How to Programming with Canvas

Using your variables y, you can simply check if it is below the height of the canvas height. if( y > c.height ){ // use the canvas height, not the context height y = 0; } Also, the way you're currently calling the timer is a bit inefficient. Instead of...

How to move a canvas element up and down for a certain amount of time with javascript

Here, I made a small example of a vibrating guitar string. It waits 2 seconds then strums the string, which vibrates for half a second. The problem you have in your code is that you're adding a time-variable to your clearInterval, which isn't possible. If you want a delay on...

Determine shape drawn on canvas from stored coordinates in an array

canvas,drawing,mobile-safari

Heres how i solved my problem finally :) var newLine = new myLine(startX, startY, endX, endY,type); myLines.push(newLine); function myLine(xStart, yStart, xEnd, yEnd,type) { this.xS = xStart; this.yS = yStart; this.xE = xEnd; this.yE = yEnd; this.type=type } And then looped through the array for (i = 0; i < myLines.length;...

HTML, Canvas Path2D alternative.

Path2D is not yet supported in all browsers. You may be able to use a polyfill such as this one to get around this.

JavaFX 8 Canvas Fonts always Bold

canvas,fonts,javafx-8

I am going to answer my own question. Instead of using: strokeText() in the GraphicsContext, I should use:fillText(). If I do that it works fine....

I want to make a viewport for a canvas game

javascript,html5,canvas,viewport

Try storing the view port in a variable. var view = {x: 0, y: 0}; Then, at the beginning of your draw loop / render function, save the canvas state and translate to the view port. ctx.save(); ctx.translate(view.x, view.y); If you want view.x and view.y to represent the center of...

http://sigmajs.org/ les mis tutorial - why are my canvases 0 height?

javascript,html5,canvas,sigma.js

Because your CSS code is false. Replace it with this : #sigma-container { position :absolute; width :500px; height :500px; } ...

How can I make different shapes of a canvas draggable and particular area of it droppable in the same canvas

javascript,canvas,drag-and-drop

Drag and drop in specifik area UPDATE: Copy of box remains at original position while it's being moved. First you need to be able to detect your rectangles. You do this by making then into objects in your code: function box(x,y,w,h,rgb) { this.x = x, this.y = y; this.xS =...

Using destination-over to save background and actual sketch

javascript,jquery,canvas,sketchjs

Assume you have a SketchJS canvas on top of an image containing a background: #wrapper{positon:relative;} #bk,#myCanvas{position:absolute;} <div id='wrapper'> <img crossOrigin='anonymous' id=bk src='yourImage.png'> <canvas id="myCanvas" width=500 height=300></canvas> </div> Then when you want to combine the Sketch with the background and save it as an image you can use destination-over compositing to...

How do I calculate logrithmic labels for a VU meter scale?

javascript,html5,audio,canvas,html5-canvas

I suppose you have a value-to pixel function. What you need to write is the inverse function of that. When you have the inverse function, you just divide the screen area to N equal parts (in the picture you have 6 regions). One region will be X pixels in width....

Spawning multiple Balls in array js

You've got a lot of syntax errors in your code, that's why it doesn't work: It will work if you remove the animframe() call out of the for loop because that's whats making it only push one ball and stopping the for loop. You have also defined the animframe() function...

Controlling canvas object with range slider

javascript,canvas,slider

The reason you're getting the error about the [object HTMLInputElement] is that you try to write the variable cx or cy while they're both DOM objects (your sliders). If you want to write the values they represent, you should ask for cx.value and cy.value respectivelly. Furthermore, you seem to have...

Create a cone with shadows

javascript,angularjs,canvas,reference

There is unfortunately no gradient type in canvas which allow you to specify a radiant gradient. You have to provide a mechanism to do so manually. You could use a shadow approach drawing the object off-screen while offsetting the shadow so it overlapped the cone base. One for light and...

Aligning StackPanel to top-center in Canvas

c#,wpf,xaml,canvas

If you don't want any input or hit testing on a certain element you should set the IsHitTestVisible property to false: <Grid> <Canvas Name="Canvas" Background="#EFECCA"> <DockPanel VerticalAlignment="Stretch" HorizontalAlignment="Stretch" Width="{Binding ActualWidth, ElementName=Canvas}" Height="{Binding ActualHeight, ElementName=Canvas}" MouseLeftButtonDown="DockPanel_MouseLeftButtonDown" TouchDown="DockPanel_TouchDown" Panel.ZIndex="2" Background="Transparent"> </DockPanel> <Button Width="50" Height="50"...

