Integration of new rectangles into silhouette data structure seems to be working properly

git-svn-id: file:///srv/devel/repo-conversion/nusu@21 d2e56fa2-650e-0410-a79f-9358c0239efd

Source/Packing/CygonRectanglePacker.Test.cs

@@ -37,7 +37,7 @@ namespace Nuclex.Support.Packing {
     public void TestSpaceEfficiency() {
       float efficiency = calculateEfficiency(new CygonRectanglePacker(70, 70));
 
-      Assert.GreaterOrEqual(efficiency, 0.75, "Packer achieves 75% efficiency");
+      Assert.GreaterOrEqual(efficiency, 0.75f, "Packer achieves 75% efficiency");
     }
 
   }

Source/Packing/CygonRectanglePacker.cs

@@ -25,6 +25,13 @@ using Microsoft.Xna.Framework;
 namespace Nuclex.Support.Packing {
 
   /// <summary>Packer using a custom algorithm by Markus Ewald</summary>
+  /// <remarks>
+  ///   This algorithms always places as close to the top as possible. So, for any new
+  ///   rectangle, the packer has to determine a X coordinate at which the rectangle
+  ///   can be placed at the highest point. To quickly discover these locations,
+  ///   the packer keeps a dynamically list of "height slices", which store the
+  ///   baseline of the rectangles that have been placed so far.
+  /// </remarks>
   public class CygonRectanglePacker : RectanglePacker {
 
     #region class SliceStartComparer
@@ -68,22 +75,111 @@ namespace Nuclex.Support.Packing {
     public override bool TryAllocate(
       int rectangleWidth, int rectangleHeight, out Point placement
     ) {
-      integrateRectangle(0, 1, 5);
+      int sliceIndex = findBestPosition(rectangleWidth, rectangleHeight);
-      integrateRectangle(20, 5, 30);
-      integrateRectangle(10, 10, 50);
-      integrateRectangle(10, 15, 25);
-      integrateRectangle(35, 20, 25);
-      integrateRectangle(40, 25, 15);
 
-      placement = Point.Zero;
+      // TODO: Rectangle might not even fit there!
-      return false;
+      if(sliceIndex == -1) {
+
+        placement = Point.Zero;
+        return false;
+
+      } else {
+
+        placement = this.heightSlices[sliceIndex];
+
+        integrateRectangle(
+          this.heightSlices[sliceIndex].X,
+          rectangleWidth,
+          this.heightSlices[sliceIndex].Y + rectangleHeight
+        );
+
+        return true;
+
+      }
+    }
+
+    /// <summary>Finds the best position for a rectangle of the given width</summary>
+    /// <param name="rectangleWidth">Width of the rectangle to find a position for</param>
+    /// <param name="rectangleHeight">Height of the rectangle to find a position for</param>
+    /// <returns>The best position for a rectangle with the specified width</returns>
+    private int findBestPosition(int rectangleWidth, int rectangleHeight) {
+      int leftSliceIndex = 0;
+      int rightSliceIndex = this.heightSlices.BinarySearch(
+        new Point(rectangleWidth, 0), SliceStartComparer.Default
+      );
+      if(rightSliceIndex < 0)
+        rightSliceIndex = ~rightSliceIndex;
+
+      int leastWastedSliceIndex = -1;
+      int leastWastedArea = MaxPackingAreaWidth * MaxPackingAreaHeight;
+
+      while(rightSliceIndex <= this.heightSlices.Count) {
+        // final time (this is the special case where the rectangle is attempted
+        // to be placed at the rightmost end of the packing area)
+      
+        /*
+                // Determine the highest slice at this position. We cannot put the rectangle
+                // any lower than this without colliding into other rectangles
+                int highest = this.heightSlices[leftSliceIndex].Y;
+                for(int index = leftSliceIndex + 1; index < rightSliceIndex; ++index)
+                  highest = Math.Max(highest, this.heightSlices[index].Y);
+
+                // Calculate the amount of space that would go to waste if the rectangle
+                // would be placed at this location
+                int wastedArea = 0;
+                for(int index = leftSliceIndex; index < rightSliceIndex - 1; ++index) {
+                  int sliceWidth = this.heightSlices[index + 1].X - this.heightSlices[index].X;
+                  wastedArea += (highest - this.heightSlices[index].Y) * sliceWidth;
+                }
+                wastedArea +=
+                  (highest - this.heightSlices[rightSliceIndex - 1].Y) *
+                  (
+                    (this.heightSlices[leftSliceIndex].X + rectangleWidth) -
+                    this.heightSlices[rightSliceIndex - 1].X
+                  );
+
+                // If this beats the current record for the least wasted area, remember this as
+                // being the best position found so far
+                if(
+                  (wastedArea < leastWastedArea) &&
+                  (this.heightSlices[leftSliceIndex].Y + rectangleHeight < MaxPackingAreaHeight)
+                ) {
+                  leastWastedArea = wastedArea;
+                  leastWastedSliceIndex = leftSliceIndex;
+
+                  // No sense looking any further if we found the perfect place!
+                  if(leastWastedArea == 0)
+                    break;
+                }
+        */
+
+
+        // If this already was the loop after the final slice, terminate it now!
+        if(rightSliceIndex == this.heightSlices.Count)
+          break;
+
+        // Advance the starting slice to the next slice start
+        ++leftSliceIndex;
+        int rightEnd = this.heightSlices[leftSliceIndex].X + rectangleWidth;
+
+        // Advance the ending slice to where the rectangle ends now
+        while(rightEnd > this.heightSlices[rightSliceIndex].X) {
+          ++rightSliceIndex;
+
+          // If the end is reached, stop shifting and make the outer loop run one final time
+          if(rightSliceIndex == this.heightSlices.Count)
+            break;
+        }
+      }
+
+      return leastWastedSliceIndex;
     }
 
