Allow cloning sub-regions of similar surfaces.

Previously the rule for clone_similar() was that the returned surface
had exactly the same size as the original, but only the contents within
the region of interest needed to be copied. This caused failures for very
large images in the xlib-backend (see test/large-source).

The obvious solution to allow cloning only the region of interest seemed
to be to simply set the device offset on the cloned surface. However, this
fails as a) nothing respects the device offset on the surface at that
layer in the compositing stack and b) possibly returning references to the
original source surface provides further confusion by mixing in another
source of device offset.

The second method was to add extra out parameters so that the
device offset could be returned separately and, for example, mixed into
the pattern matrix. Not as elegant, a couple of extra warts to the
interface, but it works - one less XFAIL...

15 files changed, 126 insertions, 30 deletions

diff --git a/src/cairo-clip.c b/src/cairo-clip.c
index cff8e40c..308da326 100644
--- a/src/cairo-clip.c
+++ b/src/cairo-clip.c
@@ -690,16 +690,22 @@ _cairo_clip_init_deep_copy (cairo_clip_t    *clip,
         }
 
         if (other->surface) {
+	    int dx, dy;
             status = _cairo_surface_clone_similar (target, other->surface,
 					           0,
 						   0,
 						   other->surface_rect.width,
 						   other->surface_rect.height,
+						   &dx, &dy,
 						   &clip->surface);
 	    if (status)
 		goto BAIL;
 
             clip->surface_rect = other->surface_rect;
+
+	    /* src offset was 0, so we expect an exact replica of the surface */
+	    assert (dx == 0);
+	    assert (dy == 0);
         }
 
         if (other->path) {
diff --git a/src/cairo-directfb-surface.c b/src/cairo-directfb-surface.c
index ecfc0f49..c24320b5 100644
--- a/src/cairo-directfb-surface.c
+++ b/src/cairo-directfb-surface.c
@@ -616,6 +616,8 @@ _cairo_directfb_surface_clone_similar (void             *abstract_surface,
                                        int               src_y,
                                        int               width,
                                        int               height,
+                                       int              *device_offset_x,
+                                       int              *device_offset_y,
                                        cairo_surface_t **clone_out)
 {
     cairo_directfb_surface_t *surface = abstract_surface;
@@ -625,9 +627,10 @@ _cairo_directfb_surface_clone_similar (void             *abstract_surface,
                 "%s( surface=%p, src=%p ).\n", __FUNCTION__, surface, src);
 
     if (src->backend == surface->base.backend) {
-        cairo_surface_reference (src);
-        *clone_out = src;
-         
+	*device_offset_x = 0;
+	*device_offset_y = 0;
+	*clone_out = cairo_surface_reference (src);
+
         return CAIRO_STATUS_SUCCESS;
     }
     else if (_cairo_surface_is_image (src)) {
@@ -685,9 +688,10 @@ _cairo_directfb_surface_clone_similar (void             *abstract_surface,
         }
         
         clone->dfbsurface->Unlock (clone->dfbsurface);
-        
+
+	*device_offset_x = 0;
+	*device_offset_y = 0;
         *clone_out = &clone->base;
-                
         return CAIRO_STATUS_SUCCESS;
     }
     
diff --git a/src/cairo-glitz-surface.c b/src/cairo-glitz-surface.c
index d067e28b..4d05e629 100644
--- a/src/cairo-glitz-surface.c
+++ b/src/cairo-glitz-surface.c
@@ -511,6 +511,8 @@ _cairo_glitz_surface_clone_similar (void	    *abstract_surface,
 				    int              src_y,
 				    int              width,
 				    int              height,
+				    int              *device_offset_x,
+				    int              *device_offset_y,
 				    cairo_surface_t **clone_out)
 {
     cairo_glitz_surface_t *surface = abstract_surface;
@@ -522,6 +524,8 @@ _cairo_glitz_surface_clone_similar (void	    *abstract_surface,
 
     if (src->backend == surface->base.backend)
     {
+	*device_offset_x = 0;
+	*device_offset_y = 0;
 	*clone_out = cairo_surface_reference (src);
 
 	return CAIRO_STATUS_SUCCESS;
@@ -2244,6 +2248,7 @@ _cairo_glitz_surface_old_show_glyphs (cairo_scaled_font_t *scaled_font,
 	    if (!glyph_private || !glyph_private->area)
 	    {
 		int glyph_width, glyph_height;
+		int device_offset_x, device_offset_y;
 
 		image = &scaled_glyphs[i]->surface->base;
 		glyph_width = scaled_glyphs[i]->surface->width;
@@ -2255,11 +2260,16 @@ _cairo_glitz_surface_old_show_glyphs (cairo_scaled_font_t *scaled_font,
 							0,
 							glyph_width,
 							glyph_height,
+							&device_offset_x,
+							&device_offset_y
 							(cairo_surface_t **)
 							&clone);
 		if (status)
 		    goto UNLOCK;
 
