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//Send questions, comments, bug reports, etc. to the authors:
//Rob Warner (rwarner@interspatial.com)
//Robert Harris (rbrt_harris@yahoo.com)
import org.eclipse.swt.SWT;
import org.eclipse.swt.events.*;
import org.eclipse.swt.layout.FillLayout;
import org.eclipse.swt.widgets.*;
/**
* This class demonstrates drawing points. It draws a sine wave.
*/
public class PointExample {
/**
* Runs the application
*/
public void run() {
Display display = new Display();
Shell shell = new Shell(display);
shell.setText("Point Example");
createContents(shell);
shell.open();
while (!shell.isDisposed()) {
if (!display.readAndDispatch()) {
display.sleep();
}
}
display.dispose();
}
/**
* Creates the main window's contents
*
* @param shell the main window
*/
private void createContents(Shell shell) {
shell.setLayout(new FillLayout());
// Create the canvas for drawing on
Canvas canvas = new Canvas(shell, SWT.NONE);
// Add the paint handler to draw the sine wave
canvas.addPaintListener(new PointExamplePaintListener());
// Use a white background
canvas.setBackground(shell.getDisplay().getSystemColor(SWT.COLOR_WHITE));
}
/**
* This class draws a sine wave using points
*/
private class PointExamplePaintListener implements PaintListener {
public void paintControl(PaintEvent e) {
// Get the canvas and its dimensions
Canvas canvas = (Canvas) e.widget;
int maxX = canvas.getSize().x;
int maxY = canvas.getSize().y;
// Calculate the middle
int halfX = (int) maxX / 2;
int halfY = (int) maxY / 2;
// Set the line color and draw a horizontal axis
e.gc.setForeground(e.display.getSystemColor(SWT.COLOR_BLACK));
e.gc.drawLine(0, halfY, maxX, halfY);
// Draw the sine wave
for (int i = 0; i < maxX; i++) {
e.gc.drawPoint(i, getNormalizedSine(i, halfY, maxX));
}
}
/**
* Calculates the sine value
*
* @param x the value along the x-axis
* @param halfY the value of the y-axis
* @param maxX the width of the x-axis
* @return int
*/
int getNormalizedSine(int x, int halfY, int maxX) {
double piDouble = 2 * Math.PI;
double factor = piDouble / maxX;
return (int) (Math.sin(x * factor) * halfY + halfY);
}
}
/**
* The application entry point
*
* @param args the command line arguments
*/
public static void main(String[] args) {
new PointExample().run();
}
}
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