HTML5 Canvas Base64 Error [closed]

javascript,html,canvas,base64

You gave imgObj1 time to load with imgObj1.onload, but you must also give img time to load by adding img.onload https://jsfiddle.net/m1erickson/tf0y1pL9/ BTW, errors are easier to spot if you format your code. ;-) var can = document.getElementById('canvas1'); var ctx = can.getContext('2d'); // create and load the first image var imgObj1...

AngularJS - ReferenceError: $ is not defined

try this: var fbcanvas = document.getElementById('fbcanvas'); instead of: var fbcanvas = $('#fbcanvas'); check if data is undefined too...

Creating a click event in Javascript Canvas

javascript,canvas,fabricjs

You can have your canvas listen for mouse clicks on itself like this: // get a reference to the canvas element var canvas=document.getElementById('ctx'); // tell canvas to listen for clicks and call "handleMouseClick" canvas.onclick=handleMouseClick; In the click handler, you'll need to know the position of your canvas relative to the...

Animating the drawing of a line in the canvas with fabric.js

I made a jsFiddle based on http://fabricjs.com/polygon-animation/ and I change it into a fabricjs Polyline. You can set the start and end values from here: var startPoints = [ {x: 1, y: 1}, {x: 2, y: 2} ]; var endPoints = [ {x: 1, y: 1}, {x: 200, y: 200}...

HTML Canvas Width

So it take some delay to resize image? So don't init it when canvas not resize yet. canvas.width = width; canvas.height = height; canvas.style.backgroundImage = "...." Hope this help....

Javascript Canvas clear/ redraw

javascript,ajax,canvas,web-worker

You need to add a beginPath() in there. rect() will accumulate rectangles to the path, clearRect() won't clear those. Also reset comp. mode and alpha as they are sticky. You could avoid beginPath() if you use fillRect() instead of rect() + fill() (added example below) as fillRect() does not add...

Stopping a Canvas Animation setInterval

The main issue is with setTimeout and clearTimeout is that they are not used correctly. The code attempts to use a reference to the method to clear the interval whereas it should be a timer reference: clearTimeout(draw); Should be: var timerRef; // global or parent scope function draw() { ......

Drawing a tournament bracket in android?

android,canvas,layout

As for question 1, yes you can absolutely change the layout dynamically. You can create several layout files and do one of two things: The first, is you can use your activity's setContentView(int) method to completely reset the activity's layout to a new view. The second would be to identify...

Detect mouse clicks on circles on HTML5 canvas

javascript,html5,canvas,click,mouseevent

With SVG, it would be easy - a circle is an element, and can have a click handler, and has fill that you can manipulate to change colour. With Canvas, you need to: save the data for each circle you draw (center and radius) capture click on canvas as cx,...

How to calculate X Y coordinates of image when window resize?

javascript,html,canvas

When the canvas element and canvas bitmap has different sizes, you need to use a factor to scale the mouse position to fit relative in the bitmap. This can be done dividing the bitmap size on the element size. Modified fiddle $("#myCanvas").click(function (event) { // get size of element and...

Context.Arc not drawing on specified coordinates

javascript,asp.net,html5,canvas

I managed to figure it out! Instead of drawing circles I drew lines. On mousedown, call moveTo(clientX,clientY) and on mouseMove call lineTo(clientX,clientY) moveTo(clientX,clientY) That way when the user clicks I have the initial position for the line, when he moves, assign the final position and update the initial position. JS:...

Add metadata (Exif) to base64

javascript,canvas,upload,exif

There is no easy way to do this. Canvas will only save out the JPEG file, then encode it as either a Data-URL or a Blob depending on the method you chose with the most basic chunks. There is no mechanism to insert custom or additional chunks into the file...

HTML5 canvas slow native function getImageData() on Mac OS

javascript,html5,canvas,getimagedata

I Highly recommend sending such works (image and or other intense data manipulations for example) to a web worker you you won't clog your call stack and your application's responsiveness. Web Workers on HTML5 Rocks helped me figure out how to use web workers for image transformations without making your...

