How to restore the transformations after a resize - javascript

I am working with Processing.js (version 1.4.8).
I have 5 white points, which coordinates I chose specifically. The black dot marks the center of the sketch! I want to be able to translate and scale my sketch. ALSO, I want it to occupy the whole window.
var mapWidth, mapHeight, canvas, pjs, centerX, centerY;
var points = [[100, 100], [300, 100], [100, 300], [300, 300], [200, 200]];
var setSize = function() {
mapWidth = $(window).outerWidth();
mapHeight = $(window).outerHeight();
if (pjs) {
pjs.size(mapWidth, mapHeight);
}
};
var clear = function() {
pjs.background(200);
};
var drawPoint = function(coordinates) {
var radius = 30;
pjs.ellipse(coordinates[0], coordinates[1], radius, radius);
};
var drawPoints = function() {
pjs.fill(255);
points.map(function(point) {
drawPoint(point);
});
};
var calculateCenter = function() {
centerX = Math.floor(mapWidth / 2);
centerY = Math.floor(mapHeight / 2);
};
var drawCenter = function() {
calculateCenter();
var radius = 10;
pjs.fill(0);
pjs.ellipse(centerX, centerY, radius, radius);
console.log("center", centerX, centerY);
};
var move = function() {
pjs.translate(200, 300);
redraw();
};
var zoomIn = function() {
pjs.scale(2, 2);
redraw();
};
var draw = function() {
clear();
drawPoints();
drawCenter();
};
var redraw = function() {
clear();
draw();
};
var addEvent = function(object, type, callback) {
if (object == null || typeof object == "undefined") return;
if (object.addEventListener) {
object.addEventListener(type, callback, false);
} else if (object.attachEvent) {
object.attachEvent("on" + type, callback);
} else {
object["on" + type] = callback;
}
};
$(function() {
canvas = document.getElementById("map");
setSize();
var pjsRun = function(processingjs) {
pjs = processingjs;
pjs.setup = function() {
pjs.size(mapWidth, mapHeight);
draw();
};
};
var p = new Processing(canvas, pjsRun);
addEvent(window, "resize", function(event) {
setSize();
redraw();
});
});
Until here, everything is fine, as you can see in this CodePen.
I want to be able to resize the window AND keep the transformations (translations, scales, ...) that I had already performed.
Please, open the CodePen and try to reproduce this weird behaviour:
1) Perform one (or two) transformation(s) using the top-right buttons
The map is translated by 200 to the right and 300 downwards.
Everything OK by now...
But the problem arises now.
2) Resize the window
The five points are again where they were before the "translate" operation.
So... Again... Is there a way to resize without losing all the transformations that had been performed?
Thanks

Like you've discovered, it appears as though calling the size() function resets the transformation matrix. The short answer to your question is that you need to keep track of the transformations, and then apply them whenever you draw something.
The longer answer to your question is that you're using Processing.js a little bit differently than people typically use it. You've left out the draw() function (note that your draw() function is not the draw() function that's automatically called 60 times per second) and are trying to code event handlers yourself. This disconnect is why you're having issues.
If I were you, I'd start with a more basic sketch that starts out using Processing's built-in draw() function. Write code that draws the scene every frame. Make sure you set the translation and scale every frame. Here's an example:
var draw = function() {
scale(scaleX, scaleY);
translate(translateX, translateY);
background(200);
fill(255);
points.map(function(point) {
ellipse(coordinates[0], coordinates[1], 30, 30);
});
fill(0);
ellipse(width/2, height/2, 10, 10);
};
Then setup event listeners that change the values of scaleX and scaleY as well as translateX and translateY. Let Processing handle the rest.

