java SWT ScrolledComposite在32768像素后切断画布生成的图像

Question

因此，我编写了一个程序，根据给定的“模型”，它会生成一个高度为50像素、长度约为84600像素的水平“时间线”条。每个像素代表一秒，因为它在24小时内以秒为单位模拟事件

问题是，在32768像素之后，该条被切断

我读过一些解决方案，比如使用ScrolledComposite只显示画布的一部分，并在滚动条通过缓冲拖动时显示新数据，但我对如何实现这一点并不熟悉

我看到的另一个解决方案是不使用ScrolledComposite，而只是使用画布。滚动，如果我的源代码正在运行（说明我的问题的测试程序）。问题很明显，滚动条无法滚动以显示整个画布，此“解决方案”的测试程序如下所示。请帮忙

package canvas;

import org.eclipse.swt.SWT;
import org.eclipse.swt.events.PaintEvent;
import org.eclipse.swt.events.PaintListener;
import org.eclipse.swt.graphics.Image;
import org.eclipse.swt.graphics.Point;
import org.eclipse.swt.graphics.Rectangle;
import org.eclipse.swt.layout.FillLayout;
import org.eclipse.swt.widgets.Canvas;
import org.eclipse.swt.widgets.Display;
import org.eclipse.swt.widgets.ScrollBar;
import org.eclipse.swt.widgets.Shell;
import org.eclipse.swt.widgets.Listener;
import org.eclipse.swt.widgets.Event;

public class Test {
static int shellStyle = SWT.NO_REDRAW_RESIZE | SWT.NO_BACKGROUND | SWT.H_SCROLL;
static int canvasStyle = SWT.NO_REDRAW_RESIZE;// | SWT.H_SCROLL | SWT.V_SCROLL;

public static void main(String[] args) {
    final Display display = new Display();
    final Shell shell = new Shell(display, shellStyle);
    shell.setLayout(new FillLayout());
    shell.setBackground(display.getSystemColor((SWT.COLOR_CYAN)));
    shell.setText("Canvas Test");
    Image image;

    final Canvas canvas = new Canvas(shell, canvasStyle);       
    canvas.setLayout(new FillLayout());
    canvas.setBackground(display.getSystemColor(SWT.COLOR_WHITE));

    final Point origin = new Point(0,0);
    final ScrollBar hBar = shell.getHorizontalBar();
    Rectangle size = canvas.getBounds();
    hBar.setMaximum(size.width);
    hBar.setMinimum(0);

    // Create a paint handler for the canvas
    canvas.addPaintListener(new PaintListener() {
      public void paintControl(PaintEvent e) {
        // Do some drawing
          e.gc.setBackground(display.getSystemColor(SWT.COLOR_DARK_YELLOW));
          e.gc.fillRectangle(100, 200, 100, 200);

          e.gc.setBackground(display.getSystemColor(SWT.COLOR_DARK_CYAN));
          e.gc.fillRectangle(900, 200, 600, 200);

          e.gc.setBackground(display.getSystemColor(SWT.COLOR_DARK_MAGENTA));
          e.gc.fillRectangle(500, 200, 300, 200);   

          e.gc.setBackground(display.getSystemColor(SWT.COLOR_GRAY));
          e.gc.fillRectangle(1600, 200, 300, 200);  
      }

    });

 // The below event handlers allow for horizontal scrolling functionality
    hBar.addListener(SWT.Selection, new Listener() {
        public void handleEvent(Event e) {
            int x = 0;
            int hSelection = hBar.getSelection();
            int destX = -hSelection - origin.x;
            Rectangle rect = shell.getBounds();
            canvas.scroll(destX, 0, x, 0, rect.width, rect.height, false);
            origin.x = -hSelection;     
            x = destX;
        }

