Getting computed/current style

E

Eric Bednarz

As a side effect of looking into browser-scripting animations I recently
started to look into retrieving CSS values with script (I do agree that
the start values of an animation should ideally be set automatically).

Incidentally, the entity known as inappropriate to cite other than as
work in progress[0] but encouraged to be referenced by the entity formerly
known as the specification/recommendation[1] says:
“Note. Dynamic movement of relatively positioned boxes can produce
animation effects in scripting environments […]â€
<http://www.w3.org/TR/CSS2/visuren.html> 9.4.3

Since I never attempted to retrieve offset values of relatively
positioned elements by script, I wrote a little test case. I included
a column for a popular general purpose library to see if there’s any
magic bullet catch provided.

<http://bednarz.nl/tmp/relative/>

To my surprise the results are actually even worse than I expected. Some
notable observations:
- the only browser I could find that returns useful results is Firefox
3.6 (with the exception of resolving conflicts)
- Opera is totally broken
- jQuery does nothing more than returning the wrong results provided by the
getComputedStyle/currentStyle branch

Encouraging start of my new hobby. :)


Pointers to any good in depth research on the general topic would be
appreciated.




[0] <http://www.w3.org/TR/CSS2/> Status of this document
[1] <http://www.w3.org/TR/2008/REC-CSS2-20080411/>
 
D

David Mark

Eric said:
As a side effect of looking into browser-scripting animations I recently
started to look into retrieving CSS values with script (I do agree that
the start values of an animation should ideally be set automatically).

In many cases, yes. There are three types of animations in My Library:
those that work as transitions (i.e. as effects options for
showElement), those that don't (e.g. the "move" effect) and those that
are dual-purpose (e.g. the "grow" effect). The latter two have to
determine their starting points. Though they are as general purpose in
this task as they come, it is a better idea to know the contexts that
work and design with those in mind.

Some styles are easier animate cross-browser than others. My latest
add-on/example, which I am polishing up today creates effects using CSS3
transform styles and was fairly challenging to get working
cross-browser. Some of my older animations (dating back to the IE4
days) use the clip style extensively, but are strictly transitional
effects (e.g. "slide"), so there was never any need to determine
starting points for those.

I've noticed that many libraries go with a kitchen sink approach and
attempt with a single effect that ostensibly animates any style. I've
always considered that to be a mistake (particularly for performance).
The CSS3 stuff I am working was inspired by Dojo's recent botched
attempt to leverage "complex styles" (e.g. clip, transforms) to create
some new "wowie" effects with their already botched animation mechanism.
They went the kitchen sink route, which ensures that calculating
starting points will be impossible.
Incidentally, the entity known as inappropriate to cite other than as
work in progress[0] but encouraged to be referenced by the entity formerly
known as the specification/recommendation[1] says:
“Note. Dynamic movement of relatively positioned boxes can produce
animation effects in scripting environments […]â€
<http://www.w3.org/TR/CSS2/visuren.html> 9.4.3

Not sure what relative positioning has to do with it.
Since I never attempted to retrieve offset values of relatively
positioned elements by script, I wrote a little test case. I included
a column for a popular general purpose library to see if there’s any
magic bullet catch provided.

In general, relative positions would be the last thing I would want to
animate as the elements' movement often affects surrounding elements
(and in the worst case, the entire document). But in certain contexts
they can be useful.

Yes, they can be a pain to retrieve as well.
To my surprise the results are actually even worse than I expected. Some
notable observations:
- the only browser I could find that returns useful results is Firefox
3.6 (with the exception of resolving conflicts)
- Opera is totally broken
- jQuery does nothing more than returning the wrong results provided by the
getComputedStyle/currentStyle branch

Of course. If you use getElementPositionStyle in My Library, you should
have much better luck. For dimensions, getElementSizeStyle.
Encouraging start of my new hobby. :)

Why aren't you using My Library? :) By coincidence, give me a day or
two and I will have a useful set of examples up that demonstrates how to
create custom effects for it. In creating the Transform add-on's
demonstration page, I refreshed my own memory of how my (somewhat
ancient and some might say primitive) effects mechanisms work and
decided it would be a good idea to share how the new add-on was created,
how it can be used and _most importantly_ how it compares to previously
created effects (e.g. the transition vs. non-transition vs. dual-purpose
concept). It will include copy and paste code snippets (some
dynamically generated) and also a primer on the alert and scrolling
anchors add-ons (the latter of which uses scrolling effects, which fall
into the non-transition category).
Pointers to any good in depth research on the general topic would be
appreciated.

