The Render X extension can draw triangles as well as trapezoids, but
the implementation has always converted them to trapezoids. This patch
moves the X server's triangle conversion code into pixman, where we
can reuse the pixman_composite_trapezoid() code.
---
pixman/pixman-trap.c | 136 ++++++++++++++++++++++++++++++++++++++++++++++++++
pixman/pixman.h | 15 ++++++
2 files changed, 151 insertions(+), 0 deletions(-)
diff --git a/pixman/pixman-trap.c b/pixman/pixman-trap.c
index a924326..31144c4 100644
--- a/pixman/pixman-trap.c
+++ b/pixman/pixman-trap.c
@@ -1,4 +1,5 @@
/*
+ * Copyright © 2002 Keith Packard, member of The XFree86 Project, Inc.
* Copyright © 2004 Keith Packard
*
* Permission to use, copy, modify, distribute, and sell this software and its
@@ -25,6 +26,7 @@
#endif
#include <stdio.h>
+#include <stdlib.h>
#include "pixman-private.h"
/*
@@ -477,3 +479,137 @@ pixman_composite_trapezoids (pixman_op_t op,
pixman_image_unref (tmp);
}
+
+static int
+greater_y (pixman_point_fixed_t *a, pixman_point_fixed_t *b)
+{
+ if (a->y == b->y)
+ return a->x > b->x;
+ return a->y > b->y;
+}
+
+/*
+ * Note that the definition of this function is a bit odd because
+ * of the X coordinate space (y increasing downwards).
+ */
+static int
+clockwise (pixman_point_fixed_t *ref,
+ pixman_point_fixed_t *a,
+ pixman_point_fixed_t *b)
+{
+ pixman_point_fixed_t ad, bd;
+
+ ad.x = a->x - ref->x;
+ ad.y = a->y - ref->y;
+ bd.x = b->x - ref->x;
+ bd.y = b->y - ref->y;
+
+ return ((pixman_fixed_32_32_t) bd.y * ad.x -
+ (pixman_fixed_32_32_t) ad.y * bd.x) < 0;
+}
+
+static void
+triangle_to_trapezoids (pixman_triangle_t *tri, pixman_trapezoid_t *traps)
+{
+ pixman_point_fixed_t *top, *left, *right, *tmp;
+
+ top = &tri->p1;
+ left = &tri->p2;
+ right = &tri->p3;
+
+ if (greater_y (top, left))
+ {
+ tmp = left;
+ left = top;
+ top = tmp;
+ }
+
+ if (greater_y (top, right))
+ {
+ tmp = right;
+ right = top;
+ top = tmp;
+ }
+
+ if (clockwise (top, right, left))
+ {
+ tmp = right;
+ right = left;
+ left = tmp;
+ }
+
+ /*
+ * Two cases:
+ *
+ * + +
+ * / \ / \
+ * / \ / \
+ * / + + \
+ * / -- -- \
+ * / -- -- \
+ * / --- --- \
+ * +-- --+
+ */
+
+ traps->top = top->y;
+ traps->left.p1 = *top;
+ traps->left.p2 = *left;
+ traps->right.p1 = *top;
+ traps->right.p2 = *right;
+
+ if (right->y < left->y)
+ traps->bottom = right->y;
+ else
+ traps->bottom = left->y;
+
+ traps++;
+
+ *traps = *(traps - 1);
+
+ if (right->y < left->y)
+ {
+ traps->top = right->y;
+ traps->bottom = left->y;
+ traps->right.p1 = *right;
+ traps->right.p2 = *left;
+ }
+ else
+ {
+ traps->top = left->y;
+ traps->bottom = right->y;
+ traps->left.p1 = *left;
+ traps->left.p2 = *right;
+ }
+}
+
+PIXMAN_EXPORT void
+pixman_composite_triangles (pixman_op_t op,
+ pixman_image_t * src,
+ pixman_image_t * dst,
+ pixman_format_code_t mask_format,
+ int x_src,
+ int y_src,
+ int x_dst,
+ int y_dst,
+ int n_tris,
+ pixman_triangle_t * tris)
+{
+ pixman_trapezoid_t *trapezoids;
+ int i;
+
+ if (n_tris <= 0)
+ return;
+
+ trapezoids = malloc (2 * n_tris * sizeof (pixman_trapezoid_t));
+ if (!trapezoids)
+ return;
+
+ for (i = 0; i < n_tris; ++i)
+ triangle_to_trapezoids (&(tris[i]), trapezoids + 2 * i);
+
+ pixman_composite_trapezoids (op, src, dst, mask_format,
+ x_src, y_src, x_dst, y_dst,
+ n_tris * 2, trapezoids);
+
+ free (trapezoids);
+}
diff --git a/pixman/pixman.h b/pixman/pixman.h
index c2f7da3..582d9cf 100644
--- a/pixman/pixman.h
+++ b/pixman/pixman.h
@@ -868,6 +868,7 @@ typedef struct pixman_edge pixman_edge_t;
typedef struct pixman_trapezoid pixman_trapezoid_t;
typedef struct pixman_trap pixman_trap_t;
typedef struct pixman_span_fix pixman_span_fix_t;
+typedef struct pixman_triangle pixman_triangle_t;
/*
* An edge structure. This represents a single polygon edge
@@ -895,6 +896,10 @@ struct pixman_trapezoid
pixman_line_fixed_t left, right;
};
+struct pixman_triangle
+{
+ pixman_point_fixed_t p1, p2, p3;
+};
/* whether 't' is a well defined not obviously empty trapezoid */
#define pixman_trapezoid_valid(t) \
@@ -960,6 +965,16 @@ void pixman_composite_trapezoids (pixman_op_t
op,
int y_dst,
int n_traps,
pixman_trapezoid_t * traps);
+void pixman_composite_triangles (pixman_op_t op,
+ pixman_image_t * src,
+ pixman_image_t * dst,
+ pixman_format_code_t
mask_format,
+ int x_src,
+ int y_src,
+ int x_dst,
+ int y_dst,
+ int n_tris,
+ pixman_triangle_t * tris);
PIXMAN_END_DECLS
--
1.7.3.1
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