Fix RegularPolyShape rotation to match TikZ

In PGF/TikZ, regular polygons with rotation 0 have a side flat at the
bottom.  RegularPolyShape now does the same, and also takes its
rotation in degrees.

5 files changed, 48 insertions, 21 deletions

diff --git a/tikzit/src/common/RegularPolyShape.h b/tikzit/src/common/RegularPolyShape.h
index 663561e..1fd8f1e 100644
--- a/tikzit/src/common/RegularPolyShape.h
+++ b/tikzit/src/common/RegularPolyShape.h
@@ -24,10 +24,26 @@
 #import <Foundation/Foundation.h>
 #import "Shape.h"
 
+/**
+ * A regular polygon
+ *
+ * Matches the "regular polygon" shape in the shapes.geometric
+ * PGF/TikZ library.
+ */
 @interface RegularPolyShape : Shape {
 }
 
-- (id)initWithSides:(int)s rotation:(float)r;
+/**
+ * Initialise a regular polygon
+ *
+ * A rotation of 0 will produce a polygon with one
+ * edge flat along the bottom (just like PGF/TikZ
+ * does it).
+ *
+ * @param sides     the number of sides the polygon should have
+ * @param rotation  the rotation of the polygon, in degrees
+ */
+- (id)initWithSides:(int)sides rotation:(int)rotation;
 
 @end
 
diff --git a/tikzit/src/common/RegularPolyShape.m b/tikzit/src/common/RegularPolyShape.m
index e5aac7a..b500377 100644
--- a/tikzit/src/common/RegularPolyShape.m
+++ b/tikzit/src/common/RegularPolyShape.m
@@ -2,8 +2,9 @@
 //  RegularPolyShape.m
 //  TikZiT
 //  
-//  Copyright 2011 Aleks Kissinger. All rights reserved.
-//  
+//  Copyright 2011 Aleks Kissinger
+//  Copyright 2012 Alex Merry
+//  All rights reserved.
 //  
 //  This file is part of TikZiT.
 //  
@@ -28,32 +29,34 @@
 
 @implementation RegularPolyShape
 
-- (id)initWithSides:(int)sides rotation:(float)rotation {
-	[super init];
-	
-	float rad = 0.25f;
-	
+- (id)initWithSides:(int)sides rotation:(int)rotation {
+	self = [super init];
+	if (self == nil)
+		return nil;
+
+	float radius = 0.25f;
+
 	NSMutableArray *nodes = [NSMutableArray arrayWithCapacity:sides];
 	NSMutableArray *edges = [NSMutableArray arrayWithCapacity:sides];
-	
+
 	float dtheta = (M_PI * 2.0f) / ((float)sides);
-	float theta = rotation;
-	int i;
+	float theta = (dtheta/2.0f) - (M_PI / 2.0f);
+	theta += degreesToRadians(rotation);
 	float maxY=0.0f, minY=0.0f;
 	NSPoint p;
-	for (i = 0; i < sides; ++i) {
-		p.x = rad * cos(theta);
-		p.y = rad * sin(theta);
+	for (int i = 0; i < sides; ++i) {
+		p.x = radius * cos(theta);
+		p.y = radius * sin(theta);
 		if (p.y<minY) minY = p.y;
 		if (p.y>maxY) maxY = p.y;
 		
 		[nodes addObject:[Node nodeWithPoint:p]];
 		theta += dtheta;
 	}
-	
+
 	float dy = (minY + maxY) / 2.0f;
-	
-	for (i = 0; i < sides; ++i) {
+
+	for (int i = 0; i < sides; ++i) {
 		p = [[nodes objectAtIndex:i] point];
 		p.y -= dy;
 		[[nodes objectAtIndex:i] setPoint:p];
@@ -63,10 +66,9 @@
 
 	paths = [[NSSet alloc] initWithObjects:edges,nil];
 
-	int degRot = (int)radiansToDegrees(rotation);
 	styleTikz = [[NSString alloc] initWithFormat:
 		@"regular polygon,regular polygon sides=%d,shape border rotate=%d",
-		sides, degRot];
+		sides, rotation];
 
 	return self;
 }
diff --git a/tikzit/src/common/Shape.m b/tikzit/src/common/Shape.m
index b74a9fc..0f1b35b 100644
--- a/tikzit/src/common/Shape.m
+++ b/tikzit/src/common/Shape.m
@@ -110,8 +110,8 @@ NSDictionary *shapeDictionary = nil;
         [[CircleShape alloc] init],
         [[RectangleShape alloc] init],
         [[DiamondShape alloc] init],
-        [[RegularPolyShape alloc] initWithSides:3 rotation:(M_PI/2.0f)],
-        [[RegularPolyShape alloc] initWithSides:3 rotation:(-M_PI/2.0f)]};
+        [[RegularPolyShape alloc] initWithSides:3 rotation:0],
+        [[RegularPolyShape alloc] initWithSides:3 rotation:180]};
 	NSMutableDictionary *shapeDict = [[NSMutableDictionary alloc] initWithObjectsAndKeys:
 									  shapes[0], SHAPE_CIRCLE,
 									  shapes[1], SHAPE_RECTANGLE,
diff --git a/tikzit/src/common/util.h b/tikzit/src/common/util.h
index 809e8ea..d868903 100644
--- a/tikzit/src/common/util.h
+++ b/tikzit/src/common/util.h
@@ -160,6 +160,11 @@ float roundToNearest(float stepSize, float val);
 float radiansToDegrees(float radians);
 
 /*!
+ @brief      Convert degrees into radians
+ */
+float degreesToRadians(float degrees);
+
+/*!
  @brief      Normalises an angle (in degrees) to fall between -179 and 180
  */
 int normaliseAngleDeg (int degrees);
diff --git a/tikzit/src/common/util.m b/tikzit/src/common/util.m
index ad04a96..762516f 100644
--- a/tikzit/src/common/util.m
+++ b/tikzit/src/common/util.m
@@ -310,6 +310,10 @@ float radiansToDegrees (float radians) {
     return (radians * 180.0f) / M_PI;
 }
 
+float degreesToRadians(float degrees) {
+    return (degrees * M_PI) / 180.0f;
+}
+
 int normaliseAngleDeg (int degrees) {
 	while (degrees > 180) {
 		degrees -= 360;