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, 61 insertions, 0 deletions

diff --git a/src/cairo-traps.c b/src/cairo-traps.c
index 42e2eb553..a6e7f94ee 100644
--- a/src/cairo-traps.c
+++ b/src/cairo-traps.c
@@ -43,6 +43,7 @@
 #include "cairo-error-private.h"
 #include "cairo-region-private.h"
 #include "cairo-slope-private.h"
+#include "cairo-traps-private.h"
 
 /* private functions */
 
@@ -608,6 +609,66 @@ _cairo_traps_extract_region (cairo_traps_t   *traps,
     return status;
 }
 
+cairo_bool_t
+_cairo_traps_to_boxes (cairo_traps_t *traps,
+		       cairo_antialias_t antialias,
+		       cairo_boxes_t *boxes)
+{
+    int i;
+
+    for (i = 0; i < traps->num_traps; i++) {
+	if (traps->traps[i].left.p1.x  != traps->traps[i].left.p2.x ||
+	    traps->traps[i].right.p1.x != traps->traps[i].right.p2.x)
+	    return FALSE;
+    }
+
+    _cairo_boxes_init (boxes);
+
+    boxes->num_boxes    = traps->num_traps;
+    boxes->chunks.base  = (cairo_box_t *) traps->traps;
+    boxes->chunks.count = traps->num_traps;
+    boxes->chunks.size  = traps->num_traps;
+
+    if (antialias != CAIRO_ANTIALIAS_NONE) {
+	for (i = 0; i < traps->num_traps; i++) {
+	    /* Note the traps and boxes alias so we need to take the local copies first. */
+	    cairo_fixed_t x1 = traps->traps[i].left.p1.x;
+	    cairo_fixed_t x2 = traps->traps[i].right.p1.x;
+	    cairo_fixed_t y1 = traps->traps[i].top;
+	    cairo_fixed_t y2 = traps->traps[i].bottom;
+
+	    boxes->chunks.base[i].p1.x = x1;
+	    boxes->chunks.base[i].p1.y = y1;
+	    boxes->chunks.base[i].p2.x = x2;
+	    boxes->chunks.base[i].p2.y = y2;
+
+	    if (boxes->is_pixel_aligned) {
+		boxes->is_pixel_aligned =
+		    _cairo_fixed_is_integer (x1) && _cairo_fixed_is_integer (y1) &&
+		    _cairo_fixed_is_integer (x2) && _cairo_fixed_is_integer (y2);
+	    }
+	}
+    } else {
+	boxes->is_pixel_aligned = TRUE;
+
+	for (i = 0; i < traps->num_traps; i++) {
+	    /* Note the traps and boxes alias so we need to take the local copies first. */
+	    cairo_fixed_t x1 = traps->traps[i].left.p1.x;
+	    cairo_fixed_t x2 = traps->traps[i].right.p1.x;
+	    cairo_fixed_t y1 = traps->traps[i].top;
+	    cairo_fixed_t y2 = traps->traps[i].bottom;
+
+	    /* round down here to match Pixman's behavior when using traps. */
+	    boxes->chunks.base[i].p1.x = _cairo_fixed_round_down (x1);
+	    boxes->chunks.base[i].p1.y = _cairo_fixed_round_down (y1);
+	    boxes->chunks.base[i].p2.x = _cairo_fixed_round_down (x2);
+	    boxes->chunks.base[i].p2.y = _cairo_fixed_round_down (y2);
+	}
+    }
+
+    return TRUE;
+}
+
 /* moves trap points such that they become the actual corners of the trapezoid */
 static void
 _sanitize_trap (cairo_trapezoid_t *t)