Add rotateAround Vector2D function.

Remove the rmgen rotateCoordinates helper function from 4256744e26 and
clean the implementation of that commit, refs #4845, #4804.
Deepfreeze mapCenter vector from 5256d8497e used here to prevent
accidental overwrites with the mutating Vector2D functions, refs #4854.

This was SVN commit r20468.

binaries/data/mods/public/globalscripts/vector.js

@@ -83,6 +83,14 @@ Vector2D.prototype.rotate = function(angle)
 		this.y * cos - this.x * sin);
 };
 
+/**
+ * Rotate radians anti-clockwise around the specified rotation center.
+ */
+Vector2D.prototype.rotateAround = function(angle, center)
+{
+	return this.sub(center).rotate(angle).add(center);
+};
+
 // Numeric 2D info functions (non-mutating)
 //
 // These methods serve to get numeric info on the vector, they don't modify the vector

binaries/data/mods/public/maps/random/corinthian_isthmus.js

@@ -45,6 +45,7 @@ InitMap();
 
 const numPlayers = getNumPlayers();
 const mapSize = getMapSize();
+const mapCenter = getMapCenter();
 
 var clPlayer = createTileClass();
 var clForest = createTileClass();
@@ -60,32 +61,33 @@ var clHill = createTileClass();
 var landHeight = getMapBaseHeight();
 var waterHeight = -4;
 
+log("Creating the main river");
 var riverWidth = scaleByMapSize(15, 70);
 var riverAngle = -Math.PI / 4;
+var riverStart = new Vector2D(mapCenter.x, 0).rotateAround(riverAngle, mapCenter);
+var riverEnd = new Vector2D(mapCenter.x, mapSize).rotateAround(riverAngle, mapCenter);
 
-var riv1 = [0, 0.5];
-var riv2 = [1, 0.5];
-
-log("Creating the main river");
-var [riverX1, riverZ1] = rotateCoordinates(...riv1, riverAngle).map(f => fractionToTiles(f));
-var [riverX2, riverZ2] = rotateCoordinates(...riv2, riverAngle).map(f => fractionToTiles(f));
 createArea(
-	new PathPlacer(riverX1, riverZ1, riverX2, riverZ2, riverWidth, 0.2, 15 * scaleByMapSize(1, 3), 0.04, 0.01),
+	new PathPlacer(riverStart.x, riverStart.y, riverEnd.x, riverEnd.y, riverWidth, 0.2, 15 * scaleByMapSize(1, 3), 0.04, 0.01),
 	new SmoothElevationPainter(ELEVATION_SET, waterHeight, 4),
 	null);
 
 log("Creating small puddles at the map border to ensure players being separated...");
-for (let [x, z] of [[riverX1, riverZ1], [riverX2, riverZ2]])
+for (let point of [riverStart, riverEnd])
 	createArea(
-		new ClumpPlacer(Math.floor(diskArea(riverWidth / 2)), 0.95, 0.6, 10, x, z),
+		new ClumpPlacer(Math.floor(diskArea(riverWidth / 2)), 0.95, 0.6, 10, point.x, point.y),
 		new SmoothElevationPainter(ELEVATION_SET, waterHeight, 4),
 		null);
 
 log("Creating passage connecting the two riversides...");
+var passageStart = riverStart.rotateAround(Math.PI / 2, mapCenter);
+var passageEnd = riverEnd.rotateAround(Math.PI / 2, mapCenter);
 createArea(
 	new PathPlacer(
-		...rotateCoordinates(...riv1, riverAngle + Math.PI / 2).map(f => fractionToTiles(f)),
-		...rotateCoordinates(...riv2, riverAngle + Math.PI / 2).map(f => fractionToTiles(f)),
+		passageStart.x,
+		passageStart.y,
+		passageEnd.x,
+		passageEnd.y,
 		scaleByMapSize(10, 30),
 		0.5,
 		3 * scaleByMapSize(1, 4),

binaries/data/mods/public/maps/random/rmgen/library.js

@@ -358,7 +358,7 @@ function getMapArea()
 
 function getMapCenter()
 {
-	return new Vector2D(g_Map.size / 2, g_Map.size / 2);
+	return deepfreeze(new Vector2D(g_Map.size / 2, g_Map.size / 2));
 }
 
 function getNumPlayers()

binaries/data/mods/public/maps/random/rmgen/math.js

@@ -12,20 +12,6 @@ function getAngle(x1, z1, x2, z2)
 	return Math.atan2(z2 - z1, x2 - x1);
 }
 
-/**
- * Revolve the given point around the given rotation center.
- */
-function rotateCoordinates(x, z, angle, centerX = 0.5, centerZ = 0.5)
-{
-	let sin = Math.sin(angle);
-	let cos = Math.cos(angle);
-
-	return [
-		cos * (x - centerX) - sin * (z - centerZ) + centerX,
-		sin * (x - centerX) + cos * (z - centerZ) + centerZ
-	];
-}
-
 /**
  * Get pointCount points equidistantly located on a circle.
  */

binaries/data/mods/public/simulation/components/tests/test_Vector.js

@@ -74,6 +74,14 @@ var brokenVector = {
 	}
 }
 
+// Test Vector2D rotation around a center
+{
+	let epsilon = 0.00000001;
+	let v1 = new Vector2D(-4, 8).rotateAround(Math.PI / 3, new Vector2D(-1, -3));
+	TS_ASSERT_EQUALS_APPROX(v1.x, 7.02627944, epsilon);
+	TS_ASSERT_EQUALS_APPROX(v1.y, 5.09807617, epsilon);
+}
+
 // Test Vector2D dot product
 {
 	TS_ASSERT_EQUALS(new Vector2D(2, 3).dot(new Vector2D(4, 5)), 23);