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POHTML5 canvas drawing problems with Chrome
 

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  1. POHTML5 canvas drawing problems with Chrome
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    <p>I'm digging into HTML5 canvas a bit, and ran into something odd using my locally installed version of Chrome. It's Chrome 29 on linux.</p> <p>I was looking at the following (sample code from HTML5 Canvas, 2 ed):</p> <pre><code>//draw a big box on the screen context.fillStyle = "black"; context.fillRect(10, 10, 200, 200); context.save(); context.beginPath(); context.rect(0, 0, 50, 50); context.clip(); //red circle context.beginPath(); context.strokeStyle = "red"; context.lineWidth=5; context.arc(100, 100, 100, (Math.PI/180)*0, (Math.PI/180)*360, false); context.stroke(); context.closePath(); context.restore(); //reclip to the entire canvas context.beginPath(); context.rect(0, 0, 500, 500); context.clip(); //draw a blue line that is not clipped context.beginPath(); context.strokeStyle = "blue"; //need list of available colors context.lineWidth=5; context.arc(100, 100, 50, (Math.PI/180)*0, (Math.PI/180)*360, false); context.stroke(); context.closePath(); </code></pre> <p>And should get:</p> <p><img src="https://i.stack.imgur.com/M4TiO.png" alt="Correct"></p> <p>But instead see:</p> <p><img src="https://i.stack.imgur.com/TuPOG.png" alt="Incorrect"></p> <p>My research suggests that Chrome canvas is in a state of flux, and that arcs have had problems in the past. However, it seems to be fine on a close version of Chrome for Windows, and Chrome 27 on another linux desktop.</p> <p>I've looked through my Chrome://flags and don't see anything that should obviously effect this.</p> <p>Any guidance would be appreciated.</p> <p><strong>EDIT:</strong></p> <p><em>I've tried variations of #enable-experimental-canvas-features and #disable-accelerated-2d-canvas in chrome://flags without any luck.</em></p> <p><strong>Here's a Fiddle:</strong></p> <p><a href="http://jsfiddle.net/QJRHE/4/" rel="nofollow noreferrer">http://jsfiddle.net/QJRHE/4/</a></p> <p><strong>Another EDIT:</strong></p> <p>This code works on Chromium 28.0.1500.71 on my machine. I'm starting to suspect this is a Chrome bug.</p>
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    1. USJohn Carter
    1. USJohn Carter
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    1. COAre you sure `context.stroke()` should be called *before* `context.closePath()`?
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      1. USBoaz
    2. COThere is no point in closing a path *after* you have stroked it :-) Try to switch those two lines and could you provide a fiddle?
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      1. POHTML5 canvas drawing problems with Chrome
      1. USepistemex
    3. COcontext.arc(100, 100, 50, 0, 2*Math.PI, false); is good enough, or at least multiply by 360 before you divide by 180... Or, yes, just use 2*Math.PI :-)
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      1. POHTML5 canvas drawing problems with Chrome
      1. USGameAlchemist
 

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