Commit Graph

1391 Commits

Author SHA1 Message Date
Robert Bragg
cd6d561f6f winsys-glx: map X window automatically if not foreign
For now we are going for the semantics that when a CoglOnscreen is first
allocated then it will automatically be mapped. This is for convenience
and if you don't want that behaviour then it is possible to instead
create an Onscreen from a foreign X window and in that case it wont be
mapped automatically.

This approach means that Cogl doesn't need onscreen_map/unmap functions
but it's possible we'll decide later that we can't avoid adding such
functions and we'll have to change these semantics.
2011-05-05 14:46:03 +01:00
Robert Bragg
4bf868c0eb cogl/configure.ac: make COGL_HAS_xyz defines public
Instead of using AC_DEFINE for the various COGL_HAS_PLATFORM defines
this now adds them to the COGL_DEFINES_SYMBOLS variable which gets
substituted into the public cogl-defines.h header.
2011-05-05 14:46:03 +01:00
Robert Bragg
f5bb20212b Adds Cogl Hello World and "X11 foreign" example applications
This adds a simple standalone Cogl application that can be used to
smoke test a standalone build of Cogl without Clutter.

This also adds an x11-foreign app that shows how a toolkit can ask Cogl
to draw to an X Window that it owns instead of Cogl being responsible
for automatically creating and mapping an X Window for CoglOnscreen.
2011-05-05 14:46:03 +01:00
Robert Bragg
711d035f44 cogl/configure.ac: add options to control driver/egl platform
This allows more detailed control over the driver and winsys features
that Cogl should have. Cogl is designed so it can support multiple
window systems simultaneously so we have enable/disable options for
the drivers (gl vs gles1 vs gles2) and options for the individual window
systems; currently glx and egl. Egl is broken down into an option
for each platform.
2011-05-05 14:46:03 +01:00
Robert Bragg
7037812ae6 EGL: Updates GDL platform support
The GDL API is used for example on intel ce4100 (aka Sodaville) based
systems as a way to allocate memory that can be composited using the
platforms overlay hardware. This updates the Cogl EGL winsys and the
support in Clutter so we can continue to support these platforms.
2011-05-05 14:46:02 +01:00
Robert Bragg
ce2da79440 Don't reference GL_STACK_OVERFLOW/UNDERFLOW for GLES
These symbols aren't available when building with GLES so only reference
them when building with OpenGL.
2011-05-05 14:46:02 +01:00
Robert Bragg
31ee65784d winsys: Expose environment variable to choose winsys
This makes it possible to override the winsys that cogl uses by setting
the COGL_RENDERER environment variable e.g. to "GLX" or "EGL"
2011-05-05 14:46:01 +01:00
Robert Bragg
dc7383b714 Add a vtable of indirection to the winsys code
So that we can dynamically select what winsys backend to use at runtime
we need to have some indirection to how code accesses the winsys instead
of simply calling _cogl_winsys* functions that would collide if we
wanted to compile more than one backend into Cogl.
2011-05-05 14:46:01 +01:00
Robert Bragg
d52e3f0cc2 texture-pixmap-x11: Move GLX code to cogl-winsys-glx.c
This moves the GLX specific code from cogl-texture-pixmap-x11.c into
cogl-winsys-glx.c. If we want the winsys components to by dynamically
loadable then we can't have GLX code scattered outside of
cogl-winsys-glx.c. This also sets us up for supporting the
EGL_texture_from_pixmap extension which is almost identical to the
GLX_texture_from_pixmap extension.
2011-05-05 14:46:01 +01:00
Robert Bragg
d5d11f1878 Moves all EGL code down from Clutter to Cogl
As was recently done for the GLX window system code, this commit moves
the EGL window system code down from the Clutter backend code into a
Cogl winsys.

