Re: [svg-developers] explaining setAttribute, setAttributeNS and carburetors
Jacob, Doug and Wade, Thanks for your assistance here. It definitely helps! regards David - Original Message - From: Jacob Beard To: svg-developers Sent: Sunday, October 17, 2010 3:59 AM Subject: Re: [svg-developers] explaining setAttribute, setAttributeNS and carburetors On Sun, Oct 17, 2010 at 6:48 AM, Doug Schepers d...@schepers.cc wrote: But in this case, the only thing to know there is that (for whatever reason) attributes are generally in the 'null' namespace (*not* in the SVG or HTML or whatever host-language namespace). I recommend teaching setAttribute for normal attributes, and setAttributeNS only for xlink:href. The DOM Level 2 Core spec has something to say about mixing namespace-aware DOM methods with non-namespace-aware DOM methods: Note: DOM Level 1 methods are namespace ignorant. Therefore, while it is safe to use these methods when not dealing with namespaces, using them and the new ones at the same time should be avoided. DOM Level 1 methods solely identify attribute nodes by their nodeName. On the contrary, the DOM Level 2 methods related to namespaces, identify attribute nodes by their namespaceURI and localName. Because of this fundamental difference, mixing both sets of methods can lead to unpredictable results. In particular, using setAttributeNS, an element may have two attributes (or more) that have the same nodeName, but different namespaceURIs. Calling getAttribute with that nodeName could then return any of those attributes. The result depends on the implementation. Similarly, using setAttributeNode, one can set two attributes (or more) that have different nodeNames but the same prefix and namespaceURI. In this case getAttributeNodeNS will return either attribute, in an implementation dependent manner. The only guarantee in such cases is that all methods that access a named item by its nodeName will access the same item, and all methods which access a node by its URI and local name will access the same node. For instance, setAttribute and setAttributeNS affect the node that getAttribute and getAttributeNS, respectively, return. http://www.w3.org/TR/DOM-Level-2-Core/core.html So, it seems like if you're strictly following the spec, mixing setAttribute and setAttributeNS might not be the best idea, as it may lead to inconsistent results across implementations. In practice, I very rarely use the non-namespaced versions (only when I need to do a bit of HTML DOM scripting in IE), so this may work just fine. Best, Jake [Non-text portions of this message have been removed] - To unsubscribe send a message to: svg-developers-unsubscr...@yahoogroups.com -or- visit http://groups.yahoo.com/group/svg-developers and click edit my membership Yahoo! Groups Links * To visit your group on the web, go to: http://groups.yahoo.com/group/svg-developers/ * Your email settings: Individual Email | Traditional * To change settings online go to: http://groups.yahoo.com/group/svg-developers/join (Yahoo! ID required) * To change settings via email: svg-developers-dig...@yahoogroups.com svg-developers-fullfeatu...@yahoogroups.com * To unsubscribe from this group, send an email to: svg-developers-unsubscr...@yahoogroups.com * Your use of Yahoo! Groups is subject to: http://docs.yahoo.com/info/terms/
Re: [svg-developers] explaining setAttribute, setAttributeNS and carburetors
Hi, Jacob- Jacob Beard wrote (on 10/17/10 3:59 AM): Note: DOM Level 1 methods are namespace ignorant. Therefore, while it is safe to use these methods when not dealing with namespaces, using them and the new ones at the same time should be avoided. Thanks for digging that up. I think the author of that may actually have been a bit confused... or at least, they didn't state the facts clearly. (There may have been a bit of propagandizing there, as well, to get people to use XML namespaces more, perhaps.) Indeed, if you try to set a namespaced attribute with setAttribute(), it won't work correctly... the attribute will be placed in the null namespace. So, when you use el.setAttribute( xlink:href, #foo ); it's the equivalent of using el.setAttributeNS( null, xlink:href, #foo ); where the local node-name (unintuitively) is 'xlink:href', not 'href' in the XLink namespace. But that's only when you're dealing with namespaces. Since most attributes are in the null namespace, and setAttribute() places everything in the null namespace, then these are equivalent and perfectly safe: el.setAttribute( fill, #f00 ); el.setAttributeNS( null, fill, #f00 ); As an aside, this is actually a rather poor design, which could have been made better if they had simply accounted for hardcoded prefixed to be bound to specific namespaces, rather than introducing the arbitrary level of abstraction where any namespace could have any prefix string; this is made a bit simpler in HTML5, which does define a few hardcoded prefixes for namespaces. Maybe in some future version of XML, XML Namespaces, or the like, this can be be expanded beyond HTML. Regards- -Doug - To unsubscribe send a message to: svg-developers-unsubscr...@yahoogroups.com -or- visit http://groups.yahoo.com/group/svg-developers and click edit my membership Yahoo! Groups Links * To visit your group on the web, go to: http://groups.yahoo.com/group/svg-developers/ * Your email settings: Individual Email | Traditional * To change settings online go to: http://groups.yahoo.com/group/svg-developers/join (Yahoo! ID required) * To change settings via email: svg-developers-dig...@yahoogroups.com svg-developers-fullfeatu...@yahoogroups.com * To unsubscribe from this group, send an email to: svg-developers-unsubscr...@yahoogroups.com * Your use of Yahoo! Groups is subject to: http://docs.yahoo.com/info/terms/
