I am creating a dynamic, interactive network diagram with php, javascript and either Canvas or SVG
However, with canvas, I don't know how to make each object selectable. i don't want to use the hidden canvas and to detect if a mouse is on an object, because I will have lots of intersecting objects and having lots of layers of canvas will be messy.
I don't know anything about SVG.
Would SVG serves the purpose better? or what is a canvas solution to this.
One advantage of SVG is that it has concrete DOM objects representing the shapes in the drawing, so you automatically get a lot of mouse event handling and event bubbling.
Alternatively, you could use EaselJS, which provides a pretty robust display-list, freeing you from managing hidden canvases.
There are some projects for building diagrams and graphics already. You could try Raphaël which is svg based, so it should be ie compatible as well.
I assume by "the hidden canvas" you mean my tutorial. It will still work with multiple objects and multiple layers, you just need to paint them in the proper z-order.
There are of course much faster (but more sophisticated) ways.
If you don't want to deal with it, SVG has all the object selection built in. Give Raphael a try as Zlatev suggests. If the performance gets too bad (Too many objects) you will have to switch to canvas, so it really depends on your number of nodes/links in your diagrams.
You will have to take care of sending data to your server (in whatever way you prefer) yourself though. There's nothing built into SVG/Canvas/Raphael that will do it for you.
Related
As far as I read about this topic d3.js uses for the main part SVG and not HTML5's Canvas. The advantages and disadvantages of SVG and Canvas are clear and already discussed. Now I found out that it is possible to use Canvas instead or in combination with SVG in d3.js. The main reason should be to get a better performance for large datasets (like cubism.js does for realtime data visualization). My question is: When I do use Canvas over SVG to get a better performance, do I have still the possibilities of interaction? I know that Canvas itself allows manipulation, but it is much harder to implement than it is for SVG. So can I maintain the interaction of SVGs when I use the d3.js Canvas approach?
First of all, D3 doesn't require any specific rendering technology as such. It is mostly (except for some specialised helpers) agnostic of whether you use HTML, SVG, Canvas or something completely different for rendering.
One of the main differences between SVG and Canvas, as you've pointed out, is that SVG has the interaction "built in", i.e. it provides facilities for event listeners and such. Canvas has none of this.
You can however get the same kind of interactivity as in SVG in Canvas. The trick is to use Javascript to monitor what the user does in relation to the various elements. For an introduction to this, see e.g. here.
Note that, depending on what kind of interaction you want exactly, there may be significant implementation effort to achieve the same as SVG already provides. Also note that this incurs a performance penalty which may negate some of the benefits of Canvas over SVG.
If I have a canvas with a circle that changes color upon clicking on it, I can use a click event on the canvas element and handle the math for that (distance formula calculation <= radius). But what if I have two circles that overlap (like a van diagram), and I click in the middle of the two circles assuming that only the top circle should change color? If the math of the first circle is applied in this case, both circles would change color.
How would I deal with events in the canvas in terms of overlapping objects like the example above? With hopefully a fast/efficient algorithm?
You might want a framework like EaselJS that has a better api for what you're trying to do. Barebones canvas 2d-context doesn't provide much in terms of display-object / sprite behavior.
Responses above also mention some sort of list to represent layers. I don't think the implementation would be very difficult, just another condition to check for along with the radius.
Canvas isn't really like Flash or like a DOM tree whereby things have sort orders or z-indexes. Its a bit more like a flat rastered image and you have to rely upon other logic in your javascript to remember the sequence & stacking order of things you have drawn.
If you need this kind of interactivity I've always found it best to use a 3rd party library (unless it really is just a case of one or two circles which dont do much).
For interactive 'shape' based javascript graphics I would sugest Raphael.js or D3 which are actually more of SVG tools than a canvas one so maybe it's not for you but they are simple and cross-browser.
There's also processing.js (js port of Processing the Java lib) which feels a bit like flash and again can track all of the levels and objects. Theres a tonne of others but thats another topic.
If it's super simple the options might be:
Hold the co-ordinates of all shapes/elements composited on the canvas inside an object or array which also tracks their z-index/sort sequence, thereby letting you know whats on top.
Using the imagedata at the mouse coordinate of the click to establish what has been clicked
using multiple canvases composited on each other and letting the DOM do the work for the click events
I'd like to be able to write an application in HTML5 that is similar to the following.
HTML5 Canvas Animals on the Beach Game with KineticJS
The problem with that demo though is the mouse over event is only accurate to the rectangle surrounding the animal. Is there any way to do this with more accuracy, be it in KinectJS or otherwise?
