of charge, to any person obtaining a copy
* of this software and associated documentation files (the "Software"), to deal
* in the Software without restriction, including without limitation the rights
* to use, copy, modify, merge, publish, distribute, sublicense, and/or sell
* copies of the Software, and to permit persons to whom the Software is
* furnished to do so, subject to the following conditions:
* <p>
* The above copyright notice and this permission notice shall be included in
* all copies or substantial portions of the Software.
* <p>
* THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
* IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
* FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
* AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
* LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
* OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN
* THE SOFTWARE.
*/
package com.iluwatar.doublebuffer;
import org.slf4j.Logger;
import org.slf4j.LoggerFactory;
/**
* FrameBuffer implementation class.
*/
public class FrameBuffer implements Buffer {
public static final int WIDTH = 10;
public static final int HEIGHT = 8;
private Pixel[] pixels = new Pixel[WIDTH * HEIGHT];
public FrameBuffer() {
clearAll();
}
@Override
public void clear(int x, int y) {
pixels[getIndex(x, y)] = Pixel.WHITE;
}
@Override
public void draw(int x, int y) {
pixels[getIndex(x, y)] = Pixel.BLACK;
}
@Override
public void clearAll() {
for (var i = 0; i < pixels.length; ++i) {
pixels[i] = Pixel.WHITE;
}
}
@Override
public Pixel[] getPixels() {
return pixels;
}
private int getIndex(int x, int y) {
return x + WIDTH * y;
}
}

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double-buffer/src/main/java/com/iluwatar/doublebuffer/Pixel.java Normal file
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/**
* The MIT License
* Copyright (c) 2014-2016 Ilkka Seppälä
* <p>
* Permission is hereby granted, free of charge, to any person obtaining a copy
* of this software and associated documentation files (the "Software"), to deal
* in the Software without restriction, including without limitation the rights
* to use, copy, modify, merge, publish, distribute, sublicense, and/or sell
* copies of the Software, and to permit persons to whom the Software is
* furnished to do so, subject to the following conditions:
* <p>
* The above copyright notice and this permission notice shall be included in
* all copies or substantial portions of the Software.
* <p>
* THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
* IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
* FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
* AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
* LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
* OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN
* THE SOFTWARE.
*/
package com.iluwatar.doublebuffer;
/**
* Pixel enum. Each pixel can be white (not drawn) or black (drawn).
*/
public enum Pixel {
WHITE(0),
BLACK(1);
private int color;
Pixel(int color) {
this.color = color;
}
}

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double-buffer/src/main/java/com/iluwatar/doublebuffer/Scene.java Normal file
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/**
* The MIT License
* Copyright (c) 2014-2016 Ilkka Seppälä
* <p>
* Permission is hereby granted, free of charge, to any person obtaining a copy
* of this software and associated documentation files (the "Software"), to deal
* in the Software without restriction, including without limitation the rights
* to use, copy, modify, merge, publish, distribute, sublicense, and/or sell
* copies of the Software, and to permit persons to whom the Software is
* furnished to do so, subject to the following conditions:
* <p>
* The above copyright notice and this permission notice shall be included in
* all copies or substantial portions of the Software.
* <p>
* THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
* IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
* FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
* AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
* LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
* OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN
* THE SOFTWARE.
*/
package com.iluwatar.doublebuffer;
import org.apache.commons.lang3.tuple.Pair;
import org.slf4j.Logger;
import org.slf4j.LoggerFactory;
import java.util.List;
/**
* Scene class. Render the output frame.
*/
public class Scene {
private static final Logger LOGGER = LoggerFactory.getLogger(Scene.class);
private Buffer[] frameBuffers;
private int current;
private int next;
/**
* Constructor of Scene.
*/
public Scene() {
frameBuffers = new FrameBuffer[2];
frameBuffers[0] = new FrameBuffer();
frameBuffers[1] = new FrameBuffer();
current = 0;
next = 1;
}
/**
* Draw the next frame.
* @param coordinateList list of pixels of which the color should be black
*/
public void draw(List<Pair<Integer, Integer>> coordinateList) {
LOGGER.info("Start drawing next frame");
LOGGER.info("Current buffer: " + current + " Next buffer: " + next);
frameBuffers[next].clearAll();
for (Pair<Integer, Integer> coordinate : coordinateList) {
var x = coordinate.getKey();
var y = coordinate.getValue();
frameBuffers[next].draw(x, y);
}
LOGGER.info("Swap current and next buffer");
swap();
LOGGER.info("Finish swapping");
LOGGER.info("Current buffer: " + current + " Next buffer: " + next);
}
public Buffer getBuffer() {
LOGGER.info("Get current buffer: " + current);
return frameBuffers[current];
}
private void swap() {
current = current ^ next;
next = current ^ next;
current = current ^ next;
}
}

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double-buffer/src/test/java/com/iluwatar/doublebuffer/AppTest.java Normal file
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/**
* The MIT License
* Copyright (c) 2014-2016 Ilkka Seppälä
* <p>
* Permission is hereby granted, free of charge, to any person obtaining a copy
* of this software and associated documentation files (the "Software"), to deal
* in the Software without restriction, including without limitation the rights
* to use, copy, modify, merge, publish, distribute, sublicense, and/or sell
* copies of the Software, and to permit persons to whom the Software is
* furnished to do so, subject to the following conditions:
* <p>
* The above copyright notice and this permission notice shall be included in
* all copies or substantial portions of the Software.
* <p>
* THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
* IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
* FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
* AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
* LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
* OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN
* THE SOFTWARE.
*/
package com.iluwatar.doublebuffer;
import org.junit.Test;
/**
* App unit test.
*/
public class AppTest {
@Test
public void testMain() {
String[] args = {};
App.main(args);
}
}

