Below is a log about a discussion we just had with Andreas on the text rendering. It seems like our thoughts are similar. Sorry if it is not that readable.
important points : - label style including label text value should be set in a style object not in the layer options, - label value should be able to deal with literals and property values, allowing concats Regards, Pierre --------------------------------------------- 11:30 AM me: hello Andreas: hi Pierre! 11:31 AM me: I'm impressed by the job done on the SLD renderer this is a big to look at 11:32 AM I working on the text rendering Andreas: thanks. I hope it will soon go into trunk, because we need this functionality in Mapbuilder. I also have an idea on text rendering. In the sld spec, there are literals and propertyValues. me: I prefer to set the label as a property in the style 11:33 AM instead of an option in the layer what do you think about that ? Andreas: This is exactly what I recommended yesterday to the other guy who was working on that me: it would follow the SLD spec Andreas: exactly. me: but I don't want to deal with SLD before it goes to trunk Andreas: And right now, I'm extending the sld parser and rule classes to also support propertyValues, not only literals. 11:34 AM me: I don't know much about propertyValues Andreas: well, a literal is a constant. If you have <PropertyValue>name</PropertyValue> 11:35 AM in your sld, this means that you do not use "name" as value, but the value of the "name" property of your feature me: understood hum, I made Mapserver write a SLD file for me this morning 11:36 AM and there is no propertyvalue hum no matter Andreas: wait a second, I'll give you a link explaining it... me: I think it's understood 11:37 AM Andreas: sorry, it's PropertyName, not PropertyValue: http://trac.osgeo.org/mapserver/ticket/1857 me: lol reported by Bart 11:38 AM it's fixed in the 5.0 version great my question then is : "how I can deal with propertyName in styles that don't come from a SLD parsing" ? Andreas: my idea is the following: 11:39 AM in the "value" of the according rule, you can have a string with a bash-like syntax: ${population} me: why not a sprint syntax ? %s 11:40 AM ok forget it doesn't work Andreas: yes, because you can concat literals and property names: me: OK this was my thoughts too Andreas: ${population} inhabitants me: great ! this was exactly the next step I wanted to get to 11:41 AM my examples already deal with literals are there any other interesting syntax we could use ? Andreas: this is all that can be done with sld. but I'm open to extensions. 11:42 AM Although I cannot think of any ATM me: it also have to work without SLD I'll try that 11:43 AM Andreas: it does. Have you seen the example georss.html in the ahocevar/sldRenderer sandbox? me: no Andreas: http://dev.openlayers.org/sandbox/ahocevar/sldRenderer/examples/georss.html me: I'll do Andreas: There a style is created without sld. me: Oh yes I did already 11:44 AM OK, last question in the OpenLayers.Style class 11:45 AM do the label style properties have to be in the same object ? as new properties (fontSize, label, labelPosition, etc...) ? or do we have to create a new OpenLayers.LabelStyle class ? 11:46 AM Andreas: it just uses the style hashes that are already there. so you do not need to create anything new when there are new style properties me: GML has a <LabelStyle> tag Andreas: SLD has font and label placement. and even more, I think. 11:47 AM me: fill, halo Andreas: yes. 11:48 AM So if you create code somewhere that uses a style.labelFont property, you can define this style in OpenLayers.Style without the need to change anything there. me: rightOK, if you don't mind, I'll put this discussion into the mailing list thread. Andreas: yes, go ahead. This is important. 11:49 AM And I will put some code and example together on the PropertyName thing. me: and probably we will be able to merge the sandboxes someday have a good day, see you 11:50 AM Andreas: have a good day too, bye! On Nov 6, 2007 10:22 AM, Pierre GIRAUD <[EMAIL PROTECTED]> wrote: > Hi, > > As said by Bart, I'm trying to get text into the renderer so that > people can have labels on vector features. > Some work is already done in the camptocamp sandbox. > > I'm having a look at your and I'll pick some good ideas in there for sure. > > Some other comments below : > > On Nov 5, 2007 8:30 PM, dave c <[EMAIL PROTECTED]> wrote: > > I posted on this last month but i didnt get any response so i went ahead > > anyways. Now what i put together is only a first pass of sorts and is a > > little crude in places but i was hoping that someone here could have a look > > at it and tell me if it could be used within openlayers as i dont want to > > have to continually be updating it myself. Of course you may not like the > > way > > i went about it or have no plans to implement text rendering. > > You're wrong : people are interested in having text rendering into OpenLayers. > We'll just have to find a common way to get it into the trunk as soon > as possible. If needed, I'll open a new wiki page so that others > interested folks can give their point of view. > > > > > Using openlayers 2.5 stable, I created a patch for this version if anyone > > wants to have a look. The patch is called patch.txt and is attached to this > > mail. So run "patch -p0 < ../patch.txt" to update. > > Your code seem a bit different from mine but not that much. I'll try > to find what is better in both. > > > > > Just a few quick points and issues i had. > > > > One reason to get text rendering working for example was, i needed to be > > able > > to output the names of certain hospitals on a map centered on there point on > > the map. Firstly i have "extractAttributes: true" and added an layer option > > called "textAttrToDisplay" which is the name of the attribute to be > > displayed within each feature that was coming from my database. > > I totally agree with Andreas on that point. It would be better if we > follow already existing terminology. The SLD's one seems correct. And > it will easier to connect to the SLD parser when it is in the trunk. > > > > > Now biggest issue i had was in svg the text was rendering upside down due to > > the "transform scale(1,-1)" and so i just created a 2nd root node called > > textroot which i appended to the renderedRoot and added all text nodes to it > > instead. Of course this wasn't an issue in vml. Is there a better way ? > > I didn't created a new root for text. Instead, I just transformed the > scale back and it just works. > A problem with having a new root may raise up when user wants to > select a feature. Events won't go through the text root node. > Though, this solution may have one advantage. This way, all the labels > are on top of the layer. > > > > > > I tried finding a quick example that you could quickly test this out on > > yourselves, but all the wfs examples i looked at in openlayers did not > > return > > any other data except there co-ordinates, but i assume a number of ye would > > be able to get it running quickly with your own local datasets. > > > > So as an example of its use, say this is some of the data returned from my > > database, > > <gml:featureMember> > > <fs:hospital fid="1"> > > <fs:geometry> > > <gml:Point> > > <gml:coordinates>99771.29,47991.03</gml:coordinates> > > </gml:Point> > > </fs:geometry> > > <fs:hospname>Bantry</fs:hospname> > > <fs:county>Co Cork</fs:county> > > <fs:he_admin_area>South</fs:he_admin_area> > > <fs:address>Bantry</fs:address> > > <fs:recordno>21</fs:recordno> > > <fs:regionname>Region 2</fs:regionname> > > </fs:hospital> > > </gml:featureMember> > > > > And i wanted to display the hospital name, i would add textAttrToDisplay as > > an > > option to the layer with the value hospname. > > > > var lOptions = { > > extractAttributes: true, > > textAttrToDisplay : 'hospname' > > } > > > > layer2 = new > > OpenLayers.Layer.WFS( "Hospital", > > "http://localhost/~dave/featureserver/featureserver.cgi/hospital?format=WFS";, > > { maxfeatures:10}, lOptions); > > map.addLayer(layer2); > > Text label should work for every possible type of Vector layer. We can > easily have examples working with simple dataset that don't need a WFS > server connection. > In my first implementation (sandbox), I don't deal with vector > features attributes. This is the next step I want to work on. > > > Regards, > Pierre > _______________________________________________ Dev mailing list [email protected] http://openlayers.org/mailman/listinfo/dev
