diff --git a/darwin/draw.m b/darwin/draw.m
index 553b4718..178dbca7 100644
--- a/darwin/draw.m
+++ b/darwin/draw.m
@@ -30,7 +30,7 @@ void uiDrawPathNewFigure(uiDrawPath *p, double x, double y)
 	CGPathMoveToPoint(p->path, NULL, x, y);
 }
 
-void uiDrawPathNewFigureWithArc(uiDrawPath *p, double xCenter, double yCenter, double radius, double startAngle, double endAngle)
+void uiDrawPathNewFigureWithArc(uiDrawPath *p, double xCenter, double yCenter, double radius, double startAngle, double sweep)
 {
 	double sinStart, cosStart;
 	double startx, starty;
@@ -42,7 +42,7 @@ void uiDrawPathNewFigureWithArc(uiDrawPath *p, double xCenter, double yCenter, d
 	startx = xCenter + radius * cosStart;
 	starty = yCenter + radius * sinStart;
 	CGPathMoveToPoint(p->path, NULL, startx, starty);
-	uiDrawPathArcTo(p, xCenter, yCenter, radius, startAngle, endAngle);
+	uiDrawPathArcTo(p, xCenter, yCenter, radius, startAngle, sweep);
 }
 
 void uiDrawPathLineTo(uiDrawPath *p, double x, double y)
@@ -52,14 +52,15 @@ void uiDrawPathLineTo(uiDrawPath *p, double x, double y)
 	CGPathAddLineToPoint(p->path, NULL, x, y);
 }
 
-void uiDrawPathArcTo(uiDrawPath *p, double xCenter, double yCenter, double radius, double startAngle, double endAngle)
+void uiDrawPathArcTo(uiDrawPath *p, double xCenter, double yCenter, double radius, double startAngle, double sweep)
 {
 	if (p->ended)
 		complain("attempt to add arc to ended path in uiDrawPathArcTo()");
+	// TODO wasn't there a relative function?
 	CGPathAddArc(p->path, NULL,
 		xCenter, yCenter,
 		radius,
-		startAngle, endAngle,
+		startAngle, startAngle + sweep,
 		NO);
 }
 
diff --git a/test/drawtests.c b/test/drawtests.c
index e1824147..d2c3a2af 100644
--- a/test/drawtests.c
+++ b/test/drawtests.c
@@ -80,16 +80,14 @@ static void drawOriginal(uiAreaDrawParams *p)
 		400, 100,
 		50,
 		30. * (M_PI / 180.),
-		// note the end angle here
-		// in GDI, the second angle to AngleArc() is relative to the start, not to 0
-		330. * (M_PI / 180.));
+		300. * (M_PI / 180.));
 	// TODO add a checkbox for this
 	uiDrawPathLineTo(path, 400, 100);
 	uiDrawPathNewFigureWithArc(path,
 		510, 100,
 		50,
 		30. * (M_PI / 180.),
-		330. * (M_PI / 180.));
+		300. * (M_PI / 180.));
 	uiDrawPathCloseFigure(path);
 	uiDrawPathEnd(path);
 	sp.Cap = uiDrawLineCapFlat;
@@ -210,7 +208,7 @@ static void drawArcs(uiAreaDrawParams *p)
 		uiDrawPathNewFigureWithArc(path,
 			x, y,
 			rad,
-			(M_PI / 4), (M_PI / 4) + angle);
+			(M_PI / 4), angle);
 		angle += add;
 		x += 2 * rad + step;
 		if (i % 6 == 5) {
diff --git a/ui.h b/ui.h
index d521e97a..05aa671f 100644
--- a/ui.h
+++ b/ui.h
@@ -379,11 +379,11 @@ _UI_EXTERN uiDrawPath *uiDrawNewPath(uiDrawFillMode fillMode);
 _UI_EXTERN void uiDrawFreePath(uiDrawPath *p);
 
 _UI_EXTERN void uiDrawPathNewFigure(uiDrawPath *p, double x, double y);
-_UI_EXTERN void uiDrawPathNewFigureWithArc(uiDrawPath *p, double xCenter, double yCenter, double radius, double startAngle, double endAngle);
+_UI_EXTERN void uiDrawPathNewFigureWithArc(uiDrawPath *p, double xCenter, double yCenter, double radius, double startAngle, double sweep);
 _UI_EXTERN void uiDrawPathLineTo(uiDrawPath *p, double x, double y);
 // notes: angles are both relative to 0 and go counterclockwise
 // TODO is the initial line segment on cairo and OS X a proper join?
-_UI_EXTERN void uiDrawPathArcTo(uiDrawPath *p, double xCenter, double yCenter, double radius, double startAngle, double endAngle);
+_UI_EXTERN void uiDrawPathArcTo(uiDrawPath *p, double xCenter, double yCenter, double radius, double startAngle, double sweep);
 _UI_EXTERN void uiDrawPathBezierTo(uiDrawPath *p, double c1x, double c1y, double c2x, double c2y, double endX, double endY);
 // TODO quadratic bezier
 _UI_EXTERN void uiDrawPathCloseFigure(uiDrawPath *p);
diff --git a/unix/draw.c b/unix/draw.c
index 71302706..5a0cc84d 100644
--- a/unix/draw.c
+++ b/unix/draw.c
@@ -55,7 +55,7 @@ void uiDrawPathNewFigure(uiDrawPath *p, double x, double y)
 	add(p, &piece);
 }
 
