Introduce a new compositor architecture

Having spent the last dev cycle looking at how we could specialize the
compositors for various backends, we once again look for the
commonalities in order to reduce the duplication. In part this is
motivated by the idea that spans is a good interface for both the
existent GL backend and pixman, and so they deserve a dedicated
compositor. xcb/xlib target an identical rendering system and so they
should be using the same compositor, and it should be possible to run
that same compositor locally against pixman to generate reference tests.

Signed-off-by: Chris Wilson <chris@chris-wilson.co.uk>

P.S. This brings massive upheaval (read breakage) I've tried delaying in
order to fix as many things as possible but now this one patch does far,
far, far too much. Apologies in advance for breaking your favourite
backend, but trust me in that the end result will be much better. :)

1 files changed, 36 insertions, 11 deletions

diff --git a/src/cairo-boxes-intersect.c b/src/cairo-boxes-intersect.c
index 230c6f018..dd4c2410f 100644
--- a/src/cairo-boxes-intersect.c
+++ b/src/cairo-boxes-intersect.c
@@ -535,19 +535,44 @@ _cairo_boxes_intersect_with_box (const cairo_boxes_t *boxes,
 				 const cairo_box_t *box,
 				 cairo_boxes_t *out)
 {
-    const struct _cairo_boxes_chunk *chunk;
     cairo_status_t status;
-    int i;
+    int i, j;
+
+    if (out == boxes) { /* inplace update */
+	struct _cairo_boxes_chunk *chunk;
+
+	out->num_boxes = 0;
+	for (chunk = &out->chunks; chunk != NULL; chunk = chunk->next) {
+	    for (i = j = 0; i < chunk->count; i++) {
+		cairo_box_t *b = &chunk->base[i];
+
+		b->p1.x = MAX (b->p1.x, box->p1.x);
+		b->p1.y = MAX (b->p1.y, box->p1.y);
+		b->p2.x = MIN (b->p2.x, box->p2.x);
+		b->p2.y = MIN (b->p2.y, box->p2.y);
+		if (b->p1.x < b->p2.x && b->p1.y < b->p2.y) {
+		    if (i != j)
+			chunk->base[j] = *b;
+		    j++;
+		}
+	    }
+	    /* XXX unlink empty chains? */
+	    chunk->count = j;
+	    out->num_boxes += j;
+	}
+    } else {
+	const struct _cairo_boxes_chunk *chunk;
 
-    _cairo_boxes_clear (out);
-    _cairo_boxes_limit (out, box, 1);
-    for (chunk = &boxes->chunks; chunk != NULL; chunk = chunk->next) {
-	for (i = 0; i < chunk->count; i++) {
-	    status = _cairo_boxes_add (out,
-				       CAIRO_ANTIALIAS_DEFAULT,
-				       &chunk->base[i]);
-	    if (unlikely (status))
-		return status;
+	_cairo_boxes_clear (out);
+	_cairo_boxes_limit (out, box, 1);
+	for (chunk = &boxes->chunks; chunk != NULL; chunk = chunk->next) {
+	    for (i = 0; i < chunk->count; i++) {
+		status = _cairo_boxes_add (out,
+					   CAIRO_ANTIALIAS_DEFAULT,
+					   &chunk->base[i]);
+		if (unlikely (status))
+		    return status;
+	    }
 	}
     }