Hi Artem,
Thanks for the detailed evaluation.
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).
Ok, let's try to do it without AWTAccessor and keep the changes in Container
as small as possible.
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.
Ok (like in approach 1). The toLayoutSpace(Point) in Container will become
protected and will do nothing. JLayer will override it.
b. Make findComponentAt() protected. It will then be overridden in JLayer
to respect its inverse transform.
I'm not so sure. First of all, there are two methods in Container that need
adustment:
- findComponentAt Impl(used for lookup of a component that provides a
cursor)
- getMouseEventTargetImpl (used for lookup of a target component for a
MouseEvent)
Both methods use a different lookup approach and follow a chain of method
invocations. Both are quite complicated and have some parameters that
influence the lookup. Overriding them in JLayer would make it necessary to
copy all that code in JLayer and just make one tiny adjustment for the
transform.
Besides, why did we introduce the toLayoutSpace(Point) method? That method
is intended to be used to have the Point transformed, like in version 2
(which you liked) but without the AWTAccessor. That method is introduced
exactly for that purpose!
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).
Hmm.. I share your doubts, but nevertheless.
You forget one thing to mention: the retargeting in LightweightDispatcher
also needs adjustment. In version 2 (which you liked) a call is made to a
private static methods toLayoutSpace(MouseEvent) which uses the AWTAccessor.
This method can be adapted to use the Container.toLayoutSpace(Point) method
to update the MouseEvent. The AWTAccessor pattern is then obsolete.
So, in summary,
1) The implementation in version 2 will be used but without the AWTAccessor.
:
2) Container.toLayoutSpace(Point) will become protected and the Container
implementation does nothing.
3) LightweightDispatcher.toLayoutSpace(MouseEvent) will remain private and
static, but will be rewritten to use Container.toLayoutSpace(Point) in a
hierachy loop.
4) LightweightDispatcher.concatenateHierarchyTransforms() will of course be
removed.
Please let me know if you agree.
Thanks
Piet
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