Here's the thing. You can make use of offsetLeft/Top to check your
work. For instance, take your relative position quandary. Note that
you should not do this with elements that have 'none' as their display
style. This should be obvious and My Library makes no attempt to shield
you from such a mistake. Other libraries will go to a lot of trouble to
display, calculate and re-hide the element in this case, but I've always
considered that a mistake (if your app is trying to determine the size
or position of an element that is not part of the layout, then it
clearly has gaps in its logic that should be exposed rather than
spackled over). Sorry to wander off in that direction, but I recently
had somebody claim mine was "broken" because of this behavior. :) So
back to the thing at hand, grab the offsetLeft and offsetTop (verify
beforehand that they are available and numbers of course) then set the
left and top styles to those. Simply put:-

var offsetLeft = el.offsetLeft;
var offsetTop = el.offsetTop;

el.style.left = offsetLeft + 'px';
el.style.top = offsetTop + 'px';

And now for the cunning bit. Compare the new offsetLeft/Top property
values to the old. If they are the same, you "guessed" right. If they
are off, vive la difference! ;)

That's basically it. You can do sizes in the exact same way. If you
think about it, there are several others (e.g. margins) that can be
determined in similar fashion. But then there are a ton of styles that
cannot be determined in any way but to deal with the computed/current
style mess and that's why context is often key to these things (i.e. you
can save yourself a lot of trouble if you consider the issues in your
CSS design). That's why I don't like GP effects (or GP anything for
that matter).

I've tested this and similar techniques in a heart-stopping number of
browsers and have never been surprised by the fact that it works in
virtually all of them.

HTH.
 
D

David Mark

David said:
Eric said:
As a side effect of looking into browser-scripting animations I recently
started to look into retrieving CSS values with script (I do agree that
the start values of an animation should ideally be set automatically).

In many cases, yes. There are three types of animations in My Library:
those that work as transitions (i.e. as effects options for
showElement), those that don't (e.g. the "move" effect) and those that
are dual-purpose (e.g. the "grow" effect). The latter two have to
determine their starting points. Though they are as general purpose in
this task as they come, it is a better idea to know the contexts that
work and design with those in mind.

Some styles are easier animate cross-browser than others. My latest
add-on/example, which I am polishing up today creates effects using CSS3
transform styles and was fairly challenging to get working
cross-browser. Some of my older animations (dating back to the IE4
days) use the clip style extensively, but are strictly transitional
effects (e.g. "slide"), so there was never any need to determine
starting points for those.

I've noticed that many libraries go with a kitchen sink approach and
attempt with a single effect that ostensibly animates any style. I've
always considered that to be a mistake (particularly for performance).
The CSS3 stuff I am working was inspired by Dojo's recent botched
attempt to leverage "complex styles" (e.g. clip, transforms) to create
some new "wowie" effects with their already botched animation mechanism.
They went the kitchen sink route, which ensures that calculating
starting points will be impossible.
Incidentally, the entity known as inappropriate to cite other than as
work in progress[0] but encouraged to be referenced by the entity formerly
known as the specification/recommendation[1] says:
“Note. Dynamic movement of relatively positioned boxes can produce
animation effects in scripting environments […]â€
<http://www.w3.org/TR/CSS2/visuren.html> 9.4.3

Not sure what relative positioning has to do with it.
Since I never attempted to retrieve offset values of relatively
positioned elements by script, I wrote a little test case. I included
a column for a popular general purpose library to see if there’s any
magic bullet catch provided.

In general, relative positions would be the last thing I would want to
animate as the elements' movement often affects surrounding elements
(and in the worst case, the entire document). But in certain contexts
they can be useful.

Yes, they can be a pain to retrieve as well.
To my surprise the results are actually even worse than I expected. Some
notable observations:
- the only browser I could find that returns useful results is Firefox
3.6 (with the exception of resolving conflicts)
- Opera is totally broken
- jQuery does nothing more than returning the wrong results provided by the
getComputedStyle/currentStyle branch

Of course. If you use getElementPositionStyle in My Library, you should
have much better luck. For dimensions, getElementSizeStyle.

I just glanced at the one for positions and it is a little more involved
that the simple example given, but that's mostly because (at the time) I
didn't want it to go through the on-the-fly testing if it didn't have
to. So there is a feature test for broken position reporting (which is
likely not comprehensive) and some other checks to skip some known
problem cases. I should really just simplify it to do the same thing in
all cases as _getting_ the styles doesn't have to be quick.

I also see you are trying to get the right and bottom styles. That I
would advise against and animate the size instead. But given some
thought, if that's the abstraction you really want, I think you can
determine those with similar techniques.
 
D

David Mark

David said:
David said:
Eric said:
As a side effect of looking into browser-scripting animations I recently
started to look into retrieving CSS values with script (I do agree that
the start values of an animation should ideally be set automatically).
In many cases, yes. There are three types of animations in My Library:
those that work as transitions (i.e. as effects options for
showElement), those that don't (e.g. the "move" effect) and those that
are dual-purpose (e.g. the "grow" effect). The latter two have to
determine their starting points. Though they are as general purpose in
this task as they come, it is a better idea to know the contexts that
work and design with those in mind.

Some styles are easier animate cross-browser than others. My latest
add-on/example, which I am polishing up today creates effects using CSS3
transform styles and was fairly challenging to get working
cross-browser. Some of my older animations (dating back to the IE4
days) use the clip style extensively, but are strictly transitional
effects (e.g. "slide"), so there was never any need to determine
starting points for those.

