* M3: shadows of images with transparent pixels follow their alpha (#1289)
A drop shadow on an image fill was hidden behind the layer's whole box, so a
transparent PNG's shadow only showed outside its bounding box. Fills that
paint their own alpha (patterns; images with transparent pixels or that leave
part of the box empty) now cast and hide drop shadows, and shade inner
shadows, by the layer's pixels, like groups. Opaque pictures keep their
outline. Each image is scanned for transparency once. Canvas, PNG, SVG and PDF.
* M3: the image shadow tests import their names explicitly (#1289)
BFlat
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