Created attachment 838 [details]
Screenshot showing the client optimization options
Looking at the code, it seems like the maximum "custom compression level" is 9, but the client options interface says it's 6.
The documentation also says it is 9.
Relevant part of the documentation:
See also bug 5909.
We should also see how to present this range in a useful manner as not all values are equally useful. Should probably also look over the documentation for this setting to make sure it is understandable. E.g. this is mainly a setting for _server_ CPU usage, not client (although that can be a side effect).
On the same theme, "best" and "fast" are probably not the clearest way to describe the trade off here.
Also note bug 7109 which covers documenting the comparing update tracker, a feature that is influenced by the compression setting.
The custom compression level description has been properly updated to range from 1-9 upstream:
There was further confusion regarding the custom compression level range in RFB proto. One place of the specification stated 1-9 and another 0-9, this has been sorted now, and the proper range is 0-9:
Fixed in TigerVNC:
This got fixed as part of the vendor drop in bug 7373.