You can design your label layer as it was only meant to be used manually, that is you can add labels by hand however you like.
Then you can create a sort of "wizard" that's capable of automatically do what you're doing by hand, that is it's capable to draw labels using data from somewhere, for example from another layer's attributes. This wizard should be able to "observe" source data to change labels accordingly. This way you separate the concern of drawing labels (it does not need to know where they come from), from the concern of keeping them synchronized. Bye Paolo Rizzi > -----Messaggio originale----- > Da: [EMAIL PROTECTED] > [mailto:[EMAIL PROTECTED] conto di > Sunburned Surveyor > Inviato: martedì 15 maggio 2007 23.18 > A: List for discussion of JPP development and use. > Oggetto: Re: [JPP-Devel] Annontations as a Layer? > > > Michael, > > You bring up an excellent point. > > You wrote: " question following from your approach is : do > you intend to > synchronize labeled geographic feature with their "label feature" ? > If both features and labels are in a distinct layer, it may > be tricky to > remove a label when the feature is deleted, or to change the label > content when a geographic attribute value changes." > > To be honest, I haven't thought that far ahead. I would like to > synchronize labels and features as you mention. For example, if the > value of the "labeled attrbute' is changes I would like to change the > label. If the "labeled feature" is deleted, i'd like to autmoatically > delete the label if the user chooses this option. > > Note that I want to allow not only labels tied to the attribute in a > specific feature, as typical of most GIS programs, but also > independent labels. > > Michael wrote: "If a label's geometry is cached in your labeled > feature, may be a > special style / renderer could display this geometry and make it > possible to manipulate it as a normal feature geometry with > jump's tools." > > This is what I had intended. I would store the "geometry" of the label > as a rectangle. This rectangle would be represented by a JTS geometry > and would be sized as the bounding box of the label with a user > specified buffer between the actual text and the rectangles outline. > > The Sunburned Surveyor > > On 5/15/07, Michaël Michaud <[EMAIL PROTECTED]> wrote: > > Hi Landon, > > > > A question following from your approach is : do you intend to > > synchronize labeled geographic feature with their "label feature" ? > > If both features and labels are in a distinct layer, it may > be tricky to > > remove a label when the feature is deleted, or to change the label > > content when a geographic attribute value changes. > > I've not thought too much about your problem, but another > solution I > > can imagine is to write a special feature implementation for labeled > > features : > > for ex. > > LabeledFeature lFeature = new LabeledFeature(Feature f) > > lFeature.getLabelPosition() > > If a label's geometry is cached in your labeled feature, may be a > > special style / renderer could display this geometry and make it > > possible to manipulate it as a normal feature geometry with > jump's tools. > > > > ok, may be just flights of fancy (is that a correct > expression ?), it it > > makes no sense, please skip it. > > > > Michael > > > > > > Martin Davis a écrit : > > > > >This approach makes sense, I think. Something similar is > done in the > > >Imagery API - an Image is just a Feature with some special > attributes, > > >which the Imagery renderer knows how to interpret (display > on the screen). > > > > > >The one trick is that if you intend your label boxes to have a > > >coordinate system which is different to the CS used by the > LayerView > > >(e.g. the one used by the Features in other Layers), you > may have to > > >pull some trickery in various places in the rendering > pipeline to get > > >this to work correctly. > > > > > >It sounds like you want to create the concept of a Layer > which renders > > >in window space, rather than Feature space. At a high > level this is > > >certainly supported (e.g. the Scale Bar draws on a "pane" > which is in > > >window space), but I'm not sure how easily this > generalizes. I would > > >instead look at keeping the label geometry in Feature > space - this will > > >be much simpler. Imagery works this way already. > > > > > >Sunburned Surveyor wrote: > > > > > > > > >>I've been thinking a little about the "test" I will be > writing for my > > >>pluggable renderer system and plug-in dependency system. > This "test" > > >>will be a new plug-in that allows the user to place and manipulate > > >>labels on the layer view. The system will be vary simple > to start, but > > >>could be expanded in the future to support more complex > label layout. > > >> > > >>The plug-in will allow the user to specify the alignment, > > >>justification, font, font size, and content of each > label. I hope to > > >>allow the content of the label to be based on the feature > attribute of > > >>a feature stored in another layer. I will also store a > rectangle that > > >>encompasses the text label with some buffer space as a > JTS geometry. > > >>This should allow the user to select labels in spatial > queries. (For > > >>example: "Select all the labels on the Road Labels layer > within 100 > > >>feet of Interstate 5".) The user will also be able to make the > > >>background rectangles visible and will have the option to control > > >>their fill color, stroke color and stroke thickness. > > >> > > >>I'm pretty sure that I can store most, if not all, of the > information > > >>for a label as attributes of a Feature object. In > essence, I want to > > >>make the labels implementations and store them in a class > that extends > > >>Layer. This means the user will be able to manipulate > these labels as > > >>they do other layers. Obviously this type of Feature will > be displayed > > >>by a custom renderer that I plug into OpenJUMP. This type > of Feature > > >>will also have to obey a strict FeatureSchema. (I can't > have someone > > >>renaming the font size attribute or deleting the font > type attribute.) > > >> > > >>Does anyone see major problems with implementing text labels as > > >>implementations of the Feature interface? Does anyone see major > > >>problems with storing these labels in an extension of the > Layer class? > > >> > > >>Do I need to create a new Label class from scratch to > avoid problems > > >>that might result from the fact that a label is not a > true geographic > > >>feature? > > >> > > >>Thanks for sharing your thoughts with me. > > >> > > >>The Sunburned Surveyor > > >> > > > >>------------------------------------------------------------ > ------------- > > >>This SF.net email is sponsored by DB2 Express > > >>Download DB2 Express C - the FREE version of DB2 express and take > > >>control of your XML. No limits. Just data. Click to get it now. > > >>http://sourceforge.net/powerbar/db2/ > > >>_______________________________________________ > > >>Jump-pilot-devel mailing list > > >>Jump-pilot-devel@lists.sourceforge.net > > >>https://lists.sourceforge.net/lists/listinfo/jump-pilot-devel > > >> > > >> > > >> > > >> > > > > > > > > > > > > > > > > -------------------------------------------------------------- > ----------- > > This SF.net email is sponsored by DB2 Express > > Download DB2 Express C - the FREE version of DB2 express and take > > control of your XML. No limits. Just data. 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