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double-buffer/src/test/java/com/iluwatar/doublebuffer/FrameBufferTest.java Normal file
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/**
* The MIT License
* Copyright (c) 2014-2016 Ilkka Seppälä
* <p>
* Permission is hereby granted, free of charge, to any person obtaining a copy
* of this software and associated documentation files (the "Software"), to deal
* in the Software without restriction, including without limitation the rights
* to use, copy, modify, merge, publish, distribute, sublicense, and/or sell
* copies of the Software, and to permit persons to whom the Software is
* furnished to do so, subject to the following conditions:
* <p>
* The above copyright notice and this permission notice shall be included in
* all copies or substantial portions of the Software.
* <p>
* THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
* IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
* FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
* AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
* LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
* OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN
* THE SOFTWARE.
*/
package com.iluwatar.doublebuffer;
import org.junit.Assert;
import org.junit.Test;
/**
* FrameBuffer unit test.
*/
public class FrameBufferTest {
@Test
public void testClearAll() {
try {
var field = FrameBuffer.class.getDeclaredField("pixels");
Pixel[] pixels = new Pixel[FrameBuffer.HEIGHT * FrameBuffer.WIDTH];
for (int i = 0; i < pixels.length; ++i) {
pixels[i] = Pixel.WHITE;
}
pixels[0] = Pixel.BLACK;
var frameBuffer = new FrameBuffer();
field.setAccessible(true);
field.set(frameBuffer, pixels);
frameBuffer.clearAll();
Assert.assertEquals(Pixel.WHITE, frameBuffer.getPixels()[0]);
} catch (NoSuchFieldException | IllegalAccessException e) {
Assert.fail("Fail to modify field access.");
}
}
@Test
public void testClear() {
try {
var field = FrameBuffer.class.getDeclaredField("pixels");
Pixel[] pixels = new Pixel[FrameBuffer.HEIGHT * FrameBuffer.WIDTH];
for (int i = 0; i < pixels.length; ++i) {
pixels[i] = Pixel.WHITE;
}
pixels[0] = Pixel.BLACK;
var frameBuffer = new FrameBuffer();
field.setAccessible(true);
field.set(frameBuffer, pixels);
frameBuffer.clear(0, 0);
Assert.assertEquals(Pixel.WHITE, frameBuffer.getPixels()[0]);
} catch (NoSuchFieldException | IllegalAccessException e) {
Assert.fail("Fail to modify field access.");
}
}
@Test
public void testDraw() {
var frameBuffer = new FrameBuffer();
frameBuffer.draw(0, 0);
Assert.assertEquals(Pixel.BLACK, frameBuffer.getPixels()[0]);
}
@Test
public void testGetPixels() {
try {
var field = FrameBuffer.class.getDeclaredField("pixels");
Pixel[] pixels = new Pixel[FrameBuffer.HEIGHT * FrameBuffer.WIDTH];
for (int i = 0; i < pixels.length; ++i) {
pixels[i] = Pixel.WHITE;
}
pixels[0] = Pixel.BLACK;
var frameBuffer = new FrameBuffer();
field.setAccessible(true);
field.set(frameBuffer, pixels);
Assert.assertEquals(pixels, frameBuffer.getPixels());
} catch (NoSuchFieldException | IllegalAccessException e) {
Assert.fail("Fail to modify field access.");
}
}
}

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double-buffer/src/test/java/com/iluwatar/doublebuffer/SceneTest.java Normal file
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/**
* The MIT License
* Copyright (c) 2014-2016 Ilkka Seppälä
* <p>
* Permission is hereby granted, free of charge, to any person obtaining a copy
* of this software and associated documentation files (the "Software"), to deal
* in the Software without restriction, including without limitation the rights
* to use, copy, modify, merge, publish, distribute, sublicense, and/or sell
* copies of the Software, and to permit persons to whom the Software is
* furnished to do so, subject to the following conditions:
* <p>
* The above copyright notice and this permission notice shall be included in
* all copies or substantial portions of the Software.
* <p>
* THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
* IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
* FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
* AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
* LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
* OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN
* THE SOFTWARE.
*/
package com.iluwatar.doublebuffer;
import org.junit.Assert;
import org.junit.Test;
import java.lang.reflect.Field;
import java.util.ArrayList;
/**
* Scene unit tests.
*/
public class SceneTest {
@Test
public void testGetBuffer() {
try {
var scene = new Scene();
var field1 = Scene.class.getDeclaredField("current");
field1.setAccessible(true);
field1.set(scene, 0);
FrameBuffer[] frameBuffers = new FrameBuffer[2];
FrameBuffer frameBuffer = new FrameBuffer();
frameBuffer.draw(0, 0);
frameBuffers[0] = frameBuffer;
var field2 = Scene.class.getDeclaredField("frameBuffers");
field2.setAccessible(true);
field2.set(scene, frameBuffers);
Assert.assertEquals(frameBuffer, scene.getBuffer());
} catch (NoSuchFieldException | IllegalAccessException e) {
Assert.fail("Fail to access private field.");
}
}
@Test
public void testDraw() {
try {
var scene = new Scene();
var field1 = Scene.class.getDeclaredField("current");
var field2 = Scene.class.getDeclaredField("next");
field1.setAccessible(true);
field1.set(scene, 0);
field2.setAccessible(true);
field2.set(scene, 1);
scene.draw(new ArrayList<>());
Assert.assertEquals(1, field1.get(scene));
Assert.assertEquals(0, field2.get(scene));
} catch (NoSuchFieldException | IllegalAccessException e) {
Assert.fail("Fail to access private field");
}
}
}