There are generally two ways:
Using custom paths with each image as hitboxes (that you manually define) then using an is-point-in-path algorithm
Using a ghost-canvas (or whatever you like to call it) as I detailed in this old tutorial. Ignore the link to the new tutorial, the old one uses what you'd want.
The first method here is much faster but requires a lot more code and manual work. The second method is pixel-perfect but much slower. Still, if you don't have an enormous amount of objects it may suit your needs.
1.) I found a canvas API called EaselJS, it does an amazing job of creating a display list for each elements you draw. They essentially become individually recognizable objects on the canvas (on one single canvas)
2.) Then I saw on http://simonsarris.com/ about this tutorial that can do drag and drop, it makes use of a hidden canvas concept for selection.
3.) And the third approach, a working approach, http://www.lucidchart.com/ , which is exactly what I'm trying to achieve, basically have every single shape on a different canvas, and use to position them. There's a huge amount of canvas.
The question is, what is the easiest way to achieve interactive network diagram as seen on http://www.lucidchart.com/
A side question is, is it better to get text input through positioning on canvas or using multiple canvas (one for rendering text) as in LucidChart
I'm the person who made the tutorials in 2. There's a lot going on here, so I'll try to explain a bit.
I use a hidden canvas for selection simply because it is easy to learn and will work for ANY kind of object (text, complex paths, rectangles, semi-transparent images). In the real diagramming library that I am writing, I don't do anything of the sort, instead I use a lot of math to determine selection. The hidden-canvas method is fine for less than 1000 objects, but eventually performance starts to suffer.
Lucidchart actually uses more than one canvas per object. And it doesn't just have them in memory, they are all there the DOM. This is an organizational choice on their part, a pretty weird one in my opinion. SVG might have made their work a lot easier if thats what they are going to do, as if seems they are doing a lot of footwork just to be able to emulate how SVG works a bit. There aren't too many good reasons to have so many canvases in the DOM if you can avoid it.
It seems to me that the advantage of them doing it that way is that if they have 10,000 objects, when you click, you only have to look at the one (small) canvas that is clicked for selection testing, instead of the entire canvas. So they did it to make their selection code a little shorter. I'd much rather only have one canvas in the DOM; their way seems needlessly messy. The point of canvas is to have a fast rendering surface instead of a thousand divs representing objects. But they just made a thousand canvases.
Anyway, to answer your question, the "easiest" way to achieve interactive network diagrams like lucidchart is to either use a library or use SVG (or an SVG library). Unfortunately there aren't too many yet. Getting all the functionality yourself in Canvas is hard but certainly doable, and will afford you better performance than SVG, especially if you plan on having more than 5,000 objects in your diagrams. Starting with EaselJS for now isn't too bad of an idea, though you'll probably find yourself modifying more and more of it as you get deeper into your project.
I am making one such interactive canvas diagramming library for Northwoods Software, but it won't be done for a few more months.
To answer the question that is sort-of in your title: The fastest method of doing interactiveness such as hit-testing is using math. Any high-performance canvas library with the features to support a lot of different types of objects will end up implementing functions like getNearestIntersectionPoint, getIntersectionsOnRect, pathContainsPoint, and so on.
As for your side question, it is my opinion that creating a text field on top of the canvas when a user wants to change text and then destroying it when the user is done entering text is the most intuitive-feeling way to get text input. Of course you need to make sure the field is positioned correctly over the text you are editing and that the font and font sizes are the same for a consistent feel.
Best of luck with your project. Let me know how it goes.
Using SVG (and maybe libraries as Raphael)!!
Then any element can receive mouse events.
Is it possible to use Raphael to manipulate an embedded SVG image? I used Raphael in the past to draw shapes, but haven't actually seen it being used to manipulate an existing SVG image. If not, is there anything else that allows me to easily change colours, add events, etc. to polygons of an embedded SVG image?
From my experience reading the Raphael.js source, I have to agree with previous posts. The only way I can think of to replace or modify the SVG is by replacing/modifying the markup/DOM itself.
All I want to add in my answer is a short, general explanation of why this is so. Raphael is designed as an SVG/VML generator. That is, Raphael makes JavaScript objects and appends their corresponding SVG/VML markup to the DOM as they are made. The objects have lots of additional properties that make them work within the Raphael framework.
It may be possible to write a plugin that can construct a Raphael object around an SVG element by reading its properties, but, I suspect that such an object may not have all the information it needs to coexist with the other Raphael objects. Certainly, no such parsing/reconstruction functionality currently exists.
Funny, yesterday I found the glitchsvgicons page doing that.
Although in a very primitive way, just using a regex replace of parts.
It can be hint, though: apparently you can use good old search/replace of text parts on SVG icons. But it is more prone to issues than using a real Dom tree...