How can I implement a zoom function in a 2D canvas?

javascript,animation,canvas

In your inner for-loop the code should be: var curIndex = y * ctx.canvas.width * 4 + x * 4; var targetIndex = Math.floor(y / zoomFactor) * ctx.canvas.width * 4 + Math.floor(x / zoomFactor) * 4; You should take the RGBA into account in the factor 4, and also the...

HTML 5 Canvas addHitRegion not working on iOS (undefined is not a function)

javascript,ios,html5,canvas

Currently the support for addHitRegion() is pretty slim on mobile devices. According to MDN, these devices are the only one supporting it at the moment of this writing (disclaimer: it's not certain MDN is entirely up to date; caniuse.com does not report any on this method): The situation is a...

slowly animate a simple line

That's actually not what you want to do: computers don't do things "slowly", especially not in a context that is single-threaded. What you want to do instead is draw lots of lines, over and over, where each next line is a little longer than the previous one. That way, it...

What is difference between fillRect(0,0,0,1) and clearRect()

(Updated to correspond to OPs changes in question:) fillRect() with ctx.fillStyle = "rgba(0, 0, 0, 1)"; will fill the region with opaque pixels, in this case black (note alpha is a normalized value [0,1]). clearRect() does the opposite, "clearing" all pixels so that the bitmap becomes transparent (technically the region...

Continuous gradient along a HTML5 canvas path

javascript,canvas,ember.js,firebase,emberfire

You can do a simple approach interpolating two colors along a line. If you need smooth/shared gradients where two lines joins at steeper angles, you would need to calculate and basically implement a line drawing algorithm from (almost) scratch. This would be out of scope for SO, so here is...

Saving an html object to firebase

You have to serialize and deserialize the image: function serialize(canvas) { return canvas.toDataURL(); } function deserialize(data, canvas) { var img = new Image(); img.onload = function() { canvas.width = img.width; canvas.height = img.height; canvas.getContext("2d").drawImage(img, 0, 0); }; img.src = data; } Based on this answer. Update 1 The canvas.toDataURL() method...

Canvas fillRect has wrong X coordinate

javascript,jquery,html,canvas

in the console i am getting the x coordinate as NaN their is no "event.x" you need to do "event.clientX" to get the X coordinate And one more thing you are first definig a var x where the value is stored, next right below it you are running a for...

Canvas - Rotate line

javascript,jquery,jquery-mobile,canvas,html5-canvas

You can use transformations to rotate a line or any shape drawn to canvas. To rotate: Translate to pivot point, ie. point of rotation Apply rotation transform Translate back Draw shape In your case, if we say rotate around the middle of the line: var cd; var ctx2; var startPoint;...

Snake Game with Mobile Button Controls

AND TIME So basically you have some errors going on. Your first one is your styling. You really need to make your styles more flexible, but this will solve the right button problem I was having. .button-pad > div { z-index: 9999; width: 50px; } http://jsfiddle.net/34oeacnm/8/ $(document).on('click', '.button-pad .button', function(e)...

How to display button over a Ad Mediator in windows phone 8?

c#,xaml,button,windows-phone-8,canvas

Just embed it in a panel like Grid so it just follows the DOM. Something like (in pseudo); <Grid> <AdMediator/> <Button/> </Grid> ...

Is it possible to make the lines move diagonally in tkinter?

python,python-3.x,canvas,tkinter

Add functions like this one: def p1_move_NE(event): global p1_y,p1_x canvas.create_line(p1_x, p1_y, p1_x + line_length, (p1_y - line_length), width=line_width, fill=p1_colour) p1_x = p1_x + line_length p1_y = p1_y - line_length Then bind it with: window.bind("9", p1_move_NE) My other advices for your program will be to use classes and generic functions like...

How to scale an image down to fit inside a canvas, without distorting the image?

html5,canvas,fabricjs

1) Determine which dimension is the one which exceeds the size of the window you want to put the image in. If both exceed the size calculate both factors and use the largest: width_factor = imagewidth / allowable_width height_factor = imageheight / allowable_height 2) Scale both the height and the...

Java - Show multiple canvases in container

java,canvas,containers

Container Layout is not set. Set the layout by like: container.setLayout(new GridLayout(1,2)); ...

How to make multiple balls drop on click?

javascript,canvas,javascript-events,html5-canvas

Just rewrite the ball object so it becomes instantiate-able: function Ball(W, H) { this.x = W; this.y = H; this.radius = 15; this.color = "blue"; this.vx = 0; this.vy = 1; } Move the methods to prototypes (this will make them shareable across instances). In addition, add an update method...