I've noticed that many libraries go with a kitchen sink approach and
attempt with a single effect that ostensibly animates any style. I've
always considered that to be a mistake (particularly for performance).
The CSS3 stuff I am working was inspired by Dojo's recent botched
attempt to leverage "complex styles" (e.g. clip, transforms) to create
some new "wowie" effects with their already botched animation mechanism.
They went the kitchen sink route, which ensures that calculating
starting points will be impossible.
Incidentally, the entity known as inappropriate to cite other than as
work in progress[0] but encouraged to be referenced by the entity formerly
known as the specification/recommendation[1] says:
“Note. Dynamic movement of relatively positioned boxes can produce
animation effects in scripting environments […]â€
<http://www.w3.org/TR/CSS2/visuren.html> 9.4.3
Not sure what relative positioning has to do with it.
Since I never attempted to retrieve offset values of relatively
positioned elements by script, I wrote a little test case. I included
a column for a popular general purpose library to see if there’s any
magic bullet catch provided.
In general, relative positions would be the last thing I would want to
animate as the elements' movement often affects surrounding elements
(and in the worst case, the entire document). But in certain contexts
they can be useful.
Yes, they can be a pain to retrieve as well.
To my surprise the results are actually even worse than I expected. Some
notable observations:
- the only browser I could find that returns useful results is Firefox
3.6 (with the exception of resolving conflicts)
- Opera is totally broken
- jQuery does nothing more than returning the wrong results provided by the
getComputedStyle/currentStyle branch
Of course. If you use getElementPositionStyle in My Library, you should
have much better luck. For dimensions, getElementSizeStyle.

I just glanced at the one for positions and it is a little more involved
that the simple example given, but that's mostly because (at the time) I
didn't want it to go through the on-the-fly testing if it didn't have
to. So there is a feature test for broken position reporting (which is
likely not comprehensive) and some other checks to skip some known
problem cases. I should really just simplify it to do the same thing in
all cases as _getting_ the styles doesn't have to be quick.

I see there is also some additional screwiness in there for determining
hypothetical styles for inline elements (i.e. what would be its style if
it were positioned). So this is not a pure position reporting function.
IIRC, the point of this added complexity was for determining the styles
needed for a positioned overlay.

So I definitely think a simplified version based on the example I posted
will serve you better than that function. It's a common theme in My
Library that some functions are too complex for their own good. I'm
making a note to break that one in two (one for getting true positions
and another to determine positions for aspiring overlays).
 
J

Jorge

(...)
Pointers to any good in depth research on the general topic would be
appreciated.

Whenever I have wanted to obtain the actual position of an element I
have used .offset[Top,Left,Height,Width] rather than getComputedStyle.
 
D

David Mark

Eric said:
As a side effect of looking into browser-scripting animations I recently
started to look into retrieving CSS values with script (I do agree that
the start values of an animation should ideally be set automatically).

Incidentally, the entity known as inappropriate to cite other than as
work in progress[0] but encouraged to be referenced by the entity formerly
known as the specification/recommendation[1] says:
“Note. Dynamic movement of relatively positioned boxes can produce
animation effects in scripting environments […]â€
<http://www.w3.org/TR/CSS2/visuren.html> 9.4.3

Since I never attempted to retrieve offset values of relatively
positioned elements by script, I wrote a little test case. I included
a column for a popular general purpose library to see if there’s any
magic bullet catch provided.

<http://bednarz.nl/tmp/relative/>

To my surprise the results are actually even worse than I expected. Some
notable observations:
- the only browser I could find that returns useful results is Firefox
3.6 (with the exception of resolving conflicts)
- Opera is totally broken
- jQuery does nothing more than returning the wrong results provided by the
getComputedStyle/currentStyle branch

I notice in FF3.6 that all is as expected until box #6, where the right
style is declared as 1px, expected to be computed as "-1px" and the
browser returns "1px" instead. Realize that the "computed" styles
offered by browsers have historically differed from what the
specification calls computed. Regardless, this is a case where the
specification semantics are irrelevant. The results are only wrong (in
a practical sense) if setting the respective styles to the retrieved
values changes the position (or size) of the box (which you will likely
find doesn't happen very often). That gets back to the techniques I
mentioned in the other post. For the right (as opposed to left)
position, the acid test should be something like:-

var offsetWidth = el.offsetWidth;
var rightStyle = yourComputedStyleWrapper(el, 'right');

if (rightStyle !== null) {
el.style.right = rightStyle;

if (el.offsetWidth != offsetWidth) {
// Adjust expectations based on the difference
}
}

A one-off feature test should not be too difficult. But again, I would
stick to animating height/width and forget about right/bottom as those
two have always been notably screwy cross-browser (e.g. some browsers
don't even render them properly).
 
D

David Mark

Jorge said:
(...)
Pointers to any good in depth research on the general topic would be
appreciated.

Whenever I have wanted to obtain the actual position of an element I
have used .offset[Top,Left,Height,Width] rather than getComputedStyle.

But that is perfectly useless for animations in many cases as you can't
set those. ;)
 
J

Jorge

Jorge said:
Whenever I have wanted to obtain the actual position of an element I
have used .offset[Top,Left,Height,Width] rather than getComputedStyle.

