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Section: http://www.whatwg.org/specs/web-apps/current-work/complete.html#complex-shapes-(paths) Comment: arcTo() -> should be "Adds a point to the current [subpath]..." Posted from: 82.231.169.179
Also, the explanation doesn't seem correct. In fact the two points (in current implementations) seem more like control points. And effective points are the ones at intersections between tangents an the circle. -- Adds two control points defining, using last point of previous subpath, 2 tangents to the circle defined by arguments. Resulting subpath is an arc starting at intersection point with the first tangent and ending at intersection point with the second tangent. -- Illustrated by the following example where the black disc is the previous subpath and gray ones control points. context.fillStyle = "gray"; context.beginPath(); context.translate(125, 25); context.moveTo(20,18); context.arcTo(40, 20, 10, 100, 100); context.lineTo(100, 100); context.stroke(); context.beginPath(); context.arc(40, 20, 4, 0, 2 * Math.PI, 1); context.arc(10, 100, 4, 0, 2 * Math.PI, 1); context.fill(); context.beginPath(); context.fillStyle = "black"; context.arc(20, 18, 4, 0, 2 * Math.PI, 1); context.fill();
Checked in as WHATWG revision r5343. Check-in comment: correct some of the informative prose http://html5.org/tools/web-apps-tracker?from=5342&to=5343
EDITOR'S RESPONSE: This is an Editor's Response to your comment. If you are satisfied with this response, please change the state of this bug to CLOSED. If you have additional information and would like the editor to reconsider, please reopen this bug. If you would like to escalate the issue to the full HTML Working Group, please add the TrackerRequest keyword to this bug, and suggest title and text for the tracker issue; or you may create a tracker issue yourself, if you are able to do so. For more details, see this document: http://dev.w3.org/html5/decision-policy/decision-policy.html Status: Accepted Change Description: see diff given below Rationale: I've changed the description to be less wrong. It's not especially useful, because I don't say how the control points work, but frankly there's a bunch of edge cases and it's pretty complicated, and I'm not sure how to define it helpfully.
Checked in as WHATWG revision r5344. Check-in comment: remove bad description of arcTo() http://html5.org/tools/web-apps-tracker?from=5343&to=5344
Seems better. Also the full explanation later on the page may help to understand the principle.