It is not possible to deploy an applet with "click to install" behavior unless DT is used to check for presence of JavaFX
before adding applet to web page.

However,
  a) this does not work if DT is not available (JS disabled, DT plugin disabled/missing, etc)
  b) this does not work with static deployment when applet is added to html statically and then
     JS function is used to "improve UE" (add splash, etc.) then it is not possible to avoid install popup from JRE
     every time page is visited

There could be many different approaches to what would be good mechanism to solve it.
E.g. we can introduce onInstallNeeded js callback and use it if JNLP need to install JavaFX.
However, we may find that FX is needed early and JS context may be not ready yet ...

Other possibility is to pass parameter to disable autoinstall of FX. This does not seem flexible enough as
if DT is not availble then then there is no way for user to request to install it.

Perhaps better way is to support "javaClickToInstall" parameter that will cause some UI to be shown in the applet area
(with question whether user wants to install it).
If this will be child window of applet area (and not top level) then JS can hide it together with applet if needed.
But if JS is not available this will provide some default click to install UI (opt in).