java - 将 Swing 组件渲染到屏幕外缓冲区

Question

我有一个在 32 位 Windows 2008 Server 上运行的 Java (Swing) 应用程序，它需要将其输出呈现为离屏图像(然后由另一个 C++ 应用程序拾取以在其他地方呈现)。大多数组件都正确呈现，除了在刚刚失去焦点的组件被另一个组件遮挡的奇怪情况下，例如有两个 JComboBoxes 彼此靠近的情况下，如果用户与较低的 JComboBoxes 交互，然后单击上面的下拉框与另一个框重叠。

在这种情况下，失去焦点的组件在遮挡它的组件之后渲染，因此出现在输出的顶部。它在正常的 Java 显示中正确呈现(在主显示器上全屏运行)，并且尝试更改有问题的组件的层没有帮助。

我正在使用自定义 RepaintManager 将组件绘制到屏幕外图像，我认为问题在于为每个相关组件调用 addDirtyRegion() 的顺序，但我想不出识别这种特定状态何时发生以防止它发生的好方法。对其进行黑客攻击，使刚刚失去焦点的对象不被重新绘制可以解决问题，但显然会导致更大的问题，即在所有其他正常情况下都不会重新绘制。

有没有办法以编程方式识别此状态，或重新排序以使其不会发生？

非常感谢，

尼克

[编辑]添加了一些代码作为示例:

重绘管理器和相关类:

class NativeObject {
    private long nativeAddress = -1;

    protected void setNativeAddress(long address) {
        if ( nativeAddress != -1 ) {
            throw new IllegalStateException("native address already set for " + this);
        }
        this.nativeAddress = address;
        NativeObjectManager.getInstance().registerNativeObject(this, nativeAddress);
    }   
}

public class MemoryMappedFile extends NativeObject {
    private ByteBuffer buffer;

    public MemoryMappedFile(String name, int size)
    {
        setNativeAddress(create(name, size));
        buffer = getNativeBuffer();
    }

    private native long create(String name, int size);

    private native ByteBuffer getNativeBuffer();

    public native void lock();

    public native void unlock();

    public ByteBuffer getBuffer() {
        return buffer;
    }
}

private static class CustomRepaintManager extends RepaintManager{       
    class PaintLog {
        Rectangle bounds;
        Component component;
        Window window;

        PaintLog(int x, int y, int w, int h, Component c) {
            bounds = new Rectangle(x, y, w, h);
            this.component = c;
        }

        PaintLog(int x, int y, int w, int h, Window win) {
            bounds = new Rectangle(x, y, w, h);
            this.window= win;
        }
    }

    private MemoryMappedFile memoryMappedFile;
    private BufferedImage offscreenImage;
    private List<PaintLog> regions = new LinkedList<PaintLog>();
    private final Component contentPane;
    private Component lastFocusOwner;
    private Runnable sharedMemoryUpdater;
    private final IMetadataSource metadataSource;
    private Graphics2D offscreenGraphics;
    private Rectangle offscreenBounds = new Rectangle();
    private Rectangle repaintBounds = new Rectangle();

    public CustomRepaintManager(Component contentPane, IMetadataSource metadataSource) {
        this.contentPane = contentPane;
        this.metadataSource = metadataSource;
        offscreenBounds = new Rectangle(0, 0, 1920, 1080);  
        memoryMappedFile = new MemoryMappedFile("SystemConfigImage", offscreenBounds.width * offscreenBounds.height * 3 + 1024);
        offscreenImage = new BufferedImage(offscreenBounds.width, offscreenBounds.height, BufferedImage.TYPE_3BYTE_BGR);
        offscreenGraphics = offscreenImage.createGraphics();

        sharedMemoryUpdater = new Runnable(){
            @Override
            public void run()
            {
                updateSharedMemory();
            }
        };
    }

    private boolean getLocationRelativeToContentPane(Component c, Point screen) {
        if(!c.isVisible()) {
            return false;
        }

        if(c == contentPane) {
            return true;
        }

        Container parent = c.getParent();
        if(parent == null) {
            System.out.println("can't get parent!");
            return true;
        }

        if(!parent.isVisible()) {
            return false;
        }

        while ( !parent.equals(contentPane)) {
            screen.x += parent.getX();
            screen.y += parent.getY();
            parent = parent.getParent();

            if(parent == null) {
                System.out.println("can't get parent!");
                return true;
            }
            if(!parent.isVisible()) {
                return false;
            }
        }
        return true;
    }

    protected void updateSharedMemory() {
        if ( regions.isEmpty() ) return;

