[news.eclipse.platform.swt] Why would introducing Thread.sleep(5000) pre

[kirillka@xxxxxxxxx (kirillka)]

Hi All,

This is my 2nd little attempts to use SWT and it's working out OK except 
for the following issue. Apologies in advance for a long message (but I 
moved all the code samples to the bottom)...

I am trying to write a screen-saver that would double as an RSS reader.

I create a shell, populate it with the StyledText widget (which will 
contain the text) and get the news stories from Reuters RSS URL (using 
Rome library).

Then I do a little for loop over all the stories and display their 
titles/texts with a 5 sec pause in between. Now, there comes my problem. 
If I comment out the line that effectively sleeps for 5 sec after each 
story, everything works: namely, the shell window appears, and text gets 
rendered on it for all the stories. If I uncomment the sleep line, the 
shell never appears, although the correct debug output goes into the 
console every 5 sec.

Here's the sleep line:

   try { Thread.sleep(5000); } catch (InterruptedException ie) {}

Below are sections of my code. First there is the main class, ImgFeedSS. 
Notice the line in createContents() method:

   f.display2(font, shell, st);

The code for that method is displayed at the bottom.

Thanks, Kirill

======================== code below =========================

Here's the main class, ImgFeedSS:

package net.kirillka.rssss;

import java.io.FileInputStream;
import java.io.FileNotFoundException;
import java.io.IOException;
import java.util.Properties;

import org.eclipse.swt.SWT;
import org.eclipse.swt.graphics.Color;
import org.eclipse.swt.graphics.Cursor;
import org.eclipse.swt.graphics.Font;
import org.eclipse.swt.graphics.ImageData;
import org.eclipse.swt.graphics.PaletteData;
import org.eclipse.swt.graphics.RGB;
import org.eclipse.swt.graphics.Rectangle;
import org.eclipse.swt.widgets.Display;
import org.eclipse.swt.widgets.Event;
import org.eclipse.swt.widgets.Listener;
import org.eclipse.swt.widgets.Shell;
import org.eclipse.swt.custom.StyledText;

public class ImgFeedSS
{
	private Properties props = null;

	/**
	 * The application entry point
	 * 
	 * @param args the command line arguments
	 */
	public static void main(String[] args) throws InterruptedException
	{
		new ImgFeedSS().run();
	}
	
	
	/**
	 * Constructor 
	 */
	public ImgFeedSS()
	{
		props = new Properties();
		try 
		{
			props.load(new FileInputStream(Constants.propertiesFile));
		}
		catch (FileNotFoundException e)
		{
			System.out.println("File " + Constants.propertiesFile + " not found. 
Using defaults.");
		}
		catch (IOException e)
		{
			System.out.println("Could not read file " + Constants.propertiesFile + 
". Using defaults.");
		}
		
		// Overwrite default values
		//if (props.containsKey("rssss.output.dir")) { Constants.outputDir = 
props.getProperty("rssss.output.dir"); } 
		//if (props.containsKey("rssss.output.prefix")) { Constants.outputPrefix 
= props.getProperty("rssss.output.prefix"); }
		if (props.containsKey("rssss.debug")) { Constants.DEBUG = new 
Boolean(props.getProperty("rssss.debug")).booleanValue(); }
	}
	

	/**
	 * Runs the application
	 */
	public void run() throws InterruptedException
	{
		final Display display = new Display();
	    final Shell shell = new Shell(display, SWT.NO_TRIM | SWT.ON_TOP); 	   
// Shell must be created with style SWT.NO_TRIM
		createContents(display, shell);
		shell.open();
		while (!shell.isDisposed())
		{
			if (!display.readAndDispatch()) { display.sleep(); }
		}
		display.dispose();
	}


	/**
	 * Creates the window contents
	 * 
	 * @param shell the parent shell
	 */
	private void createContents(Display display, Shell shell) throws 
InterruptedException
	{
		/**
		 * Black out the shell and make it fill up the whole display 
		 */
		//Browser browser = new Browser(shell, SWT.NONE);
	    shell.setBackground(display.getSystemColor(SWT.COLOR_BLACK));
		Rectangle r = shell.getDisplay().getPrimaryMonitor().getBounds();
		shell.setSize(r.width, r.height);
		shell.setLocation(1000, 0); // for debugging
		//shell.setLocation(0, 0); 
		//shell.forceActive(); // i thought this is necessary to have it on top, 
but the Shell constructor takes care of that
		//shell.forceFocus(); // i thought this is necessary to catch keyboard 
events, but they get caught anyways

	    /**
	     * create a cursor with a transparent image and hide it forever 
(until we exit)
	     */
	    Color white = display.getSystemColor(SWT.COLOR_WHITE);
	    Color black = display.getSystemColor(SWT.COLOR_BLACK);
	    PaletteData palette = new PaletteData(new RGB[] { white.getRGB(), 
black.getRGB() });
	    ImageData sourceData = new ImageData(16, 16, 1, palette);
	    sourceData.transparentPixel = 0;
	    Cursor cursor = new Cursor(display, sourceData, 0, 0);
		shell.setCursor(cursor);
		