But that is perfectly useless for animations in many cases as you can't
set those.  ;)

I said "to obtain" not "to set", David Mark. :)
 
D

David Mark

Jorge said:
Jorge said:
Whenever I have wanted to obtain the actual position of an element I
have used .offset[Top,Left,Height,Width] rather than getComputedStyle.
But that is perfectly useless for animations in many cases as you can't
set those. ;)

I said "to obtain" not "to set", David Mark. :)

Which has no bearing on this discussion, "Jorge". :(
 
G

Garrett Smith

Eric said:
As a side effect of looking into browser-scripting animations I recently
started to look into retrieving CSS values with script (I do agree that
the start values of an animation should ideally be set automatically).

Incidentally, the entity known as inappropriate to cite other than as
work in progress[0] but encouraged to be referenced by the entity formerly
known as the specification/recommendation[1] says:
“Note. Dynamic movement of relatively positioned boxes can produce
animation effects in scripting environments […]â€
<http://www.w3.org/TR/CSS2/visuren.html> 9.4.3

Since I never attempted to retrieve offset values of relatively
positioned elements by script, I wrote a little test case. I included
a column for a popular general purpose library to see if there’s any
magic bullet catch provided.

"Offset" values and top/left style values are different things.
Offset", to me, is about the badly defined and highly inconsistent
"offsetTop", "offsetLeft", and "offsetParent". These properties are
different in IE8, IE7, IE6, Safari 4, Safari 3, Safari 2, and so on. For
every major browser version, there is a different meaning to offsetTop.
So take 5 browsers and take the latest 3 versions, that is a total of 15
different implementations of offsetTop.

I think of animation as being a transition from one state to another in
a given amount of time.

That transition is a dynamic abstraction, and so if we are talking about
animation css style properties, then the animation would not use
offsets, but would use style properties.

FWIS, the code appends relatively positioned children to an BODY that,
in most modern browsers, will have a margin.

What I do not understand is the "expected" column. What are the
expectations coming from?
To my surprise the results are actually even worse than I expected. Some
notable observations:
- the only browser I could find that returns useful results is Firefox
3.6 (with the exception of resolving conflicts)
- Opera is totally broken
- jQuery does nothing more than returning the wrong results provided by the
getComputedStyle/currentStyle branch

To retrieve element coordinate offsets with jQuery, jQuery's offset
method would be the method for that.
 
D

David Mark

Garrett said:
Eric said:
As a side effect of looking into browser-scripting animations I recently
started to look into retrieving CSS values with script (I do agree that
the start values of an animation should ideally be set automatically).

Incidentally, the entity known as inappropriate to cite other than as
work in progress[0] but encouraged to be referenced by the entity
formerly
known as the specification/recommendation[1] says:
“Note. Dynamic movement of relatively positioned boxes can produce
animation effects in scripting environments […]â€
<http://www.w3.org/TR/CSS2/visuren.html> 9.4.3

Since I never attempted to retrieve offset values of relatively
positioned elements by script, I wrote a little test case. I included
a column for a popular general purpose library to see if there’s any
magic bullet catch provided.

"Offset" values and top/left style values are different things. Offset",
to me, is about the badly defined and highly inconsistent "offsetTop",
"offsetLeft", and "offsetParent". These properties are different in IE8,
IE7, IE6, Safari 4, Safari 3, Safari 2, and so on. For every major
browser version, there is a different meaning to offsetTop. So take 5
browsers and take the latest 3 versions, that is a total of 15 different
implementations of offsetTop.

Do you still not understand bow my solution to this problem works?
We've been over this. It doesn't matter how those properties differ per
browser. That's a red herring. What does matter is how they differ on
manipulating the CSS. It's about relatives, not absolutes (and I'm not
talking about the position styles). ;)
I think of animation as being a transition from one state to another in
a given amount of time.

That's what they are. Though I often use the term "transition" to
describe a subset of my effects that relate to showing and hiding
elements. I suppose that could be confusing and will have to think
about that as I update the effects documentation for My Library.
That transition is a dynamic abstraction, and so if we are talking about
animation css style properties, then the animation would not use
offsets, but would use style properties.

Of course. As mentioned to "Jorge", you sure as hell can't set the
offset* properties. They are strictly used to determine required
adjustments to certain styles.
FWIS, the code appends relatively positioned children to an BODY that,
in most modern browsers, will have a margin.

What I do not understand is the "expected" column. What are the
expectations coming from?

The specs I imagine; which, as mentioned, are fairly irrelevant to the
task. What matters is the identity tests (e.g. if you set a style to
its retrieved computed/cascaded style *does it change*. That's the
basic concept and it is very powerful if you can grasp it.
To retrieve element coordinate offsets with jQuery, jQuery's offset
method would be the method for that.

That's another red herring. The absolute position has nothing to do
with it. Try setting the style left/top properties based on _that_ and
you will find that you have nothing close to a GP solution.
 
D

David Mark

David said:
Garrett said:
Eric said:
As a side effect of looking into browser-scripting animations I recently
started to look into retrieving CSS values with script (I do agree that
the start values of an animation should ideally be set automatically).