Related

measure length of line drawn on image in javascript

I would like to measure the length of a line drawn on a image uploaded in html code. I have found a script that use canvas element and enable me to draw a line, rectangle or free line.
The next step I would like to implement is to be able to draw a line, rectangle or free line on a image uploaded but in case of I choose to draw a line to have the possibility to measure the length of a line by setting a scale manually.
I know that in js there is the string string.length but it is not good for my purpose.
Here below there are the two code I have found, I am trying to modify and put together but without any success even because I am not very practical.
If anyone will help me to putting together the two code or give me some advice how to do it I will be very grateful.
This is the html code for draw in a rectangle
<!DOCTYPE html>
<html lang="en">
<head>
<meta charset="utf-8">
<title>Canvas Paint - Example 5</title>
<style type="text/css">
#container { position: relative; }
#imageView { border: 1px solid #000; }
#imageTemp { position: absolute; top: 1px; left: 1px; }
</style>
</head>
<body>
<p><label>Drawing tool: <select id="dtool">
<option value="line">Line</option>
<option value="rect">Rectangle</option>
<option value="pencil">Pencil</option>
</select></label></p>
<div id="container">
<canvas id="imageView" width="400" height="300">
<p>Unfortunately, your browser is currently unsupported by our web
application. We are sorry for the inconvenience.</p>
</canvas>
</div>
<script type="text/javascript" src="example-5.js"></script>
</body>
</html>
This the relating js code:
// Keep everything in anonymous function, called on window load.
if(window.addEventListener) {
window.addEventListener('load', function () {
var canvas, context, canvaso, contexto;
// The active tool instance.
var tool;
var tool_default = 'line';
function init () {
// Find the canvas element.
canvaso = document.getElementById('imageView');
if (!canvaso) {
alert('Error: I cannot find the canvas element!');
return;
}
if (!canvaso.getContext) {
alert('Error: no canvas.getContext!');
return;
}
// Get the 2D canvas context.
contexto = canvaso.getContext('2d');
if (!contexto) {
alert('Error: failed to getContext!');
return;
}
// Add the temporary canvas.
var container = canvaso.parentNode;
canvas = document.createElement('canvas');
if (!canvas) {
alert('Error: I cannot create a new canvas element!');
return;
}
canvas.id = 'imageTemp';
canvas.width = canvaso.width;
canvas.height = canvaso.height;
container.appendChild(canvas);
context = canvas.getContext('2d');
// Get the tool select input.
var tool_select = document.getElementById('dtool');
if (!tool_select) {
alert('Error: failed to get the dtool element!');
return;
}
tool_select.addEventListener('change', ev_tool_change, false);
// Activate the default tool.
if (tools[tool_default]) {
tool = new tools[tool_default]();
tool_select.value = tool_default;
}
// Attach the mousedown, mousemove and mouseup event listeners.
canvas.addEventListener('mousedown', ev_canvas, false);
canvas.addEventListener('mousemove', ev_canvas, false);
canvas.addEventListener('mouseup', ev_canvas, false);
}
// The general-purpose event handler. This function just determines the mouse
// position relative to the canvas element.
function ev_canvas (ev) {
if (ev.layerX || ev.layerX == 0) { // Firefox
ev._x = ev.layerX;
ev._y = ev.layerY;
} else if (ev.offsetX || ev.offsetX == 0) { // Opera
ev._x = ev.offsetX;
ev._y = ev.offsetY;
}
// Call the event handler of the tool.
var func = tool[ev.type];
