Hello Daniel,
On 17.11.2013 15:09, Daniel Blaukopf wrote:
Hi Pavel,
I think we we do use CSS to configure feel as well as look - and this
is feel, not look - but I also don’t feel strongly about whether this
needs to be in CSS.
This was exactly my point.
I like your idea of simply picking the closest touch sensitive node
that is within range. That puts the burden on the touch event to
describe what region it covers. On the touch screens we are currently
looking at, a region would be defined as an oval - a combination of
centre point, X diameter and Y diameter. However the touch region can
be any shape, so might need to be represented as a Path.
I don't think we need to be precise about the shape, all of this is
about fixing the imprecise touch where the shape is rather accidental, I
think even a circle with an average diameter would be sufficient to
achieve the goal.
Iterating over pixels just isn’t going to work though. If we have a
300dpi display the touch region could be 150 pixels across and have an
area of nearly 18000 pixels. Instead we’d want a way to ask a parent
node, “In your node hierarchy, which of your nodes’ borders is closest
to this region”. So we’d need to come up with an efficient algorithm
to answer this question. We’d only ask this question for nodes with
extended capture zone.
The nodes with extended capture zone may be fully or partially hidden
behind nodes without it and this needs to be taken into account. How
would it be done when the question would be limited to nodes with
extended capture zone? And even if it wasn't, what would the position of
the border tell us about the area covered by the node? It can be a
line.. Also what I wanted to achieve is pick the node which has visible
pixels in the picking area even if its border is hidden behind other
node or is somewhere far away. This wouldn't be possible, would it?
We could reasonably limit the algorithm to dealing with convex shapes.
Can we? What about paths, polygons etc?
Then we can consider an imaginary line L from the node center point to
the touch center point. The intersection of L with the node perimeter
is the closest point of contact.
It isn't. Imagine a very wide and flat (small height) rectangle and the
touch point directly above its upper-left corner. The closest point is
the corner, not the point on L which is close to rectangle's center and
may be many times farther.
If this point is also within the touch area then we have a potential
match. We iterate over all nearby nodes with extended capture zone in
order to find the best match.
This will then be O(n) in both time and space for n nearby nodes,
given constant time to find the intersection of L with the node
perimeter. This assumption will be true for rectangular, oval and
rounded rectangle nodes.
So in summary, if I understand this algorithm correctly I don't think
it's going to work. On the other hand, I admit that computing 18000
pixels is probably not viable. Right now I don't have any solution, I'll
continue thinking..
Thanks,
Pavel
Thanks,
Daniel
On Nov 15, 2013, at 11:09 PM, Pavel Safrata <pavel.safr...@oracle.com
<mailto:pavel.safr...@oracle.com>> wrote:
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 <https://javafx-jira.kenai/>.
com/browse/RT-34136> for logging this, or open a new JIRA for it
Thanks,
Assaf
