<Swing Dev> Fw: review request for 6899434: Add affine transformsupport to JLayer

[Artem Ananiev]

Hi, Piet,

let's try to find if these two approaches could be combined together. 
What I personally like is:

1. There's no changed in Component (approach 1).

2. AWTAccessor is not changed and not used (approach 1).

3. Small changes in Container (approach 2).

As you correctly noticed, we need some (private or public) API to do 
both forward and reverse transforms - to find a component under mouse 
and to send a translated mouse event. Why couldn't we make the following 
minimal changes then:

a. Introduce a new protected method toLayoutSpace() - or whatever it's 
named - which does nothing by default, but overridden in JLayer to 
respect its transform.

b. Make findComponentAt() protected. It will then be overridden in 
JLayer to respect its inverse transform.

As a side effect, this would give the developers a flexibility to use 
non-affine transforms. They will even be able to use different 
transforms for forward and reverse operations, but I doubt anyone will 
want this (or we could add an explicit warning to JavaDoc about this).

Thanks,

Artem

On 2/8/2010 2:27 PM, Piet Blok wrote:
> Hi Artem,
>
> To demonstrate the implemention via the AWTAccessor pattern, I created a
> version 2 implementation:
>
> http://www.pbjar.org/OpenJDK/6899434/version-2/webrev/
>
> This implementation is much cleaner than the original one.
>
> Looking forward for yout comments,
> Piet
>
>
>
>> Hi Artem,
>>
>> The problem with making existing methods public is that it solves only
>> half of the problem at hand:
>>
>> 1) Locate the correct component (can be solved)
>>
>> 2) Recalculating the mouse point from rendered space to layout space
>> is not solved because the locating methods only return a component.
>> Recalculation is needed to correctly set a mouse point in the new
>> events, relative to the target component.
>>
>> In my proposed implementation the shift caused by transformations is
>> stored when looking up the target (for future use: creating new events
>> from the original event). This future is quite an immediate future
>> because creating a new event from an existing event will always be
>> directly preceded by looking up that target event.
>>
>> An alternative would be to again iterate through the hierarchy and do
>> the transformations. This must be done in LightweightDispatcher in the
>> methods:
>>
>> 1) retargetMouseEvent (an inverse transform is needed, so the new
>> Container method getConvertedPoint can be used)
>>
>> 2) eventDispatched. Unfortunately here an ordinary transform is
>> needed, so a second new Container method must be defined that does an
>> ordinary transform.
>>
>> But.... a completely different approach is also possible. I did this
>> in an earlier version, so I know that it works. With this approach no
>> new public or protected methods need to be introduced and no existing
>> methods need to go public or protected. All remains private or package
>> private.
>>
>> That approach is as follows:
>>
>> 1) Define the AffineTransform as a private field in Component.
>>
>> 2) Use the AWTAccessor pattern to make the transform available in
>> Container and LightweightDispatcher and in swing classes.
>>
>> 3) In Container and LightweightDispatcher, get the transform and do
>> transformations when needed.
>>
>> In my opinion, the solution with the AWTAccessor pattern is the
>> cleanest. However, it requires Component and AWTAccessor to be touched.
>>
>> Please let me know what you think.
>>
>> Piet
>>
>>
>>
>>> Hi, Piet,
>>>
>>> I haven't looked through the entire webrev and inspected mostly an
>>> AWT part of the fix. A question is whether it's possible to get rid
>>> of the new "conversionShift" field in Container, to make
>>> transformations support really stateless?
>>>
>>> Another option to consider is to make some of the existing methods
>>> (e.g. getMouseEventTargetImpl()) public instead of introducing new ones.
>>>
>>> Thanks,
>>>
>>> Artem
>>>
>>> On 1/28/2010 8:21 PM, Piet Blok wrote:
>>>> Hello all,
>>>>
>>>> review request for 6899434: Add affine transform support to JLayer
>>>>
>>>> The webrev: http://www.pbjar.org/OpenJDK/6899434/webrev/
>>>>
>>>> The patch covers all the requested functionality. It is concentrated in
>>>> JLayer class, keeping in mind to affect the library as little as
>>>> possible.
>>>>
>>>> 1) A setter and getter for the transform in JLayer
>>>>
>>>> 2) The paint method in JLayer has been adapted to use the transform
>>>>
>>>> 3) RepaintManager has been adapted to propagate repaint requests from
>>>> the view or any of its children to the top level JLayer and have the
>>>> dirty region transformed.
>>>>
>>>> 4) java.awt.Container and java.awt.LightweightDispatcher (both in the
>>>> same source) have been adapted to redispatch MouseEvents to the
>>>> intended
>>>> target component. The lookup for the component that provides a custon
>>>> cursor has also been adapted.
>>>>
>>>> 5) To enable Container to do necessary reculculations, a protected
>>>> method has been introduced that will be overridden by JLayer:
>>>> protected Point getConvertedPoint(Point point).
>>>> (If someone can suggest a better name for this method I'm glad to hear)
>>>>
>>>> 6) A package private method in SwingUtilities has been added that helps
>>>> JPopupMenu and ToolTipManager to find the correct popup location.
>>>> JPopupMenu and ToolTipManager have been changed to use this new method
>>>> in their calculations.
>>>>
>>>> 7) Two jtreg tests have been added.
>>>>
>>>> Looking forward for comments.
>>>>
>>>> Thanks,
>>>> Piet
>>>>
>>>>
>>>>
>>>
>>
>>
>>
>
>