if (func) {
func(ev);
}
}
// The event handler for any changes made to the tool selector.
function ev_tool_change (ev) {
if (tools[this.value]) {
tool = new tools[this.value]();
}
}
// This function draws the #imageTemp canvas on top of #imageView, after which
// #imageTemp is cleared. This function is called each time when the user
// completes a drawing operation.
function img_update () {
contexto.drawImage(canvas, 0, 0);
context.clearRect(0, 0, canvas.width, canvas.height);
}
// This object holds the implementation of each drawing tool.
var tools = {};
// The drawing pencil.
tools.pencil = function () {
var tool = this;
this.started = false;
// This is called when you start holding down the mouse button.
// This starts the pencil drawing.
this.mousedown = function (ev) {
context.beginPath();
context.moveTo(ev._x, ev._y);
tool.started = true;
};
// This function is called every time you move the mouse. Obviously, it only
// draws if the tool.started state is set to true (when you are holding down
// the mouse button).
this.mousemove = function (ev) {
if (tool.started) {
context.lineTo(ev._x, ev._y);
context.stroke();
}
};
// This is called when you release the mouse button.
this.mouseup = function (ev) {
if (tool.started) {
tool.mousemove(ev);
tool.started = false;
img_update();
}
};
};
// The rectangle tool.
tools.rect = function () {
var tool = this;
this.started = false;
this.mousedown = function (ev) {
tool.started = true;
tool.x0 = ev._x;
tool.y0 = ev._y;
};
this.mousemove = function (ev) {
if (!tool.started) {
return;
}
var x = Math.min(ev._x, tool.x0),
y = Math.min(ev._y, tool.y0),
w = Math.abs(ev._x - tool.x0),
h = Math.abs(ev._y - tool.y0);
context.clearRect(0, 0, canvas.width, canvas.height);
if (!w || !h) {
return;
}
context.strokeRect(x, y, w, h);
};
this.mouseup = function (ev) {
if (tool.started) {
tool.mousemove(ev);
tool.started = false;
img_update();
}
};
};
// The line tool.
tools.line = function () {
var tool = this;
this.started = false;
this.mousedown = function (ev) {
tool.started = true;
tool.x0 = ev._x;
tool.y0 = ev._y;
};
this.mousemove = function (ev) {
if (!tool.started) {
return;
}
context.clearRect(0, 0, canvas.width, canvas.height);
context.beginPath();
context.moveTo(tool.x0, tool.y0);
context.lineTo(ev._x, ev._y);
context.stroke();
context.closePath();
};
this.mouseup = function (ev) {
if (tool.started) {
tool.mousemove(ev);
tool.started = false;
img_update();
}
};
};
init();
}, false); }
// vim:set spell spl=en fo=wan1croql tw=80 ts=2 sw=2 sts=2 sta et ai cin fenc=utf-8 ff=unix:
While the code for drawing a line and measured the length is at this link:
https://openlayers.org/en/latest/examples/measure.html?q=measure+line
Let's say that canvas in which image is being rendered is of x pixels wide and y pixels height with aspect ratio of x/y, and original dimensions of image is w pixels and h pixels with aspect ratio of w/h.
Now take two points (x1,y1), (x2,y2)
x distance in image units = abs(x1 - x2) * w / x; // now units are in image dimension
y distance in image units = abs(y1- y2) * h / y; // now units are in image dimension
When i say the units are in image dimension
for example an image of 200 meters fitted in 100px width of canvas, now a length of 50 px is 50 * (200/100) meters = 100 meters
so coming for your original question
The length of line between two points is now s = Math.sqrt(Math.pow(x distance in image units, 2) + Math.pow(y distance in image units, 2))
Note: I did not put code as i felt it is better explained in conceptual way,although i feel this question goes better in math.stackexchange