		/**
		 * Show feed results onscreen
		 */
		StyledText st = new StyledText(shell, SWT.BORDER | SWT.WRAP | 
SWT.READ_ONLY); // | SWT.V_SCROLL);
		st.setBounds(0, 0, shell.getSize().x, shell.getSize().y);
		st.setBackground(display.getSystemColor(SWT.COLOR_RED));
		st.setForeground(display.getSystemColor(SWT.COLOR_YELLOW));
		Font font = new Font(display,"Arial",16,SWT.NORMAL);
		st.setFont(font);

		FeedFactory factory = new FeedFactory();
		HtmlFeed f = (HtmlFeed) factory.build(Constants.feedUrlString);		
		f.display2(font, shell, st);
		
		/**
		 * exit screen-saver whenever any key is pressed
		 */
		st.addListener(SWT.KeyDown, new Listener() 
		{
			public void handleEvent(Event e)
			{
				System.exit(0);
			}
		});

		/**
		 * exit screen-saver whenever mouse is double-clicked
		 */
		st.addListener(SWT.MouseDoubleClick, new Listener() 
		{
			public void handleEvent(Event e)
			{
				System.exit(0);
			}
		});
	}

}


Here's display2() and a couple of helper functions. Note that this is work 
in progress and a lot of irregularities in the code for now (hopefully :) 
..

	public void display2(final Font font, final Shell s, final StyledText st) 
throws InterruptedException
	{
		System.out.println("HtmlFeed.display2 (using StyledText):");
		final SyndFeed sf = super.getSf();

		String text = ""; 
		System.out.println("HtmlFeed.display2: before the loop");
		for (Object fe : sf.getEntries())
		{
			//get title and text of the entry
			SyndContent title = ((SyndEntry)fe).getTitleEx();
			SyndContent content = (SyndContent) ((SyndEntry)fe).getDescription(); 
//use description field
			System.out.println("HtmlFeed.display2: title: " + title);
			
			if (content == null) // if it's empty, use content # 1
			{
				content = (SyndContent) ((SyndEntry)fe).getContents().get(0);
			}
			
			if (content == null) // if that's empty - return 
			{
				System.out.println("Skipping: " + fe);
				continue; // nothing to display. next loop item, please
			}
			else // content not null, we go on!
			{
				text = htmlToText(content.getValue());
				if (Constants.DEBUG) { System.out.println(text); }
				text = layout2(font, s.getDisplay(), text, s);
				text = title.getValue() + "\n" + text + "\n\n";
				System.out.println("HtmlFeed.display2: text: " + text);
				st.append("\n\n\n" + text);
				// pause a few sec
				Thread.sleep(5000);
				// Commenting out the sleep line below makes the shell window reappear 
- no idea why
				//try { Thread.sleep(5000); } catch (InterruptedException ie) {}
				st.invokeAction(ST.PAGE_DOWN);
			}
		}
		System.out.println("All the news that fit to print - all done!");
	}

	private String layout2(Font f, Display d, String t, Shell s)
	{
		if (Constants.DEBUG) { System.out.println("Full text: [" + t + "]"); }
		if (Constants.DEBUG) { System.out.println("Full text length: [" + 
t.length() + "]"); }
		StringBuffer b = new StringBuffer();
		Rectangle monitor = d.getBounds();
		int lineWidth = getLineLength2(s, monitor, f); // compute the length of 
line
		
		int pos = 0;  // position of the last space in a given line
		int curr = 0; // current position
		String line = "";
		while(curr + lineWidth <= t.length()) // read all lines but the last one 
(which can be incomplete)
		{
			line = t.substring(curr, curr + lineWidth); // get the next lineWidth 
characters into line var
			if (Constants.DEBUG) { System.out.println("Raw Line: [" + line + "]"); }
			pos = line.lastIndexOf(" "); // position of last space in the line var
			if (Constants.DEBUG) { System.out.println("Last index of space: " + 
pos); }
			line = line.substring(0, pos);   // correct the line variable
			if (Constants.DEBUG) { System.out.println("Corrected Line: [" + line + 
"]"); }
			b.append(line);
			b.append("\n");
			if (Constants.DEBUG) { System.out.println("Buffer b is now:\n" + 
b.toString()); }
			curr = curr + line.length() + 1;
		}
		
		// read the last (possibly short) line
		line = t.substring(curr); // get the remainder of t into line var
		if (Constants.DEBUG) { System.out.println("Last (short?) Line: [" + line 
+ "]"); }
		b.append(line);
		b.append("\n\n");
		if (Constants.DEBUG) { System.out.println("Buffer b is now:\n" + 
b.toString()); }

		return b.toString();
	}

	private int getLineLength2(Shell sh, Rectangle r, Font f)
	{
		String s = "a";
		sh.setFont(f);
		GC gc = new GC(sh);
		while(gc.textExtent(s).x < r.width)
		{
			s += "a"; // increment test string			
		}
		if (Constants.DEBUG) { System.out.println("Line length is " + 
(s.length()-1)); }
		return s.length()-1;
	}