+		assert (device_offset_x = 0);
+		assert (device_offset_y = 0);
+
 		x_offset = scaled_glyphs[i]->surface->base.device_transform.x0;
 		y_offset = scaled_glyphs[i]->surface->base.device_transform.y0;
 		x1 = _cairo_lround (glyphs[i].x - x_offset);
diff --git a/src/cairo-image-surface.c b/src/cairo-image-surface.c
index 297c9472..7a429663 100644
--- a/src/cairo-image-surface.c
+++ b/src/cairo-image-surface.c
@@ -779,11 +779,14 @@ _cairo_image_surface_clone_similar (void		*abstract_surface,
 				    int                  src_y,
 				    int                  width,
 				    int                  height,
+				    int                 *device_offset_x,
+				    int                 *device_offset_y,
 				    cairo_surface_t    **clone_out)
 {
     cairo_image_surface_t *surface = abstract_surface;
 
     if (src->backend == surface->base.backend) {
+	*device_offset_x = *device_offset_y = 0;
 	*clone_out = cairo_surface_reference (src);
 
 	return CAIRO_STATUS_SUCCESS;
diff --git a/src/cairo-pattern.c b/src/cairo-pattern.c
index 60b1c2b1..b6db8cf1 100644
--- a/src/cairo-pattern.c
+++ b/src/cairo-pattern.c
@@ -1247,6 +1247,7 @@ _cairo_pattern_acquire_surface_for_gradient (cairo_gradient_pattern_t *pattern,
     pixman_gradient_stop_t pixman_stops_static[2];
     pixman_gradient_stop_t *pixman_stops = pixman_stops_static;
     unsigned int i;
+    int device_offset_x, device_offset_y;
 
     if (pattern->n_stops > ARRAY_LENGTH(pixman_stops_static)) {
 	pixman_stops = _cairo_malloc_ab (pattern->n_stops, sizeof(pixman_gradient_stop_t));
@@ -1396,7 +1397,10 @@ _cairo_pattern_acquire_surface_for_gradient (cairo_gradient_pattern_t *pattern,
     pixman_image_unref (pixman_image);
 
     status = _cairo_surface_clone_similar (dst, &image->base,
-					   0, 0, width, height, out);
+					   0, 0, width, height,
+					   &device_offset_x,
+					   &device_offset_y,
+					   out);
 
     cairo_surface_destroy (&image->base);
 
@@ -1829,7 +1833,14 @@ _cairo_pattern_acquire_surface_for_surface (cairo_surface_pattern_t   *pattern,
 	}
 
 	status = _cairo_surface_clone_similar (dst, pattern->surface,
-					       x, y, width, height, out);
+					       x, y, width, height,
+					       &x, &y, out);
+	if (status == CAIRO_STATUS_SUCCESS && (x != 0 || y != 0)) {
+	    cairo_matrix_t m;
+
+	    cairo_matrix_init_translate (&m, -x, -y);
+	    cairo_matrix_multiply (&attr->matrix, &attr->matrix, &m);
+	}
     }
 
     return status;
diff --git a/src/cairo-quartz-surface.c b/src/cairo-quartz-surface.c
index 52cd6915..13c6d728 100644
--- a/src/cairo-quartz-surface.c
+++ b/src/cairo-quartz-surface.c
@@ -1580,6 +1580,8 @@ _cairo_quartz_surface_clone_similar (void *abstract_surface,
 				     int              src_y,
 				     int              width,
 				     int              height,
+				     int             *device_offset_x,
+				     int             *device_offset_y,
 				     cairo_surface_t **clone_out)
 {
     cairo_quartz_surface_t *new_surface = NULL;
@@ -1598,6 +1600,8 @@ _cairo_quartz_surface_clone_similar (void *abstract_surface,
 	*clone_out = (cairo_surface_t*)
 	    _cairo_quartz_surface_create_internal (NULL, CAIRO_CONTENT_COLOR_ALPHA,
 						   width, height);
+	*device_offset_x = 0;
+	*device_offset_y = 0;
 	return CAIRO_STATUS_SUCCESS;
     }
 