Note: currently the cogl/configure.ac is hard coded to only build the GLX
winsys so currently this is only available when building Cogl as part
of Clutter.
2011-05-05 14:46:01 +01:00
Robert Bragg
8399f5e61c remove references to unused DRM_SURFACELESS EGL platform
The "DRM_SURFACELESS" EGL platform was invented when we were adding the
wayland backend to Clutter but in the end we added a dedicated backend
instead of extending the EGL backend so actually the platform name isn't
used.
2011-05-05 14:46:01 +01:00
Neil Roberts
d832172988 cogl-context: Initialize context->stub_winsys
If Cogl is built using a full Winsys then it wasn't initialising
context->stub_winsys which sometimes made it crash later on.
2011-04-21 16:45:21 +01:00
Neil Roberts
14b6c0459f cogl-winsys-stub: Remove _cogl_winsys_has_feature
Commit b061f737 moved _cogl_winsys_has_feature to the common winsys
code so there's no need to define it in the stub winsys any more. This
was breaking builds for backends using the stub winsys.
2011-04-20 18:43:02 +01:00
Neil Roberts
dcd23dc220 cogl-winsys-glx: Fix the comparison in find_onscreen_for_xid
The comparison for finding onscreen framebuffers in
find_onscreen_for_xid had a small thinko so that it would ignore
framebuffers when the negation of the type is onscreen. This ends up
doing the right thing anyway because the onscreen type has the value 0
and the offscreen type has the value 1 but presumably it would fail if
we ever added any other framebuffer types.
2011-04-20 18:20:25 +01:00
Neil Roberts
16bfa27d43 cogl-winsys: Move _cogl_winsys_has_feature to cogl-winsys.c
The code for _cogl_winsys_has_feature will be identical in all of the
winsys backends for the time being, so it seems to make sense to have
it in the common cogl-winsys.c file.
2011-04-20 18:20:20 +01:00
Neil Roberts
4a7762d6d7 cogl-context: Store winsys features in an array of unsigned ints
Previously the mask of available winsys features was stored in a
CoglBitmask. That isn't the ideal type to use for this because it is
intended for a growable array of bits so it can allocate extra memory
if there are more than 31 flags set. For the winsys feature flags the
highest used bit is known at compile time so it makes sense to
allocate a fixed array instead. This is conceptually similar to the
CoglDebugFlags which are stored in an array of integers with macros to
test a bit in the array. This moves the macros used for CoglDebugFlags
to cogl-flags.h and makes them more generic so they can be shared with
CoglContext.
2011-04-20 18:20:10 +01:00
Neil Roberts
f6ae9decaa cogl-renderer: Move the XEvent filters to be generic for all renderers
Instead of having cogl_renderer_xlib_add_filter and friends there is
now cogl_renderer_add_native_filter which can be used regardless of
the backend. The callback function for the filter now just takes a
void pointer instead of an XEvent pointer which should be interpreted
differently depending on the backend. For example, on Xlib it would
still be an XEvent but on Windows it could be a MSG. This simplifies
the code somewhat because the _cogl_xlib_add_filter no longer needs to
have its own filter list when a stub renderer is used because there is
always a renderer available.

cogl_renderer_xlib_handle_event has also been renamed to
cogl_renderer_handle_native_event. This just forwards the event on to
all of the listeners. The backend renderer is expected to register its
own event filter if it wants to process the events in some way.
2011-04-20 18:17:06 +01:00
Emmanuele Bassi
cbbf76f280 cogl/glx: Silence a compiler warning 2011-04-18 15:53:25 +01:00
James Athey
d0739ca0ba GL_IMG_TEXTURE_NPOT extension enables TEXTURE_NPOT features on GLES
Older drivers for PowerVR SGX hardware have the vendor-specific
GL_IMG_TEXTURE_NPOT extension instead of the
functionally-equivalent GL_OES_TEXTURE_NPOT extension.
2011-04-13 14:34:31 +01:00
Emmanuele Bassi
5e530ca9bb Silence another compiler warning 2011-04-12 21:02:14 +01:00
Emmanuele Bassi
9840321501 Silence the compiler by removing unused variables 2011-04-12 20:37:22 +01:00
Emmanuele Bassi
29e5531486 glx: Protect GLX SwapEvent symbols
We need to guard the usage of symbols related to the
GLX_INTEL_swap_event extension, to avoid breaking on platforms and/or
versions of Mesa that do not expose that extension.
2011-04-12 20:37:22 +01:00
Robert Bragg
2bbb0d895b Make cogl_framebuffer_get_width/height experimental public API
It's generally useful to be able to query the width and height of a
framebuffer and we expect to need this in Clutter when we move the
eglnative backend code into Cogl since Clutter will need to read back
the fixed size of the framebuffer when realizing the stage.
2011-04-11 17:54:36 +01:00
Robert Bragg
1928f7ec0e backend: remove untested fruity backend
This backend hasn't been used for years now and so because it is
untested code and almost certainly doesn't work any more it would be a
burdon to continue trying to maintain it. Considering that we are now
looking at moving OpenGL window system integration code down from
Clutter backends into Cogl that will be easier if we don't have to
consider this backend.
2011-04-11 17:54:36 +01:00
Robert Bragg
efb570fdae Adds the ability to build Cogl standalone
This adds an autogen.sh, configure.ac and build/autotool files etc under
clutter/cogl and makes some corresponding Makefile.am changes that make
it possible to build and install Cogl as a standalone library.

