- From: Justin Novosad <junov@chromium.org>
- Date: Mon, 8 Aug 2011 16:55:26 -0400
Hi, This inquiry is regarding this page of the specification: http://www.whatwg.org/specs/web-apps/current-work/multipage/the-canvas-element.html In section 4.8.11.1.10 Images, about drawImage(), it is stated that "If one of the sw or sh arguments is zero, the implementation must raise an INDEX_SIZE_ERR exception" There are no other references to other circumstances under which INDEX_SIZE_ERR should be thrown, and there is no indication of what the correct behavior is when the source rectangle is completely or partially outside the bounds of the source image. Right now there are discrepancies in how different browsers handle this situation. -WebKit throws INDEX_SIZE_ERR when the source rectangle is completely out of bounds -Internet Explorer 9 does not throw an exception (which I believe is the correct behavior, given the current wording of the spec) -Firefox 5 throws an INDEX_SIZE_ERR if the source rectangle is out of bounds to the top or left (negative sx or sy) Also, this test agrees with (or perhaps influenced) the WebKit interpretation of the specification: http://w3c-test.org/html/tests/submission/PhilipTaylor/canvas/2d.drawImage.outsidesource.html This matter is currently under investigation in WebKit: https://bugs.webkit.org/show_bug.cgi?id=65709 On the Firefox side, a patch was recently submitted to remove the exception (be like IE) https://bugzilla.mozilla.org/show_bug.cgi?id=664107 Thanks providing clarification, Justin
Received on Monday, 8 August 2011 13:55:26 UTC