NewsScroller: NewsMessage.java
package crackers.Scroller;
/**
* This class represents an individual message item in the NewsScroller applet.
* This way, each message can take care of it's own position vs. the applet and
* draw itself.
* <P>
* Each message may contain a URL (and optional target, as found in <A HREF>
* HTML tags) to jump to when it is clicked upon.
* <P>
* This program is copyrighted 1999 by the author under the GNU Public License
* (GPL). Full text of this license is available at
* <A HREF="http://www.gnu.org">GNU.org</A>.
* <P>
* For full usage information, see
* <A HREF="http://www.io.com/~crackers">my web pages</A>.
*
* @author E. A. Graham, Jr. (crackers@io.com)
* @version 2.0
* @see NewsScroller
*/
import java.awt.*;
import java.applet.*;
import java.util.*;
import java.io.*;
import java.net.URL;
import java.net.MalformedURLException;
class NewsMessage {
/**
* The current top position of this message (in pixels).
*/
private int top;
/**
* The height of this message (in pixels).
*/
private int height;
/**
* The maximum width of a line (in pixels). Used for calculating the
* wrapping of lines.
*/
private int maxWidth = 0;
/**
* A URL associated with this message, if any.
*/
private URL link = null;
/**
* A URL target, if any.
*/
private String target = null;
/**
* The font for headlines.
*/
private Font headFont;
/**
* The fontmetric for headlines. Pre-calculated to save those previous
* milliseconds.
*/
private FontMetrics headFM;
/**
* The lines that compose this message's headline.
*/
Vector vHeadline = new Vector();
/**
* The font for the body text.
*/
private Font bodyFont;
/**
* The fontmetric for bodylines. Pre-calculated to save those previous
* milliseconds.
*/
private FontMetrics bodyFM;
/**
* The lines that compose this message's body.
*/
Vector vBody = new Vector();
/**
* The constructor for a new message.
* @param startat the initial position relative to the top of the applet
* @param width the width of the viewable area within the applet
* @param g the graphics context for the applet (to calculate fonts and
* metrics)
* @param fontHead the font to use for headlines
* @param fontBody the font to use for body lines
*/
NewsMessage (int startat,int width,Graphics g,Font fontHead,Font fontBody)
{
// no height initially (duh!) and set the top to the starting position
height = 0;
top = startat;
// hang on to all the other things we need later on
headFont = fontHead;
headFM = g.getFontMetrics(fontHead);
bodyFont = fontBody;
bodyFM = g.getFontMetrics(fontBody);
maxWidth = width - 10; // give it a touch of slack
}
/**
* Change the position of this message. Since the applet is always scrolling
* "up", the position is actually decremented towards 0.
* @param amount the amount to change position
*/
protected void movePosition(int amount)
{
top -= amount;
}
/**
* Reset the current top of this message to another value.
* @param newtop the new position for the top of the message
*/
protected void resetTop(int newtop)
{
top = newtop;
}
/**
* Get the current position of the bottom of this message.
* @return the position of the bottom of the last line in the message in
* pixels
*/
protected int getBottom()
{
return top + height;
}
/**
* Get the current position of the top of this message.
* @return the position of the top of the first headline in pixels
*/
protected int getTop()
{
return top;
}
/**
* Set the link URL for this message. Takes either an absolute URL or a
* relative one to the HTML page the applet is on. If it's invalid, it
* remains unset.
* @param docbase the URL of the HTML page of the applet
* @param s the name of the URL to create
*/
protected void setLink(URL docbase,String s)
{
try
{
if (s.indexOf("http://") >= 0 )
link = new URL(s);
else
link = new URL(docbase,s);
}
catch (MalformedURLException e)
{
link = null;
}
}
/**
* Get this message's URL if the given position is somewhere inside of it.
* @param y the position to check against
* @return the message's URL or null if the position is outside of it
*/
protected URL click(int y)
{
if (y >= top && y <= (top + height))
return(link);
return(null);
}
/**
* Set the URL target for this message.
* @param target the URL target
*/
protected void setTarget(String t)
{
target = new String(t);
}
/**
* Get the URL target for this message.