Some notable things about this are:
A standalone installation of Cogl installs 3 pkg-config files;
cogl-1.0.pc, cogl-gl-1.0.pc and cogl-2.0.pc. The second is only for
compatibility with what clutter installed though I'm not sure that
anything uses it so maybe we could remove it. cogl-1.0.pc is what
Clutter would use if it were updated to build against a standalone cogl
library. cogl-2.0.pc is what you would use if you were writing a
standalone Cogl application.

A standalone installation results in two libraries currently, libcogl.so
and libcogl-pango.so. Notably we don't include a major number in the
sonames because libcogl supports two major API versions; 1.x as used by
Clutter and the experimental 2.x API for standalone applications.
Parallel installation of later versions e.g. 3.x and beyond will be
supportable either with new sonames or if we can maintain ABI then we'll
continue to share libcogl.so.

The headers are similarly not installed into a directory with a major
version number since the same headers are shared to export the 1.x and
2.x APIs (The only difference is that cogl-2.0.pc ensures that
-DCOGL_ENABLE_EXPERIMENTAL_2_0_API is used). Parallel installation of
later versions is not precluded though since we can either continue
sharing or later add a major version suffix.
2011-04-11 17:54:36 +01:00
Robert Bragg
d40cdfa3e1 Moves all GLX code down from Clutter to Cogl
This migrates all the GLX window system code down from the Clutter
backend code into a Cogl winsys. Moving OpenGL window system binding
code down from Clutter into Cogl is the biggest blocker to having Cogl
become a standalone 3D graphics library, so this is an important step in
that direction.
2011-04-11 17:54:36 +01:00
Robert Bragg
bcd97f35ea Adds renderer,display,onscreen-template and swap-chain stubs
As part of the process of splitting Cogl out as a standalone graphics
API we need to introduce some API concepts that will allow us to
initialize a new CoglContext when Clutter isn't there to handle that for
us...

The new objects roughly in the order that they are (optionally) involved
in constructing a context are: CoglRenderer, CoglOnscreenTemplate,
CoglSwapChain and CoglDisplay.

Conceptually a CoglRenderer represents a means for rendering.  Cogl
supports rendering via OpenGL or OpenGL ES 1/2.0 and those APIs are
accessed through a number of different windowing APIs such as GLX, EGL,
SDL or WGL and more. Potentially in the future Cogl could render using
D3D or even by using libdrm and directly banging the hardware. All these
choices are wrapped up in the configuration of a CoglRenderer.

Conceptually a CoglDisplay represents a display pipeline for a renderer.
Although Cogl doesn't aim to provide a detailed abstraction of display
hardware, on some platforms we can give control over multiple display
planes (On TV platforms for instance video content may be on one plane
and 3D would be on another so a CoglDisplay lets you select the plane
up-front.)

Another aspect of CoglDisplay is that it lets us negotiate a display
pipeline that best supports the type of CoglOnscreen framebuffers we are
planning to create. For instance if you want transparent CoglOnscreen
framebuffers then we have to be sure the display pipeline wont discard
the alpha component of your framebuffers. Or if you want to use
double/tripple buffering that requires support from the display
pipeline.