Draw arc on canvas from two x,y points and a center x,y point

javascript,canvas,html5-canvas,automatic-ref-counting,trigonometry

The arc() method works only with angles so points has to be converted based on their location and distance to center (distance, representing the radius, has to be the same for both in this case). The signature of arc() is: void arc(unrestricted double x, unrestricted double y, unrestricted double radius,...

Change a straight line into a curved line when length is overtaken

javascript,html,canvas

I would probably do something like this: Define a holding array with number of entries based on a resolution Map the lines into that array setting 1's very there would be a line range, 0's for the gap. Define a target shape such as an oval (can be any shape...

which is more performant,

javascript,html5,video,canvas

No, all the cost of decoding a video frame is still there. Using a canvas would in addition to that add more cost, not less. If the video is without sound you could temporary pause the video while scrolling, as well as pause it permanently when out of view: var...

Fabric.js copy paste of selected group

javascript,canvas,fabricjs

Thanks to Nistor for helping to get me started. I had to do some additional work to get the result I wanted. Here is my paste function (note that I am using Angular but others can adapt as necessary). Objects must be copied to the clipboard array prior to this...

DrawImage is not drawing in a canvas

javascript,html5,canvas,drawimage

In your function function loadImg() { var loadTile = new Image(); loadTile.src = 'Top/x+y+/' + tileToLoad + ".png"; loadTile.onload = function() { ctx.drawImage(loadTile, tileToLoadX, tileToLoadY); }; console.log("Successfully loaded tile " + tileToLoad); }; The variables tileToLoad, tileToLoadX and tileToLoadY belong to the function imageSearch() as local variables and would be...

a border where you can not go through (canvas game)

javascript,css,html5,canvas

You need a concept called "clamping". Clamping is limiting a value within a specified range. You want to clamp your ship's horizontal position to be no less than 0 and no greater than the canvas width. You want to clamp your ship's vertical position to be no less than 0...

How can I make a button who draws a line

javascript,html,button,canvas,htmlbutton

This is how I did it - https://jsfiddle.net/jadeallencook/wnhmgya7/ HTML <center> <div id="myLine"></div> <br /> <button id="myButton"> Draw Line </button> </center> <script src="https://ajax.googleapis.com/ajax/libs/jquery/2.1.1/jquery.min.js"></script> CSS #myLine { height: 1px; width: 0px; background: black; margin-top: 25px; } .animate { -webkit-animation: myfirst 5s; animation: myfirst 5s; } @keyframes myfirst { 0% {width: 0px;} 100%...

I'm trying to call a method in a constructer every second for 15 seconds but setInterval doesn't seem to work

canvas,svg,javafx,graphicscontext

You need to pass a bound reference to bob.update var intervalID = setInterval(bob.update.bind(bob), 1000); ...

Finding non transparent filled areas in images on javascript canvas

javascript,image,canvas

Here's an outline to get you started: Use context.getImageData to get the pixel data from the canvas, Scan the pixel data for the first non-transparent pixel, Use the "marching squares" algorithm to find the border path points around the circle or rectangle: Draw border around nontransparent part of image on...

JavaFX: How to use the GraphicsContext method appendSVGPath(String svgpath)

Canvas isn't like the scene graph, stroking and filling paths does not happen automatically. Instead you need to feed your path segments to the canvas, then explicitly call fill() or stroke() to have those operations applied. For more information, see the "path rendering" section at the front of the GraphicsContext...

How to select particular area in canvas? [closed]

javascript,jquery,html5,canvas

You can define the area you want to fill using an image mask that fits on top of your image - this step is something for Photoshop/GIMP. For example, having your shoe as-is: Create a mask for it leaving the heal in the original position (it makes it easier to...

How to load TIFF image with fabric.js?

javascript,canvas,fabricjs

This is not really a problem with FabricJS, but more that browsers in general does not support the TIFF file format. IE and Safari being exceptions as well as some less mainstream browsers. Workarounds However, it is possible to read and parse TIFF files manually. To read TIFF you can...

Circle div in CSS doesn't show in canvas properly

javascript,css,canvas,html2canvas

The border-radius must be the half of the width/height. So setting it to 10px – or even better 50% will render a smooth circle: div { width: 20px; height: 20px; border-radius: 50%; background: red; } http://jsfiddle.net/hmjqLz3p/...

