Given a combination of a large scaling matrix and a large line, we can
easily generate a half line width that is unrepresentable in our 24.8
fixed-point. This leads to spurious errors later, such as generating
negative height boxes, and so asking pixman to fill to infinity. To
avoid this, we can check for overflow in calculating the half line with,
though we still lack adequate range checking on the final stroke path.
References: https://bugs.webkit.org/show_bug.cgi?id=16793
Signed-off-by: Chris Wilson <chris@chris-wilson.co.uk>
Cc: magomez@igalia.com
Tested-by: Bryce Harrington <bryce@osg.samsung.com>
Acked-by: Bryce Harrington <bryce@osg.samsung.com>
Given the criteria of the rectlinear stroker that it only handles
horizontal and vertical line segments, and eliminates degenerate
segments before stroking, we must be careful not to apply a join between
two horizontal segments (for example if the intervening vertical segment
was degenerate and so elided). A miter join between two colinear
segments is empty, yet we were blissfully extending the line caps to
cover the join.
Fixes: outline-tolerance
Bugzilla: https://bugzilla.mozilla.org/show_bug.cgi?id=407107
Signed-off-by: Chris Wilson <chris@chris-wilson.co.uk>
A typo using half_line_x instead of half_line_y when emitting dashed
segments of the rectilinear stroke.
Signed-off-by: Chris Wilson <chris@chris-wilson.co.uk>
If the stroke is too large, the strokes around the box overlap and we
fail to generate the canonical form of the boxes. So if we detect that
the boxes overlap, feed them through the tessellator to reduce them to
canonical form.
Fixes line-width-overlap.
Based on a patch by Paulo Zanoni <paulo.r.zanoni@intel.com>
Signed-off-by: Chris Wilson <chris@chris-wilson.co.uk>
Having spent the last dev cycle looking at how we could specialize the
compositors for various backends, we once again look for the
commonalities in order to reduce the duplication. In part this is
motivated by the idea that spans is a good interface for both the
existent GL backend and pixman, and so they deserve a dedicated
compositor. xcb/xlib target an identical rendering system and so they
should be using the same compositor, and it should be possible to run
that same compositor locally against pixman to generate reference tests.
Signed-off-by: Chris Wilson <chris@chris-wilson.co.uk>
P.S. This brings massive upheaval (read breakage) I've tried delaying in
order to fix as many things as possible but now this one patch does far,
far, far too much. Apologies in advance for breaking your favourite
backend, but trust me in that the end result will be much better. :)
As handling joins/caps between line segments shorter than
half_line_width is tricky.
Rather than also fixing the bug in traps, remove that code. The plan is
to avoiding hitting the traps code, short-circuiting several steps along
the fast rectangular paths.
Fixes line-width-overlap.
Signed-off-by: Chris Wilson <chris@chris-wilson.co.uk>