@@ -1608,6 +1612,8 @@ _cairo_quartz_surface_clone_similar (void *abstract_surface,
 	    *clone_out = (cairo_surface_t*)
 		_cairo_quartz_surface_create_internal (NULL, CAIRO_CONTENT_COLOR_ALPHA,
 						       qsurf->extents.width, qsurf->extents.height);
+	    *device_offset_x = 0;
+	    *device_offset_y = 0;
 	    return CAIRO_STATUS_SUCCESS;
 	}
     }
@@ -1646,7 +1652,9 @@ _cairo_quartz_surface_clone_similar (void *abstract_surface,
 
     CGImageRelease (quartz_image);
 
-FINISH:    
+FINISH:
+    *device_offset_x = src_x;
+    *device_offset_y = src_y;
     *clone_out = (cairo_surface_t*) new_surface;
 
     return CAIRO_STATUS_SUCCESS;
diff --git a/src/cairo-surface-fallback-private.h b/src/cairo-surface-fallback-private.h
index 82c56256..a4a05dc7 100644
--- a/src/cairo-surface-fallback-private.h
+++ b/src/cairo-surface-fallback-private.h
@@ -124,6 +124,8 @@ _cairo_surface_fallback_clone_similar (cairo_surface_t  *surface,
 				       int               src_y,
 				       int               width,
 				       int               height,
+				       int              *device_offset_x,
+				       int              *device_offset_y,
 				       cairo_surface_t **clone_out);
 
 #endif
diff --git a/src/cairo-surface-fallback.c b/src/cairo-surface-fallback.c
index dc96a041..056ea4ec 100644
--- a/src/cairo-surface-fallback.c
+++ b/src/cairo-surface-fallback.c
@@ -1251,6 +1251,8 @@ _cairo_surface_fallback_clone_similar (cairo_surface_t	*surface,
 				       int		 src_y,
 				       int		 width,
 				       int		 height,
+				       int		*device_offset_x,
+				       int		*device_offset_y,
 				       cairo_surface_t **clone_out)
 {
     cairo_status_t status;
@@ -1280,9 +1282,11 @@ _cairo_surface_fallback_clone_similar (cairo_surface_t	*surface,
     status = cairo_status (cr);
     cairo_destroy (cr);
 
-    if (status == CAIRO_STATUS_SUCCESS)
+    if (status == CAIRO_STATUS_SUCCESS) {
+	*device_offset_x = src_x;
+	*device_offset_y = src_y;
 	*clone_out = new_surface;
-    else
+    } else
 	cairo_surface_destroy (new_surface);
 
     return status;
diff --git a/src/cairo-surface.c b/src/cairo-surface.c
index df6659d8..6ca877b2 100644
--- a/src/cairo-surface.c
+++ b/src/cairo-surface.c
@@ -1127,6 +1127,8 @@ _cairo_surface_clone_similar (cairo_surface_t  *surface,
 			      int               src_y,
 			      int               width,
 			      int               height,
+			      int              *device_offset_x,
+			      int              *device_offset_y,
 			      cairo_surface_t **clone_out)
 {
     cairo_status_t status = CAIRO_INT_STATUS_UNSUPPORTED;
@@ -1140,8 +1142,12 @@ _cairo_surface_clone_similar (cairo_surface_t  *surface,
 	return _cairo_error (CAIRO_STATUS_SURFACE_FINISHED);
 
     if (surface->backend->clone_similar) {
-	status = surface->backend->clone_similar (surface, src, src_x, src_y,
-						  width, height, clone_out);
+	status = surface->backend->clone_similar (surface, src,
+						  src_x, src_y,
+						  width, height,
+						  device_offset_x,
+						  device_offset_y,
+						  clone_out);
 
 	if (status == CAIRO_INT_STATUS_UNSUPPORTED) {
 	    /* If we failed, try again with an image surface */
@@ -1151,6 +1157,8 @@ _cairo_surface_clone_similar (cairo_surface_t  *surface,
 		    surface->backend->clone_similar (surface, &image->base,
 						     src_x, src_y,
 						     width, height,
+						     device_offset_x,
+						     device_offset_y,
 						     clone_out);
 
 		_cairo_surface_release_source_image (src, image, image_extra);
@@ -1161,8 +1169,12 @@ _cairo_surface_clone_similar (cairo_surface_t  *surface,
     /* If we're still unsupported, hit our fallback path to get a clone */
     if (status == CAIRO_INT_STATUS_UNSUPPORTED)
 	status =
-	    _cairo_surface_fallback_clone_similar (surface, src, src_x, src_y,
-						   width, height, clone_out);
+	    _cairo_surface_fallback_clone_similar (surface, src,
+						   src_x, src_y,
+						   width, height,
+						   device_offset_x,
+						   device_offset_y,
+						   clone_out);
 
