Remove clip handling from generic surface layer.

Handling clip as part of the surface state, as opposed to being part of
the operation state, is cumbersome and a hindrance to providing true proxy
surface support. For example, the clip must be copied from the surface
onto the fallback image, but this was forgotten causing undue hassle in
each backend. Another example is the contortion the meta surface
endures to ensure the clip is correctly recorded. By contrast passing the
clip along with the operation is quite simple and enables us to write
generic handlers for providing surface wrappers. (And in the future, we
should be able to write more esoteric wrappers, e.g. automatic 2x FSAA,
trivially.)

In brief, instead of the surface automatically applying the clip before
calling the backend, the backend can call into a generic helper to apply
clipping. For raster surfaces, clip regions are handled automatically as
part of the composite interface. For vector surfaces, a clip helper is
introduced to replay and callback into an intersect_clip_path() function
as necessary.

Whilst this is not primarily a performance related change (the change
should just move the computation of the clip from the moment it is applied
by the user to the moment it is required by the backend), it is important
to track any potential regression:

ppc:
Speedups
========
image-rgba         evolution-20090607-0    1026085.22 0.18% -> 672972.07 0.77%:  1.52x speedup
▌
image-rgba         evolution-20090618-0    680579.98 0.12% -> 573237.66  0.16%:  1.19x speedup
▎
image-rgba      swfdec-fill-rate-4xaa-0    460296.92 0.36% -> 407464.63  0.42%:  1.13x speedup
▏
image-rgba      swfdec-fill-rate-2xaa-0    128431.95 0.47% -> 115051.86  0.42%:  1.12x speedup
▏
Slowdowns
=========
image-rgba     firefox-periodic-table-0    56837.61 0.78% -> 66055.17    3.20%:  1.09x slowdown
▏

1 files changed, 56 insertions, 27 deletions

diff --git a/src/cairo.c b/src/cairo.c
index 3e590496a..2470b0d69 100644
--- a/src/cairo.c
+++ b/src/cairo.c
@@ -44,6 +44,10 @@
 
 #define CAIRO_TOLERANCE_MINIMUM	_cairo_fixed_to_double(1)
 
+#if !defined(INFINITY)
+#define INFINITY HUGE_VAL
+#endif
+
 static const cairo_t _cairo_nil = {
   CAIRO_REFERENCE_COUNT_INVALID,	/* ref_count */
   CAIRO_STATUS_NO_MEMORY,	/* status */
@@ -57,7 +61,8 @@ static const cairo_t _cairo_nil = {
     FALSE,			/* has_current_point */
     FALSE,			/* has_curve_to */
     FALSE,			/* is_box */
-    FALSE,			/* is_region */
+    FALSE,			/* maybe_fill_region */
+    TRUE,			/* is_empty_fill */
     {{{NULL,NULL}}}		/* link */
   }}
 };
@@ -496,25 +501,28 @@ cairo_push_group_with_content (cairo_t *cr, cairo_content_t content)
 {
     cairo_status_t status;
     cairo_rectangle_int_t extents;
+    const cairo_rectangle_int_t *clip_extents;
     cairo_surface_t *parent_surface, *group_surface = NULL;
+    cairo_bool_t is_empty;
 
     if (unlikely (cr->status))
 	return;
 
     parent_surface = _cairo_gstate_get_target (cr->gstate);
-    /* Get the extents that we'll use in creating our new group surface */
-    status = _cairo_surface_get_extents (parent_surface, &extents);
-    if (unlikely (status))
-	goto bail;
-    status = _cairo_clip_intersect_to_rectangle (_cairo_gstate_get_clip (cr->gstate), &extents);
-    if (unlikely (status))
-	goto bail;
 
-    group_surface = cairo_surface_create_similar (parent_surface,
-						  content,
-						  extents.width,
-						  extents.height);
-    status = cairo_surface_status (group_surface);
+    /* Get the extents that we'll use in creating our new group surface */
+    is_empty = _cairo_surface_get_extents (parent_surface, &extents);
+    clip_extents = _cairo_clip_get_extents (_cairo_gstate_get_clip (cr->gstate));
+    if (clip_extents != NULL)
+	is_empty = _cairo_rectangle_intersect (&extents, clip_extents);
+
+    group_surface = _cairo_surface_create_similar_solid (parent_surface,
+							 content,
+							 extents.width,
+							 extents.height,
+							 CAIRO_COLOR_TRANSPARENT,
+							 TRUE);
+    status = group_surface->status;
     if (unlikely (status))
 	goto bail;
 
@@ -2340,7 +2348,7 @@ cairo_in_stroke (cairo_t *cr, double x, double y)
     cairo_bool_t inside = FALSE;
 
     if (unlikely (cr->status))
-	return 0;
+	return FALSE;
 
     status = _cairo_gstate_in_stroke (cr->gstate,
 				      cr->path,
@@ -2370,16 +2378,10 @@ cairo_in_stroke (cairo_t *cr, double x, double y)
 cairo_bool_t
 cairo_in_fill (cairo_t *cr, double x, double y)
 {
-    cairo_bool_t inside;
-
     if (unlikely (cr->status))
-	return 0;
-
-    _cairo_gstate_in_fill (cr->gstate,
-			   cr->path,
-			   x, y, &inside);
+	return FALSE;
 
-    return inside;
+    return _cairo_gstate_in_fill (cr->gstate, cr->path, x, y);
 }
 
 /**
@@ -2600,8 +2602,6 @@ cairo_clip_extents (cairo_t *cr,
 		    double *x1, double *y1,
 		    double *x2, double *y2)
 {
-    cairo_status_t status;
-
     if (unlikely (cr->status)) {
 	if (x1)
 	    *x1 = 0.0;
@@ -2615,9 +2615,38 @@ cairo_clip_extents (cairo_t *cr,
 	return;
     }
 
-    status = _cairo_gstate_clip_extents (cr->gstate, x1, y1, x2, y2);
-    if (unlikely (status))
-	_cairo_set_error (cr, status);
+    if (! _cairo_gstate_clip_extents (cr->gstate, x1, y1, x2, y2)) {
+	*x1 = -INFINITY;
+	*y1 = -INFINITY;
+	*x2 = +INFINITY;
+	*y2 = +INFINITY;
+    }
+}
+
+/**
+ * cairo_in_clip:
+ * @cr: a cairo context
+ * @x: X coordinate of the point to test
+ * @y: Y coordinate of the point to test
+ *
+ * Tests whether the given point is inside the area that would be
+ * visible through the current clip, i.e. the area that would be filled by
+ * a cairo_paint() operation.
+ *
+ * See cairo_clip(), and cairo_clip_preserve().
+ *
+ * Return value: A non-zero value if the point is inside, or zero if
+ * outside.
+ *
+ * Since: 1.10
+ **/
+cairo_bool_t
+cairo_in_clip (cairo_t *cr, double x, double y)
+{
+    if (unlikely (cr->status))
+	return FALSE;
+
+    return _cairo_gstate_in_clip (cr->gstate, x, y);
 }
 
 static cairo_rectangle_list_t *