onMatrixChanged() flawed?

It calls getDisplayRect() to calculate the display rectangle which in turn uses the drawable intrinsic dimensions. This seems flawed to me. When I try, for instance, with a 700 pixel wide image, I get displayRect.right values well above 1,000 which is clearly wrong. I'll report back with some suggestions shortly but at first sight, the most obvious change would be to map the currently visible rectangle instead of the whole drawable to start with.