[Pixman] [PATCH 11/15] pixman-filter: integral splitting is only needed for triangle filter

[spitzak at gmail.com]

From: Bill Spitzak <spitzak at gmail.com>

Only the triangle is discontinuous at 0. The other filters resemble a
cubic closely enough that Simpsons integration works without
splitting.

Changes by Søren: Rebase without the changes to the integral function,
update comment to match the new code.

Signed-off-by: Bill Spitzak <spitzak at gmail.com>
Signed-off-by: Søren Sandmann <soren.sandmann at gmail.com>
Reviewed-by: Søren Sandmann <soren.sandmann at gmail.com>
---
 pixman/pixman-filter.c | 11 +++++------
 1 file changed, 5 insertions(+), 6 deletions(-)

diff --git a/pixman/pixman-filter.c b/pixman/pixman-filter.c
index ecff852..878cf9d 100644
--- a/pixman/pixman-filter.c
+++ b/pixman/pixman-filter.c
@@ -160,18 +160,17 @@ integral (pixman_kernel_t kernel1, double x1,
 	  pixman_kernel_t kernel2, double scale, double x2,
 	  double width)
 {
-    /* If the integration interval crosses zero, break it into
-     * two separate integrals. This ensures that filters such
-     * as LINEAR that are not differentiable at 0 will still
-     * integrate properly.
+    /* The LINEAR filter is not differentiable at 0, so if the
+     * integration interval crosses zero, break it into two
+     * separate integrals.
      */
-    if (x1 < 0 && x1 + width > 0)
+    if (kernel1 == PIXMAN_KERNEL_LINEAR && x1 < 0 && x1 + width > 0)
     {
 	return
 	    integral (kernel1, x1, kernel2, scale, x2, - x1) +
 	    integral (kernel1, 0, kernel2, scale, x2 - x1, width + x1);
     }
-    else if (x2 < 0 && x2 + width > 0)
+    else if (kernel2 == PIXMAN_KERNEL_LINEAR && x2 < 0 && x2 + width > 0)
     {
 	return
 	    integral (kernel1, x1, kernel2, scale, x2, - x2) +
-- 
1.9.1