        List<PaintLog> regionsCopy = new LinkedList<PaintLog>();

        synchronized ( regions ) {
            regionsCopy.addAll(regions);
            regions.clear();
        }

        memoryMappedFile.lock();
        ByteBuffer mappedBuffer = memoryMappedFile.getBuffer();
        int imageDataSize = offscreenImage.getWidth() * offscreenImage.getHeight() * 3;
        mappedBuffer.position(imageDataSize);

        if ( mappedBuffer.getInt() == 0 ) {
            repaintBounds.setBounds(0, 0, 0, 0);
        } else {
            repaintBounds.x = mappedBuffer.getInt();
            repaintBounds.y = mappedBuffer.getInt();
            repaintBounds.width = mappedBuffer.getInt();
            repaintBounds.height = mappedBuffer.getInt();
        }

        for ( PaintLog region : regionsCopy ) {
            if ( region.component != null  && region.bounds.width > 0 && region.bounds.height > 0) {
                Point regionLocation = new Point(region.bounds.x, region.bounds.y);
                Point screenLocation = region.component.getLocation();
                boolean isVisible = getLocationRelativeToContentPane(region.component, screenLocation);

                if(!isVisible) {
                    continue;
                }

                if(region.bounds.x != 0 && screenLocation.x == 0 || region.bounds.y != 0 && screenLocation.y == 0){
                    region.bounds.width += region.bounds.x;
                    region.bounds.height += region.bounds.y;
                }

                Rectangle2D.intersect(region.bounds, offscreenBounds, region.bounds);

                if ( repaintBounds.isEmpty() ){
                    repaintBounds.setBounds( screenLocation.x, screenLocation.y, region.bounds.width, region.bounds.height);
                } else {
                    Rectangle2D.union(repaintBounds, new Rectangle(screenLocation.x, screenLocation.y, region.bounds.width, region.bounds.height), repaintBounds);
                }

                offscreenGraphics.translate(screenLocation.x, screenLocation.y);

                region.component.paint(offscreenGraphics);

                DataBufferByte byteBuffer = (DataBufferByte) offscreenImage.getData().getDataBuffer();
                int srcIndex = (screenLocation.x + screenLocation.y * offscreenImage.getWidth()) * 3;
                byte[] srcData = byteBuffer.getData();

                int maxY = Math.min(screenLocation.y + region.bounds.height, offscreenImage.getHeight());
                int regionLineSize = region.bounds.width * 3;

                for (int y = screenLocation.y; y < maxY; ++y){
                    mappedBuffer.position(srcIndex);

                    if ( srcIndex + regionLineSize > srcData.length ) {
                        break;
                    }
                    if ( srcIndex + regionLineSize > mappedBuffer.capacity() ) {
                        break;
                    }
                    try {
                        mappedBuffer.put( srcData, srcIndex, regionLineSize);
                    }
                    catch ( IndexOutOfBoundsException e) {
                        break;
                    }
                    srcIndex += 3 * offscreenImage.getWidth();
                }

                offscreenGraphics.translate(-screenLocation.x, -screenLocation.y);
                offscreenGraphics.setClip(null);

            } else if ( region.window != null ){    
                repaintBounds.setBounds(0, 0, offscreenImage.getWidth(), offscreenImage.getHeight() );

                offscreenGraphics.setClip(repaintBounds);

                contentPane.paint(offscreenGraphics);

                DataBufferByte byteBuffer = (DataBufferByte) offscreenImage.getData().getDataBuffer();
                mappedBuffer.position(0);
                mappedBuffer.put(byteBuffer.getData());
            }
        }

        mappedBuffer.position(imageDataSize);
        mappedBuffer.putInt(repaintBounds.isEmpty() ? 0 : 1);
        mappedBuffer.putInt(repaintBounds.x);
        mappedBuffer.putInt(repaintBounds.y);
        mappedBuffer.putInt(repaintBounds.width);
        mappedBuffer.putInt(repaintBounds.height);
        metadataSource.writeMetadata(mappedBuffer);

        memoryMappedFile.unlock();
    }

    @Override
    public void addDirtyRegion(JComponent c, int x, int y, int w, int h) {
        super.addDirtyRegion(c, x, y, w, h);
        synchronized ( regions ) {
            regions.add(new PaintLog(x, y, w, h, c));
        }
        SwingUtilities.invokeLater(sharedMemoryUpdater);
    }

