[[ CanvasPathArcTo ]] Add elliptical arc "arc to ... " path command to canvas syntax.

livecodeian · livecodeian · commit 04cf4afb6ecb · 2015-03-19T12:48:34.000Z
diff --git a/engine/src/canvas.mlc b/engine/src/canvas.mlc
@@ -2674,6 +2674,9 @@ public foreign handler MCCanvasPathMoveTo(in pPoint as Point, inout xPath as Pat
 public foreign handler MCCanvasPathLineTo(in pPoint as Point, inout xPath as Path) returns nothing binds to "<builtin>"
 public foreign handler MCCanvasPathCurveThroughPoint(in pThrough as Point, in pTo as Point, inout xPath as Path) returns nothing binds to "<builtin>"
 public foreign handler MCCanvasPathCurveThroughPoints(in pThroughA as Point, in pThroughB as Point, in pTo as Point, inout xPath as Path) returns nothing binds to "<builtin>"
+
+public foreign handler MCCanvasPathEllipticArcToWithFlagsWithRadiiAsList(in pTo as Point, in pRadii as List, in pRotation as CanvasFloat, in pLargest as bool, in pClockwise as bool, inout xPath as Path) returns nothing binds to "<builtin>"
+
 public foreign handler MCCanvasPathClosePath(inout xPath as Path) returns nothing binds to "<builtin>"
 
 /*
@@ -2748,6 +2751,42 @@ begin
 	MCCanvasPathCurveThroughPoints(mThroughA, mThroughB, mTo, mPath)
 end syntax
 
+
+/*
+Summary:	Adds an arc to a path.
+
+mEnd:		An expression which evaluates to a point.
+mRadii:		An expression which evaluates to a list of numbers.
+mAngle:		An expression which evaluates to a number.
+mPath:		An expression which evaluates to a path.
+
+Description:	Adds an arc from the previous point to <mEnd> on <mPath>, following a section of an ellipse with the given radii & angle.
+  As there can be two different ellipses that match the parameters, and two potential arcs for each ellipse, the *largest*, *smallest*, *clockwise*, and *anticlockwise* options allow one arc to specified from the four potential arcs.
+
+Example:
+	variable tPath
+	put the empty path into tPath
+
+	// Begin a new subpath
+	move to point [25, 50] on tPath
+
+	// Continue path with an arc to 50,25
+	arc to point [50, 25] with radii [25, 25] rotated by 0 taking smallest clockwise route on tPath
+
+	// Begin a new subpath
+	move to point [75, 50] on tPath
+	// Continue path with a large arc to 50,75
+	arc to point [50, 75] with radii [25, 25] rotated by 0 taking largest clockwise route on tPath
+
+Tags:	Canvas
+*/
+syntax PathOperationEllipticArcToWithFlags is statement
+	"arc" "to" <mEnd: Expression> "with" "radii" <mRadii: Expression> "rotated" "by" <mAngle: Expression> "taking" ( "largest" <mLargest=true> | "smallest" <mLargest=false> ) ( "clockwise" <mClockwise=true> | "anticlockwise" <mClockwise=false> ) "route" "on" <mPath: Expression>
+begin
+	MCCanvasPathEllipticArcToWithFlagsWithRadiiAsList(mEnd, mRadii, mAngle, mLargest, mClockwise, mPath)
+end syntax
+
+
 /*
 Summary:	Closes the current subpath of a path.
 
diff --git a/engine/src/module-canvas.cpp b/engine/src/module-canvas.cpp
@@ -3690,6 +3690,36 @@ void MCCanvasPathClosePath(MCCanvasPathRef &x_path)
 	MCGPathRelease(t_path);
 }
 
+void MCCanvasPathEllipticArcToWithFlagsWithRadiiAsList(MCCanvasPointRef p_to, MCProperListRef p_radii, MCCanvasFloat p_rotation, bool p_largest, bool p_clockwise, MCCanvasPathRef &x_path)
+{
+	bool t_success;
+	t_success = true;
+	
+	MCGPathRef t_path;
+	t_path = nil;
+	
+	if (t_success)
+	{
+		MCGPathMutableCopy(*MCCanvasPathGet(x_path), t_path);
+		t_success = MCGPathIsValid(t_path);
+	}
+	
+	MCGPoint t_radii;
+	if (t_success)
+		t_success = MCProperListToRadii(p_radii, t_radii);
+	
+	if (t_success)
+	{
+		MCGPathArcTo(t_path, MCGSizeMake(t_radii.x, t_radii.y), p_rotation, p_largest, p_clockwise, *MCCanvasPointGet(p_to));
+		t_success = MCGPathIsValid(t_path);
+	}
+	
+	if (t_success)
+		MCCanvasPathSetMCGPath(t_path, x_path);
+	
+	MCGPathRelease(t_path);
+}
+
 ////////////////////////////////////////////////////////////////////////////////
 
 // Effect
diff --git a/libgraphics/src/path.cpp b/libgraphics/src/path.cpp
@@ -776,14 +776,23 @@ static void _MCGPathEllipticArc(MCGPathRef self, const MCGSize &p_radii, MCGFloa
 	
 	p_angle = fmodf(p_angle + 2 * M_PI, 2 * M_PI);
 	
+	MCGPoint t_mid;
+	t_mid = MCGPointGetMidPoint(t_last, p_end_point);
+	
 	MCGPoint t_p;
-	t_p = MCGPointRotate(MCGPointMake((t_last.x - p_end_point.x) / 2, (t_last.y - p_end_point.y) / 2), -p_angle);
+	t_p = MCGPointRotate(MCGPointTranslate(t_last, -t_mid.x, -t_mid.y), -p_angle);
 	
 	MCGSize t_radii;
 	t_radii = MCGSizeMake(MCAbs(p_radii.width), MCAbs(p_radii.height));
 	
+	MCGFloat t_rx2, t_ry2, t_x2, t_y2;
+	t_rx2 = _sqr(t_radii.width);
+	t_ry2 = _sqr(t_radii.height);
+	t_x2 = _sqr(t_p.x);
+	t_y2 = _sqr(t_p.y);
+	
 	MCGFloat t_a;
-	t_a = (_sqr(t_p.x) / _sqr(t_radii.width)) + (_sqr(t_p.y) / _sqr(t_radii.height));
+	t_a = (t_x2 / t_rx2) + (t_y2 / t_ry2);
 	
 	MCGPoint t_c;
 	
@@ -797,22 +806,13 @@ static void _MCGPathEllipticArc(MCGPathRef self, const MCGSize &p_radii, MCGFloa
 	else
 	{
 		MCGFloat t_scale;
-		MCGFloat t_rx2, t_ry2, t_x2, t_y2;
-		t_rx2 = _sqr(t_radii.width);
-		t_ry2 = _sqr(t_radii.height);
-		t_x2 = _sqr(t_p.x);
-		t_y2 = _sqr(t_p.y);
-		
 		t_scale = sqrtf((t_rx2 * t_ry2 - t_rx2 * t_y2 - t_ry2 * t_x2) / (t_rx2 * t_y2 + t_ry2 * t_x2));
 		if (p_large_arc == p_sweep)
 			t_scale *= -1;
 		
 		t_c = MCGPointMake(t_scale * t_radii.width * t_p.y / t_radii.height, t_scale * -t_radii.height * t_p.x / t_radii.width);
 	}
 	
-	MCGPoint t_mid;
-	t_mid = MCGPointGetMidPoint(t_last, p_end_point);
-	
 	MCGPoint t_center;
 	t_center = MCGPointTranslate(MCGPointRotate(t_c, p_angle), t_mid.x, t_mid.y);
 	
