Use PDF 're' operator for rectangle paths

Modify cairo-pdf-operators.c to emit to 're' path operator when the
path contains only a rectangle. This can only be done when the path is
logically equivilent to the the path drawn by the 're'
operator. Otherwise dashed strokes may start on the wrong line.

ie the path must be equivalent to:

  cairo_move_to (cr, x, y);
  cairo_rel_line_to (cr, width, 0);
  cairo_rel_line_to (cr, 0, height);
  cairo_rel_line_to (cr, -width, 0);
  cairo_close_path (cr);

which is also equivilent to cairo_rectangle().

src/cairo-path-fixed.c

@@ -802,3 +802,27 @@ _cairo_path_fixed_is_box (cairo_path_fixed_t *path,
 
     return FALSE;
 }
+
+/**
+ * Check whether the given path contains a single rectangle
+ * that is logically equivalent to:
+ *   cairo_move_to (cr, x, y);
+ *   cairo_rel_line_to (cr, width, 0);
+ *   cairo_rel_line_to (cr, 0, height);
+ *   cairo_rel_line_to (cr, -width, 0);
+ *   cairo_close_path (cr);
+ */
+cairo_bool_t
+_cairo_path_fixed_is_rectangle (cairo_path_fixed_t *path,
+				cairo_box_t        *box)
+{
+    cairo_path_buf_t *buf = &path->buf_head.base;
+
+    if (!_cairo_path_fixed_is_box (path, box))
+	return FALSE;
+
+    if (buf->points[0].y == buf->points[1].y)
+	return TRUE;
+
+    return FALSE;
+}

src/cairo-pdf-operators.c

@@ -328,6 +328,23 @@ _cairo_pdf_path_close_path (void *closure)
     return _cairo_output_stream_get_status (info->output);
 }
 
+static cairo_status_t
+_cairo_pdf_path_rectangle (pdf_path_info_t *info, cairo_box_t *box)
+{
+    double x1 = _cairo_fixed_to_double (box->p1.x);
+    double y1 = _cairo_fixed_to_double (box->p1.y);
+    double x2 = _cairo_fixed_to_double (box->p2.x);
+    double y2 = _cairo_fixed_to_double (box->p2.y);
+
+    cairo_matrix_transform_point (info->path_transform, &x1, &y1);
+    cairo_matrix_transform_point (info->path_transform, &x2, &y2);
+    _cairo_output_stream_printf (info->output,
+				 "%f %f %f %f re ",
+				 x1, y1, x2 - x1, y2 - y1);
+
+    return _cairo_output_stream_get_status (info->output);
+}
+
 /* The line cap value is needed to workaround the fact that PostScript
  * and PDF semantics for stroking degenerate sub-paths do not match
  * cairo semantics. (PostScript draws something for any line cap
@@ -346,6 +363,7 @@ _cairo_pdf_operators_emit_path (cairo_pdf_operators_t 	*pdf_operators,
     cairo_output_stream_t *word_wrap;
     cairo_status_t status, status2;
     pdf_path_info_t info;
+    cairo_box_t box;
 
     word_wrap = _word_wrap_stream_create (pdf_operators->stream, 79);
     status = _cairo_output_stream_get_status (word_wrap);
@@ -355,13 +373,17 @@ _cairo_pdf_operators_emit_path (cairo_pdf_operators_t 	*pdf_operators,
     info.output = word_wrap;
     info.path_transform = path_transform;
     info.line_cap = line_cap;
-    status = _cairo_path_fixed_interpret (path,
-					  CAIRO_DIRECTION_FORWARD,
-					  _cairo_pdf_path_move_to,
-					  _cairo_pdf_path_line_to,
-					  _cairo_pdf_path_curve_to,
-					  _cairo_pdf_path_close_path,
-					  &info);
+    if (_cairo_path_fixed_is_rectangle (path, &box)) {
+	status = _cairo_pdf_path_rectangle (&info, &box);
+    } else {
+	status = _cairo_path_fixed_interpret (path,
+					      CAIRO_DIRECTION_FORWARD,
+					      _cairo_pdf_path_move_to,
+					      _cairo_pdf_path_line_to,
+					      _cairo_pdf_path_curve_to,
+					      _cairo_pdf_path_close_path,
+					      &info);
+    }
 
     status2 = _cairo_output_stream_destroy (word_wrap);
     if (status == CAIRO_STATUS_SUCCESS)

src/cairo-ps-surface.c

@@ -169,6 +169,8 @@ _cairo_ps_surface_emit_header (cairo_ps_surface_t *surface)
 				 "/l { lineto } bind def\n"
 				 "/c { curveto } bind def\n"
 				 "/h { closepath } bind def\n"
+				 "/re { exch dup neg 3 1 roll 5 3 roll moveto 0 rlineto\n"
+				 "      0 exch rlineto 0 rlineto closepath } bind def\n"
 				 "/S { stroke } bind def\n"
 				 "/f { fill } bind def\n"
 				 "/f* { eofill } bind def\n"

src/cairoint.h

@@ -1399,6 +1399,10 @@ cairo_private cairo_bool_t
 _cairo_path_fixed_is_box (cairo_path_fixed_t *path,
                           cairo_box_t *box);
 
+cairo_private cairo_bool_t
+_cairo_path_fixed_is_rectangle (cairo_path_fixed_t *path,
+				cairo_box_t        *box);
+
 /* cairo_path_fill.c */
 cairo_private cairo_status_t
 _cairo_path_fixed_fill_to_traps (cairo_path_fixed_t *path,