- From: Chris Lilley <chris@w3.org>
- Date: Thu, 8 Dec 2011 22:35:45 +0100
- To: SVG WG <public-svg-wg@w3.org>
Hello SVG WG,
Minutes in html at
http://www.w3.org/2011/12/08-svg-minutes.html
and below as text
SVG Working Group Teleconference
08 Dec 2011
[2]Agenda
[2] http://lists.w3.org/Archives/Public/public-svg-wg/2011OctDec/0100.html
See also: [3]IRC log
[3] http://www.w3.org/2011/12/08-svg-irc
Attendees
Present
[IPcaller], ed, heycam, Tav, cyril, Doug_Schepers, ChrisL,
Vincent_Hardy
Regrets
Chair
Cameron
Scribe
ChrisL
Contents
* [4]Topics
1. [5]Sydney f2f
2. [6]text metrics with display: none
3. [7]ignoring trailing semicolons
4. [8]jltf draft review request
5. [9]function based input for animation
6. [10]mesh gradients
* [11]Summary of Action Items
_________________________________________________________
<trackbot> Date: 08 December 2011
<shepazu>
[12]http://blogs.msdn.com/b/ie/archive/2011/12/07/moving-to-standard
s-based-web-graphics-in-ie10.aspx
[12] http://blogs.msdn.com/b/ie/archive/2011/12/07/moving-to-standards-based-web-graphics-in-ie10.aspx
<heycam> cool!
<Tav> cool+!
<scribe> scribenick: ChrisL
<scribe> chair: heycam
Sydney f2f
cc: updated wiki page, location is the novotel
[13]http://www.w3.org/Graphics/SVG/WG/wiki/F2F/Sydney_2012
[13] http://www.w3.org/Graphics/SVG/WG/wiki/F2F/Sydney_2012
cyril: room for 18 people and good connection, checking on vpn and
when the room is open. Should be 8am to 7pm to give us flexibility
<heycam> [14]https://www.w3.org/2002/09/wbs/19480/SydneyF2F2012/
[14] https://www.w3.org/2002/09/wbs/19480/SydneyF2F2012/
cyril: tea, coffee, and lunch included. Three on-site restaurants.
Booked weds-sat inclusive. Rate at the hotel for rooms, shortly
shepazu: conflicting audio wg meeting, might prevent me from
attending
heycam: is this the w3c travel restriction?
shepazu: w3c nowadays does not like sending two staff contacts to a
group. But this makes less sense if the staff contacts are active
technicalcontributors rather than just process guardians
... will sort out soon whether i can attend
ChrisL: should be there, doctor permission, working on travel plans.
responded to survey
cyril: nothing else i can think of - if there are questions please
ask
... vegetarians and other dietary restrictions taken into account
for lunch
text metrics with display: none
<heycam> [15]http://www.w3.org/mid/4ED2EB0B.3050701@mozilla.com
[15] http://www.w3.org/mid/4ED2EB0B.3050701@mozilla.com
heycam: brian birtles brought it up. Behaviour of svg dom text
methods to get number of characters, extent, points along a line of
text
... and whether they count glyphs with display: none. In some cases
the imps count characters in the dom
... replied with my opinion
<heycam> ack
<heycam> ack
<heycam> CL: should be simple, we have definitions for what
visibility:hidden and display:none means
<heycam> … also we have a difference between characters in backing
store and what's displayed
<heycam> … everything that's display:none isn't in the render tree,
which you must be doing if you're measuring the text, they're not
there, they don't have a position
<heycam> … that's separate from indexing into the characters
heycam: agree it should be clear from the spec
... indexing should be based on characters in the backing store.
Other imps dfo not count the display: none characters for indexing
<ed> getNumberOfChars definition from 1.1SE [[ Returns the total
number of characters available for rendering within the current
element, which includes referenced characters from ‘tref’ reference,
regardless of whether they will be rendered. ]]
heycam: there is an issue of what to return if you ask about
characters that are not rendered. need to decide on 0, or NaN or
what
cyril: it can be hard to know if the font engine is only activated
when displayingcharacters
heycam: can depend on glyph shapingand substitution. metrics only
returned on characters that are displayed
<ed>
[16]http://www.w3.org/TR/SVG11/text.html#__svg__SVGTextContentElemen
t__getNumberOfChars
[16] http://www.w3.org/TR/SVG11/text.html#__svg__SVGTextContentElement__getNumberOfChars
ChrisL: I see erik posted about what 1.1se says
heycam: Its not inconsistent
ChrisL: But for the actual position along a path, it does depend on
display: none
heycam: wondered about displaying the position where it *would* be
... but its not the right way as it depends on what that character
is
... and you want to avoid the layout of the text
... so its better to throw an exception or return NaN
ChrisL: which is better, NaN or exceptions?
