Hello,
let me start with a few comments.
"changing behavior based on which nodes have listeners on them" -
absolutely not. We have capturing, bubbling, hierarchical event types,
so we can't decide which nodes listen (in the extreme case, scene can
handle Event.ANY and perform actions on the target node based on the
event type).
"position does not fall in the boundaries of the node" - I don't think
it will be very harmful. Of course it's possible for users to write
handlers that will be affected, but I don't think it happens often, it
seems quite hard to invent such handler. The delivery mechanism should
be absolutely fine with it, we have other cases like that (for instance,
dragging can be delivered to a node completely out of mouse position).
Of course picking a 3D node in its capture zone would mean useless
PickResult (texture coordinates etc.)
CSS-accessible vs. property-only - I don't have a strong opinion. I
agree it's rather "feel" than "look", on the other hand I think there
are such things already (scrollbar policy for instance).
Now I'll bring another problem to the concept. Take the situation from
Daniel's original picture with two siblings competing for the capture zones:
http://i.imgur.com/ELWamYp.png
Put each of the red children to its own group - they are no longer
siblings, but the competition should still work.
The following may be a little wild, but anyway - have one of the
siblings with capture zone and the other one without it, the one without
it partly covering the one with it. Wouldn't it be great if the capture
zone was present around the visible part of the node (reaching over the
edge of the upper node)? I think it would be really intuitive (fuzzy
picking of what you see), but it's getting pretty complicated.
From now on, I'll call the node with enabled capture zone "touch
sensitive".
The only algorithm I can think of that would provide great results is:
- Pick normally at the center. If the picked node is touch sensitive,
return it.
- Otherwise, run picking for each pixel in the touch area, find the
closest one belonging to a touch sensitive node and return that node (if
there is none, then of course return the node at the center).
Obviously we can hardly do so many picking rounds. But it can be
significantly optimized:
- Perform the area picking in one pass, filling an array - representing
pixels - by the nodes picked on them
- Descend only when bounds intersect with the picking area
- Don't look farther from the center than the already found best match
- Don't look at pixels with already picked node
- For many nodes (rectangular, circular, with pickOnBounds etc.),
instead of testing containment many times, we can quickly tell the
intersection with the picking area
- Perhaps also checking each nth pixel would be sufficient
This algorithm should be reasonably easy to code and very robust (not
suffering from various node-arrangement corner-cases), but I'm still not
sure about the performance (depends mostly on the capture zone size -
30-pixel zones may result in calling contains() nearly thousand times
which might kill it). But perhaps (hopefully) it can be perfected. Right
now I can't see any other algorithm that would work well and would
result in more efficient implementation (the search for overlapping
nodes and closest borders etc. is going to be pretty complicated as
well, if it's even possible to make it work).
What do you think? Any better ideas?
Pavel
On 13.11.2013 22:09, Daniel Blaukopf wrote:
Hi Seeon,
Summarizing our face to face talk today:
I see that the case described by Pavel is indeed a problem and agree
with you that not every node needs to be a participant in the
competition for which grabs touch input. However I’m not keen on the
idea of changing behavior based on which nodes have listeners on them.
CSS seems like the place to do this (as I think Pavel suggested
earlier). In Pavel’s case, either:
- the upper child node has the CSS tag saying “enable extended
capture zone” and the lower child doesn’t: then the upper child’s
capture zone will extend over the lower child
- or both will have the CSS tag, in which case the upper child’s
capture zone would be competing with the lower child’s capture zone.
As in any other competition between capture zones the nearest node
should win. The effect would be the same as if the regular matching
rules were applied on the upper child. It would also be the same as if
only the lower child had an extended capture zone. However, I’d
consider this case to be bad UI programming.
We agreed that “in a competition between capture zones, pick the node
whose border is nearest the touch point” was a reasonable way to
resolve things.
