Thanks for your answer. Sounds very good, but a little bite difficult than i thought :-)
I´ll try it with Lienzo Am Dienstag, 19. Mai 2015 02:12:52 UTC+2 schrieb Jens: > > You paint into a canvas using its Context2D object > (canvas.getContext2d()). It has a bunch of methods for still styles and > shapes. > > Since canvas is just something you paint on you can not attach a handler > for each painted rectangle, a painted rectangle is just pixels. You need to > attach a handler to the canvas itself and then use some math to figure out > which painted shape has been clicked. To be able to do that you would need > to store every painted shape in a data structure, e.g. for a rectangle > store x,y and maybe z axis as well as width and height. To make a rectangle > visible/invisible on click you also have to store the visibility > information somewhere. > > In graphics language the above data structure is called a scene graph > which is a model that describes the scene you want to render. Once you have > build up your scene graph you can render its information to a canvas. Based > on user input you would modify the scene graph and then repaint it to the > canvas again (either the whole graph or you would calculate which parts of > the canvas need to be repainted based on the changes in the scene graph). > > In short: I would use a library that allows you to build such a scene > graph. From the top of my head I only know lienzo but I never used it. > > https://github.com/ahome-it/lienzo-core > > > -- J. > > -- You received this message because you are subscribed to the Google Groups "Google Web Toolkit" group. To unsubscribe from this group and stop receiving emails from it, send an email to [email protected]. To post to this group, send email to [email protected]. Visit this group at http://groups.google.com/group/google-web-toolkit. For more options, visit https://groups.google.com/d/optout.