CoglOnscreenTemplate and CoglSwapChain are how we describe our default
CoglOnscreen framebuffer configuration which can affect the
configuration of the display pipeline.

The default/simple way we expect most CoglContexts to be constructed
will be via something like:

 if (!cogl_context_new (NULL, &error))
   g_error ("Failed to construct a CoglContext: %s", error->message);

Where that NULL is for an optional "display" parameter and NULL says to
Cogl "please just try to do something sensible".

If you want some more control though you can manually construct a
CoglDisplay something like:

 display = cogl_display_new (NULL, NULL);
 cogl_gdl_display_set_plane (display, plane);
 if (!cogl_display_setup (display, &error))
   g_error ("Failed to setup a CoglDisplay: %s", error->message);

And in a similar fashion to cogl_context_new() you can optionally pass
a NULL "renderer" and/or a NULL "onscreen template" so Cogl will try to
just do something sensible.

If you need to change the CoglOnscreen defaults you can provide a
template something like:
  chain = cogl_swap_chain_new ();
  cogl_swap_chain_set_has_alpha (chain, TRUE);
  cogl_swap_chain_set_length (chain, 3);

  onscreen_template = cogl_onscreen_template_new (chain);
  cogl_onscreen_template_set_pixel_format (onscreen_template,
                                           COGL_PIXEL_FORMAT_RGB565);

  display = cogl_display_new (NULL, onscreen_template);
  if (!cogl_display_setup (display, &error))
    g_error ("Failed to setup a CoglDisplay: %s", error->message);
2011-04-11 17:54:35 +01:00
Robert Bragg
e80a2b9b2f rename winsys files to be more consistent
This tries to make the naming style of files under cogl/winsys/
consistent with other cogl source files. In particular private header
files didn't have a '-private' infix.
2011-04-11 17:54:35 +01:00
Robert Bragg
9f19244971 Add temporary cogl-clutter.h to aid splitting out Cogl
This gives us a way to clearly track the internal Cogl API that Clutter
depends on. The aim is to split Cogl out from Clutter into a standalone
3D graphics API and eventually we want to get rid of any private
interfaces for Clutter so its useful to have a handle on that task.
Actually it's not as bad as I was expecting though.
2011-04-11 17:54:35 +01:00
Robert Bragg
0b45110302 framebuffer: expose experimental cogl_get_draw_framebuffer
This renames the two internal functions _cogl_get_draw/read_buffer
as cogl_get_draw_framebuffer and _cogl_get_read_framebuffer. The
former is now also exposed as experimental API.
2011-04-11 15:28:53 +01:00
Robert Bragg
aa1e45267b framebuffer: track context as CoglFramebuffer member
The long term goal with the Cogl API is that we will get rid of the
default global context. As a step towards this, this patch tracks a
reference back to the context in each CoglFramebuffer so in a lot of
cases we can avoid using the _COGL_GET_CONTEXT macro.
2011-04-11 15:28:47 +01:00
Robert Bragg
5c7ce809c1 remove unused _cogl_features_init prototype
There is no corresponding implementation of _cogl_features_init any more
so it was simply an oversight that the prototype wasn't removed when the
implementation was removed.
2011-04-11 15:26:25 +01:00
Robert Bragg
7fc6613fe9 Remove unused _cogl_swap_buffers_notify
Recently _cogl_swap_buffers_notify was added (in 142b229c5c) so that
Cogl would be notified when Clutter performs a swap buffers request for
a given onscreen framebuffer. It was expected this would be required for
the recent cogl_read_pixel optimization that was implemented (ref
1bdb0e6e98) but in the end it wasn't used.

