Re: CLDC1.1+Jsr184+HW acc+reliable=impossible?

On 8/3/07, Robin Chaddock <[email protected]> wrote:
> I'm curious how the jsr184 api is designed to support underlying hardware
> acceleration when built upon the cldc1.1 platform.
>
> a) CLDC implementations are not required to provide finalizer support; so
> the platform cannot guarantee garbage collection of Java objects will
> trigger the release of their native resources)
> b) Very few of the Java classes (infact only Graphics3D?) have provision for
> explicit dispose()/destroy()/release() methods.
>
> These 2 limitations when coupled together make me think that providing a
> reliable implementation of the jsr184 api when built upon a platform that
> supports only the minimal feature set for CLDC1.1 compatibility is
> fundamentally impossible.
>
> Obviously if the CLDC implementation went beyond it's needed minimum specs,
> such as offering an under-the-hood means of performing object finalization,
> or made the garbage collector aware of native graphics resources - then
> implementing a hardware accelerated jsr184 api would not be so difficult.
>
> This observation appears to approximate reality, as a vast number of
> handsets that 'support' jsr184 do so in very hap-hazard way - typically
> leaking native resources from every proverbial orifice. (Nokias tend to be
> the primarily culprits, but SE and other manufacturers have their fair share
> of broken implementations too)
>

Java's finalize method has been much maligned in Java SE so I find it
curious that you're advocating it for Java ME.  I view finalize as a
last ditch cleanup hook that should be avoided in practice (by
explicit cleanup).

Which additional resources could benefit from explicit cleanup methods?

MIDlets have a few finalize-like notifications already, such as
Canvas.hideNotify(), MIDlet.pauseApp() and MIDlet.destroyApp().

Is it possible for the cleanup methods to hook into one of these?

If so, freeing the HW-acc resources on hideNotify and reacquiring them
on showNotify is the most conservative approach.

--
Joe Bowbeer

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