Fabric.JS and Fabric-Brush - Can't add to lower canvas

I'm trying to use Fabric.js with Fabric Brush This issue that I'm running into is that Fabric Brush only puts the brush strokes onto the Top Canvas and not the lower canvas. (The stock brushes in fabric.js save to the bottom canvas) I think I need to convert "this.canvas.contextTop.canvas" to an object and add that object to the the lower canvas. Any ideas?
I've tried running:
this.canvas.add(this.canvas.contextTop)
in
onMouseUp: function (pointer) {this.canvas.add(this.canvas.contextTop)}
But I'm getting the error
Uncaught TypeError: obj._set is not a function
So the contextTop is CanvasHTMLElement context. You cannot add it.
You can add to the fabricJS canvas just fabric.Object derived classes.
Look like is not possible for now.
They draw as pixel effect and then they allow you to export as an image.
Would be nice to extend fabricJS brush interface to create redrawable objects.
As of now with fabricJS and that particular version of fabric brush, the only thing you can do is:
var canvas = new fabric.Canvas(document.getElementById('c'))
canvas.freeDrawingBrush = new fabric.CrayonBrush(canvas, {
width: 70,
opacity: 0.6,
color: "#ff0000"
});
canvas.isDrawingMode = true
canvas.on('mouse:up', function(opt) {
if (canvas.isDrawingMode) {
var c = fabric.util.copyCanvasElement(canvas.upperCanvasEl);
var img = new fabric.Image(c);
canvas.contextTopDirty = true;
canvas.add(img);
canvas.isDrawingMode = false;
}
})
<script src="https://cdnjs.cloudflare.com/ajax/libs/fabric.js/2.4.1/fabric.min.js"></script>
<script src="https://tennisonchan.github.io/fabric-brush/bower_components/fabric-brush/dist/fabric-brush.min.js"></script>
<button>Enter free drawing</button>
<canvas id="c" width="500" height="500" ></canvas>
That is just creating an image from the contextTop and add as an object.
I have taken the approach suggested by AndreaBogazzi and modified the Fabric Brush so that it does the transfer from upper to lower canvas (as an image) internal to Fabric Brush. I also used some code I found which crops the image to a smaller bounding box so that is smaller than the full size of the canvas. Each of the brushes in Fabric Brush has an onMouseUp function where the code should be placed. Using the case of the SprayBrush, the original code here was:
onMouseUp: function(pointer) {
},
And it is replaced with this code:
onMouseUp: function(pointer){
function trimbrushandcopytocanvas() {
let ctx = this.canvas.contextTop;
let pixels = ctx.getImageData(0, 0, canvas.upperCanvasEl.width, canvas.upperCanvasEl.height),
l = pixels.data.length,
bound = {
top: null,
left: null,
right: null,
bottom: null
},
x, y;
// Iterate over every pixel to find the highest
// and where it ends on every axis ()
for (let i = 0; i < l; i += 4) {
if (pixels.data[i + 3] !== 0) {
x = (i / 4) % canvas.upperCanvasEl.width;
y = ~~((i / 4) / canvas.upperCanvasEl.width);
if (bound.top === null) {
bound.top = y;
}
if (bound.left === null) {
bound.left = x;
} else if (x < bound.left) {
bound.left = x;
}
if (bound.right === null) {
bound.right = x;
} else if (bound.right < x) {
bound.right = x;
}
if (bound.bottom === null) {
bound.bottom = y;
} else if (bound.bottom < y) {
bound.bottom = y;
}
}
}
// Calculate the height and width of the content
var trimHeight = bound.bottom - bound.top,
trimWidth = bound.right - bound.left,
trimmed = ctx.getImageData(bound.left, bound.top, trimWidth, trimHeight);
// generate a second canvas
var renderer = document.createElement('canvas');
renderer.width = trimWidth;
renderer.height = trimHeight;
// render our ImageData on this canvas
renderer.getContext('2d').putImageData(trimmed, 0, 0);
var img = new fabric.Image(renderer,{
scaleY: 1./fabric.devicePixelRatio,
scaleX: 1./fabric.devicePixelRatio,
left: bound.left/fabric.devicePixelRatio,
top:bound.top/fabric.devicePixelRatio
});
this.canvas.clearContext(ctx);
canvas.add(img);
}
setTimeout(trimbrushandcopytocanvas, this._interval); // added delay because last spray was on delay and may not have finished
},
The setTimeout function was used because Fabric Brush could still be drawing to the upper canvas after the mouseup event occurred, and there were occasions where the brush would continue painting the upper canvas after its context was cleared.

How can I create a new object with multiple methods?

