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cogl-path: Don't try to union sub paths

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When drawing a path with only a single sub path, Cogl uses the
'even-odd' fill rule which means that if a part of the path intersects
with another part then the intersection would be inverted. However
when combining sub paths it treats them as separate paths and then
unions them together. This doesn't match the semantics of the even-odd
rule in SVG and Cairo. This patch makes it so that a new sub path is
just drawn as another triangle fan so that it will continue to invert
the stencil buffer. This is also much simpler and more efficient as
well as being more correct.

http://bugzilla.openedhand.com/show_bug.cgi?id=2088
This commit is contained in:
Neil Roberts 2010-04-19 18:54:40 +01:00
parent 7f629f626e
commit 8afea98437
1 changed files with 0 additions and 24 deletions
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24
cogl/cogl-path.c
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@ -189,7 +189,6 @@ _cogl_add_path_to_stencil_buffer (CoglHandle path_handle,
gboolean need_clear) gboolean need_clear)
{ {
unsigned int path_start = 0; unsigned int path_start = 0;
unsigned int sub_path_num = 0;
float bounds_x; float bounds_x;
float bounds_y; float bounds_y;
float bounds_w; float bounds_w;
@ -288,30 +287,7 @@ _cogl_add_path_to_stencil_buffer (CoglHandle path_handle,
GE (glDrawArrays (GL_TRIANGLE_FAN, 0, GE (glDrawArrays (GL_TRIANGLE_FAN, 0,
MIN (node->path_size, path->path_size - path_start))); MIN (node->path_size, path->path_size - path_start)));
if (sub_path_num > 0)
{
/* Union the two stencil buffers bits into the least
significant bit */
GE (glStencilMask (merge ? 6 : 3));
GE (glStencilOp (GL_ZERO, GL_REPLACE, GL_REPLACE));
cogl_rectangle (bounds_x, bounds_y,
bounds_x + bounds_w, bounds_y + bounds_h);
/* Make sure the rectangle hits the stencil buffer before
* directly changing other GL state. */
_cogl_journal_flush ();
/* NB: The journal flushing may trash the modelview state and
* enable flags */
_cogl_matrix_stack_flush_to_gl (modelview_stack,
COGL_MATRIX_MODELVIEW);
_cogl_enable (enable_flags);
GE (glStencilOp (GL_INVERT, GL_INVERT, GL_INVERT));
}
GE (glStencilMask (merge ? 4 : 2));
path_start += node->path_size; path_start += node->path_size;
sub_path_num++;
} }
if (merge) if (merge)