Incidentally, the entity known as inappropriate to cite other than as
work in progress[0] but encouraged to be referenced by the entity
formerly
known as the specification/recommendation[1] says:
“Note. Dynamic movement of relatively positioned boxes can produce
animation effects in scripting environments […]â€
<http://www.w3.org/TR/CSS2/visuren.html> 9.4.3

Since I never attempted to retrieve offset values of relatively
positioned elements by script, I wrote a little test case. I included
a column for a popular general purpose library to see if there’s any
magic bullet catch provided.
"Offset" values and top/left style values are different things. Offset",
to me, is about the badly defined and highly inconsistent "offsetTop",
"offsetLeft", and "offsetParent". These properties are different in IE8,
IE7, IE6, Safari 4, Safari 3, Safari 2, and so on. For every major
browser version, there is a different meaning to offsetTop. So take 5
browsers and take the latest 3 versions, that is a total of 15 different
implementations of offsetTop.

Do you still not understand bow my solution to this problem works?
We've been over this. It doesn't matter how those properties differ per
browser. That's a red herring. What does matter is how they differ on
manipulating the CSS. It's about relatives, not absolutes (and I'm not
talking about the position styles). ;)

Matter of fact, I am tired of this basic idea (among others) being
obscured by off-track comments about offset* properties. It's
positively maddening. The described technique is useful for animations,
drag and drop or any time you need to get these styles such that they
*will not change the box* on setting them back. It has _nothing_ to do
with what the specs say about "computed" styles or the lack of formal
specs (or consistent cross-browser behavior) for the offset* properties.
All inconsistencies are *factored out* of the equation by design.

<FAQENTRY>

How do I get the current left/top/right/bottom/height/width/etc. styles?

I think I've explained the concept enough times. It's staggeringly
simple (which is why it works). Shouldn't take ten minutes to write an
entry explaining it and sample code. But I'm not writing a word of it
(more than I already have) until it is confirmed that the FAQ maintainer
understands the underlying ideas.

On a related note, that viewport measurement entry is long past due for
an update as well. I've demonstrated the basic generic feature test (as
opposed to the "quirkaround" found in the current entry. The
explanation needs to be changed as well.

http://www.cinsoft.net/viewport.asp
 
G

Garrett Smith

David said:
David said:
Garrett said:
Eric Bednarz wrote:
As a side effect of looking into browser-scripting animations I recently
started to look into retrieving CSS values with script (I do agree that
the start values of an animation should ideally be set automatically).

Incidentally, the entity known as inappropriate to cite other than as
work in progress[0] but encouraged to be referenced by the entity
formerly
known as the specification/recommendation[1] says:
“Note. Dynamic movement of relatively positioned boxes can produce
animation effects in scripting environments […]â€
<http://www.w3.org/TR/CSS2/visuren.html> 9.4.3

Since I never attempted to retrieve offset values of relatively
positioned elements by script, I wrote a little test case. I included
a column for a popular general purpose library to see if there’s any
magic bullet catch provided.

Reading the spec and writing tests is probably better use of time than
learning a library that does it.

I recall you posted a concept in "getComputedStyle Where is My LI", but
as explained there (repeatedly, IIRC), that concept would fail in some
cases.

It doesn't matter how those properties differ per
Matter of fact, I am tired of this basic idea (among others) being
obscured by off-track comments about offset* properties. It's
positively maddening. The described technique is useful for animations,
drag and drop or any time you need to get these styles such that they
*will not change the box* on setting them back. It has _nothing_ to do
with what the specs say about "computed" styles or the lack of formal
specs (or consistent cross-browser behavior) for the offset* properties.
All inconsistencies are *factored out* of the equation by design.

I fail to see how offset coordinates are useful for animations. For
animations, one or more style properties will vary over the course of
the transition, and the transition is best if written as time-based.

Although offsetTop/Left may happen to be the same as CSS left top
values, they are not a corollary. offsetLeft/Top may include margin,
padding, and or border, and may be magic for the root element in various
ways depending on browser and version. In order to use these properties,
it is important to understand the consequences of what happens in what
situation.

They may "work" in a given situation, but how they perform in other
another situation will varies.
<FAQENTRY>

How do I get the current left/top/right/bottom/height/width/etc. styles?

I think I've explained the concept enough times. It's staggeringly
simple (which is why it works). Shouldn't take ten minutes to write an
entry explaining it and sample code. But I'm not writing a word of it
(more than I already have) until it is confirmed that the FAQ maintainer
understands the underlying ideas.

I'm not sure that I understand your idea.

I fail to see what setting style.right have to do with offsetWidth.

A function that returns a string value or null is intransitive.

The null check `rightStyle !== null` could be avoided by having function
`yourComputedStyleWrapper` always return a string value.

| var offsetWidth = el.offsetWidth;
| var rightStyle = yourComputedStyleWrapper(el, 'right');
|
| if (rightStyle !== null) {
| el.style.right = rightStyle;
|
| if (el.offsetWidth != offsetWidth) {
| // Adjust expectations based on the difference
| }
| }

Ideal solutions are simple, but a solution that is simple does not
necessarily work. does not guarantee that something will work.
On a related note, that viewport measurement entry is long past due for
an update as well. I've demonstrated the basic generic feature test (as
opposed to the "quirkaround" found in the current entry. The
explanation needs to be changed as well.

http://www.cinsoft.net/viewport.asp

How is that related?
 