I am trying to follow this tutorial here https://www.smashingmagazine.com/2012/10/design-your-own-mobile-game/ and I am stuck on the second part. (2. A Blank Canvas)
I am not sure where to put the POP.Draw object. Does it go inside of the var POP{} brackets where the other objects are created? I've tried keeping it inside, outside, and in the init function which I don't think makes sense. The purpose is to create methods within the new Draw object so they can be called later to create pictures in the canvas.
Here is my current code. It is the same as the one in the link:
var POP = {
//setting up initial values
WIDTH: 320,
HEIGHT: 480,
// we'll set the rest of these
//in the init function
RATIO: null,
currentWidth: null,
currentHeight: null,
canvas: null,
ctx: null,
init: function() {
//the proportion of width to height
POP.RATIO = POP.WIDTH / POP.HEIGHT;
//these will change when the screen is resized
POP.currentWidth = POP.WIDTH;
POP.currentHeight = POP.HEIGHT;
//this is our canvas element
POP.canvas = document.getElementsByTagName('canvas')[0];
//setting this is important
//otherwise the browser will
//default to 320x200
POP.canvas.width = POP.WIDTH;
POP.canvas.width = POP.HEIGHT;
//the canvas context enables us to
//interact with the canvas api
POP.ctx = POP.canvas.getContext('2d');
//we need to sniff out Android and iOS
// so that we can hide the address bar in
// our resize function
POP.ua = navigator.userAgent.toLowerCase();
POP.android = POP.ua.indexOf('android') > -1 ? true : false;
POP.ios = (POP.ua.indexOf('iphone') > -1 || POP.ua.indexOf('ipad') > -1) ? true : false;
//we're ready to resize
POP.resize();
POP.Draw.clear();
POP.Draw.rect(120, 120, 150, 150, 'green');
POP.Draw.circle(100, 100, 50, 'rgba(225,0,0,0.5)');
POP.Draw.text('Hello WOrld', 100, 100, 10, "#000");
},
resize: function() {
POP.currentHeight = window.innerHeight;
//resize the width in proportion to the new height
POP.currentWidth = POP.currentHeight * POP.RATIO;
//this will create some extra space on the page
//allowing us to scroll past the address bar thus hiding it
if (POP.android || POP.ios) {
document.body.style.height = (window.innerHeight + 50) + 'px';
}
//set the new canvas style width and height note:
//our canvas is still 320 x 400 but we're essentially scaling it with css
POP.canvas.style.width = POP.currentWidth + 'px';
POP.canvas.style.height = POP.currentHeight + 'px';
//we use a timeout here because some mobile browsers
//don't fire if there is not a short delay
window.selfTimeout(function() {
window.scrollTo(0, 1);
})
//this will create some extra space on the page
//enabling us to scroll past the address bar
//thus hiding it
if (POP.android || POP.ios) {
document.body.style.height = (window.innerHeight + 50) + 'px';
}
}
};
window.addEventListener('load', POP.init, false);
window.addEventListener('resize', POP.resize, false);
//abstracts various canvas operations into standalone functions
POP.Draw = {
clear: function() {
POP.ctx.clearRect(0, 0, POP.WIDTH, POP.HEIGHT);
},
rect: function(x, y, w, h, col) {
POP.ctx.fillStyle = col;
POP.ctx.fillRect(x, y, w, h);
},
circle: function(x, y, r, col) {
POP.ctx.fillStyle = col;
POP.ctx.beginPath();
POP.ctx.arc(x + 5, y + 5, r, 0, Math.PI * 2, true);
POP.ctx.closePath();
POP.ctx.fill();
},
text: function(string, x, y, size, col) {
POP.ctx.font = 'bold' + size + 'px Monospace';
POP.ctx.fillStyle = col;
POP.ctx.fillText(string, x, y);
}
};
SOLVED
I didn't realize but the completed code is on the webpage. I downloaded it and looked at the example for answers.
I solved the issue by placing the POP.Draw.clear, POP.Draw.rect methods before calling the POP.resize() method. I'm not really sure why the order matters, but it does.