-void uiDrawPathNewFigureWithArc(uiDrawPath *p, double xCenter, double yCenter, double radius, double startAngle, double endAngle)
+void uiDrawPathNewFigureWithArc(uiDrawPath *p, double xCenter, double yCenter, double radius, double startAngle, double sweep)
 {
 	struct piece piece;
 
@@ -64,7 +64,7 @@ void uiDrawPathNewFigureWithArc(uiDrawPath *p, double xCenter, double yCenter, d
 	piece.d[1] = yCenter;
 	piece.d[2] = radius;
 	piece.d[3] = startAngle;
-	piece.d[4] = endAngle;
+	piece.d[4] = sweep;
 	add(p, &piece);
 }
 
@@ -78,7 +78,7 @@ void uiDrawPathLineTo(uiDrawPath *p, double x, double y)
 	add(p, &piece);
 }
 
-void uiDrawPathArcTo(uiDrawPath *p, double xCenter, double yCenter, double radius, double startAngle, double endAngle)
+void uiDrawPathArcTo(uiDrawPath *p, double xCenter, double yCenter, double radius, double startAngle, double sweep)
 {
 	struct piece piece;
 
@@ -87,7 +87,7 @@ void uiDrawPathArcTo(uiDrawPath *p, double xCenter, double yCenter, double radiu
 	piece.d[1] = yCenter;
 	piece.d[2] = radius;
 	piece.d[3] = startAngle;
-	piece.d[4] = endAngle;
+	piece.d[4] = sweep;
 	add(p, &piece);
 }
 
@@ -154,7 +154,7 @@ static void runPath(uiDrawPath *p, cairo_t *cr)
 				piece->d[0],
 				piece->d[1],
 				piece->d[2],
-				piece->d[4],
+				piece->d[3] + piece->d[4],
 				piece->d[3]);
 			break;
 		case lineTo:
diff --git a/windows/draw.c b/windows/draw.c
index 7862e2a2..9c2f7569 100644
--- a/windows/draw.c
+++ b/windows/draw.c
@@ -165,7 +165,7 @@ static void doDrawArc(ID2D1GeometrySink *sink, double startX, double startY, dou
 	ID2D1GeometrySink_AddArc(sink, &as);
 }
 
-void uiDrawPathNewFigureWithArc(uiDrawPath *p, double xCenter, double yCenter, double radius, double startAngle, double endAngle)
+void uiDrawPathNewFigureWithArc(uiDrawPath *p, double xCenter, double yCenter, double radius, double startAngle, double sweep)
 {
 	double startX, startY;
 	double endX, endY;
@@ -175,8 +175,8 @@ void uiDrawPathNewFigureWithArc(uiDrawPath *p, double xCenter, double yCenter, d
 	uiDrawPathNewFigure(p, startX, startY);
 
 	// draw the arc
-	arcEndpoint(xCenter, yCenter, radius, endAngle, &endX, &endY);
-	doDrawArc(p->sink, startX, startY, endX, endY, radius, endAngle - startAngle);
+	arcEndpoint(xCenter, yCenter, radius, startAngle + sweep, &endX, &endY);
+	doDrawArc(p->sink, startX, startY, endX, endY, radius, sweep);
 }
 
 void uiDrawPathLineTo(uiDrawPath *p, double x, double y)
@@ -188,7 +188,7 @@ void uiDrawPathLineTo(uiDrawPath *p, double x, double y)
 	ID2D1GeometrySink_AddLine(p->sink, pt);
 }
 
-void uiDrawPathArcTo(uiDrawPath *p, double xCenter, double yCenter, double radius, double startAngle, double endAngle)
+void uiDrawPathArcTo(uiDrawPath *p, double xCenter, double yCenter, double radius, double startAngle, double sweep)
 {
 	double startX, startY;
 	double endX, endY;
@@ -198,8 +198,8 @@ void uiDrawPathArcTo(uiDrawPath *p, double xCenter, double yCenter, double radiu
 	uiDrawPathLineTo(p, startX, startY);
 
 	// draw the arc
-	arcEndpoint(xCenter, yCenter, radius, endAngle, &endX, &endY);
-	doDrawArc(p->sink, startX, startY, endX, endY, radius, endAngle - startAngle);
+	arcEndpoint(xCenter, yCenter, radius, startAngle + sweep, &endX, &endY);
+	doDrawArc(p->sink, startX, startY, endX, endY, radius, sweep);
 }
 
 void uiDrawPathBezierTo(uiDrawPath *p, double c1x, double c1y, double c2x, double c2y, double endX, double endY)