heycam: in the past we have not used NaN. Either is better than
returning zero
ChrisL: exceptions can return information on why its not displayed -
display: none or off the end of the path or clipped or whatever.
more extensible also
heycam: true
ChrisL; Does the text need changes?
heycam: yes, display: none not handled. indexing is covered but
could be clearer
ed: if its called on textPath or tspan, indexes are from start of
that element not the start of the <text> element
ChrisL: so we have a rationale on how it should work, we now need to
check the text, make changes, add examples and tests
... if these apply to 1.2SE should we add errata?
shepazu: no, a lot of work
ChrisL: yes, if it applies to 1.1
shepazu: remind people how long it took for 1.1se
heycam: mostly because it was a whole new edition, not justerrata
ChrisL: mainly the delay was getting implementations to pass
shepazu: fine to document errata for bugs
... want to avoid refactoring
ChrisL: (scribe missed)
heycam: for this particular issue its a sentence or two
... decide on case by case basis depending on effort needed to
backport
<scribe> ACTION: cameron to propose wording changes and write tests
for text metrics with display: none [recorded in
[17]http://www.w3.org/2011/12/08-svg-minutes.html#action01]
<trackbot> Created ACTION-3180 - Propose wording changes and write
tests for text metrics with display: none [on Cameron McCormack -
due 2011-12-15].
heycam: will reply on thread to update based on this discussion
ignoring trailing semicolons
<heycam> [18]http://www.w3.org/mid/4ED303C7.4010901@mozilla.com
[18] http://www.w3.org/mid/4ED303C7.4010901@mozilla.com
heycam; also from brian, this is for smil animation. some content on
web uses semicolon termination rather than separation so the lest
thing in the attr is a semicolon
scribe: some implementations accept and ignore it, some consider it
invalid. brian proposes to allow ignoring
shepazu; recall this in 1.1 timeframe, i was on Dr Olaf's side and
matching smil was important. Since changed opinion and think
pragmatic choice is to be inconsistent to maximise compat with
implementations and content
heycamq: my view also
<heycam> CL: I want to distinguish ignoring a trailing semicolon and
ignoring null values in the middle of a list
<heycam> … dr olaf's point is that you can have null values and they
can be meaningful, and we shouldn't disallow that
<heycam> … if a null value at the end doesn't make a difference just
ignoring it is a workable solution
heycam: proposal was just to allow a trailing semicolon and if you
have a list of strings then you need an extra semicolon at the end
to distinguish that case
shepazu: most real world cases are not expecting a trailing
semicolon to be a null value
... most people dont understand the smil enough. common in aloop in
script to just output semicolon always
... and also implementatins don't do that
heycam: much more common
... quirky part is requiring ;;; when you really do want a null last
value
shepazu: wish we could search web to see the actual usage
ed: requiring an extra semicolon is not that bad
heycam: we shoud reuse smil unless we have a reason not to , but
should not let it constrain us when we need to improve and clarify
things
<scribe> ACTION: erik to reply on trailing semicolon thread
[recorded in
[19]http://www.w3.org/2011/12/08-svg-minutes.html#action02]
<trackbot> Created ACTION-3181 - Reply on trailing semicolon thread
[on Erik Dahlström - due 2011-12-15].