Thanks,
Daniel
On Nov 13, 2013, at 12:31 PM, Seeon Birger <seeon.bir...@oracle.com
<mailto:seeon.bir...@oracle.com>> wrote:
Hi Pavel,
Your example of 'child over child' is an interesting case which
raises some design aspects of the desired picking algorithm:
1. Which node to pick when one node has a 'strict containership' over
the touch center and the other node only has a fuzzy containership
(the position falls in the fuzzy area).
2. Accounting for z-order for extended capture zone area.
3. Accounting for parent-child relationship.
Referring to your 'child over child' example:
http://i.imgur.com/e92qEJA.jpg
The conflict would arise were touch point center position falls in
the capture zone area of child2 but also clearly falls in the strict
bounds of child1.
Generally, when two control nodes compete on same touch event (e.g.
child1 & child2 in Daniel's diagram), it seems that we would like to
give priority to "strict containership" over "fuzzy containership".
But in your case it's probably not the desired behavior.
Also note that in the general case there's almost always exists come
container/background node that strictly contains the touch point, but
it would probably be an ancestor of the child node, so the usual
parent-child relationship order will give preference to the child.
One way out it is to honor the usual z-order for the extended area of
child2, so when a touch center hits the fuzzy area of child2, then
child2 would be picked.
But is not ideal for Daniel's example:
http://i.imgur.com/ELWamYp.png
where the 2 nodes don't strictly overlap, but their capture zones do.
Preferring one child by z-order (which matches the order of children
in the parent) is not natural here. And we might better choose the
node which is "closer"
To the touch point.
So to summarize I suggest this rough picking algorithm:
1. Choose all uppermost nodes which are not transparent to mouse
events and contain the touch point center either strictly or by their
capture zone.
2. Remove all nodes that is strictly overlapped by another node and
is below that node by z-order.
3. Out of those left choose the "closest" node. (the concept of
"closet" should employ some calculation which might not be trivial in
the general case).
4. Once a node has been picked, we follow the usual node chain list
for event processing.
Care must be taken so we not break the current model for event
processing. For example, if a node is picked by its capture zone, it
means that the position does not fall in the boundaries of the node,
so existing event handling code that relies on that would break. So I
think the capture zone feature should be selectively enabled for
certain type of nodes such buttons or other classic controls.
Regards,
Seeon
-----Original Message-----
From: Pavel Safrata
Sent: Tuesday, November 12, 2013 1:11 PM
To: Daniel Blaukopf
Cc: OpenJFX
Subject: Re: discussion about touch events
(Now my answer using external link)
Hello Daniel,
this is quite similar to my idea described earlier. The major
difference is the "fair division of capture zones" among siblings.
It's an interesting idea, let's explore it. What pops first is that
children can also overlap. So I think it would behave like this
(green capture zones
omitted):
Child in parent vs. Child over child: http://i.imgur.com/e92qEJA.jpg
..wouldn't it? From user's point of view this seems confusing, both
cases look the same but behave differently. Note that in the case on
the right, the parent may be still the same, developer only adds a
fancy background as a new child and suddenly the red child can't be
hit that easily. What do you think? Is it an issue? Or would it not
behave this way?
Regards,
Pavel
On 12.11.2013 12:06, Daniel Blaukopf wrote:
(My original message didn't get through to openjfx-dev because I used
inline images. I've replaced those images with external links)
On Nov 11, 2013, at 11:30 PM, Pavel Safrata
<pavel.safr...@oracle.com <mailto:pavel.safr...@oracle.com>
<mailto:pavel.safr...@oracle.com>> wrote:
On 11.11.2013 17:49, Tomas Mikula wrote:
On Mon, Nov 11, 2013 at 1:28 PM, Philipp Dörfler
<phdoerf...@gmail.com
<mailto:phdoerf...@gmail.com><mailto:phdoerf...@gmail.com>> wrote:
I see the need to be aware of the area that is covered by fingers
rather than just considering that area's center point.