     /* We should never get UNSUPPORTED here, so if we have an error, bail. */
     if (status)
@@ -1171,8 +1183,8 @@ _cairo_surface_clone_similar (cairo_surface_t  *surface,
     /* Update the clone's device_transform (which the underlying surface
      * backend knows nothing about) */
     if (*clone_out != src) {
-        (*clone_out)->device_transform = src->device_transform;
-        (*clone_out)->device_transform_inverse = src->device_transform_inverse;
+	(*clone_out)->device_transform = src->device_transform;
+	(*clone_out)->device_transform_inverse = src->device_transform_inverse;
     }
 
     return status;
diff --git a/src/cairo-win32-private.h b/src/cairo-win32-private.h
index 8cbea878..dd05a2df 100644
--- a/src/cairo-win32-private.h
+++ b/src/cairo-win32-private.h
@@ -160,6 +160,8 @@ _cairo_win32_surface_clone_similar (void *abstract_surface,
 				    int src_y,
 				    int width,
 				    int height,
+				    int *device_offset_x,
+				    int *device_offset_y,
 				    cairo_surface_t **clone_out);
 
 static inline void
diff --git a/src/cairo-win32-surface.c b/src/cairo-win32-surface.c
index 395d818d..883441c4 100644
--- a/src/cairo-win32-surface.c
+++ b/src/cairo-win32-surface.c
@@ -443,6 +443,8 @@ _cairo_win32_surface_clone_similar (void *abstract_surface,
 				    int src_y,
 				    int width,
 				    int height,
+				    int *device_offset_x,
+				    int *device_offset_y,
 				    cairo_surface_t **clone_out)
 {
     cairo_content_t src_content;
@@ -470,9 +472,11 @@ _cairo_win32_surface_clone_similar (void *abstract_surface,
 
     _cairo_pattern_fini (&pattern.base);
 
-    if (status == CAIRO_STATUS_SUCCESS)
+    if (status == CAIRO_STATUS_SUCCESS) {
+	*device_offset_x = src_x;
+	*device_offset_y = src_y;
 	*clone_out = new_surface;
-    else
+    } else
 	cairo_surface_destroy (new_surface);
 
     return status;
diff --git a/src/cairo-xcb-surface.c b/src/cairo-xcb-surface.c
index 7251824b..7aa80bdd 100644
--- a/src/cairo-xcb-surface.c
+++ b/src/cairo-xcb-surface.c
@@ -695,6 +695,8 @@ _cairo_xcb_surface_clone_similar (void			*abstract_surface,
 				  int                    src_y,
 				  int                    width,
 				  int                    height,
+				  int                   *device_offset_x,
+				  int                   *device_offset_y,
 				  cairo_surface_t     **clone_out)
 {
     cairo_xcb_surface_t *surface = abstract_surface;
@@ -704,6 +706,8 @@ _cairo_xcb_surface_clone_similar (void			*abstract_surface,
 	cairo_xcb_surface_t *xcb_src = (cairo_xcb_surface_t *)src;
 
 	if (_cairo_xcb_surface_same_screen(surface, xcb_src)) {
+	    *device_offset_x = 0;
+	    *device_offset_y = 0;
 	    *clone_out = cairo_surface_reference (src);
 
 	    return CAIRO_STATUS_SUCCESS;
@@ -716,14 +720,20 @@ _cairo_xcb_surface_clone_similar (void			*abstract_surface,
 	    return surface->base.status;
 
 	clone = (cairo_xcb_surface_t *)
-	    _cairo_xcb_surface_create_similar (surface, content,
-					       image_src->width, image_src->height);
+	    _cairo_xcb_surface_create_similar (surface, content, width, height);
 	if (clone->base.status)
 	    return clone->base.status;
 
-	_draw_image_surface (clone, image_src, src_x, src_y,
-			     width, height, src_x, src_y);
+	status = _draw_image_surface (clone, image_src,
+		                      src_x, src_y,
+		                      width, height, x, y);
+	if (status) {
+	    cairo_surface_destroy (&clone->base);
+	    return status;
+	}
 
