Java Option Definitions

Michael Ossmann michael.ossmann "at"
Sat, 26 Jan 2002 18:57:47 +0000

On Thu, Jan 24, 2002 at 08:25:05PM -0500, Lonnie Cumberland wrote:
> could someone please tell me where I can read some information on the
> Java Options for VNC and in particular on these:
>  <param name="CopyRect" value="Fast">
>  <param name="Raw pixel drawing" value="Reliable">

I don't think there is any documentation for these.  You'll have to look
through the source.  From a quick look, it appears to me that you should
always set both these to Fast.  The Reliable Raw pixel drawing method
appears incredibly inefficient:

      for (int j = y; j < (y + h); j++) {
        for (int k = x; k < (x + w); k++) {
          int pixel =;
          sg.fillRect(k, j, 1, 1);
          pig.fillRect(k, j, 1, 1);

My guess is that the only reason it was ever there was for some
debugging purpose.  These options don't exist in the TightVNC Java
client which looks like it implements the equivalent of "Fast" for both

> I am trying to find a was to speed up the screen updates on the
> client machines and also the colors seem to be off even though I am
> running only 16 bit resolution from my Linux box.

Did you explicitly set the color depth for both the client and the
vncserver processes?

> Any ideas on way to speed up the screen updtes and enhance the colors
> would be greatly appreciated.

Using 8 bit color can speed things up considerably.  Always use
CopyRect.  If bandwidth is not an issue, use hextile encoding rather
than tight or zlib to reduce latency and cpu load.  Try the TightVNC
Java client.

Mike Ossmann, Tarantella/UNIX Engineer/Instructor
Alternative Technology, Inc.
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