    @Override
    public void addDirtyRegion(Window window, int x, int y, int w, int h) {
        super.addDirtyRegion(window, x, y, w, h);
        synchronized (regions) {    
            regions.add(new PaintLog(x, y, w, h, window));
        }
        SwingUtilities.invokeLater(sharedMemoryUpdater);
    }
}

出现问题的小组:

private static class EncodingParametersPanel extends JPanel implements ActionListener
{
    private JLabel label1 = new JLabel();
    private JComboBox comboBox1 = new JComboBox();

    private JLabel label2 = new JLabel();
    private JComboBox comboBox2 = new JComboBox();

    private JLabel label3 = new JLabel();
    private JComboBox comboBox3 = new JComboBox();

    private JButton setButton = new JButton();

    public EncodingParametersPanel()
    {
        super(new BorderLayout());

        JPanel contentPanel = new JPanel(new VerticalFlowLayout());
        JPanel formatPanel = new JPanel(new VerticalFlowLayout());

        sdiFormatPanel.setBorder(BorderFactory.createTitledBorder(BorderFactory.createLoweredBevelBorder(), "Format"));

        label1.setText("First Option:");
        label2.setText("Second Option:");
        label3.setText("Third OPtion:");

        setButton.addActionListener(this);

        formatPanel.add(label1);
        formatPanel.add(comboBox1);
        formatPanel.add(label2);
        formatPanel.add(comboBox2);
        formatPanel.add(label3);
        formatPanel.add(comboBox3);

        contentPanel.add(formatPanel);

        contentPanel.add(setButton);

        add(contentPanel);
    }
}

使用此示例，如果用户与 comboBox2 交互，然后与 comboBox1 交互，comboBox1 的下拉菜单会与 comboBox2 重叠，但 comboBox2 会在其之上重绘。

Answer 1

我发现了一些可能有助于您所看到的东西。

在用于处理窗口重绘的updateSharedMemory 代码中，代码调用了contentPane.paint。这是最有可能的罪魁祸首，因为 Window 可能不是您的 contentPane。 JPopupMenu 的代码(由 JComboBox 使用)可以选择将弹出窗口显示为重量级组件。因此，Window 可能是 JComboBox 之一的弹出窗口。

此外，sharedMemoryUpdater 被安排在 EDT 上，一旦事件队列为空，它就会运行。因此，调用 addDirtyRegion 和调用 updateSharedMemory 之间可能存在延迟。在 updateSharedMemory 中调用了 region.component.paint。如果任何已排队的事件更改 component，则绘制调用的实际结果可能会有所不同。

测试的一些建议:

像这样创建 sharedMemoryUpdater:

    private Runnable scheduled = null;

    sharedMemoryUpdater = Runnable {
        public void run() {
            scheduled = null;
            updateSharedMemory();
        }
    }

然后，在addDirtyRegion

    if (scheduled == null) {
        scheduled = sharedMemoryUpdater;
        SwingUtilities.invokeLater(sharedMemoryUpdater);
    }

这将减少 sharedMemoryUpdater 的调用次数(在我的测试中减少了 99%)。由于对 addDirtyRegion 的所有调用都应该在 EDT 上发生，因此您不需要在 scheduled 上进行同步，但添加不会有太大影响。

由于存在滞后，要处理的区域数量可能会变得非常大。在我的测试中，我看到它一度超过 400。

这些更改将减少操作区域列表所花费的时间，因为创建 1 个新列表比创建复制现有列表所需的所有条目更快。

private final Object regionLock = new Opject;
private List<PaintLog> regions = new LinkedList<PaintLog>();

// In addDirtyRegions()
synchronized(regionLock) {
    regions.add(...);
}

// In updateSharedMemory()
List<PaintLog> regionsCopy;
List<PaintLog> tmp = new LinkedList<PaintLog>()
synchronized(regionLock) {
    regionsCopy = regions;
    regions = tmp;
}