[svg-developers] explaining setAttribute, setAttributeNS and carburetors
I don't really understand carburetors, but I have a vague idea that they control the richness of the fuel mixture so as to calibrate the rate of combustion in the engine -- for me, the following issue is similar. Perhaps you can help. I'm trying to explain how to do a wee bit of DOM scripting to those who don't necessarily have any programming background, let alone DOM scripting in SVG. I generally get around the topic on my own, okay, without really understanding some of the more esoteric subjects like DOCTYPE and namespaces and so forth -- I just do what people tell me to and it usually works. In truth, I consider all such things to be incantations required for me to pay homage to the systems gurus who have figured out how to glue all the pieces together. They are like taxes, and it is generally not crucial that I understand them so long as I do what is required. On the other hand, once every so often I find myself having to explain things to others. And it is at these times that I find myself thinking that perhaps I should understand such myseries (did I forget a t in the last word? oops) a bit deeper than I do. Hence the following question: I know that R.setAttributeNS(null,fill, red)is the proper construction (for SVG but not HTML), rather than R.setAttribute(fill, red)I also know that in every SVG viewer I have seen, the latter has equivalent behavior to the former (for SVG but not HTML), . I think I was told once that the SVG spec (or maybe it is the XML spec, or one or another DOM spec), for some mysterious reason, leaves room for some future browser manufacturer to make a browser in which the latter construction wouldn't work. So, as per my oversimplified understanding, we use the more arcane construction (and its extra seven keystrokes and the extra 80,000 neural synapses) in anticipation of such a possible future. I truly don't rue the seven keystrokes, as much as all the norepinephrine, seratonin and the like. So as I say, it is not important that I understand it. There may be, already, a shortage of norepinephrine which would preclude me from ever understanding it. But what words might I use to explain this oddity to others? If I happen to understand your explanation that will be a serendipitous but unexpected side-effect! cheers David - To unsubscribe send a message to: svg-developers-unsubscr...@yahoogroups.com -or- visit http://groups.yahoo.com/group/svg-developers and click edit my membership Yahoo! Groups Links * To visit your group on the web, go to: http://groups.yahoo.com/group/svg-developers/ * Your email settings: Individual Email | Traditional * To change settings online go to: http://groups.yahoo.com/group/svg-developers/join (Yahoo! ID required) * To change settings via email: svg-developers-dig...@yahoogroups.com svg-developers-fullfeatu...@yahoogroups.com * To unsubscribe from this group, send an email to: svg-developers-unsubscr...@yahoogroups.com * Your use of Yahoo! Groups is subject to: http://docs.yahoo.com/info/terms/
Re: [svg-developers] explaining setAttribute, setAttributeNS and carburetors
Hi David, Let me start by saying that I don't have a definitive answer on this, but I do have some vague recollections that might help. On Sat, 16 Oct 2010 21:39:39 -0400 ddailey ddai...@zoominternet.net wrote: I don't really understand carburetors, but I have a vague idea that they control the richness of the fuel mixture so as to calibrate the rate of combustion in the engine -- for me, the following issue is similar. Perhaps you can help. I'm trying to explain how to do a wee bit of DOM scripting to those who don't necessarily have any programming background, let alone DOM scripting in SVG. I generally get around the topic on my own, okay, without really understanding some of the more esoteric subjects like DOCTYPE and namespaces and so forth -- I just do what people tell me to and it usually works. In truth, I consider all such things to be incantations required for me to pay homage to the systems gurus who have figured out how to glue all the pieces together. They are like taxes, and it is generally not crucial that I understand them so long as I do what is required. On the other hand, once every so often I find myself having to explain things to others. And it is at these times that I find myself thinking that perhaps I should understand such myseries (did I forget a t in the last word? oops) a bit deeper than I do. Hence the following question: I know that R.setAttributeNS(null,fill, red)is the proper construction (for SVG but not HTML), rather than R.setAttribute(fill, red)I also know that in every SVG viewer I have seen, the latter has equivalent behavior to the former (for SVG but not HTML), . I remember in the early days of XML, namespaces did not exist and any tools/languages that did the DOM-thing were built around the second model. Later, namespaces were added and as the tools/languages began sprouting the first form. During that time, I remember many people