Re: [Inkscape-devel] Bug in Blend Modes, Please Help
2013/9/28 Martin Owens <doctormo@...400...>:
Hey Devs,
Blocking bug lp:850992 [1] is proving impossible to get a handle on for
different devs who are not familiar with the blend code base and it's
resisting attempts to let us learn about it.
We could do with a heavy-hitting genius who hopefully knows something
about the blend modes for layers to figure this out. I'm betting it's a
single line fix when the little worm is rooted out.
I found the following clues:
1. After grouping, I can only select the invisible top rectangle by
clicking on the part where it should obscure the lower one. Clicking
on the parts where it should be drawn, but there is nothing below it
has no effect. This indicates that there is something seriously wrong
going on with bboxes.
2. The invisibility persists when zooming in/out, indicating that the
display tree is in this incorrect state even after a call to
Drawing::update() that should force-update everything (reset =
STATE_ALL) and a full redraw.
PS: This is probably unrelated to this bug, but the recently
introduced code handling _filter_bbox is wrong. _filter_bbox should
NOT be set using area_enlarge(). area_enlarge() is intended to compute
the dependency region of the filter, and exists only because we render
in tiles. _drawbox must ultimately come from SVG data, because the
filter effect region is specified explicitly in the SVG (by default it
corresponds to 120% of the object width and height), rather than
implicitly by the filter primitives used.
Regards, Krzysztof