I'd guess that this adds a new layer of complexity, though. For
instance:
Say we have a button on some background and both the background and
the button do have an onClick listener attached. If you tap the
button in a way that the touched area's center point is outside of
the buttons boundaries - what event will be fired? Will both the
background and the button receive a click event? Or just either the
background or the button exclusively? Will there be a new event
type which gets fired in case of such area-based taps?
My suggestion would therefore be to have an additional area tap
event which gives precise information about diameter and center of
the tap. Besides that there should be some kind of "priority" for
choosing which node's onClick will be called.
What about picking the one that is closest to the center of the touch?
There is always something directly on the center of the touch
(possibly the scene background, but it can have event handlers too).
That's what we pick right now.
Pavel
What Seeon, Assaf and I discussed earlier was building some fuzziness
into the node picker so that instead of each node capturing only
events directly on top of it:
Non-fuzzy picker: http://i.imgur.com/uszql8V.png
..nodes at each level of the hierarchy would capture events beyond
their borders as well:
Fuzzy picker: http://i.imgur.com/ELWamYp.png
In the above, "Parent" would capture touch events within a certain
radius around it, as would its children "Child 1" and "Child 2". Since
"Child 1" and "Child 2" are peers, they would have a sharp division
between them, a watershed on either side of which events would go to
one child node or the other. This would also apply if the peer nodes
were further apart; they would divide the no-man's land between them.
Of course this no-man's land would be part of "Parent" and could could
be touch-sensitive - but we won't consider "Parent" as an event target
until we have ruled out using one of its children's extended capture
zones.
The capture radius could either be a styleable property on the nodes,
or could be determined by the X and Y size of a touch point as
reported by the touch screen. We'd still be reporting a touch point,
not a touch area. The touch target would be, as now, a single node.
This would get us more reliable touch capture at leaf nodes of the
node hierarchy at the expense of it being harder to tap the
background. This is likely to be a good trade-off.
Daniel
Tomas
Maybe the draw order / order in the scene graph / z buffer value
might be sufficient to model what would happen in the real,
physical world.
Am 11.11.2013 13:05 schrieb "Assaf Yavnai"
<assaf.yav...@oracle.com <mailto:assaf.yav...@oracle.com>
<mailto:assaf.yav...@oracle.com>>:
The ascii sketch looked fine on my screen before I sent the mail
:( I hope the idea is clear from the text (now in the reply dialog
its also look good)
Assaf
On 11/11/2013 12:51 PM, Assaf Yavnai wrote:
Hi Guys,
I hope that I'm right about this, but it seems that touch events
in glass are translated (and reported) as a single point events
(x & y) without an area, like pointer events.
AFAIK, the controls response for touch events same as mouse
events (using the same pickers) and as a result a button press,
for example, will only triggered if the x & y of the touch event
is within the control area.
This means that small controls, or even quite large controls
(like buttons with text) will often get missed because the 'strict'
node picking,
although from a UX point of view it is strange as the user
clearly pressed on a node (the finger was clearly above it) but
nothing happens...
With current implementation its hard to use small features in
controls, like scrollbars in lists, and it almost impossible to
implement something like 'screen navigator' (the series of small
dots in the bottom of a smart phones screen which allow you to
jump directly to a 'far away'
screen)
To illustrate it consider the bellow low resolution sketch, where
the "+"
is the actual x,y reported, the ellipse is the finger touch area
and the rectangle is the node.
With current implementation this type of tap will not trigger the
node handlers
__
/ \
/ \
___/ __+_ \___ in this scenario the 'button' will not get
pressed
| \ / |
|___\ ___ / __ |
\___/
If your smart phone support it, turn on the touch debugging
options in settings and see that each point translate to a quite
large circle and what ever fall in it, or reasonably close to it,
get picked.
I want to start a discussion to understand if my perspective is
accurate and to understand what can be done, if any, for the
coming release or the next one.
We might use recently opened RT-34136 <https://javafx-jira.kenai.
com/browse/RT-34136> for logging this, or open a new JIRA for it
Thanks,
Assaf
