Java Tutorial/SWT 2D Graphics/Line

Draw a thick line

import org.eclipse.swt.graphics.GC;
import org.eclipse.swt.widgets.Display;
import org.eclipse.swt.widgets.Shell;
public class ThickLinkDraw {
  public static void main(String[] args) {
    Display display = new Display();
    Shell shell = new Shell(display);
    shell.open();
    GC gc = new GC(shell);
    gc.setLineWidth(4);
    gc.drawRectangle(20, 20, 100, 100);
    gc.dispose();
    while (!shell.isDisposed()) {
      if (!display.readAndDispatch())
        display.sleep();
    }
    display.dispose();
  }
}

Drawing multiple lines

import org.eclipse.swt.SWT;
import org.eclipse.swt.events.PaintEvent;
import org.eclipse.swt.events.PaintListener;
import org.eclipse.swt.layout.FillLayout;
import org.eclipse.swt.widgets.Canvas;
import org.eclipse.swt.widgets.Display;
import org.eclipse.swt.widgets.Shell;
public class DrawMultipleLine {
  public static void main(String[] args) {
    Display display = new Display();
    Shell shell = new Shell(display);
    shell.setText("Canvas Example");
    shell.setLayout(new FillLayout());
    Canvas canvas = new Canvas(shell, SWT.NONE);
    canvas.addPaintListener(new PaintListener() {
      public void paintControl(PaintEvent e) {
        e.gc.setLineWidth(4);
        int[] points = { 0, 0, 100, 0, 0, 100, 100, 100, 0, 200};
        e.gc.drawPolyline(points);
      }
    });
    shell.open();
    while (!shell.isDisposed()) {
      if (!display.readAndDispatch()) {
        display.sleep();
      }
    }
    display.dispose();
  }
}

Drawing Points, Lines and set line width

drawLine() takes four integers that define two Cartesian points, relative to the upper-left corner of the component.

import org.eclipse.swt.SWT;
import org.eclipse.swt.events.PaintEvent;
import org.eclipse.swt.events.PaintListener;
import org.eclipse.swt.layout.FillLayout;
import org.eclipse.swt.widgets.Canvas;
import org.eclipse.swt.widgets.Display;
import org.eclipse.swt.widgets.Shell;
public class DrawPointLineWidth {
  public static void main(String[] args) {
    Display display = new Display();
    Shell shell = new Shell(display);
    shell.setText("Canvas Example");
    shell.setLayout(new FillLayout());
    Canvas canvas = new Canvas(shell, SWT.NONE);
    canvas.addPaintListener(new PaintListener() {
      public void paintControl(PaintEvent e) {
        Canvas canvas = (Canvas) e.widget;
        int maxX = canvas.getSize().x;
        int maxY = canvas.getSize().y;
        int halfX = (int) maxX/2;
        int halfY = (int) maxY/2;
        e.gc.setForeground(e.display.getSystemColor(SWT.COLOR_BLUE));
        e.gc.setLineWidth(10);
        e.gc.drawLine(halfX, 0, halfX, maxY);
        e.gc.drawLine(0, halfY, maxX, halfY);
      }
    });
    shell.open();
    while (!shell.isDisposed()) {
      if (!display.readAndDispatch()) {
        display.sleep();
      }
    }
    display.dispose();
  }
}

Draw line

import org.eclipse.swt.graphics.GC;
import org.eclipse.swt.widgets.Display;
import org.eclipse.swt.widgets.Shell;
public class DrawLine {
  public static void main(String[] args) {
    Display display = new Display();
    Shell shell = new Shell(display);
    shell.open();
    GC gc = new GC(shell);
    gc.drawLine(0, 0, 19, 19);
    gc.drawLine(19, 0, 0, 19);
    gc.dispose();
    while (!shell.isDisposed()) {
      if (!display.readAndDispatch())
        display.sleep();
    }
    display.dispose();
  }
}

Line Join Style: JOIN_BEVEL, JOIN_MITER, JOIN_ROUND

import org.eclipse.swt.SWT;
import org.eclipse.swt.graphics.GC;
import org.eclipse.swt.widgets.Display;
import org.eclipse.swt.widgets.Event;
import org.eclipse.swt.widgets.Listener;
import org.eclipse.swt.widgets.Shell;
public class LineJoinStyleBevelMiterRound {
  public static void main(String[] args) {
    final Display display = new Display();
    Shell shell = new Shell(display);
    shell.addListener(SWT.Paint, new Listener() {
      public void handleEvent(Event event) {
        int x = 20, y = 20, w = 120, h = 60;
        GC gc = event.gc;
        gc.setForeground(display.getSystemColor(SWT.COLOR_BLUE));
        gc.setLineWidth(10);
        
        int[] joins = { SWT.JOIN_BEVEL, SWT.JOIN_MITER, SWT.JOIN_ROUND };
        for (int i = 0; i < joins.length; i++) {
          gc.setLineJoin(joins[i]);
          gc.drawPolygon(new int[] { x, y, x + w / 2, y + h, x + w, y });
          y += h + 20;
        }
      }
    });
    shell.open();
    while (!shell.isDisposed()) {
      if (!display.readAndDispatch())
        display.sleep();
    }
    display.dispose();
  }
}

Setting Line caps

import org.eclipse.swt.SWT;
import org.eclipse.swt.graphics.GC;
import org.eclipse.swt.widgets.Display;
import org.eclipse.swt.widgets.Event;
import org.eclipse.swt.widgets.Listener;
import org.eclipse.swt.widgets.Shell;
public class LineCapsSetting {
  public static void main(String[] args) {
    final Display display = new Display();
    Shell shell = new Shell(display);
    shell.addListener(SWT.Paint, new Listener() {
      public void handleEvent(Event event) {
        int x = 20, y = 20, w = 120, h = 60;
        GC gc = event.gc;
        gc.setForeground(display.getSystemColor(SWT.COLOR_BLUE));
        gc.setLineWidth(10);
        int[] caps = { SWT.CAP_FLAT, SWT.CAP_ROUND, SWT.CAP_SQUARE };
        for (int i = 0; i < caps.length; i++) {
          gc.setLineCap(caps[i]);
          gc.drawLine(x, y, x + w, y);
          y += 20;
        }
      }
    });
    shell.open();
    while (!shell.isDisposed()) {
      if (!display.readAndDispatch())
        display.sleep();
    }
    display.dispose();
  }
}