JSPlumb: Resize HTML5 Canvas depending on Content - javascript

So, to explain my scenario: I want to create an online "finite state machine"-webapp which is capable to visualize the automaton-concepts (deterministic, non-deterministic) and later on does some logic like minimizing and so on to help students comprehend these abstract concepts in a way of experimenting around.
So for my views, I thought about JSPlumb as the way to go (other recommendations are appreciated) - but I can't find the option to "resize" the HTML5 Canvas in JSPlumb. For lets say automatons with 100 nodes, a 640x480 canvas wouldn't be very nice, so what it should be is, starting with a canvas of 640x480, clicking and dragging on the side of the canvas, the user could extend it to its needs. Sure about that, the previously drawn elements should keep their places.
So, my question is: Is it possible to do this with jsplumb or do I need to code it myself? If I need to code it myself, any hints on where to start changing the jsplumb files would be highly appreciated.

JSPlumb is not using the canvas, as far as I know, it's using SVG or VML on old IE browser.
This problably means that you can resize the SVG object via the appropriate width & height property, but AFAIK, this is not automatic.

Related

jsPlumb and Fabric.js integration

I have built a web application in fabric.js where the user adds and draws several graphical elements over an originally blank canvas. My application has arrived to the point in which some of these graphical elements need to be interactively connected (i.e. connected by the user using the mouse). I am trying to design the best way to include these connections in the canvas since, due to aesthetic considerations, drawing lines with fabric might not be best solution for this.
I have run into jsPlumb and found several examples of connections between div and other dom elements. My specific question is: Is it possible to use the jsPlumb functionalities within the objects that fabric.js draws in the canvas. If so, does anyone have an example of this? In case this integration between jsPlumb and fabric.js is not possible, what would be the best way to achieve this?
Many thanks to all in advance.
IMHO, this integration doesn't make much sense.
Everything that fabricjs provides can be done using `jsPlumb', of course animation would require a bit of coding, but it's fairly possible.
Another reason is fabricjs deals with canvas, whereas jsPlumb deals with DOM elements, their integration would be more pain, than coding the actual requirement entirely in jsPlumb.

Irregular image drag & drop using HTML5 canvas

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.

Approach comparison: EaselJS vs Multiple Canvases vs Hidden Canvas for interactiveness

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.

Between SVG and canvas, which is better suited for manipulating/animating several images? Maybe neither and just use css3 transforms?

The 2nd part of the question is, which javascript library is better/easier to manipulate images with? I won't be actually drawing any shapes or anything. Other info: I'll be using jQuery and don't need to support all browsers, just webkit.
Edit:
More information: the current design is to layout/draw several rows/columns of images in a grid-like layout, with the image in the center being in "focus" (a little larger, with a border or something and some text next to it). The tricky thing is that we want the whole canvas of images to appear to slide/glide over to bring another random image into focus. So obviously the number of images in this grid needs to exceed what is visible in the viewport so that when the transition occurs there are always images occupying the canvas. Other than moving the images around, I won't be blurring them or otherwise modifying them. Eventually we will add user interactions like clicking/touching on a visible image to bring it to focus manually.
Let me know if this is not clear or still confusing.
I ran across scripty2 which seems like an alternative to using canvas/SVG for my purposes. I also started farting around with EaselJS last night, and it seems like this might work, but I'm wondering if it'll end up being more work/complex than just using standard HTML/CSS and a tool like Scripty2 to aid with animations and click/touch events. Just looking for any suggestions. Thanks!
The answer depends on your manipulation and animation.
If it's just translations, CSS wins for speed compared to canvas. I haven't tested, but I feel confident it easily beats SVG for the same sort of thing.
If you're going to be doing non-affine transformations or otherwise messing with the images (e.g. blurring them) you clearly want Canvas.
If you need event handlers per object, you clearly want a retained-mode drawing system like SVG or HTML+CSS. I haven't done enough CSS3 transforms to say how they compare in terms of speed to SVG, but they clearly do not have the robust transformation DOM of SVG.
This is a rather subjective question (or suite of questions) and you haven't yet given sufficient information for a clear answer to be possible.

Selecting a non-standard image area in a web application

This question is for a web application.
And maybe it's a stupid question but I was wondering if there is a way to
generate a polygon with 4 points, so that the user can himself drag
each point to create it's own (As an example, let's say that we want to remove a window from an image that it is not at a normal angle) .Is it possible?. I can't seem to
find anything after a few hours of search.
Look into the SVG and Canvas APIs. These will allow you to do vector drawings that can be updated via Javascript. For your stated purpose, updating the DOM of SVG documents might be easier. Canvas is more like a 2D bitmap, so you'd need to work out a lot of the drawing code yourself.
SVG Specs: http://www.w3.org/Graphics/SVG/
Canvas Specs: http://www.whatwg.org/specs/web-apps/current-work/
Note that SVG only works in IE with a plugin. Canvas works in IE only with Google exCanvas support.
Sounds like a job for the <canvas> tag or a Flash interface.

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