- From: Rik Cabanier <cabanier@gmail.com>
- Date: Mon, 20 Aug 2012 19:53:37 -0700
- To: Michael Day <mikeday@yeslogic.com>
- Cc: whatwg@lists.whatwg.org
On Mon, Aug 20, 2012 at 5:55 PM, Michael Day <mikeday@yeslogic.com> wrote: > Hi Rik, > > The 'scale(2,1)' set up a different coordinate system. You can rewrite >> your code from this: >> >> ctx.lineTo(100, 100); >> ctx.scale(2, 1); >> ctx.arcTo(100, 100, 100, 200, 100); >> >> to this: >> >> ctx.scale(2, 1); >> *ctx.lineTo(50, 100);* >> >> ctx.arcTo(100, 100, 100, 200, 100); >> > > Right, these will produce the same arc. But how should this be implemented > in the user agent? > > It's almost like it is getting the last point in the previous subpath, > transforming it by the inverse of the current transformation matrix, > generating the arc, and then transforming the arc by the matrix. > Yes, that is one way of implementing it. This is not specific to arcTo; this happens with all drawing operators. > > Is this what Firefox and Chrome do? There is no hint of this in the spec, > which is quite ambiguous about how the current transform should affect > previous subpaths. > I don't know. It just depends how they implemented in. They might apply the CTM to all the coordinates or keep the coordinates and pass them along with the CTM to the drawing system.
Received on Tuesday, 21 August 2012 02:54:08 UTC