clarify StaticSpriteBatch depth documentation

Items will now be drawn in an arbitrary order.

MLEM/Misc/StaticSpriteBatch.cs

@@ -7,8 +7,9 @@ using MLEM.Extensions;
 namespace MLEM.Misc {
     /// <summary>
     /// A static sprite batch is a variation of <see cref="SpriteBatch"/> that keeps all batched items in a <see cref="VertexBuffer"/>, allowing for them to be drawn multiple times.
-    /// To add items to a static sprite batch, use <see cref="ClearBatch"/> to clear currently batched items, <see cref="BeginBatch"/> to begin batching, <c>Add</c> and its various overloads to add batch items and <see cref="EndBatch"/> to end batching.
+    /// To add items to a static sprite batch, use <see cref="BeginBatch"/> to begin batching, <see cref="ClearBatch"/> to clear currently batched items, <c>Add</c> and its various overloads to add batch items, <see cref="Remove"/> to remove them again, and <see cref="EndBatch"/> to end batching.
     /// To draw the batched items, call <see cref="Draw"/>.
+    /// Unlike a <see cref="SpriteBatch"/>, items added to a static sprite batch will be drawn in an arbitrary order. If depth sorting is desired, the <see cref="GraphicsDeviceManager"/>'s <see cref="GraphicsDeviceManager.PreferredDepthStencilFormat"/> should be modified to include depth, and a <see cref="DepthStencilState"/> that takes depth into account should be passed to <see cref="Draw"/>.
     /// </summary>
     public class StaticSpriteBatch : IDisposable {
 
@@ -19,13 +20,13 @@ namespace MLEM.Misc {
         /// <summary>
         /// The amount of vertices that are currently batched
         /// </summary>
-        public int Vertices => this.vertices.Count;
+        public int Vertices => this.items.Count * 4;
 
         private readonly GraphicsDevice graphicsDevice;
         private readonly SpriteEffect spriteEffect;
 
         private readonly List<VertexBuffer> vertexBuffers = new List<VertexBuffer>();
-        private readonly List<VertexPositionColorTexture> vertices = new List<VertexPositionColorTexture>();
+        private readonly ISet<Item> items = new HashSet<Item>();
         private IndexBuffer indices;
         private Texture2D texture;
         private bool batching;
@@ -43,7 +44,6 @@ namespace MLEM.Misc {
         /// <summary>
         /// Begins batching.
         /// Call this method before calling <c>Add</c> or any of its overloads.
-        /// Note that, if <see cref="ClearBatch"/> was not called, items that are batched will be appended to the existing batch.
         /// </summary>
         /// <exception cref="InvalidOperationException">Thrown if this batch is currently batching already</exception>
         public void BeginBatch() {
@@ -62,28 +62,34 @@ namespace MLEM.Misc {
                 throw new InvalidOperationException("Not batching");
             this.batching = false;
 
-            // if we didn't add any batch items, we don't have to recalculate anything
+            // if we didn't add or remove any batch items, we don't have to recalculate anything
             if (!this.batchChanged)
                 return;
             this.batchChanged = false;
 
             // ensure we have enough vertex buffers
-            var requiredBuffers = (this.vertices.Count / (MaxBatchItems * 4F)).Ceil();
+            var requiredBuffers = (this.items.Count / (float) MaxBatchItems).Ceil();
             while (this.vertexBuffers.Count < requiredBuffers)
                 this.vertexBuffers.Add(new VertexBuffer(this.graphicsDevice, VertexPositionColorTexture.VertexDeclaration, MaxBatchItems * 4, BufferUsage.WriteOnly));
 
             // fill vertex buffers
+            var dataIndex = 0;
             var arrayIndex = 0;
-            var totalIndex = 0;
-            while (totalIndex < this.vertices.Count) {
-                var now = Math.Min(this.vertices.Count - totalIndex, Data.Length);
-                this.vertices.CopyTo(totalIndex, Data, 0, now);
-                this.vertexBuffers[arrayIndex++].SetData(Data);
-                totalIndex += now;
+            foreach (var item in this.items) {
+                Data[dataIndex++] = item.TopLeft;
+                Data[dataIndex++] = item.TopRight;
+                Data[dataIndex++] = item.BottomLeft;
+                Data[dataIndex++] = item.BottomRight;
+                if (dataIndex >= Data.Length) {
+                    this.vertexBuffers[arrayIndex++].SetData(Data);
+                    dataIndex = 0;
+                }
             }
+            if (dataIndex > 0)
+                this.vertexBuffers[arrayIndex].SetData(Data);
 
             // ensure we have enough indices
-            var maxItems = Math.Min(this.vertices.Count / 4, MaxBatchItems);
+            var maxItems = Math.Min(this.items.Count, MaxBatchItems);
             // each item has 2 triangles which each have 3 indices
             if (this.indices == null || this.indices.IndexCount < 6 * maxItems) {
                 var newIndices = new short[6 * maxItems];
@@ -109,19 +115,6 @@ namespace MLEM.Misc {
             }
         }
 
