Add extents to clone_similar (fixing subimage_copy performance bug)

This fixes a huge performance bug (entire image was being pushed to X
server in order to copy a tiny piece of it). I see up to 50x improvement
from subimage_copy (which was designed to expose this problem) but also
a 5x improvement in some text performance cases.

 xlib-rgba              subimage_copy-512    3.93 2.46% ->   0.07 2.71%: 52.91x faster
███████████████████████████████████████████████████▉
 xlib-rgb               subimage_copy-512    4.03 1.97% ->   0.09 2.61%: 44.74x faster
███████████████████████████████████████████▊
 xlib-rgba              subimage_copy-256    1.02 2.25% ->   0.07 0.56%: 14.42x faster
█████████████▍
 xlib-rgba        text_image_rgb_over-256   63.21 1.53% ->  11.87 2.17%:  5.33x faster
████▍
 xlib-rgba       text_image_rgba_over-256   62.31 0.72% ->  11.87 2.82%:  5.25x faster
████▎
 xlib-rgba     text_image_rgba_source-256   67.97 0.85% ->  16.48 2.23%:  4.13x faster
███▏
 xlib-rgba      text_image_rgb_source-256   68.82 0.55% ->  16.93 2.10%:  4.07x faster
███▏
 xlib-rgba              subimage_copy-128    0.19 1.72% ->   0.06 0.85%:  3.10x faster
██▏

1 files changed, 13 insertions, 5 deletions

diff --git a/src/cairo-directfb-surface.c b/src/cairo-directfb-surface.c
index fdff40ac..e724ed67 100644
--- a/src/cairo-directfb-surface.c
+++ b/src/cairo-directfb-surface.c
@@ -548,6 +548,10 @@ _cairo_directfb_surface_release_dest_image (void                  *abstract_surf
 static cairo_status_t
 _cairo_directfb_surface_clone_similar (void             *abstract_surface,
                                        cairo_surface_t  *src,
+				       int               src_x,
+				       int               src_y,
+				       int               width,
+				       int               height,
                                        cairo_surface_t **clone_out)
 {
     cairo_directfb_surface_t *surface = abstract_surface;
@@ -583,19 +587,23 @@ _cairo_directfb_surface_clone_similar (void             *abstract_surface,
             cairo_surface_destroy ((cairo_surface_t *)clone);
             return CAIRO_STATUS_NO_MEMORY;
         }
+
+	dst += pitch * src_y;
+	src += image_src->stride * src_y;
         
         if (image_src->format == CAIRO_FORMAT_A1) {
             /* A1 -> A8 */
-            for (i = 0; i < image_src->height; i++) {
-                for (j = 0; j < image_src->width; j++)
+            for (i = 0; i < height; i++) {
+                for (j = src_x; j < src_x + width; j++)
                     dst[j] = (src[j>>3] & (1 << (j&7))) ? 0xff : 0x00;
                 dst += pitch;
                 src += image_src->stride;
             }
         }
-        else {     
-            for (i = 0; i < image_src->height; i++) {
-                direct_memcpy( dst, src, image_src->stride );
+        else {
+	    /* A8 -> A8 */
+            for (i = 0; i < height; i++) {
+                direct_memcpy( dst+src_x, src+src_x, sizeof(*dst)*width );
                 dst += pitch;
                 src += image_src->stride;
             }