From 7ecbeee84ea3e20b69ad1282869f528e2ce393d9 Mon Sep 17 00:00:00 2001
From: Paul Ramsey <pramsey@cleverelephant.ca>
Date: Tue, 19 Jun 2012 20:47:45 +0000
Subject: [PATCH] ST_InterpolatePoint returns empty M value (#1873)

git-svn-id: http://svn.osgeo.org/postgis/trunk@9955 b70326c6-7e19-0410-871a-916f4a2858ee
---
 liblwgeom/cunit/cu_ptarray.c | 10 ++++++++++
 liblwgeom/ptarray.c          | 16 ++++------------
 2 files changed, 14 insertions(+), 12 deletions(-)

diff --git a/liblwgeom/cunit/cu_ptarray.c b/liblwgeom/cunit/cu_ptarray.c
index 47eeec89f..7ecec2dfd 100644
--- a/liblwgeom/cunit/cu_ptarray.c
+++ b/liblwgeom/cunit/cu_ptarray.c
@@ -258,6 +258,16 @@ static void test_ptarray_locate_point(void)
 	CU_ASSERT_EQUAL(dist, 0.0);
 
 	lwline_free(line);
+	line = lwgeom_as_lwline(lwgeom_from_text("LINESTRING M (0 0 0, 10 0 20)"));
+
+	p.x = 5; p.y = 0;
+	loc = ptarray_locate_point(line->points, &p, &dist, &l);
+	CU_ASSERT_EQUAL(loc, 0.5);
+	CU_ASSERT_EQUAL(dist, 0.0);
+	CU_ASSERT_EQUAL(l.m, 10.0);	
+
+	lwline_free(line);
+
 }
 
 static void test_ptarray_isccw(void)
diff --git a/liblwgeom/ptarray.c b/liblwgeom/ptarray.c
index eab44e4d3..571f3f7db 100644
--- a/liblwgeom/ptarray.c
+++ b/liblwgeom/ptarray.c
@@ -1001,20 +1001,12 @@ ptarray_locate_point(const POINTARRAY *pa, const POINT4D *p4d, double *mindistou
 	LWDEBUGF(3, "mindist: %g", mindist);
 
 	/*
-	 * If mindist is not 0 we need to project the
+	 * We need to project the
 	 * point on the closest segment.
 	 */
-	if ( FP_GT(mindist, 0.0) )
-	{
-		getPoint4d_p(pa, seg, &start4d);
-		getPoint4d_p(pa, seg+1, &end4d);
-		closest_point_on_segment(p4d, &start4d, &end4d, proj4d);
-	}
-	else
-	{
-		if ( proj4d)
-			*proj4d = *p4d;
-	}
+	getPoint4d_p(pa, seg, &start4d);
+	getPoint4d_p(pa, seg+1, &end4d);
+	closest_point_on_segment(p4d, &start4d, &end4d, proj4d);
 	
 	/* Copy 4D values into 2D holder */
 	proj.x = proj4d->x;
-- 
2.50.1