Since it wasn't used in the end this patch removes the API.
2011-04-11 15:26:25 +01:00
Robert Bragg
c415818537 cogl: consolidate _create_context_driver + _features_init
This moves the functionality of _cogl_create_context_driver from
driver/{gl,gles}/cogl-context-driver-{gl,gles}.c into
driver/{gl,gles}/cogl-{gl,gles}.c as a static function called
initialize_context_driver.

cogl-context-driver-{gl,gles}.[ch] have now been removed.
2011-04-11 15:26:25 +01:00
Robert Bragg
e9b1ca0165 cogl: Adds experimental cogl_context_new() API
This adds a new experimental function (you need to define
COGL_ENABLE_EXPERIMENTAL_API to access it) which takes us towards being
able to have a standalone Cogl API. This is really a minor aesthetic
change for now since all the GL context creation code still lives in
Clutter but it's a step forward none the less.

Since our current designs introduce a CoglDisplay object as something
that would be passed to the context constructor this provides a stub
cogl-display.h with CoglDisplay typedef.

_cogl_context_get_default() which Clutter uses to access the Cogl
context has been modified to use cogl_context_new() to initialize
the default context.

There is one rather nasty hack used in this patch which is that the
implementation of cogl_context_new() has to forcibly make the allocated
context become the default context because currently all the code in
Cogl assumes it can access the context using _COGL_GET_CONTEXT including
code used to initialize the context.
2011-04-11 15:26:20 +01:00
Robert Bragg
fdbc741770 cogl: rename cogl-context.h cogl-context-private.h
Since we plan to add public cogl_context_* API we need to rename the
current cogl-context.h which contains private member details.
2011-04-11 15:18:12 +01:00
Neil Roberts
16a6c77089 cogl-pango-glyph-cache: Fix the flags passed to cogl_atlas_new
In 047227fb cogl_atlas_new was changed so that it can take a flags
parameter to specify whether to clear the new atlases and whether to
copy images to the new atlas after reorganisation. This was done so
that the atlas code could be shared with the glyph cache. At some
point during the development of this patch the flag was just a single
boolean instead and this is accidentally how it is used from the glyph
cache. The glyph cache therefore passes 'TRUE' as the set of flags
which means it will only get the 'clear' flag and not the
'disable-migration' flag. When the glyph cache gets full it will
therefore try to copy the texture to the new atlas as well as
redrawing them with cairo. This causes problems because the glyph
cache needs to work in situations where there is no FBO support.
2011-04-06 17:36:00 +01:00
Neil Roberts
472e8e8f4e cogl-pipeline: Be careful not to take ownership of root layer
In _cogl_pipeline_prune_empty_layer_difference if the layer's parent
has no owner then it just takes ownership of it. However this could
theoretically end up taking ownership of the root layer because
according to the comment above in the same function that should never
have an owner. This patch just adds an extra check to ensure that the
unowned layer has a parent.

http://bugzilla.clutter-project.org/show_bug.cgi?id=2588
2011-04-05 18:24:09 +01:00
Robert Bragg
7de3655298 pipeline: reclaim ownership if reverting to layer ancestor
In _cogl_pipeline_prune_empty_layer_difference if we are reverting to
the immediate parent of an empty/redundant layer then it is not enough
to simply add a reference to the pipeline's ->layer_differences list
without also updating parent_layer->owner to point back to its new
owner.

This oversight was leading us to break the invariable that all layers
referenced in layer_differences have an owner and was also causing us to
break another invariable whereby after calling
_cogl_pipeline_layer_pre_change_notify the returned layer must always be
owned by the given 'required_owner'.

http://bugzilla.clutter-project.org/show_bug.cgi?id=2588
2011-04-05 18:24:09 +01:00
Emmanuele Bassi
12b622a320 offscreen: Plug a leak in an error path
When creating a CoglOffscreen we take a reference on the texture handle,
but in case of error we never release it.

