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gl/msaa: Prevent stroke overlap

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When stroking we do not send our polygon to the tessellator, so
it may have overlapping stroke components. Use the stencil buffer
to prevent stroke components from overlapping.
This commit is contained in:
Henry (Yu) Song 2011-10-11 09:08:38 -07:00 • committed by Martin Robinson
parent 138e595c11
commit a60bb83f28
1 changed files with 36 additions and 0 deletions
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36
src/cairo-gl-msaa-compositor.c
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@ -297,6 +297,37 @@ _stroke_shaper_add_quad (void *closure,
quad);
}
static cairo_int_status_t
_prevent_overlapping_drawing (cairo_gl_context_t *ctx,
cairo_gl_composite_t *setup,
cairo_composite_rectangles_t *composite,
cairo_bool_t used_stencil_buffer_for_clip)
{
if (! _cairo_gl_ensure_stencil (ctx, setup->dst))
return CAIRO_INT_STATUS_UNSUPPORTED;
if (_cairo_pattern_is_opaque (&composite->source_pattern.base,
&composite->source_sample_area))
return CAIRO_INT_STATUS_SUCCESS;
if (used_stencil_buffer_for_clip == FALSE) {
/* Enable the stencil buffer, even if we have no clip so that
we can use it below to prevent overlapping shapes. We initialize
it all to one here which represents infinite clip. */
glDepthMask (GL_TRUE);
glEnable (GL_STENCIL_TEST);
glClearStencil (1);
glClear (GL_STENCIL_BUFFER_BIT);
glStencilFunc (GL_EQUAL, 1, 1);
}
/* This means that once we draw to a particular pixel nothing else can
be drawn there until the stencil buffer is reset or the stencil test
is disabled. */
glStencilOp (GL_ZERO, GL_ZERO, GL_ZERO);
return CAIRO_INT_STATUS_SUCCESS;
}
static cairo_int_status_t
_cairo_gl_msaa_compositor_stroke (const cairo_compositor_t *compositor,
cairo_composite_rectangles_t *composite,
@ -340,6 +371,11 @@ _cairo_gl_msaa_compositor_stroke (const cairo_compositor_t *compositor,
if (unlikely (status))
goto finish;
status = _prevent_overlapping_drawing (info.ctx, &info.setup, composite,
used_stencil_buffer_for_clip);
if (unlikely (status))
goto finish;
status = _cairo_path_fixed_stroke_to_shaper ((cairo_path_fixed_t *) path,
style,
ctm,