package swtSnippet;

import org.eclipse.swt.SWT;
import org.eclipse.swt.layout.FillLayout;
import org.eclipse.swt.opengl.GLCanvas;
import org.eclipse.swt.opengl.GLData;
import org.eclipse.swt.widgets.Canvas;
import org.eclipse.swt.widgets.Display;
import org.eclipse.swt.widgets.Event;
import org.eclipse.swt.widgets.Shell;

/**
 * This snippet serves two purposes:<p>
 *
 * Demonstrate Eclipse Bug #573782 - https://bugs.eclipse.org/bugs/show_bug.cgi?id=573782<br>
 * On Eclipse 4.14, using a GLCanvas, it is not redrawn after paintControl runs.<p>
 *
 * Demonstrate Eclipse Bug #570649 - https://bugs.eclipse.org/bugs/show_bug.cgi?id=570649<br>
 * On Eclipse 4.19, using a GLCanvas, it throws an error on the readAndDispatch call.<p>
 *
 * When it runs correctly, it opens a Shell with a red line that moves around when you move your mouse over
 * the canvas.
 */
public class SWTSnippet {

	public static void main( String[] args ) {
		Display display = new Display();
		Shell shell = new Shell( display );
		shell.setLayout( new FillLayout() );
		shell.setBounds( 100, 100, 400, 400 );

		// This does not work.
		Canvas canvas = new GLCanvas( shell, SWT.NONE, new GLData() );

		// This works.
		// Canvas canvas = new Canvas( shell, SWT.NONE );

		canvas.addListener( SWT.Paint, event -> handlePaint( event ) );
		canvas.addListener( SWT.MouseMove, event -> canvas.redraw() );

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

	private static void handlePaint( Event event ) {
		int xBegin = 10 + (int) ( Math.random() * 10 );
		int xEnd = 390 - (int) ( Math.random() * 10 );
		int yBegin = 10 + (int) ( Math.random() * 10 );
		int yEnd = 350 - (int) ( Math.random() * 10 );

		event.gc.setLineWidth( 3 );
		event.gc.setForeground( Display.getDefault().getSystemColor( SWT.COLOR_RED ) );
		event.gc.drawLine( xBegin, yBegin, xEnd, yEnd );
	}
}