D

David Mark

Garrett said:
David said:
David said:
Garrett Smith wrote:
Eric Bednarz wrote:
As a side effect of looking into browser-scripting animations I
recently
started to look into retrieving CSS values with script (I do agree
that
the start values of an animation should ideally be set automatically).

Incidentally, the entity known as inappropriate to cite other than as
work in progress[0] but encouraged to be referenced by the entity
formerly
known as the specification/recommendation[1] says:
“Note. Dynamic movement of relatively positioned boxes can produce
animation effects in scripting environments […]â€
<http://www.w3.org/TR/CSS2/visuren.html> 9.4.3

Since I never attempted to retrieve offset values of relatively
positioned elements by script, I wrote a little test case. I included
a column for a popular general purpose library to see if there’s any
magic bullet catch provided.

Reading the spec and writing tests is probably better use of time than
learning a library that does it.

Or, just understand some basic equations... The specs are irrelevant
and tests should just confirm your equations are genuine.

Oh for Christ's sake. Really?!
I recall you posted a concept in "getComputedStyle Where is My LI", but
as explained there (repeatedly, IIRC), that concept would fail in some
cases.

No, you are just not seeing the forest for the trees (as happened last
time we had this discussion). Is anyone else confused by what I mean by
"checking your work" with offset* properties?
It doesn't matter how those properties differ per

I fail to see how offset coordinates are useful for animations.

Yes, you fail.
For
animations, one or more style properties will vary over the course of
the transition, and the transition is best if written as time-based.

What does that have to do with the price of beans in Somalia? We are
talking about finding the *initial* styles when they are either
unavailable (often in IE) or you simply want to make sure they are
correct to the pixel (rather than assuming that the browsers' often
"computed" styles are bug-free).
Although offsetTop/Left may happen to be the same as CSS left top
values, they are not a corollary.

Here you go again. You are going off in the weeds. Stop and think
about what I wrote.
offsetLeft/Top may include margin,
padding, and or border, and may be magic for the root element in various
ways depending on browser and version. In order to use these properties,
it is important to understand the consequences of what happens in what
situation.

Nope. The differences are irrelevant for this example. They are
*factored out* of the equations.
They may "work" in a given situation, but how they perform in other
another situation will varies.

You just don't get what I'm saying and I'm tired of trying to explain it
to you. Hopefully the OP has an easier time with the concepts.
I'm not sure that I understand your idea.

I know you don't and it absolutely drives me nuts.
I fail to see what setting style.right have to do with offsetWidth.

I never use the - right - position, but ISTM that setting it will affect
the width of the element.
A function that returns a string value or null is intransitive.

Stop and consider the simpler case of left/top and perhaps you will get it.
The null check `rightStyle !== null` could be avoided by having function
`yourComputedStyleWrapper` always return a string value.

That's beside the point (and contrary to the way computed style methods
work).
| var offsetWidth = el.offsetWidth;
| var rightStyle = yourComputedStyleWrapper(el, 'right');
|
| if (rightStyle !== null) {
| el.style.right = rightStyle;
|
| if (el.offsetWidth != offsetWidth) {
| // Adjust expectations based on the difference
| }
| }

Ideal solutions are simple, but a solution that is simple does not
necessarily work. does not guarantee that something will work.

No kidding. Just so happens that _this_ simple solution does work (at
least I can vouch for left/top/height/width without question). YMMV
with right/bottom.
How is that related?

Related to you burying my (often simple) feature testing ideas in a
bunch of unrelated specification quoting and other confusion (which
results in nothing getting settled in the FAQ).
 
D

David Mark

David said:
Garrett said:
David said:
David Mark wrote:
Garrett Smith wrote:
Eric Bednarz wrote:
As a side effect of looking into browser-scripting animations I
recently
started to look into retrieving CSS values with script (I do agree
that
the start values of an animation should ideally be set automatically).

Incidentally, the entity known as inappropriate to cite other than as
work in progress[0] but encouraged to be referenced by the entity
formerly
known as the specification/recommendation[1] says:
“Note. Dynamic movement of relatively positioned boxes can produce
animation effects in scripting environments […]â€
<http://www.w3.org/TR/CSS2/visuren.html> 9.4.3

Since I never attempted to retrieve offset values of relatively
positioned elements by script, I wrote a little test case. I included
a column for a popular general purpose library to see if there’s any
magic bullet catch provided.
Reading the spec and writing tests is probably better use of time than
learning a library that does it.

Or, just understand some basic equations... The specs are irrelevant
and tests should just confirm your equations are genuine.

Oh for Christ's sake. Really?!
I recall you posted a concept in "getComputedStyle Where is My LI", but
as explained there (repeatedly, IIRC), that concept would fail in some
cases.

No, you are just not seeing the forest for the trees (as happened last
time we had this discussion). Is anyone else confused by what I mean by
"checking your work" with offset* properties?
It doesn't matter how those properties differ per
I fail to see how offset coordinates are useful for animations.