running across and reporting problems with the setAttributeNS() methods not working consistently among tools when working with XML having namespaces. After lots of discussion and consternation, it seems the consensus was that setAttribute( ... ) was not safe to use when any namespaces were present and setAttributeNS( null, ... ) was the preferred approach. Fast-forward a few years of cargo-culting that approach and this became firmly entrenched as best practice. Meanwhile tools and language support have improved. I think it was last year on one of the XML mailing lists I follow that someone challenged this practice with examples to back up the fact that many implementations appear to be consistent that setAttribute( ... ) is the same as setAttribute( null, ... ). Hopefully, someone has a definitive answer on this. As I said all I have are anecdotes, and my (admittedly fuzzy) memory. I think I was told once that the SVG spec (or maybe it is the XML spec, or one or another DOM spec), for some mysterious reason, leaves room for some future browser manufacturer to make a browser in which the latter construction wouldn't work. So, as per my oversimplified understanding, we use the more arcane construction (and its extra seven keystrokes and the extra 80,000 neural synapses) in anticipation of such a possible future. I truly don't rue the seven keystrokes, as much as all the norepinephrine, seratonin and the like. So as I say, it is not important that I understand it. There may be, already, a shortage of norepinephrine which would preclude me from ever understanding it. But what words might I use to explain this oddity to others? If I happen to understand your explanation that will be a serendipitous but unexpected side-effect! G. Wade -- That's what I love about GUIs: They make simple tasks easier, and complex tasks impossible. -- John William Chambless, 39v25i$2...@whale.st.usm.edu - To unsubscribe send a message to: svg-developers-unsubscr...@yahoogroups.com -or- visit http://groups.yahoo.com/group/svg-developers and click edit my membership Yahoo! Groups Links * To visit your group on the web, go to: http://groups.yahoo.com/group/svg-developers/ * Your email settings: Individual Email | Traditional * To change settings online go to: http://groups.yahoo.com/group/svg-developers/join (Yahoo! ID required) * To change settings via email: svg-developers-dig...@yahoogroups.com svg-developers-fullfeatu...@yahoogroups.com * To unsubscribe from this group, send an email to: svg-developers-unsubscr...@yahoogroups.com * Your use of Yahoo! Groups is subject to: http://docs.yahoo.com/info/terms/
Re: [svg-developers] explaining setAttribute, setAttributeNS and carburetors
Hi, David- ddailey wrote (on 10/16/10 9:39 PM): I know that R.setAttributeNS(null,fill, red)is the proper construction (for SVG but not HTML), rather than Actually, that works with any XML language, XHTML included (provided it is real XHTML, and not served as text/html). R.setAttribute(fill, red)I also know that in every SVG viewer I have seen, the latter has equivalent behavior to the former (for SVG but not HTML), . Both are fine for SVG; they are equivalent in this case. The only place they are not equivalent is when the attribute is in a separate namespace, as with xlink:href; then, unfortunately, setAttributeNS is needed. Another example of namespaced attributes is certain metadata attributes, or custom attributes; both Illustrator and Inkscape produce these, so it's good to have a grounding in them for advanced SVG stuff. But in this case, the only thing to know there is that (for whatever reason) attributes are generally in the 'null' namespace (*not* in the SVG or HTML or whatever host-language namespace). I recommend teaching setAttribute for normal attributes, and setAttributeNS only for xlink:href. (Note that a younger me was rather outspoken about using setAttributeNS, as I thought it clarified the subtleties of namespaces through making them explicit. I no longer feel that way, and think that people should do what is easiest; there is a little pain involved in learning namespaces, and as much as possible, we should remove that pain. Bad Younger Me, no cookie.) I think I was told once that the SVG spec (or maybe it is the XML spec, or one or another DOM spec), for some mysterious reason, leaves room for some future browser manufacturer to make a browser in which the latter construction wouldn't work. I don't believe any spec says so, but even if it does, that's not going to happen. The current trend is for increased API simplicity, so newer specs and existing browsers will not go that way. setAttribute is safe and future-proof. Hope that helps- -Doug - To unsubscribe send a message to: svg-developers-unsubscr...@yahoogroups.com -or- visit http://groups.yahoo.com/group/svg-developers and click edit my membership Yahoo! Groups Links * To visit your group on the web, go to: http://groups.yahoo.com/group/svg-developers/ * Your email settings: Individual Email | Traditional * To change settings online go to: http://groups.yahoo.com/group/svg-developers/join (Yahoo! ID required) * To change settings via email: svg-developers-dig...@yahoogroups.com svg-developers-fullfeatu...@yahoogroups.com * To unsubscribe from this group, send an email to: svg-developers-unsubscr...@yahoogroups.com * Your use of Yahoo! Groups is subject to: http://docs.yahoo.com/info/terms/