We should take that reference only on success.

http://bugzilla.clutter-project.org/show_bug.cgi?id=2620
2011-04-04 14:42:36 +01:00
Emmanuele Bassi
bb79fb43e5 Merge remote-tracking branch 'elliot/cookbook-effects-basic'
* elliot/cookbook-effects-basic:
  docs: Remove checks for whether an effect is disabled
  docs: Add recipe about implementing a ClutterEffect
  docs: Add example of setting background color with ClutterEffect
  docs: Add example of a border added through ClutterEffect
2011-03-21 12:34:41 +00:00
Neil Roberts
f38b7a78fb cogl: Use GHookList instead of CoglCallbackList
glib already has a data type to manage a list of callbacks called a
GHookList so we might as well use it instead of maintaining Cogl's own
type. The glib version may be slightly more efficient because it
avoids using a GList and instead encodes the prev and next pointers
directly in the GHook structure. It also has more features than
CoglCallbackList.
2011-03-14 18:18:15 +00:00
Robert Bragg
034d273030 culling: Don't cull actors not being painted on the stage
Previously we were applying the culling optimization to any actor
painted without considering that we may be painting to an offscreen
framebuffer where the stage clip isn't applicable.

For now we simply expose a getter for the current draw framebuffer
and we can assume that a return value of NULL corresponds to the
stage.

Note: This will need to be updated as stages start to be backed by real
CoglFramebuffer objects and so we won't get NULL in those cases.
2011-03-10 21:02:29 +00:00
Jasper St. Pierre
30fa4e1a20 cogl-clip-state: Adapt to experimental cogl2 API.
The current clip state implementation couldn't be used in
conjunction with the CoglPath experimental API.

http://bugzilla.clutter-project.org/show_bug.cgi?id=2594

Signed-off-by: Neil Roberts <neil@linux.intel.com>
2011-03-10 13:05:43 +00:00
Neil Roberts
cbe9d758d5 cogl-path: Optimise paths that are just a rectangle
Drawing and clipping to paths is generally quite expensive because the
geometry has to be tessellated into triangles in a single VBO which
breaks up the journal batching. If we can detect when the path
contains just a single rectangle then we can instead divert to calling
cogl_rectangle which will take advantage of the journal, or by pushing
a rectangle clip which usually ends up just using the scissor.

This patch adds a boolean to each path to mark when it is a
rectangle. It gets cleared whenever a node is added or gets set to
TRUE whenever cogl2_path_rectangle is called. This doesn't try to
catch cases where a rectangle is composed by cogl_path_line_to and
cogl_path_move_to commands.
2011-03-09 18:28:48 +00:00
Neil Roberts
9b7f362ea4 cogl-shader-boilerplate: Specify default precision earlier
In 9ff04e8a99 the builtin uniforms were moved to the common shader
boilerplate. However the common boilerplate is positioned before the
default precision specifier on GLES2 so it would fail to compile
because the uniforms end up with no precision in the fragment
shader. This patch just moves the precision specifier to above the
common boilerplate.
2011-03-08 13:21:24 +00:00
Robert Bragg
d4a5d70ee0 util: optimize _clutter_util_fully_transform_vertices
Instead of unconditionally combining the modelview and projection
matrices and then iterating each of the vertices to call
cogl_matrix_transform_point for each one in turn we now only combine the
matrices if there are more than 4 vertices (with less than 4 vertices
its less work to transform them separately) and we use the new
cogl_vertex_{transform,project}_points APIs which can hopefully
vectorize the transformations.

Finally the perspective divide and viewport scale is done in a separate
loop at the end and we don't do the spurious perspective divide and
viewport scale for the z component.
2011-03-07 13:26:20 +00:00
Robert Bragg
962b84ed56 matrix: adds 2d view transform conveniences
This adds two new experimental functions to cogl-matrix.c:
cogl_matrix_view_2d_in_perspective and cogl_matrix_view_2d_in_frustum
which can be used to setup a view transform that maps a 2D coordinate
system (0,0) top left and (width,height) bottom right to the current
viewport.

Toolkits such as Clutter that want to mix 2D and 3D drawing can use
these APIs to position a 2D coordinate system at an arbitrary depth
inside a 3D perspective projected viewing frustum.
2011-03-07 13:26:19 +00:00
Robert Bragg
bc372d2734 viewport: consistently use floats for viewports
OpenGL < 4.0 only supports integer based viewports and internally we
have a mixture of code using floats and integers for viewports. This
patch switches all viewports throughout clutter and cogl to be
represented using floats considering that in the future we may want to
take advantage of floating point viewports with modern hardware/drivers.
2011-03-07 13:26:19 +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