Yes, you fail.
For
animations, one or more style properties will vary over the course of
the transition, and the transition is best if written as time-based.

What does that have to do with the price of beans in Somalia? We are
talking about finding the *initial* styles when they are either
unavailable (often in IE) or you simply want to make sure they are
correct to the pixel (rather than assuming that the browsers' often
"computed" styles are bug-free).
Although offsetTop/Left may happen to be the same as CSS left top
values, they are not a corollary.

Here you go again. You are going off in the weeds. Stop and think
about what I wrote.
offsetLeft/Top may include margin,
padding, and or border, and may be magic for the root element in various
ways depending on browser and version. In order to use these properties,
it is important to understand the consequences of what happens in what
situation.

Nope. The differences are irrelevant for this example. They are
*factored out* of the equations.
They may "work" in a given situation, but how they perform in other
another situation will varies.

You just don't get what I'm saying and I'm tired of trying to explain it
to you. Hopefully the OP has an easier time with the concepts.
I'm not sure that I understand your idea.

I know you don't and it absolutely drives me nuts.
I fail to see what setting style.right have to do with offsetWidth.

I never use the - right - position, but ISTM that setting it will affect
the width of the element.
A function that returns a string value or null is intransitive.

Stop and consider the simpler case of left/top and perhaps you will get it.
The null check `rightStyle !== null` could be avoided by having function
`yourComputedStyleWrapper` always return a string value.

That's beside the point (and contrary to the way computed style methods
work).
| var offsetWidth = el.offsetWidth;
| var rightStyle = yourComputedStyleWrapper(el, 'right');
|
| if (rightStyle !== null) {
| el.style.right = rightStyle;
|
| if (el.offsetWidth != offsetWidth) {
| // Adjust expectations based on the difference
| }
| }

Ideal solutions are simple, but a solution that is simple does not
necessarily work. does not guarantee that something will work.

No kidding. Just so happens that _this_ simple solution does work (at
least I can vouch for left/top/height/width without question). YMMV
with right/bottom.
How is that related?

Related to you burying my (often simple) feature testing ideas in a
bunch of unrelated specification quoting and other confusion (which
results in nothing getting settled in the FAQ).

What the hell. I will try one more time to explain the computed style
trick. God knows, I have nothing better to do but repeat the same
simple concepts over and over.

If you have offsetLeft/Top properties that are numbers you can:-

1. Store them in variables
2. Set the left/top styles to the same (in pixels)
3. Check to see if the offsetLeft/Top properties *changed*

Now, if they didn't change, you've got your start points and can proceed
with the animation (or drag or overlay or whatever) without taking any
further action.

If they did change, what do you suppose your next action should be? I
know I'll regret this, but I'm leaving that as an exercise. And any
mention of the word "intransitive" or citing anything in the
specifications will mean an automatic failure. And don't bother peeking
at My Library either; as mentioned, its rendition of this is too
complicated for its own good.
 
D

David Mark

David said:
David said:
Garrett said:
David Mark wrote:
David Mark wrote:
Garrett Smith wrote:
Eric Bednarz wrote:
As a side effect of looking into browser-scripting animations I
recently
started to look into retrieving CSS values with script (I do agree
that
the start values of an animation should ideally be set automatically).

Incidentally, the entity known as inappropriate to cite other than as
work in progress[0] but encouraged to be referenced by the entity
formerly
known as the specification/recommendation[1] says:
“Note. Dynamic movement of relatively positioned boxes can produce
animation effects in scripting environments […]â€
<http://www.w3.org/TR/CSS2/visuren.html> 9.4.3

Since I never attempted to retrieve offset values of relatively
positioned elements by script, I wrote a little test case. I included
a column for a popular general purpose library to see if there’s any
magic bullet catch provided.

Reading the spec and writing tests is probably better use of time than
learning a library that does it.
Or, just understand some basic equations... The specs are irrelevant
and tests should just confirm your equations are genuine.
"Offset" values and top/left style values are different things.
Offset",
to me, is about the badly defined and highly inconsistent "offsetTop",
"offsetLeft", and "offsetParent". These properties are different in
IE8,
IE7, IE6, Safari 4, Safari 3, Safari 2, and so on. For every major
browser version, there is a different meaning to offsetTop. So take 5
browsers and take the latest 3 versions, that is a total of 15
different
implementations of offsetTop.
Do you still not understand bow my solution to this problem works?
No.
Oh for Christ's sake. Really?!
We've been over this.
I recall you posted a concept in "getComputedStyle Where is My LI", but
as explained there (repeatedly, IIRC), that concept would fail in some
cases.
No, you are just not seeing the forest for the trees (as happened last
time we had this discussion). Is anyone else confused by what I mean by
"checking your work" with offset* properties?
It doesn't matter how those properties differ per
browser. That's a red herring. What does matter is how they differ on
manipulating the CSS. It's about relatives, not absolutes (and I'm not
talking about the position styles). ;)

Matter of fact, I am tired of this basic idea (among others) being
obscured by off-track comments about offset* properties. It's
positively maddening. The described technique is useful for animations,
drag and drop or any time you need to get these styles such that they
*will not change the box* on setting them back. It has _nothing_ to do
with what the specs say about "computed" styles or the lack of formal
specs (or consistent cross-browser behavior) for the offset* properties.
All inconsistencies are *factored out* of the equation by design.

