On Tue, 29 Jan 2013, Dirk Schulze wrote: > > The spec doesn't have any wording about the behavior on non-invertible > CTMs on Canvas contexts. Is it still possible to add segments to the > current path once a CTM is not invertible anymore? Does the path get > rejected completely then? Implementations are fairly different. > > Here are two examples (code attached at the end of the mail as well): > > http://jsfiddle.net/Dghuh/1/ > http://jsfiddle.net/Dghuh/2/ > > Note that the path is stroked after restoring the initial CTM in both > examples. > > The first one does scale(0), which should make the CTM non-invertibe, > WebKit still applies lineTo and closePath for some reason. IE and FF > refuse to draw anything.
scale(0) is invalid, and should throw an exception. If you do scale(0,0), the browsers act the same as with your second test that uses setTransform() with 6 zeros. > The second does setTransform(0,0,0,0,0,0), which should reset the CTM to > a zero matrix (again, not invertible). IE, Opera and FF draw a line to > 0,0 and close the path afterwards (which kind of makes sense, since the > universe is convoluted to one point). WebKit refuses the lineTo command > and closes the path as expected. WebKit seems to just be wrong here, and the others right. > This is an edge case, but should still be clarified in the spec. I don't understand what there is to clarify. In both cases, the behaviour seems well-defined: if you're transforming everything to zero, that's what the result will be. Zero. Firefox's behaviour is the right one. -- Ian Hickson U+1047E )\._.,--....,'``. fL http://ln.hixie.ch/ U+263A /, _.. \ _\ ;`._ ,. Things that are impossible just take longer. `._.-(,_..'--(,_..'`-.;.'