     /// <summary>Integrates a new rectangle into the height slice table</summary>
     /// <param name="left">Position of the rectangle's left side</param>
-    /// <param name="bottom">Position of the rectangle's lower side</param>
     /// <param name="width">Width of the rectangle</param>
-    private void integrateRectangle(int left, int bottom, int width) {
+    /// <param name="bottom">Position of the rectangle's lower side</param>
+    private void integrateRectangle(int left, int width, int bottom) {
 
       // Find the first slice that is touched by the rectangle
       int startSlice = this.heightSlices.BinarySearch(
@@ -97,7 +193,6 @@ namespace Nuclex.Support.Packing {
         // We scored a direct hit, so we can replace the slice we have hit
         firstSliceOriginalHeight = this.heightSlices[startSlice].Y;
         this.heightSlices[startSlice] = new Point(left, bottom);
-        ++startSlice;
 
       } else { // No direct hit, slice starts inside another slice
 
@@ -108,58 +203,56 @@ namespace Nuclex.Support.Packing {
 
       }
 
-      // Special case, the rectangle was on the last slice, so we cannot
+      int right = left + width;
-      // use the start slice + 1 as start index for the binary search
+      ++startSlice;
+
+      // Special case, the rectangle started on the last slice, so we cannot
+      // use the start slice + 1 for the binary search and the possibly already
+      // modified start slice height now only remains in our temporary
+      // firstSliceOriginalHeight variable
       if(startSlice >= this.heightSlices.Count) {
-      } else {
+
-        int right = left + width;
+        // If the slice ends within the last slice (usual case, unless it has the
+        // exact same with the packing area has), add another slice to return to the
+        // original height at the end of the rectangle.
+        if(right < MaxPackingAreaWidth)
+          this.heightSlices.Add(new Point(right, firstSliceOriginalHeight));
+
+      } else { // The rectangle doesn't start on the last slice
 
         int endSlice = this.heightSlices.BinarySearch(
           startSlice, this.heightSlices.Count - startSlice,
           new Point(right, 0), SliceStartComparer.Default
         );
-      }
 
-      //this.heightSlices.RemoveRange(startSlice, endSlice - startSlice);
+        // Another direct hit on the final slice's end?
-/*
+        if(endSlice > 0) {
-      int nextSlice = firstSlice + 1;
-      bool isLastSlice = (nextSlice >= this.heightSlices.Count);
 
-*/
+          this.heightSlices.RemoveRange(startSlice, endSlice - startSlice);
-/*      
 
+        } else { // No direct hit, rectangle ends inside another slice
 
-        int nextSlice = firstSlice + 1;
+          endSlice = ~endSlice;
-        bool isLastSlice = (nextSlice >= this.heightSlices.Count);
 
-        // 
+          // Find out to which height we need to return at the right end of
-        bool endsInFirstSlice;
+          // the rectangle
-        if(isLastSlice)
+          int returnHeight;
-          endsInFirstSlice = right < MaxPackingAreaWidth;
+          if(endSlice == startSlice)
-        else
+            returnHeight = firstSliceOriginalHeight;
-          endsInFirstSlice = right < this.heightSlices[nextSlice].X;
+          else
+            returnHeight = this.heightSlices[endSlice - 1].Y;
+
+          // Remove all slices covered by the rectangle and began a new slice at
+          // its end to return to the height the slice in which the rectangle ends
+          // has had.
+          this.heightSlices.RemoveRange(startSlice, endSlice - startSlice);
+          if(right < MaxPackingAreaWidth)
+            this.heightSlices.Insert(startSlice, new Point(right, returnHeight));
 
-        if(endsInFirstSlice) {
-          this.heightSlices.Insert(
-            nextSlice, new Point(right, this.heightSlices[firstSlice].Y)
-          );
-          this.heightSlices[firstSlice] = new Point(left, bottom);
-          return;
-        } else { // Integrated rect continues beyond the discovered slice
-          this.heightSlices[firstSlice] = new Point(left, bottom);
         }
 
-      } else {
-
-        firstSlice = ~firstSlice;
-
-        //firstSliceOriginalHeight = this.heightSlices[firstSlice].Y;
-
-        this.heightSlices.Insert(firstSlice, new Point(left, bottom));
-        ++firstSlice;
-
       }
-*/
+
     }
 
     /// <summary>Stores the height silhouette of the rectangles</summary>