These are the most frequently asked questions that I get about LED Sign. I will continue to add new questions/answers as they arise. So, if you have any questions concerning LED Sign, check this FAQ first. If you do not find an answer to your question, feel free to contact me (Darrick Brown) at dbrown@cs.hope.edu.
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Q: I downloaded the LEDSign.tar.gz and have it installed on my
machine. When I try to load the page in Netscape 2.0 I get a
"Applet can't start: applet not initialized" error and the applet
does not run. How do I fix this?
A: This problem can be caused by two situations:
1. You need to load the page over a URL with "http://...". If you
are loading it localy with "file://..." you will get the
initialization error.
2. You need to make sure that all the file names and paths are
correct in the <applet> tag in the html page. If the applet
can't find the files that it needs it won't be able to run and
it will give the "init" error.
<applet codebase="../LED" code="LED.class" width=519 height=64>
<param name="script" value="../scripts/Demo.led">
<param name="font" value="../fonts/default.font">
<param name="border" value="3">
<param name="bordercolor" value="100,130,130">
<param name="spacewidth" value="3">
<param name="wth" value="100">
<param name="ledsize" value="3">
<blockquote>
<hr>
If you were using a Java-enabled browser,
you would see a scrolling text sign instead of this paragraph.
<hr>
</blockquote>
</applet>
This is the example tag that is found in LED.html in the
distribution. The tags that are critical are codebase, code,
script, and font. These paths and files must be correct
including capitialization. Codebase is the path to where the
".class" files can be found. Code is the main bytecode
"executable" file. Script is the LED script that the sign will
run. And font is the font file that the sign will use to
display the characters.
If you are working on a Win95/NT system and your version of tar
changes file name size (truncates to the MS-DOS 8.3) or
changes capitalization, then change the file/paths names so they
match the following structure. This is what the LEDSign
hierarchy should look like: (the slashes will be backslashes if
you are on MS-Windows95/NT).
./LEDSign
./LEDSign/LED
./LEDSign/LED/Index.java
./LEDSign/LED/LED.class
./LEDSign/LED/FuncInfo.java
./LEDSign/LED/LED.java
./LEDSign/LED/Pixelize.class
./LEDSign/LED/Script.class
./LEDSign/LED/Script.java
./LEDSign/LED/LEDMessage.class
./LEDSign/LED/Letters.class
./LEDSign/LED/Index.class
./LEDSign/LED/linkList.class
./LEDSign/LED/FuncInfo.class
./LEDSign/LED/LEDMessage.java
./LEDSign/LED/Letters.java
./LEDSign/LED/linkList.java
./LEDSign/README
./LEDSign/Revisions
./LEDSign/WWW
./LEDSign/WWW/LED.html
./LEDSign/WWW/script.html
./LEDSign/WWW/font.html
./LEDSign/WWW/options.html
./LEDSign/fonts
./LEDSign/fonts/default.font
./LEDSign/fonts/charter.font
./LEDSign/index.html
./LEDSign/scripts
./LEDSign/scripts/Demo.led
./LEDSign/scripts/example.led
./LEDSign/COPYRIGHT
Once all the paths and filenames are correct. The applet will
run.
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Q: When I try to load the applet I get a list of errors that looks like:
[no properties loaded, using defaults]
Thread-1 find class LED
Opening stream to: file:/C:/java/demo/ledsign/led/LED.class to get LED
Thread-1 find class Pixelize
Opening stream to: file:/C:/java/demo/ledsign/led/Pixelize.class to get Pixelize
*** Security Exception: file.read:\C:\java\demo\ledsign\led\Pixelize.class ***
sun.applet.AppletSecurityException: security.file.read: \C:\java\demo\ledsign\le
d\Pixelize.class
at sun.applet.AppletSecurity.checkRead(AppletSecurity.java:226)
at java.io.FileInputStream.(FileInputStream.java:49)
.
.
.
What is going on? How can I fix this?
A: This is a security exception. There are two things that could be
happening.
1. The permissions on the .class, script, and/or font files are set
incorrectly. Make sure that these files are readable by everyone.
2. The your security settings in netscape are too strict. Check your
security settings (under the "Options" menu in netscape). Change
them to be more lenient and make sure that the "Disable java" option
is off.
In the example above, netscape is throwing an error because it has
"illeagally" accessed "Pixelize.class".
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Q: Is possible to use two or more fonts at same time?
A: No, not with the current version of LEDSign. I am considering
adding this to the next version of LEDSign. It will be somewhat
difficult to add. So, I might add it, maybe not.
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Q: Can I make a font file to use special unicode (2-byte) characters such
as a Chinese or Japanese character set?
A: No. This would require a relatively large modification of the source
code. It will probably never be supported. However, you could design a
font file that assigns each of the ascii characters to a unicode
character.
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