Randomly appearing text in html page

javascript,html5,css3,canvas,html5-canvas

Here's one way to animate words into a final sentence: https://jsfiddle.net/m1erickson/q7tpsnmv/ Define some word objects in an array: var words=[]; words.push({ text:'Welcome', // starting x,y of the word offscreen x0:Math.random()*cw, y0:(Math.random()*100)+ch, // ending position of the word onscreen x1:20, y1:50, // font-size size:10, // delay before starting to animate this...

How to get the value for one function to another?

You could call check(num) inside the setInterval() function with a condition: if(i < 30){ draw(num); i++; } else { check(num); } You should also then end your loop as this will keep running indefinitely. To do this assign the interval to a variable: var myInterval = setInterval(function() { And then...

How to know whether the mousedown event is occured on where we want in canvas?

c#,windows-phone-7,canvas

An explanation of what your code is testing. This part of your code... ((dx * dx) + (dy * dy) < circleRadius * circleRadius) ...uses the Pythagorean Theorem to mathematically test if the mouse is inside the circumference of a circle. (dx * dx) + (dy * dy) measures the...

Canvas borders c# ( Windows Phone 7)

I`ve fixed this problem. I had just to create another canvas below and set ZIndex to higher paremeter For the bottom Canvas Canvas.ZIndex = 1 For the top Canvas Canvas.ZIndex = 0 Its just about the priority of ZIndex...

How to map tapped event for a single object in a canvas control in XAML?

c#,xaml,canvas,foreach

I think you should try something like this: foreach (UIElement ball in playArea.Children) { if(ball is ContentControl) ball.Tapped += ball_Tapped; } } void ball_Tapped(object sender, TappedRoutedEventArgs e) { ContentControl ball = sender as ContentControl; double top = Canvas.GetTop(ball); animateBall(ball, top, playArea.ActualHeight, "(Canvas.Top)"); } ...

Displaying tooltips on mouse hover on shapes/position(coordinates) on canvas

html5,canvas,tooltip

You can test if the mouse is over one of your circular hot-spots like this: var hotspots=[ {x:100,y:100,radius:20,tip:'You are over 100,100'}, {x:100,y:200,radius:20,tip:'You are over 100,200'}, ]; var dx=mouseX-hotspot[0].x; var dy=mouseY-hotspot[0].y; if(dx*dx+dy*dy<hotspot[0].radius*hotspot[0].radius){ // it's over hotspot[0] } Here's example code and a Demo: Note: you don't need to show the circular...

How to create infinite raphael canvas

javascript,canvas,raphael

One solution is to perform a check on all your objects to see if they're inside or outside your current canvas size. If it's outside, you give the canvas new width/height. Here's a working example (although not using dragable objects) just to show the idea: var c = document.getElementById("canvas"); var...

Resize function canvas loaded on shrinked browser and expanded

You just need to change the canvas to c in the event listener; http://jsbin.com/zigoto/1/edit?js,output var c = document.getElementById('c'), largeHeader = document.getElementById('h'); var w = c.width = window.innerWidth, h = c.height = window.innerHeight, ctx = c.getContext('2d'), spawnProb = 1, numberOfMoves = [8, 16], //[min, max] distance = [50, 200], attenuator =...

How does the browser process image sources?

android,canvas,bitmap,drawable

It's simply a matter of what the browser supports. The browser will look at the protocol header of the string and if it recognizes it try to interpret it. For example: If it starts with "http://" or "https://" it will parse the rest of the string with that as a...

Canvas element does not resize when using ReactJS and PaperJS together

javascript,html,canvas,reactjs,paperjs

You'll have to use the data-paper-resize prop, since React doesn't recognize the resize prop. <canvas id="myCanvas" data-paper-resize /> See Canvas Configuration and Supported Attributes....

Redraw text over clearRect HTML5 Canvas

jquery,html5,canvas

One possible solution is that you move all your clearRect()'s out from the else-statements to the top and clear it from the start. Then you add text in a second step. That way you can also group the if-statements together to form a if-else if relationship (crappy explanation, just look...

Android Bitmap on Canvas from External File

How about something like: Bitmap bitmap = BitmapFactory.decodeFile(pathToFile); canvas.drawBitmap(bitmap, ...); ...