Mouse position is only read on the first frame

i have been having trouble with reading a mouse position on a canvas. The code is working (semi) correctly as it reads the position when clicking he canvas in IE but only on one frame, in chrome it is just displaying the value as 0.
Here is the full code:
<script>
var blip = new Audio("blip.mp3");
blip.load();
var levelUp = new Audio("levelUp.mp3");
levelUp.load();
var canvas = document.getElementById('game');
var context = canvas.getContext('2d');
context.font = '18pt Calibri';
context.fillStyle = 'white';
//load and draw background image
var bgReady = false;
var background = new Image();
background.src = 'images/background.jpg';
background.onload = function(){
bgReady = true;
}
var startMessage = 'Click the canvas to start';
//load plane image
var planeReady = false;
var planeImage = new Image();
planeImage.src = 'images/plane.png';
planeImage.onload = function() {
planeReady = true;
}
//load missile image
var missileReady = false;
var missileImage = new Image();
missileImage.src = 'images/missile-flipped.gif';
missileImage.onload = function() {
missileReady = true;
}
//initialise lives and score
var score = 0;
var lives = 3;
var missilesLaunched = 0;
var missileSpeed = 5;
var level = 1;
var missileX = 960;
var missileY = Math.random() * 500;
if (missileY > 480) {
missileY = 480;
}
function getMousePos(canvas, event) {
return {
x: input.x - rect.left,
y: input.y - rect.top
};
}
function update_images(event) {
var pos = getMousePos(canvas.getBoundingClientRect(), mouseInput);
planeImage.y = pos.y;
missileX = missileX - missileSpeed;
if (missileX < - 70) {
missilesLaunched++;
missileX = 960;
missileY = Math.random() * 500;
if (missileY > 480) {
missileY = 480;
}
blip.play();
score = missilesLaunched;
if (score % 5 == 0) {
missileSpeed = missileSpeed + 2;
level++;
levelUp.play();
}
}
}
function reload_images() {
if (bgReady = true) {
context.drawImage(background, 0, 0);
}
if (planeReady = true) {
context.drawImage(planeImage, 10, planeImage.y);
}
if (missileReady = true) {
context.drawImage(missileImage, missileX, missileY);
}
context.fillText('Lives: ' + lives, 200, 30);
context.fillText('Score: ' + score, 650, 30);
context.fillText('Level: ' + missileSpeed, 420, 30);
context.fillText('Position: ' + missileImage.y, 420, 70);
}
function main(event) {
var mouseInput = { x: 0, y: 0 };
document.addEventListener("mousemove", function (event) {
mouseInput.x = event.clientX;
mouseInput.y = event.clientY;
});
update_images(event);
reload_images();
if (lives > 0) {
window.requestAnimationFrame(main);
}
else {
}
}
function start() {
context.drawImage(background, 0, 0);
context.fillText('Click the canvas to start', 350, 250);
function startMain(event) {
game.removeEventListener("click", startMain);
main(event);
}
canvas.addEventListener("mousedown", startMain);
}
start();
</script>
Joe, you should actually be capturing the mouse position every time you click...
...but you're actually also starting a new game (without stopping the old one), every time you click, too.
First problem: starting game engine several times to draw on the same instance of the canvas
Solution:
In your start function, you need to remove the mousedown event listener, after you've triggered it.
function start () {
// ... other setup
function startMain (event) {
canvas.removeEventListener("click", startMain);
main(event);
}
canvas.addEventListener("click", startMain);
}
Now it will only listen for the first click, before starting, and will only start once.
Second Problem: mouse doesn't update as expected
Solution: two issues here...
...first, you are passing event into main on first call...
...after that, you're passing main into requestAnimationFrame.
requestAnimationFrame won't call it with an event, it will call it with the number of microseconds (or ms or some other unit as a fractional precision of ms) since the page was loaded.
So the first time you got main({ type: "mousedown", ... });.
The next time you get main(4378.002358007);
So lets refactor the startMain we had above, so that main never ever collects an event, just a time.
function startMain ( ) {
canvas.removeEventListener("click", startMain);
requestAnimationFrame(main);
}
The next problem is that even if you were getting just events, you're only ever capturing a click event (which as we mentioned earlier, fires a new copy of the game logic).
Your solution is to separate the code which catches mouse events from the code which reads mouse position.
var mouseInput = { x: 0, y: 0 };
document.addEventListener("mousemove", function (event) {
mouseInput.x = event.clientX;
mouseInput.y = event.clientY;
});
function getMousePos (rect, input) {
return {
x : input.x - rect.left,
y : input.y - rect.top
};
}
// currently in updateImages (should not be there, but... a different story)
var pos = getMousePos(canvas.getBoundingClientRect(), mouseInput);
You've got other problems, too...
You're calling getMousePos and passing in game at the moment. I don't see where game is defined in your JS, so either you're making game somewhere else (begging for bugs), or it's undefined, and your app blows up right there.
You should really be building this with your console / dev-tools open, in a hands-on fashion, and cleaning bugs in each section, as you go.