+	*device_offset_x = src_x;
+	*device_offset_y = src_y;
 	*clone_out = &clone->base;
 
 	return CAIRO_STATUS_SUCCESS;
diff --git a/src/cairo-xlib-surface.c b/src/cairo-xlib-surface.c
index 9da13f92..ed534c12 100644
--- a/src/cairo-xlib-surface.c
+++ b/src/cairo-xlib-surface.c
@@ -1134,6 +1134,8 @@ _cairo_xlib_surface_clone_similar (void			*abstract_surface,
 				   int                   src_y,
 				   int                   width,
 				   int                   height,
+				   int                  *device_offset_x,
+				   int                  *device_offset_y,
 				   cairo_surface_t     **clone_out)
 {
     cairo_xlib_surface_t *surface = abstract_surface;
@@ -1146,6 +1148,8 @@ _cairo_xlib_surface_clone_similar (void			*abstract_surface,
 	cairo_xlib_surface_t *xlib_src = (cairo_xlib_surface_t *)src;
 
 	if (_cairo_xlib_surface_same_screen (surface, xlib_src)) {
+	    *device_offset_x = 0;
+	    *device_offset_y = 0;
 	    *clone_out = cairo_surface_reference (src);
 
 	    return CAIRO_STATUS_SUCCESS;
@@ -1156,25 +1160,30 @@ _cairo_xlib_surface_clone_similar (void			*abstract_surface,
 	if (! CAIRO_FORMAT_VALID (image_src->format))
 	    return CAIRO_INT_STATUS_UNSUPPORTED;
 
-	if (image_src->width > XLIB_COORD_MAX || image_src->height > XLIB_COORD_MAX)
-	    return CAIRO_STATUS_NO_MEMORY;
+	if (width > XLIB_COORD_MAX || height > XLIB_COORD_MAX)
+	    return _cairo_error (CAIRO_STATUS_NO_MEMORY);
 
 	clone = (cairo_xlib_surface_t *)
-	    _cairo_xlib_surface_create_similar_with_format (surface, image_src->format,
-						image_src->width, image_src->height);
+	    _cairo_xlib_surface_create_similar_with_format (surface,
+		                                            image_src->format,
+							    width, height);
 	if (clone == NULL)
 	    return CAIRO_INT_STATUS_UNSUPPORTED;
 
 	if (clone->base.status)
 	    return clone->base.status;
 
-	status = _draw_image_surface (clone, image_src, src_x, src_y,
-			              width, height, src_x, src_y);
+	status = _draw_image_surface (clone, image_src,
+				      src_x, src_y,
+			              width, height,
+				      0, 0);
 	if (status) {
 	    cairo_surface_destroy (&clone->base);
 	    return status;
 	}
 
+	*device_offset_x = src_x;
+	*device_offset_y = src_y;
 	*clone_out = &clone->base;
 
 	return CAIRO_STATUS_SUCCESS;
diff --git a/src/cairoint.h b/src/cairoint.h
index 4929db67..b55a05fd 100644
--- a/src/cairoint.h
+++ b/src/cairoint.h
@@ -551,9 +551,12 @@ struct _cairo_surface_backend {
      * 1. It is as compatible as possible with @surface (in terms of
      *    efficiency)
      *
-     * 2. It has the same size as @src
+     * 2. It has the same contents as @src within the given rectangle.
      *
-     * 3. It has the same contents as @src within the given rectangle.
+     * 3. The offset of the similar surface with respect to the original
+     *    surface is returned in the device transform vector.
+     *    - if you clone the entire surface, this vector is zero.
+     *    - if you clone (src_x, src_y)x(w, h) the vector is (src_x, src_y);
      */
     cairo_warn cairo_status_t
     (*clone_similar)            (void                   *surface,
@@ -562,6 +565,8 @@ struct _cairo_surface_backend {
 				 int                     src_y,
 				 int                     width,
 				 int                     height,
+				 int                    *device_offset_x,
+				 int                    *device_offset_y,
 				 cairo_surface_t       **clone_out);
 
     /* XXX: dst should be the first argument for consistency */
@@ -1819,6 +1824,8 @@ _cairo_surface_clone_similar (cairo_surface_t  *surface,
 			      int               src_y,
 			      int               width,
 			      int               height,
+			      int              *device_offset_x,
+			      int              *device_offset_y,
 			      cairo_surface_t **clone_out);
 
 cairo_private cairo_surface_t *
diff --git a/src/test-fallback-surface.c b/src/test-fallback-surface.c
index e720e88e..94f352f2 100644
--- a/src/test-fallback-surface.c
+++ b/src/test-fallback-surface.c
@@ -176,11 +176,15 @@ _test_fallback_surface_clone_similar (void		  *abstract_surface,
 				      int                  src_y,
 				      int                  width,
 				      int                  height,
+				      int                 *device_offset_x,
+				      int                 *device_offset_y,
 				      cairo_surface_t    **clone_out)
 {
     test_fallback_surface_t *surface = abstract_surface;
 
     if (src->backend == surface->base.backend) {
+	*device_offset_x = 0;
+	*device_offset_y = 0;
 	*clone_out = cairo_surface_reference (src);
 
 	return CAIRO_STATUS_SUCCESS;