jltf draft review request
<heycam> [20]http://www.w3.org/mid/4ED5148B.6030100@w3.org
[20] http://www.w3.org/mid/4ED5148B.6030100@w3.org
<heycam> CL: I had a look at this
<heycam> … I was familiar with the previous one
<heycam> … they've added a new section
<heycam> … in terms of SVG, given that currently SVG doesn't
understand how to so more than one line of text -- it doesn't do
layout, or page layout -- and most of this is layout of formatted
text on a page
<heycam> … the affect on SVG is minimal
<heycam> … it does have things about character classes, which might
affect us
<heycam> … so we neither violate it or prohibit it, it doesn't
affect us
<heycam> … as soon as we get wrapping text, 1.2T textArea or HTML
text in a box
<heycam> … there's nothing about ligature formation in there
<heycam> … didn't see anything about :first-letter, which would
affect us
<heycam> … so from a quick pass looking at it, I don't think there's
much impact on SVG directly
heycam: little on layout requirements in figures
<heycam> CL: there is some information about figures, but it's mroe
about layout of figures/captions in the document
ChrisL: yes, nothing on callouts in diagrams
... wonder if this is missing because there is nothing there or
because they didn't consider it
shepazu: its mainlky informed by traditional print media
... example, us uses a green check(tick) for ok and red cross fro
wrong
in japan its a check for wrong and a circle for ok
scribe: there are iconographic conventions that differ in japan.
could be in their scope
ChrisL: we should reply asking them to cover this
shepazu; and we cn also say that we integrate the things that affect
layout via css
<scribe> ACTION: chris respond to jlft review request [recorded in
[21]http://www.w3.org/2011/12/08-svg-minutes.html#action03]
<trackbot> Created ACTION-3182 - Respond to jlft review request [on
Chris Lilley - due 2011-12-15].
function based input for animation
<heycam>
[22]http://www.w3.org/mid/001301ccad4b$c6355c40$52a014c0$@net
[22] http://www.w3.org/mid/001301ccad4b$c6355c40$52a014c0$@net
heycam: this one we asked david for clarificationand he replied
... he wants animate motion but targetting explicit attributes not
the transform
<heycam> <animatePath xlink:href="#curve1" xattribute="cx"
yattribute="cy"/>
<heycam> <animatePath xlink:href="#curve2" xattribute="rx"
yattribute="ry"/>
heycam: he wants to take x and y positions from the curves and apply
them to particular attributes
<heycam> CL: this reminds me of a comment we got a long time ago,
whose profession was an animator
<heycam> … they wanted smooth curves through things, and you
couldn't do much without decomposing beziers into separate
animations
<heycam> … I'm wondering if this feature would let us do what he
wanted
<heycam> … he wanted to be able to animate any attribute as a smooth
function, rather than giving a pointwise list of values and going
dot to dot
heycam: can get this if you animate with a list of values and use
keysplines
... animate motion gives you an essy way to do (paced animation)
<heycam> CL: if you use keySplines, that only gives you smoothness
across a single pair of values, not curve continuity
<heycam> … you would have to calculate it yourself
<heycam> … and I'm not sure you can in all cases
<heycam> … you're looking for tangent continuity where the pieces
join
<ed> note that some svg implementations allow keySpline values
outside the 0..1 range
<heycam> … we've already decided to include catmull rom curves,
which give you curve continuity
ChrisL: yes its valuable for overshoot
heycam: yes for the controlpoints, not sure about the curves
ed: proposal is not much harder than what we already have, it
introduces no new element-to-element dependencies
... so this is not so hard to implement
... and if its useful then we could investigate more
<heycam> CM: I want to be slightly more convinced about use cases,
but I can believe after this discussion that there are some
<heycam> DS: can we say we'll look into variations on this theme for
SVG2, without going in to too much detail?
<heycam> CM: I think that's fine
<heycam>
[23]http://www.w3.org/Graphics/SVG/WG/wiki/SVG2_Requirements_Input#F
unction-based_input_for_.3Canimate.3E
[23] http://www.w3.org/Graphics/SVG/WG/wiki/SVG2_Requirements_Input#Function-based_input_for_.3Canimate.3E
<scribe> scribenick: ChrisL
resolution: we will support path-based animations of pairs of
attributes
<scribe> ACTION: erik to reply to david about function-based
animation [recorded in
[24]http://www.w3.org/2011/12/08-svg-minutes.html#action04]
<trackbot> Created ACTION-3183 - Reply to david about function-based
animation [on Erik Dahlström - due 2011-12-15].
cyril: are these restricted to animating attributes on the same
element
ChrisL: no
heycam: consistent with existing limitation as you can have two
animations, one for x and one for y
mesh gradients
[25]http://www.w3.org/Graphics/SVG/WG/wiki/SVG2GradientsComments
[25] http://www.w3.org/Graphics/SVG/WG/wiki/SVG2GradientsComments
<cyril>
[26]http://www.w3.org/Graphics/SVG/WG/wiki/SVG2GradientsComments
[26] http://www.w3.org/Graphics/SVG/WG/wiki/SVG2GradientsComments
cyril; reviewed this and was reading a paper explaining gradient
mesh technologies
scribe: played in inkscape and illustrator which behave differently
... illustrator shows four patches for editing, but they dont
produce that rendering.