* @return the URL target
*/
protected String getTarget()
{
return target;
}
/**
* Append a new headline to this message.
* @param s the line to add
*/
protected void addHeadLine(String s)
{
addLine(vHeadline,s,headFM);
}
/**
* Append a new body line to this message.
* @param s the line to add
*/
protected void addMessageLine(String s)
{
addLine(vBody,s,bodyFM);
}
/**
* Add a line to the message. Calculates line-wrapping so text fits within
* the viewable area and updates the height (in pixels) of the message.
* <P>
* Words that are too long for a line by themselves are chopped. Blank lines
* are also allowed.
* @param v the portion of the message this line is to be appended to
* (headlines or body lines)
* @param line the line of text to add
* @param fm the FontMetrics to use for this line
*/
private void addLine(Vector v,String line,FontMetrics fm)
{
// line heights
int h = fm.getHeight();
// add a blank line - fake it by putting a newline in
if (line.length() == 0)
{
v.addElement("\n");
height += h;
return;
}
// If there's already text in there, grab the last line so we can wrap
// it. Remove it so it can be re-appended, depening on the wrapping.
String s;
if (v.size() > 0)
{
s = (String)v.lastElement();
if (s.equals("\n"))
s = line;
else
{
v.removeElement(s);
height -= h;
s += " " + line;
}
}
// otherwise, it's the first line in this portion
else
s = line;
// break our working copy apart on spaces
String t = null;
StringTokenizer toke = new StringTokenizer(s," ");
while (toke.hasMoreTokens())
{
String last = t;
String lastToken = toke.nextToken();
if (t==null)
t = lastToken;
else
t += " " + lastToken;
// now it's too long
if (fm.stringWidth(t) > maxWidth)
{
// eep! the last word itself was too long!
// whittle it down to something that will fit
if (last == null || t.indexOf(' ') < 0)
{
int x;
for (x = 1; x < t.length(); x++)
{
String t2 = t.substring(0,x);
if (fm.stringWidth(t2+"-") > maxWidth) break;
}
v.addElement(t.substring(0,x-1) + "-");
t = t.substring(x);
}
// otherwise, just append the last known line
else
{
v.addElement(last);
t = lastToken;
}
height += h;
}
}
// examine the last remnant
// once again, too long for the line - we can assume it's one word
// because of the nature of the loop above
while (fm.stringWidth(t) > maxWidth)
{
int x;
for (x = 1; x < t.length(); x++)
{
String t2 = t.substring(0,x);
if (fm.stringWidth(t2+"-") > maxWidth) break;
}
v.addElement(t.substring(0,x-1) + "-");
height += h;
t = t.substring(x);
}
// add the last remains
v.addElement(t);
height += h;
}
/**
* Draw the text of this message on the specified Graphics object with the
* specified colors.
* @param g the Graphics object to draw on -- usually an off-screen image
* @param border the width of the border
* @param headColor the color for headlines
* @param msgColor the color for normal text
* @param urlColor the color for linked text
*/
protected void draw (Graphics g,int border,
Color headColor,Color msgColor,Color urlColor)
{
// is this thing even in the picture?
if (top+height <= 0) return;
// do the headlines
g.setColor(headColor);
g.setFont(headFont);
int startat = drawline(g,vHeadline,border,headFM,top);
// then do the message
g.setColor(link==null ? msgColor : urlColor);
g.setFont(bodyFont);
drawline(g,vBody,border,bodyFM,startat);
}
/**
* Draws the specified vector of lines onto a Graphics object using the
* params.
* @param g the Graphics object to draw on -- usually an off-screen image
* @param v the Vector of text lines to draw
* @param border the width of the border
* @param fm the font metrics for the font
* @param start the position to start drawing at
* @return the ending position of this group of lines
*/
private int drawline(Graphics g,Vector v,int border,FontMetrics fm,int start)
{
int h = fm.getHeight();
int y = fm.getAscent();
for (Enumeration e = v.elements(); e.hasMoreElements(); ) {
String s = (String)e.nextElement();
if (s.equals("\n")) s = " ";
g.drawString(s,border+5,start+y);
start += h;
}
return start;
}
}
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