Improving and optimizing the dropout prevention algorithm

with splitting gx_default_fill_parallelogram into 2 variants.

DETAILS:

This patch almost changes a disabled code.
A simple reorganization of some enabled code should not
cause a behavior difference.

Filling a "small" character, we always subdivide trapezoids into
rectangles instead passing them to device virtual function.
It allows :

1. Not passing narrow trapezoids to applications
which implement fill_trapezoid with own means;
Narrow trapezoids could cause dropouts in there.

2. Optimize variants of fill_trapezoid algorithm which
are used for different purposes (preventing about 10% slowdown
with shadings).

We believe this change isn't harmful because
regularly we render small characters to cache device,
which simply forwards trapezoids to default implementation.
Alternatively we could insert a check for narrow trapezoids
into loop_fill_trap, but such check appears complex and
it would sensibly reduce performance.

New files added : gdevddrw.h, gxdtfill.h .
Change to lib.mak accounts them.

Besides that, with dropout prevention we now skip empty paths
in characters, because Adobe doesn't paint them.

git-svn-id: http://svn.ghostscript.com/ghostscript/trunk@3450 a1074d23-0009-0410-80fe-cf8c14f379e6

1 files changed, 28 insertions, 0 deletions

diff --git a/gs/src/gdevddrw.h b/gs/src/gdevddrw.h
new file mode 100644
index 000000000..0299d04ce
--- /dev/null
+++ b/gs/src/gdevddrw.h
@@ -0,0 +1,28 @@
+/* Copyright (C) 2002 artofcode LLC. All rights reserved.
+  
+  This software is provided AS-IS with no warranty, either express or
+  implied.
+  
+  This software is distributed under license and may not be copied,
+  modified or distributed except as expressly authorized under the terms
+  of the license contained in the file LICENSE in this distribution.
+  
+  For more information about licensing, please refer to
+  http://www.ghostscript.com/licensing/. For information on
+  commercial licensing, go to http://www.artifex.com/licensing/ or
+  contact Artifex Software, Inc., 101 Lucas Valley Road #110,
+  San Rafael, CA  94903, U.S.A., +1(415)492-9861.
+*/
+
+/* $Id$ */
+/* Prototypes of some polygon and image drawing procedures */
+
+#ifndef gdevddrw_INCLUDED
+#  define gdevddrw_INCLUDED
+
+#if DROPOUT_PREVENTION
+dev_proc_fill_trapezoid(gx_fill_trapezoid_narrow);
+#endif
+
+#endif /* gdevddrw_INCLUDED */
+