Commit Graph

3 Commits

Author SHA1 Message Date
Neil Roberts
4f6fe6f0e2 Fixes for --disable-glib
This fixes some problems which were stopping --disable-glib from
working properly:

• A lot of the public headers were including glib.h. This shouldn't be
  necessary because the API doesn't expose any glib types. Otherwise
  any apps would require glib in order to get the header.

• The public headers were using G_BEGIN_DECLS. There is now a
  replacement macro called COGL_BEGIN_DECLS which is defined in
  cogl-types.h.

• A similar fix has been done for G_GNUC_NULL_TERMINATED and
  G_GNUC_DEPRECATED.

• The CFLAGS were not including $(builddir)/deps/glib which was
  preventing it finding the generated glibconfig.h when building out
  of tree.

Reviewed-by: Robert Bragg <robert@linux.intel.com>

(cherry picked from commit 4138b3141c2f39cddaea3d72bfc04342ed5092d0)
2013-01-22 17:48:05 +00:00
Robert Bragg
b3d9f313d4 util: tune point_in_poly test for polys in screen coords
This makes a change to the original point_in_poly algorithm from:
http://www.ecse.rpi.edu/Homepages/wrf/Research/Short_Notes/pnpoly.html

The aim was to tune the test so that tests against screen aligned
rectangles are more resilient to some in-precision in how we transformed
that rectangle into screen coordinates. In particular gnome-shell was
finding that for some stage sizes then row 0 of the stage would become a
dead zone when going through the software picking fast-path and this was
because the y position of screen aligned rectangles could end up as
something like 0.00024 and the way the algorithm works it doesn't have
any epsilon/fuz factor to consider that in-precision.

We've avoided introducing an epsilon factor to the comparisons since we
feel there's a risk of changing some semantics in ways that might not be
desirable. One of those is that if you transform two polygons which
share an edge and test a point close to that edge then this algorithm
will currently give a positive result for only one polygon.

Another concern is the way this algorithm resolves the corner case where
the horizontal ray being cast to count edge crossings may cross directly
through a vertex. The solution is based on the "idea of Simulation of
Simplicity" and "pretends to shift the ray infinitesimally down so that
it either clearly intersects, or clearly doesn't touch". I'm not
familiar with the idea myself so I expect a misplaced epsilon is likely
to break that aspect of the algorithm.

The simple solution this patch applies is to pixel align the polygon
vertices which should eradicate most noise due to in-precision.

https://bugzilla.gnome.org/show_bug.cgi?id=641197
2011-03-07 13:26:19 +00:00
Robert Bragg
1f0826543e cogl: Adds _cogl_util_point_in_polygon API
This adds a utility function that can determine if a given point
intersects an arbitrary polygon, by counting how many edges a
"semi-infinite" horizontal ray crosses from that point. The plan is to
use this for a software based read-pixel fast path that avoids using the
GPU to rasterize journaled primitives and can instead intersect a point
being read with quads in the journal to determine the correct color.
2011-01-21 16:18:11 +00:00