I fail to see how offset coordinates are useful for animations.
Yes, you fail.
For
animations, one or more style properties will vary over the course of
the transition, and the transition is best if written as time-based.
What does that have to do with the price of beans in Somalia? We are
talking about finding the *initial* styles when they are either
unavailable (often in IE) or you simply want to make sure they are
correct to the pixel (rather than assuming that the browsers' often
"computed" styles are bug-free).
Although offsetTop/Left may happen to be the same as CSS left top
values, they are not a corollary.
Here you go again. You are going off in the weeds. Stop and think
about what I wrote.
offsetLeft/Top may include margin,
padding, and or border, and may be magic for the root element in various
ways depending on browser and version. In order to use these properties,
it is important to understand the consequences of what happens in what
situation.
Nope. The differences are irrelevant for this example. They are
*factored out* of the equations.
They may "work" in a given situation, but how they perform in other
another situation will varies.
You just don't get what I'm saying and I'm tired of trying to explain it
to you. Hopefully the OP has an easier time with the concepts.
<FAQENTRY>

How do I get the current left/top/right/bottom/height/width/etc. styles?

I think I've explained the concept enough times. It's staggeringly
simple (which is why it works). Shouldn't take ten minutes to write an
entry explaining it and sample code. But I'm not writing a word of it
(more than I already have) until it is confirmed that the FAQ maintainer
understands the underlying ideas.

I'm not sure that I understand your idea.
I know you don't and it absolutely drives me nuts.
I fail to see what setting style.right have to do with offsetWidth.
I never use the - right - position, but ISTM that setting it will affect
the width of the element.

I should clarify this. Throughout I have been referring to the case of
right/bottom set _in addition to_ left/top. But if left/top are auto,
then right/bottom are just as trivial to compute as left/top. It is the
case where _both_ sides (e.g. left and right) are set to something other
than auto that dimensions come into play. That is a very odd case and
should not be used as some browsers won't render it properly anyway
(just document that it is to be avoided). Instead, set left/top and
height/width to achieve the same box.

This addresses the odd case where left and right are set to something
other than auto.

But will only vary in the case where left/top are not auto. As
counter-intuitive as it may seem, this will work fine for right/bottom
if left/top are auto:-

var offsetLeft = el.offsetLeft;

el.style.right = offsetLeft + 'px';

if (el.offsetLeft != offsetLeft) {
// Adjust according to difference (hint)
}

I don't think I've ever found the need to position an element (with
script) by right/bottom. I've always found it more intuitive to
calculate left/top, but I suppose I should add an option to my
positionElement function to use the other sides as it would be simpler
for some contexts (i.e. wouldn't have to subtract the height and/or
width of the element to determine the destination position).

HTH
 
G

Garrett Smith

[snip a bunch of noise]
If you have offsetLeft/Top properties that are numbers you can:-

1. Store them in variables
2. Set the left/top styles to the same (in pixels)
3. Check to see if the offsetLeft/Top properties *changed*

Now, if they didn't change, you've got your start points and can proceed
with the animation (or drag or overlay or whatever) without taking any
further action.

If they did change, what do you suppose your next action should be? I
know I'll regret this, but I'm leaving that as an exercise. And any
mention of the word "intransitive" or citing anything in the
specifications will mean an automatic failure. And don't bother peeking
at My Library either; as mentioned, its rendition of this is too
complicated for its own good.

Is there a point to any of this?

Does this follow from what you wrote: "How do I get the current
left/top/right/bottom/height/width/etc. styles?"
 
G

Garrett Smith

David said:
Garrett said:
David said:
David Mark wrote:
Garrett Smith wrote:
David Mark wrote:
David Mark wrote:
Garrett Smith wrote:
Eric Bednarz wrote:
[snip a bunch of noise]

You truly are hopeless. You really should be following me ("cinsoft" on
Twitter). Good luck with the FAQ. :)
I don't have much interest in following someone who cannot explain the
reason for his own code (but keep up the marketing and you're bound to
get some fool who will).
 
D

David Mark

Garrett said:
David said:
Garrett said:
David Mark wrote:
David Mark wrote:
Garrett Smith wrote:
David Mark wrote:
David Mark wrote:
Garrett Smith wrote:
Eric Bednarz wrote:
[snip a bunch of noise]

You truly are hopeless. You really should be following me ("cinsoft" on
Twitter). Good luck with the FAQ. :)
I don't have much interest in following someone who cannot explain the
reason for his own code (but keep up the marketing and you're bound to
get some fool who will).

Once again, you are blind. Good luck with that!
 

Ask a Question

Want to reply to this thread or ask your own question?

You'll need to choose a username for the site, which only take a couple of moments. After that, you can post your question and our members will help you out.

Ask a Question

Members online

Forum statistics

Threads
473,744
Messages
2,569,482
Members
44,900
Latest member
Nell636132

Latest Threads

Top