Rotating charts in Chart JS

javascript,canvas,charts,rotation

There's no way to rotate the chartJS but not rotate the tips :-\ On the bright side, it's easy enough to code yourself from previous Stackoverflow posts! A polar chart is a set of concentric wedges as shown in this Stackoverflow post: Creating Polar Area Chart using Canvas Tooltips are...

Javascript Canvas, can't draw multiple images

The reason for only seeing 1 enemy is becuase you're using the wrong variable to the x and y coordinates. You were using the variable enemy that you used to make the enemies. Change the last row in your moveEnemy function from images.enemy.draw(CONTEXT, enemy.posX, enemy.posY); to images.enemy.draw(CONTEXT, myEnemy.posX, myEnemy.posY); ...

Converting Text view to bitmap returns null

java,android,canvas,bitmap,textview

You did not add the text view to the the screen. Once you add it, the view height and width will be calculated for rendering and then only view will be drawn and you can get the bitmap out of it. Do the three things, Add the textview to the...

Text in canvas to show in timed sequences using jQuery?

javascript,canvas,radians

There are several issues with this code. As @Jackson suggest, you have used wrong jquery function toggle() instead of toggleClass(). Secondly, your footer has margin-top property set to -700px which cause this element to disappear since your canvas and "No" button in summary have about 400px height. So your footer...

Fill color for an arc drawed by canvas

html5,canvas

You need to define a continuous path to be able to fill it with a single color if you don't want to use line-width. Using two arcs means you need to "reverse" one of them so their end-points connect correctly without crossing. You can do this by using the counter-close...

Facebook Canvas login - session not created?

php,facebook,canvas

Well, I decided to take a leap of faith, and now things have progressed. I: a) set up a FacebookRedirectLoginHelper at the top of my app b) get the loginUrl from that, using a pointer to my app (mydomain.com/myapp), and present that for authorization c) user clicks on that link,...

HTML canvas breaking when keyboard is shown at landscape orientation

javascript,android,css,html5,canvas

Try using fixed position for it: canvas { position: fixed; left:0; top:0; height: 100%; width: 100%; z-index: -1; /* place in background */ } ...

Create a picture frame type border

html,css,canvas,svg,css-shapes

If you don't have to support IE8 and less, you can use one pseudo-element and background-image to achieve the frame effect and also have it responsive with minimal code. The inner box is generated using the pseudo element and the angled parts on all sides are achieved using angled linear-gradient...

Highchart Polar chart multiple background colors to SVG

javascript,jquery,canvas,svg,highcharts

The problem is you that created backgrounds are not part of the chart. In fact, add them in the chart.events.load event, and will be included in the exported SVG: http://jsfiddle.net/9eqh0xrj/5/ chart: { polar: true, renderTo: 'container', events: { load: modelMe } }, And example for function: function modelMe() { var...

How to alter a degree value into an actual x/y position change?

Yes, all angles in JavaScript are in radians. In addition, the canvas context has 0° point to the right so you need to subtract 90° from all angles if you want 0° to be straight up: var angle = (movement.degrees - 90) / 180 * Math.PI; // compensate angle -90°,...

Canvas image not loading correctly in Firefox unless cached

Thank you, K3N! By only calling generateRGBKs once and adding a callback to its imgComp, the issue was resolved. function loadFontColours() { console.log("loading font colours"); console.log(font); var start = new Date().getTime(); var rgbks = generateRGBKs(font, function() { colourLookupTable[0].fontBuf = generateTintImage(rgbks, font, 240, 240, 240); colourLookupTable[1].fontBuf = generateTintImage(rgbks, font, 242, 178,...

How to make a Javafx Image Crop App

java,image,canvas,graphics,javafx

Your question is too much to be answered on StackOverflow. I suggest you start with reading the official Oracle documentation about JavaFX. However, since it's an interesting topic, here's the answer in code. There are several things you need to consider: use an ImageView as container use a ScrollPane in...

Safari on Mobile blocks window.open [closed]

It looks to me like you're calling window.open indirectly, not in direct response to a user event. Most browsers will block those calls (I'm surprised Chrome isn't, but I don't know a lot basically anything about canvas rendering). You may have to break up your logic into two buttons: One...

After drawing Stroke on Canvas, adding a stroke to another object changes all the strokes