... because they use bilinear interpolation between vertices, not
across patches
cyril: illustrator is generating hundreds of patches to give a
smooth result
... this difference is confusing for people
... in tav's example he uses degenerate meshes with coincident
points, to loose the bilinear interpolation
tav: forgot how i had done it and ran into the same problem as you
cyril: wanted it to be clear that what we have now cannot make
smooth gradients across patches. paper linked from my page describes
another type with color derivatives at mesh points
... paper says that illustrator and corel draw estimate these
derivatives based on a cubic interpolation of the color between two
mesh vertices
... so you have white and red, and you assume a cubic spline
interpolation, use that as a derivative for the color
... want to propose changes to the requirements document, add to
tensor product meshes to list of existing technologies
... and decide if we want those as well
<heycam> ack
<heycam> CL: once you have multiple patches, sometimes you want a
discontinuity
<heycam> … if you think about it as a 2D curve, sometimes you want
them to be continuous, sometimes a sharp change, sometimes
discontiuous
<heycam> … you tend to do that by duplicating control points
<heycam> … first I agree we want smooth interpolation
<heycam> … but you don't always want it
<heycam> … at some extent we're comfortable adding this because
cairo etc. supports it
<heycam> … is there support in underlying libraries for these more
complicated patches?
<heycam> … or can you split them up programmatically so the author
doesn't need to do it, and it doesn't need to be in the DOM?
cyril: agree we need both smooth and sharp interpolation
... also agree its interesting to see what the underlying libraries
have
tav: adobe pdf and postscript only support tensor, whichis coons
with one additional control pooint
cyril: yes there is a difference between what illustrator supports
and what pdf/ps support
tav: how often does this bite you? in black and white its obvious
but when drawing natural objects how often do you meet this?
cyril: graphic designers want control over the transition, smooth to
sharp
tav: can we rely on authoring software to generate this?
<heycam> CL: it's not better if documents need to include many many
small patches
cyril: not asking for the svg to be changed
<heycam> CL: we're also adding catmull rom, perceptually linear
colour spaces, those two things will help with smoother gradients
<heycam> … if the coons patches are doing bilinear interpolation,
can we just say that it uses bicubic? taking two patches into
account?
<heycam> … would that totally break what libraries have?
tav: libraries now create each patch separately
<scribe> ACTION: cyril to add Tensor-product patch meshes to the
list of technologies in the requirements document [recorded in
[27]http://www.w3.org/2011/12/08-svg-minutes.html#action05]
<trackbot> Created ACTION-3184 - Add Tensor-product patch meshes to
the list of technologies in the requirements document [on Cyril
Concolato - due 2011-12-15].
heycam: smooth gradients are a should, if support mens native
support in the language, we might decide not to based on library
support
cyril: and possible fallback to authoring tools
... wil ledit the rwquirements document
<scribe> meeting: SVG WG telcon
Summary of Action Items
[NEW] ACTION: cameron to propose wording changes and write tests for
text metrics with display: none [recorded in
[28]http://www.w3.org/2011/12/08-svg-minutes.html#action01]
[NEW] ACTION: chris respond to jlft review request [recorded in
[29]http://www.w3.org/2011/12/08-svg-minutes.html#action03]
[NEW] ACTION: cyril to add Tensor-product patch meshes to the list
of technologies in the requirements document [recorded in
[30]http://www.w3.org/2011/12/08-svg-minutes.html#action05]
[NEW] ACTION: erik to reply on trailing semicolon thread [recorded
in [31]http://www.w3.org/2011/12/08-svg-minutes.html#action02]
[NEW] ACTION: erik to reply to david about function-based animation
[recorded in
[32]http://www.w3.org/2011/12/08-svg-minutes.html#action04]
[End of minutes]
--
Chris Lilley Technical Director, Interaction Domain
W3C Graphics Activity Lead, Fonts Activity Lead
Co-Chair, W3C Hypertext CG
Member, CSS, WebFonts, SVG Working Groups
Received on Thursday, 8 December 2011 21:35:50 UTC