    });

    shell.addListener(SWT.Resize, new Listener() {
        public void handleEvent(Event e) {
          Rectangle rect = canvas.getClientArea();
          Rectangle client = shell.getClientArea();
          hBar.setMaximum(rect.width);
          hBar.setThumb(Math.min(rect.width, client.width));
          int hPage = rect.width - client.width;
          int hSelection = hBar.getSelection();
          if (hSelection >= hPage) {
            if (hPage <= 0)
              hSelection = 0;
            origin.x = -hSelection;
          }
          shell.redraw();
        }
      });

    shell.open();
    while(!shell.isDisposed()) {
        if(!display.readAndDispatch()) {
            display.sleep();
        }
    }
    display.dispose();

}
}

编辑：嘿，谢谢p12t 只是一个问题。。。这一行： 终点时间线尺寸=新点（84600,50）

那么，这是否意味着每个x轴像素都有一个“点”，但向下50个y轴像素？例如： ++++++++++

因此，每个“+符号”是一个水平x轴像素，84600个“点”是“周期”，如图所示，向下50个y轴像素。我对这一点的理解正确吗？ （顺便说一句，上面的例子说明了10点）

你认为我做错了什么？或者我执行错误了

Answer 1

使用Canvas#scroll(..)绝对是一种方法。我修正了你的例子，画了一个从0到84600的刻度，所以它高于32k的“物理”极限

import org.eclipse.swt.SWT;
import org.eclipse.swt.events.PaintEvent;
import org.eclipse.swt.events.PaintListener;
import org.eclipse.swt.graphics.Point;
import org.eclipse.swt.graphics.Rectangle;
import org.eclipse.swt.layout.FillLayout;
import org.eclipse.swt.widgets.Canvas;
import org.eclipse.swt.widgets.Display;
import org.eclipse.swt.widgets.Event;
import org.eclipse.swt.widgets.Listener;
import org.eclipse.swt.widgets.ScrollBar;
import org.eclipse.swt.widgets.Shell;

public class Test {
static int canvasStyle = SWT.NO_REDRAW_RESIZE | SWT.H_SCROLL; // | SWT.V_SCROLL;

public static void main(String[] args) {
    final Display display = new Display();
    final Shell shell = new Shell(display);
    shell.setLayout(new FillLayout());
    shell.setBackground(display.getSystemColor((SWT.COLOR_CYAN)));
    shell.setText("Canvas Test");

    final Canvas canvas = new Canvas(shell, canvasStyle);       
    canvas.setForeground(display.getSystemColor(SWT.COLOR_BLACK));
    canvas.setBackground(display.getSystemColor(SWT.COLOR_WHITE));

    final Point timelineSize = new Point(84600, 50);
    final Point offset = new Point(0,0);
    final ScrollBar hBar = canvas.getHorizontalBar();

    // Create a paint handler for the canvas
    canvas.addPaintListener(new PaintListener() {
      public void paintControl(PaintEvent e) {
        for (int x = 100; x < timelineSize.x; x += 100)
        {
          e.gc.drawLine(x + offset.x, 0, x + offset.x, 20);
          e.gc.drawText(Integer.toString(x), x + offset.x, 30, true);
        }
      }
    });

 // The below event handlers allow for horizontal scrolling functionality
    hBar.addListener(SWT.Selection, new Listener() {
        public void handleEvent(Event e) {
            int hSelection = hBar.getSelection();
            int destX = -hSelection - offset.x;
            canvas.scroll(destX, 0, 0, 0, timelineSize.x, timelineSize.y, false);
            offset.x = -hSelection;     
        }
    });

    canvas.addListener(SWT.Resize, new Listener() {
        public void handleEvent(Event e) {
          Rectangle client = canvas.getClientArea();
          hBar.setMaximum(timelineSize.x);
          hBar.setThumb(Math.min(timelineSize.x, client.width));
          int hPage = timelineSize.y - client.width;
          int hSelection = hBar.getSelection();
          if (hSelection >= hPage) {
            if (hPage <= 0)
              hSelection = 0;
            offset.x = -hSelection;
          }
          shell.redraw();
        }
      });

    shell.open();
    while(!shell.isDisposed()) {
        if(!display.readAndDispatch()) {
            display.sleep();
        }
    }
    display.dispose();

  }
}