Region PickOnBounds default setting

John Hendrikx hjohn at
Thu Jun 21 04:39:23 PDT 2012

Not sure if interested, but coming from someone who has never seen this 
before... I must say it certainly looks counter-intuitive.  Why does the 
evilPane have such big bounds?  It is restricted in layout to a max size 
of (50,50)... and thus I would expect the blue child to be clipped and 
the pane Bounds to be reduced to no more than (50,50).

But I guess that is because of the tree style rendering that JavaFX 
does, where nodes can exceed their layout bounds when 
effects/translations are applied... as I said, it certainly looks 
counter-intuitive, in more ways than one coming from someone who is used 
to Container/Groups strictly sized to fit their children, and clipping 
the children that will not fit.


On 21/06/2012 10:44, Pavel Safrata wrote:
> Hi Daniel,
> On 20.6.2012 21:55, Daniel Zwolenski wrote:
>>>> Assuming I understand the problem then I've hit this sort of layout 
>>>> problem and my instinct was to look
>>>> I'm not sure I agree with the bug description when it says that 
>>>> "both visually and in source code there is nothing in between the 
>>>> pane and the child". In code there is a pane. Visually there would 
>>>> be a pane if you set styles on it.
>>> The pane from the description is small and is in a top-left corner. 
>>> It can be styled, and you can see it there. There is no code that 
>>> would make the pane big to cover the whole scene, there is no way to 
>>> make it visible in the whole area, because it's just not there.
>> I am perhaps missing something, but "Pane's bounds will then cover 
>> whole sceen" implies to me the pane is stretched, so if I styled it I 
>> would see it stretched. The description of #2 is a bit vague to me 
>> though. I guess a code example would clear this up but it probably 
>> doesn't matter that I dont understand.
> The pane is not necessarily stretched to embrace all its children. 
> I've attached a code example that shows the problem.
>>>> I'm guessing, for example, if this fix went in it would break all 
>>>> my 'glasspanes'?
>>> I cannot say unless I know how your glasspanes are implemented...
>> I use glass panes to block the screen in two cases: when loading and 
>> behind a light box (ie embedded dialog).
>> In both cases my glass pane is just a pane (eg BorderPane) added to 
>> the top of a StackPane with the rest of the app added to a lower 
>> layer of the stack. In the loading case it has no children, in the 
>> dialog case it's child is the dialog.
>> The loading one is transparent but has an in-progress cursor when you 
>> mouse over. In the dialog case, the pane is a translucent grey, 
>> though you could style it differently and transparent would be a 
>> valid style (making the fill color define if it is clickable would 
>> not be nice for me and is a little scary).
>> In both cases the point of it is that it blocks mouse input to the 
>> scene. I'd prefer this didn't break in a future release (sorry!). If 
>> auto updating (my nemesis) wasn't on then I'd be ok for it to change 
>> and then I fix my apps before moving to a higher version but it 
>> magically working one day and not the next would be pretty nasty for me.
> It would break your glass panes only if they have no fill (which I 
> agree is bad enough). Pane with transparent fill would still block 
> mouse events. I'm not sure why this is scary, this approach is used 
> everywhere in FX except of Region.
>>>> As such, I don't think it needs to be a default attribute now that 
>>>> it's in place the other way round but I do think it needs to be 
>>>> clear and intuitive how to deal with it.
>>> I'm really sad that we've let this go that far, it could have been 
>>> fixed before our first release. If the decision comes that it's too 
>>> late by now, the way how to deal with it will be clear 
>>> (setPickOnBounds(false)), but I doubt it is (and could be) intuitive.
>> For me the current default behavior seems intuitive: the pane is 
>> clickable for whatever area it takes up. I get the feeling I might be 
>> missing something here though as it is obviously a concern for some 
>> people. Sorry if I have misunderstood.
> I think the attached example shows pane that is clickable in area that 
> it doesn't take up.
>> For me the only problem with the current approach is that in some 
>> cases I'd like a pane used purely for layout (anchor pane as top 
>> layer of a StackPane is a prime candidate) to not catch mouse clicks 
>> but the children on it still should. Calling setPickOnBounds(false) 
>> and setShape(null) to do this is not intuitive to me but I'm glad I 
>> now know its possible as I've struggled with this before (and 
>> possibly raised a bug, will have to check).
> This is exactly the most common problem that would be solved. You see 
> you're glad that you now know how to solve it, but other users will 
> keep bumping into this issue..
> Thanks,
> Pavel
>>> Thanks,
>>> Pavel
>>>> On 20/06/2012, at 5:41 AM, Richard Bair<richard.bair at>   
>>>> wrote:
>>>>> Hi folks,
>>>>> We have an issue which has been in the platform from before 2.0: 
>>>>>  A better 
>>>>> explanation of the issue can be found on 
>>>>> From 12258:
>>>>>> Region behaves counter-intuitively regarding mouse event 
>>>>>> delivering. It reacts on mouse events everywhere in its bounds 
>>>>>> and people are often confused by it. Here are two simple examples:
>>>>>> 1) You create let's say HBox just because you want it to layout 
>>>>>> its children. The HBox catches all mouse events in the whole area 
>>>>>> given by its bounds. Often it's hard to understand what area it 
>>>>>> is (with children of different size or with some other layout 
>>>>>> stretches taking place).
>>>>>> 2) You create a small Pane in top-left corner of the scene with a 
>>>>>> child in bottom-right corner of the scene. Pane's bounds will 
>>>>>> then cover whole sceen and you won't be able to click on anything 
>>>>>> else than the pane and its child. Users don't understand why, 
>>>>>> because both visually and in source code there is nothing in 
>>>>>> between the pane and the child.
>>>>>> Moreover, region may have a shape associated and the behavior 
>>>>>> here is also strange. If you create a region with a shape inside 
>>>>>> its bounds, it's just ignored. You can also create a shape 
>>>>>> somewhere else, then it extends region's bounds and it reacts on 
>>>>>> mouse click everywhere between the shape and the region.
>>>>> This issue has to do with the semantics of picking on a Region. 
>>>>> For Region we have had pickOnBounds set to true by default, which 
>>>>> yields the above behaviors. We can change it to false by default, 
>>>>> but then need to update a bunch of skins (for example the up/down 
>>>>> arrows of scroll bar, the thumb of a slider, the down arrow of a 
>>>>> combo box button, etc) so that they switch back to having 
>>>>> pickOnBounds set to true by default so that the target area for 
>>>>> clicks is larger. We could just change the default for Pane and 
>>>>> not for Region, although we use StackPane in Skins and would have 
>>>>> to update them anyhow. It seems that for a normal layout container 
>>>>> the behavior really should be pickOnBounds=false by default, but 
>>>>> for UI controls usages and such you generally want it true.
>>>>> I'm not certain making this change is worth being backwards 
>>>>> incompatible (semantically, binary compatibility would remain). 
>>>>> But what do you think?
>>>>> Richard

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