Add RenderAddTraps. Rewrite trapezoid rendering code.

1 files changed, 120 insertions, 0 deletions

diff --git a/render/renderedge.h b/render/renderedge.h
new file mode 100644
index 000000000..d621d9dcf
--- /dev/null
+++ b/render/renderedge.h
@@ -0,0 +1,120 @@
+/*
+ * $Id$
+ *
+ * Copyright © 2004 Keith Packard
+ *
+ * Permission to use, copy, modify, distribute, and sell this software and its
+ * documentation for any purpose is hereby granted without fee, provided that
+ * the above copyright notice appear in all copies and that both that
+ * copyright notice and this permission notice appear in supporting
+ * documentation, and that the name of Keith Packard not be used in
+ * advertising or publicity pertaining to distribution of the software without
+ * specific, written prior permission.  Keith Packard makes no
+ * representations about the suitability of this software for any purpose.  It
+ * is provided "as is" without express or implied warranty.
+ *
+ * KEITH PACKARD DISCLAIMS ALL WARRANTIES WITH REGARD TO THIS SOFTWARE,
+ * INCLUDING ALL IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS, IN NO
+ * EVENT SHALL KEITH PACKARD BE LIABLE FOR ANY SPECIAL, INDIRECT OR
+ * CONSEQUENTIAL DAMAGES OR ANY DAMAGES WHATSOEVER RESULTING FROM LOSS OF USE,
+ * DATA OR PROFITS, WHETHER IN AN ACTION OF CONTRACT, NEGLIGENCE OR OTHER
+ * TORTIOUS ACTION, ARISING OUT OF OR IN CONNECTION WITH THE USE OR
+ * PERFORMANCE OF THIS SOFTWARE.
+ */
+
+#ifndef _RENDEREDGE_H_
+#define _RENDEREDGE_H_
+
+#include "picturestr.h"
+
+#define MAX_ALPHA(n)	((1 << (n)) - 1)
+#define N_Y_FRAC(n)	((n) == 1 ? 1 : (1 << ((n)/2)) - 1)
+#define N_X_FRAC(n)	((1 << ((n)/2)) + 1)
+
+#define STEP_Y_SMALL(n)	(xFixed1 / N_Y_FRAC(n))
+#define STEP_Y_BIG(n)	(xFixed1 - (N_Y_FRAC(n) - 1) * STEP_Y_SMALL(n))
+
+#define Y_FRAC_FIRST(n)	(STEP_Y_SMALL(n) / 2)
+#define Y_FRAC_LAST(n)	(Y_FRAC_FIRST(n) + (N_Y_FRAC(n) - 1) * STEP_Y_SMALL(n))
+
+#define STEP_X_SMALL(n)	(xFixed1 / N_X_FRAC(n))
+#define STEP_X_BIG(n)	(xFixed1 - (N_X_FRAC(n) - 1) * STEP_X_SMALL(n))
+
+#define X_FRAC_FIRST(n)	(STEP_X_SMALL(n) / 2)
+#define X_FRAC_LAST(n)	(X_FRAC_FIRST(n) + (N_X_FRAC(n) - 1) * STEP_X_SMALL(n))
+
+#define RenderSamplesX(x,n)	((n) == 1 ? 0 : (xFixedFrac (x) + X_FRAC_FIRST(n)) / STEP_X_SMALL(n))
+
+/*
+ * An edge structure.  This represents a single polygon edge
+ * and can be quickly stepped across small or large gaps in the
+ * sample grid
+ */
+
+typedef struct {
+    xFixed   x;
+    xFixed   e;
+    xFixed   stepx;
+    xFixed   signdx;
+    xFixed   dy;
+    xFixed   dx;
+
+    xFixed   stepx_small;
+    xFixed   stepx_big;
+    xFixed   dx_small;
+    xFixed   dx_big;
+} RenderEdge;
+
+/*
+ * Step across a small sample grid gap
+ */
+#define RenderEdgeStepSmall(edge) { \
+    edge->x += edge->stepx_small;   \
+    edge->e += edge->dx_small;	    \
+    if (edge->e > 0)		    \
+    {				    \
+	edge->e -= edge->dy;	    \
+	edge->x += edge->signdx;    \
+    }				    \
+}
+
+/*
+ * Step across a large sample grid gap
+ */
+#define RenderEdgeStepBig(edge) {   \
+    edge->x += edge->stepx_big;	    \
+    edge->e += edge->dx_big;	    \
+    if (edge->e > 0)		    \
+    {				    \
+	edge->e -= edge->dy;	    \
+	edge->x += edge->signdx;    \
+    }				    \
+}
+
+xFixed
+RenderSampleCeilY (xFixed y, int bpp);
+
+xFixed
+RenderSampleFloorY (xFixed y, int bpp);
+
+void
+RenderEdgeStep (RenderEdge *e, int n);
+
+void
+RenderEdgeInit (RenderEdge	*e,
+		int		bpp,
+		xFixed		y_start,
+		xFixed		x_top,
+		xFixed		y_top,
+		xFixed		x_bot,
+		xFixed		y_bot);
+
+void
+RenderLineFixedEdgeInit (RenderEdge *e,
+			 int	    bpp,
+			 xFixed	    y,
+			 xLineFixed *line,
+			 int	    x_off,
+			 int	    y_off);
+
+#endif /* _RENDEREDGE_H_ */