<AWT Dev> Proposal for consolidation of KeyboardFocusManagerPeer

[Oleg Sukhodolsky]

On Tue, Nov 15, 2011 at 1:44 PM, Roman Kennke <roman at kennke.org> wrote:
> Find attached a patch that illustrates the idea (couldn't find a recent
> version of webrev tool online, at least not in
> http://openjdk.java.net/guide/codeReview.html/webrevHelp.html).
>
> It basically moves identical/equivalent code from the peers to java.awt
> package. Notice that this is not yet complete, with this change, the
> methods shouldNativelyFocusHeavyweight() and
> processSynchronousLightweightTransfer() can be removed from the
> KeyboardFocusManagerAccessor and KeyboardFocusManagerPeerImpl classes.
>
> Maybe I am missing something important, i.e. why this code has to be in
> the peers and needs to jump through hoops to satisfy the KFM. ?

I think this is due to the fact that [WX]ComponentPeer are not the
only implementation of ComponentPeer interface,
we also have NullComponentPeer (or something like that) for
lightweight components.
and the code you are moving should be called for heavyweight components only.

Oleg.
>
> Regards, Roman
>
> Am Montag, den 14.11.2011, 22:35 +0100 schrieb Roman Kennke:
>> Hi there,
>>
>> One thing that's bugging me for a while is how the ComponentPeer's
>> requestFocus() method is supposed to work. As far as I could figure out,
>> it's basically always like this (I use KFMHelper to call the
>> corresponding KeyboardFocusManager's private methods by reflection):
>>
>>     public boolean requestFocus(Component lightweightChild, boolean
>> temporary,
>>             boolean focusedWindowChangeAllowed, long time, Cause cause)
>> {
>>         if (KFMHelper.processSynchronousLightweightTransfer(window,
>>                 lightweightChild, temporary, focusedWindowChangeAllowed,
>> time)) {
>>             return true;
>>         }
>>
>>         int result = KFMHelper.shouldNativelyFocusHeavyweight(window,
>>                 lightweightChild, temporary, focusedWindowChangeAllowed,
>> time,
>>                 cause);
>>
>>         switch (result) {
>>         case KFMHelper.SNFH_FAILURE:
>>             return false;
>>         case KFMHelper.SNFH_SUCCESS_PROCEED:
>>                     requestFocusImpl(window, lightweightChild,
>> temporary,
>>                                  focusedWindowChangeAllowed, time,
>> cause);
>>         case KFMHelper.SNFH_SUCCESS_HANDLED:
>>             // Either lightweight or excessive request - all events are
>>             // generated.
>>             return true;
>>         default:
>>             return false;
>>         }
>>     }
>>
>> The only thing that really differs between implementations would be the
>> requestFocusImpl() method call in the SNFH_SUCCESS_PROCEED case. The
>> rest seems to be the same in all implementations, except that in one
>> case (Windows I believe) it is done in JNI while in others (X11) it's
>> done by reflection.
>>
>> I think this can be consolidated by doing the above directly in the
>> KeyboardFocusManager, before calling the peer requestFocus(), and have
>> the peer's requestFocus() only do the requestFocusImpl() handling. This
>> way we could avoid duplicate code and avoid reflection/JNI altogether.
>>
>> Maybe I am missing something?
>>
>> If not, I would work on a patch to move the above KeyboardFocusManager
>> calls into the KFM and have the peer only bothers with the part that is
>> requestFocusImpl() in the above example. Does that sound reasonable? It
>> would certainly make some things simpler in OpenJDK as well as Cacio and
>> the JavaFX SwingView that I am working on.
>>
>> Best regards, Roman
>>
>>
>>
>
>