On Aug 23, 2010, at 4:33 AM, Maciej Stachowiak wrote: > > > - tx, ty are the origin of the parent's coordinate system relative to the > origin for its layer. When a layer paints, it establishes a CTM such that its > own origin is 0, 0 (I think). >
They are relative to a painting root, which will basically either be the document or a compositing layer. > The more obvious way, given the variable names, would be to make x(), y() an > IntPoint, with a name like originInParentCoordinates() It already is an IntPoint internally. There's already a method to access it as a point. IntPoint location() const > (hopefully less verbose, but you get the idea). tx, ty could be named > parentOffsetFromLayerCoordinates or something. This seems to be the intent of > the names - that x,y is a point and tx, ty is a translation. But this doesn't > work in point/size logic. You repeatedly add x(), y() to tx, ty to get a new > tx, ty. But that means you're adding a point to a size and expecting to get a > new size - but that's not how it works. > I think a helper method that does the right thing solves this problem (rather than having to flip what x/y and tx/ty mean just to do some math operation). dave
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