Snap.svg - drag event handler

Question is about the onstart event handler for Element.drag in the newly announced Snap.svg.
The intention of the code below is to register event handlers for the start and stop of a drag (onstart/onstop) on an svg object.
var s = Snap(800,600);
var bigCircle = s.circle(300,150,100);
bigCircle.drag(null,
function(){
console.log("Move started");
},
function(){
console.log("Move stopped");
}
);
The console messages work fine on drag start and stop, but the null overrides the default onmove function - resulting in no actual drag happening. How do I pass something that says "I don't want to mess with the default onmove"?
(Note: I'd prefer to register an event handler by means of assignment, like the familiar onClick, but that's a different matter.)
Note added after few hours:
The Raphael.js documentation and examples provide some clues. At least now I know how to pass in a proper function for onmove that provides the default move behavior:
var s = Snap(800,600);
var bigCircle = s.circle(300,150,100);
start = function() {
this.ox = parseInt(this.attr("cx"));
this.oy = parseInt(this.attr("cy"));
console.log("Start move, ox=" + this.ox + ", oy=" + this.oy);
}
move = function(dx, dy) {
this.attr({"cx": this.ox + dx, "cy": this.oy + dy});
}
stop = function() {
this.ox = parseInt(this.attr("cx"));
this.oy = parseInt(this.attr("cy"));
console.log("Stop move, ox=" + this.ox + ", oy=" + this.oy);
}
bigCircle.drag(move, start, stop);
I'm not sure if I'm misunderstanding what you exactly want...don't you want to implement the drag ?
So for example...
var s = Snap(400,400);
var bigCircle = s.circle(150, 150, 100);
var moveFunc = function (dx, dy, posx, posy) {
this.attr( { cx: posx , cy: posy } ); // basic drag, you would want to adjust to take care of where you grab etc.
};
bigCircle.drag( moveFunc,
function(){
console.log("Move started");
},
function(){
console.log("Move stopped");
}
);
JSBin here http://jsbin.com/akoCAkA/1/edit?html,js,output
There is an example how to drag with SnapSVG here: http://svg.dabbles.info/snaptut-drag.html
var s = Snap("#svgout");
var rect = s.rect(20,20,40,40);
var circle = s.circle(60,150,50);
var move = function(dx,dy) {
this.attr({
transform: this.data('origTransform') + (this.data('origTransform') ? "T" : "t") + [dx, dy]
});
}
var start = function() {
this.data('origTransform', this.transform().local );
}
var stop = function() {
console.log('finished dragging');
}
rect.drag(move, start, stop );
circle.drag(move, start, stop );
After struggling for some hours to do this with snap.js, I finally discovered svg.js and its draggable plugin, with which it is so much easier:
var draw = SVG('svg');
var circle = draw.circle(10).attr({cx:30,cy:30,fill:'#f06'});
circle.dragend = function(delta, event) {
alert(this.attr('cx'))
}
circle.draggable();
So, I switched to svg.js ...
The eve.on method wasn't working for me, so I did some poking around and managed to recreate the onmove function. The other two (onstart and onend) require no specific code to work apparently:
var S = Snap(300,300);
var bigCircle = S.circle(150, 150, 100);
bigCircle.drag(onDragMove, onDragStart, onDragEnd);
var ddx = 0;
var ddy = 0;
var dxDone = 0;
var dyDone = 0;
function onDragMove (dx, dy, posx, posy) {
dx = dx + dxDone; // dx and dy reset to 0 for some reason when this function begins
dy = dy + dyDone; // retain the last move's position as the starting point
this.attr( { transform: 't'+dx+','+dy } );
ddx = dx;
ddy = dy;
console.log('moving...');
};
function onDragStart(x,y,e) {
console.log('start!');
};
function onDragEnd(e) {
dxDone = ddx;
dyDone = ddy;
console.log('end!');
};
Please note however that this should only be used for one dragged object at a time. If you need a custom drag for another object, you'll have to rename the functions (ie onDragStart2) and the four variables declared outside of them (ie ddx2) after duplicating it.
Also, the 'transform' string format I passed (tx,y) came from what I found after doing console.log( this.attr('transform') ). I'm not familiar with matrix() just yet, so this way seemed easier.
Hope this helps!
I can't drag group elements with custom handlers, s.drag() makes it possible. So i searched further found its possible.
Documentation:
Additionaly following drag events are triggered: drag.start. on start, drag.end. on > end and drag.move. on every move. When element is dragged over another element > drag.over. fires as well.
Solution:
s.drag();
eve.on("snap.drag.start." + s.id, function () {
console.log('cool');
});
eve.on("snap.drag.move." + s.id, function () {
console.log('cooler');
});
eve.on("snap.drag.end." + s.id, function () {
console.log('way cool');
});
eve is not documented on snapsvg it is available on raphael. i don't know this is proper way or hack.
Try this
var paper = Snap("#main");
var object = paper.circle(300,150,100)
object .attr({
stroke: "#000",
strokeWidth: 10,
strokeLinecap:"round"
});
var move1 = function(dx,dy, posx, posy) {
this.transform(this.data('origTransform') + (this.data('origTransform') ? "T" : "t") + [dx, dy])
};
var start = function() {
this.data('origTransform', this.transform().local );
}
var stop = function() {
console.log('dragging done');
}
object.drag(move1, start, stop );

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