From b82cfbb95e48c9848e7fee52112336c659033137 Mon Sep 17 00:00:00 2001
From: Hannes Janetzek <hannes.janetzek@gmail.com>
Date: Fri, 1 Mar 2013 22:53:01 +0100
Subject: [PATCH] limit maximum scanlines to bbox

---
 src/org/oscim/renderer/ScanBox.java | 106 ++++++++--------------------
 1 file changed, 29 insertions(+), 77 deletions(-)

diff --git a/src/org/oscim/renderer/ScanBox.java b/src/org/oscim/renderer/ScanBox.java
index 103553e8..684d7495 100644
--- a/src/org/oscim/renderer/ScanBox.java
+++ b/src/org/oscim/renderer/ScanBox.java
@@ -15,9 +15,11 @@
 
 package org.oscim.renderer;
 
-import android.util.FloatMath;
 
 public abstract class ScanBox {
+	/*
+	 * ported from Polymaps: Layer.js
+	 */
 
 	static class Edge {
 		float x0, y0, x1, y1, dx, dy;
@@ -42,12 +44,28 @@ public abstract class ScanBox {
 	private Edge ab = new Edge();
 	private Edge bc = new Edge();
 	private Edge ca = new Edge();
+	private float minX, maxX;
+
 	protected byte mZoom;
 
 	abstract void setVisible(int y, int x1, int x2);
 
 	public void scan(float[] coords, byte zoom) {
 		mZoom = zoom;
+
+		maxX = Float.MIN_VALUE;
+		minX = Float.MAX_VALUE;
+
+		for(int i = 0; i < 8; i += 2){
+			float x = coords[i];
+			if (x > maxX)
+				maxX = x;
+			if (x < minX)
+				minX = x;
+		}
+		maxX = (float)Math.ceil(maxX);
+		minX = (float)Math.floor(minX);
+
 		// top-left -> top-right
 		ab.set(coords[0], coords[1], coords[2], coords[3]);
 		// top-right ->  bottom-right
@@ -100,8 +118,8 @@ public abstract class ScanBox {
 	private void scanSpans(Edge e0, Edge e1) {
 
 		// scan the y-range of the edge with less dy
-		int y0 = (int) Math.max(0, FloatMath.floor(e1.y0));
-		int y1 = (int) Math.min((1 << mZoom), FloatMath.ceil(e1.y1));
+		int y0 = (int) Math.max(0, Math.floor(e1.y0));
+		int y1 = (int) Math.min((1 << mZoom), Math.ceil(e1.y1));
 
 		// sort edge by x-coordinate
 		if (e0.x0 == e1.x0 && e0.y0 == e1.y0) {
@@ -123,19 +141,6 @@ public abstract class ScanBox {
 		float m0 = e0.dx / e0.dy;
 		float m1 = e1.dx / e1.dy;
 
-		// FIXME, something is wrong here, with a steep angle
-		// 'fill' can shoot far over the area in one direction
-		int maxSlope = 8;
-		if (m0 > maxSlope)
-			m0 = maxSlope;
-		else if (m0 < -maxSlope)
-			m0 = -maxSlope;
-
-		if (m1 > maxSlope)
-			m1 = maxSlope;
-		else if (m1 < -maxSlope)
-			m1 = -maxSlope;
-
 		// e0 goes to the right, e1 to the left
 		int d0 = e0.dx > 0 ? 1 : 0; // use y + 1 to compute x0
 		int d1 = e1.dx < 0 ? 1 : 0; // use y + 1 to compute x1
@@ -147,75 +152,22 @@ public abstract class ScanBox {
 			if (dy > e0.dy)
 				dy = e0.dy;
 
-			float x0 = FloatMath.ceil(e0.x0 + m0 * dy);
+			float x0 = (float)Math.ceil(e0.x0 + m0 * dy);
 
 			dy = d1 + y - e1.y0;
 			if (dy > e1.dy)
 				dy = e1.dy;
 
-			float x1 = FloatMath.floor(e1.x0 + m1 * dy);
+			float x1 = (float)Math.floor(e1.x0 + m1 * dy);
+
+			if (x1 < minX)
+				x1 = minX;
+
+			if (x0 > maxX)
+				x0 = maxX;
 
 			if (x1 < x0)
 				setVisible(y, (int) x1, (int) x0);
 		}
 	}
-
-	/*
-	 * ported from Polymaps: Layer.js Copyright (c) 2010, SimpleGeo and Stamen
-	 * Design
-	 */
-
-	//	// scan-line conversion
-	//	function edge(a, b) {
-	//	  if (a.row > b.row) { var t = a; a = b; b = t; }
-	//	  return {
-	//	    x0: a.column,
-	//	    y0: a.row,
-	//	    x1: b.column,
-	//	    y1: b.row,
-	//	    dx: b.column - a.column,
-	//	    dy: b.row - a.row
-	//	  };
-	//	}
-	//
-	//	// scan-line conversion
-	//	function scanSpans(e0, e1, ymin, ymax, scanLine) {
-	//	  var y0 = Math.max(ymin, Math.floor(e1.y0)),
-	//	      y1 = Math.min(ymax, Math.ceil(e1.y1));
-	//
-	//	  // sort edges by x-coordinate
-	//	  if ((e0.x0 == e1.x0 && e0.y0 == e1.y0)
-	//	      ? (e0.x0 + e1.dy / e0.dy * e0.dx < e1.x1)
-	//	      : (e0.x1 - e1.dy / e0.dy * e0.dx < e1.x0)) {
-	//	    var t = e0; e0 = e1; e1 = t;
-	//	  }
-	//
-	//	  // scan lines!
-	//	  var m0 = e0.dx / e0.dy,
-	//	      m1 = e1.dx / e1.dy,
-	//	      d0 = e0.dx > 0, // use y + 1 to compute x0
-	//	      d1 = e1.dx < 0; // use y + 1 to compute x1
-	//	  for (var y = y0; y < y1; y++) {
-	//	    var x0 = m0 * Math.max(0, Math.min(e0.dy, y + d0 - e0.y0)) + e0.x0,
-	//	        x1 = m1 * Math.max(0, Math.min(e1.dy, y + d1 - e1.y0)) + e1.x0;
-	//	    scanLine(Math.floor(x1), Math.ceil(x0), y);
-	//	  }
-	//	}
-	//
-	//	// scan-line conversion
-	//	function scanTriangle(a, b, c, ymin, ymax, scanLine) {
-	//	  var ab = edge(a, b),
-	//	      bc = edge(b, c),
-	//	      ca = edge(c, a);
-	//
-	//	  // sort edges by y-length
-	//	  if (ab.dy > bc.dy) { var t = ab; ab = bc; bc = t; }
-	//	  if (ab.dy > ca.dy) { var t = ab; ab = ca; ca = t; }
-	//	  if (bc.dy > ca.dy) { var t = bc; bc = ca; ca = t; }
-	//
-	//	  // scan span! scan span!
-	//	  if (ab.dy) scanSpans(ca, ab, ymin, ymax, scanLine);
-	//	  if (bc.dy) scanSpans(ca, bc, ymin, ymax, scanLine);
-	//	}
-
 }