-        /// <summary>
-        /// Clears the batch, removing all currently batched vertices.
-        /// After this operation, <see cref="Vertices"/> will return 0.
-        /// </summary>
-        /// <exception cref="InvalidOperationException">Thrown if this batch is currently batching</exception>
-        public void ClearBatch() {
-            if (this.batching)
-                throw new InvalidOperationException("Cannot clear while batching");
-            this.vertices.Clear();
-            this.texture = null;
-            this.batchChanged = true;
-        }
-
         /// <summary>
         /// Draws this batch's content onto the <see cref="GraphicsDevice"/>'s current render target (or the back buffer) with the given settings.
         /// Note that this method should not be called while a regular <see cref="SpriteBatch"/> is currently active.
@@ -148,7 +141,7 @@ namespace MLEM.Misc {
 
             var totalIndex = 0;
             foreach (var buffer in this.vertexBuffers) {
-                var tris = Math.Min(this.vertices.Count - totalIndex, buffer.VertexCount) / 4 * 2;
+                var tris = Math.Min(this.items.Count * 4 - totalIndex, buffer.VertexCount) / 4 * 2;
                 if (tris <= 0)
                     break;
                 this.graphicsDevice.SetVertexBuffer(buffer);
@@ -178,8 +171,9 @@ namespace MLEM.Misc {
         /// <param name="origin">Center of the rotation. 0,0 by default.</param>
         /// <param name="scale">A scaling of this sprite.</param>
         /// <param name="effects">Modificators for drawing. Can be combined.</param>
-        /// <param name="layerDepth">A depth of the layer of this sprite.</param>
-        public void Add(Texture2D texture, Vector2 position, Rectangle? sourceRectangle, Color color, float rotation, Vector2 origin, Vector2 scale, SpriteEffects effects, float layerDepth) {
+        /// <param name="layerDepth">A depth of the layer of this sprite. See <see cref="StaticSpriteBatch"/> documentation for information on enabling depth support.</param>
+        /// <returns>The <see cref="Item"/> that was created from the added data</returns>
+        public Item Add(Texture2D texture, Vector2 position, Rectangle? sourceRectangle, Color color, float rotation, Vector2 origin, Vector2 scale, SpriteEffects effects, float layerDepth) {
             origin *= scale;
 
             Vector2 size, texTl, texBr;
@@ -204,9 +198,9 @@ namespace MLEM.Misc {
                 (texBr.X, texTl.X) = (texTl.X, texBr.X);
 
             if (rotation == 0) {
-                this.Add(texture, position - origin, size, color, texTl, texBr, layerDepth);
+                return this.Add(texture, position - origin, size, color, texTl, texBr, layerDepth);
             } else {
-                this.Add(texture, position, -origin, size, (float) Math.Sin(rotation), (float) Math.Cos(rotation), color, texTl, texBr, layerDepth);
+                return this.Add(texture, position, -origin, size, (float) Math.Sin(rotation), (float) Math.Cos(rotation), color, texTl, texBr, layerDepth);
             }
         }
 
@@ -222,9 +216,10 @@ namespace MLEM.Misc {
         /// <param name="origin">Center of the rotation. 0,0 by default.</param>
         /// <param name="scale">A scaling of this sprite.</param>
         /// <param name="effects">Modificators for drawing. Can be combined.</param>
-        /// <param name="layerDepth">A depth of the layer of this sprite.</param>
-        public void Add(Texture2D texture, Vector2 position, Rectangle? sourceRectangle, Color color, float rotation, Vector2 origin, float scale, SpriteEffects effects, float layerDepth) {
-            this.Add(texture, position, sourceRectangle, color, rotation, origin, new Vector2(scale), effects, layerDepth);
+        /// <param name="layerDepth">A depth of the layer of this sprite. See <see cref="StaticSpriteBatch"/> documentation for information on enabling depth support.</param>
+        /// <returns>The <see cref="Item"/> that was created from the added data</returns>
+        public Item Add(Texture2D texture, Vector2 position, Rectangle? sourceRectangle, Color color, float rotation, Vector2 origin, float scale, SpriteEffects effects, float layerDepth) {
+            return this.Add(texture, position, sourceRectangle, color, rotation, origin, new Vector2(scale), effects, layerDepth);
         }
 
         /// <summary>
@@ -238,8 +233,9 @@ namespace MLEM.Misc {
         /// <param name="rotation">A rotation of this sprite.</param>
         /// <param name="origin">Center of the rotation. 0,0 by default.</param>
         /// <param name="effects">Modificators for drawing. Can be combined.</param>
-        /// <param name="layerDepth">A depth of the layer of this sprite.</param>
-        public void Add(Texture2D texture, Rectangle destinationRectangle, Rectangle? sourceRectangle, Color color, float rotation, Vector2 origin, SpriteEffects effects, float layerDepth) {
+        /// <param name="layerDepth">A depth of the layer of this sprite. See <see cref="StaticSpriteBatch"/> documentation for information on enabling depth support.</param>
+        /// <returns>The <see cref="Item"/> that was created from the added data</returns>
+        public Item Add(Texture2D texture, Rectangle destinationRectangle, Rectangle? sourceRectangle, Color color, float rotation, Vector2 origin, SpriteEffects effects, float layerDepth) {
             Vector2 texTl, texBr;
             if (sourceRectangle.HasValue) {
                 var src = sourceRectangle.Value;
@@ -262,9 +258,9 @@ namespace MLEM.Misc {
                 (texBr.X, texTl.X) = (texTl.X, texBr.X);
 
             if (rotation == 0) {
-                this.Add(texture, destinationRectangle.Location.ToVector2() - origin, destinationRectangle.Size.ToVector2(), color, texTl, texBr, layerDepth);
+                return this.Add(texture, destinationRectangle.Location.ToVector2() - origin, destinationRectangle.Size.ToVector2(), color, texTl, texBr, layerDepth);
             } else {
-                this.Add(texture, destinationRectangle.Location.ToVector2(), -origin, destinationRectangle.Size.ToVector2(), (float) Math.Sin(rotation), (float) Math.Cos(rotation), color, texTl, texBr, layerDepth);
+                return this.Add(texture, destinationRectangle.Location.ToVector2(), -origin, destinationRectangle.Size.ToVector2(), (float) Math.Sin(rotation), (float) Math.Cos(rotation), color, texTl, texBr, layerDepth);
             }
         }
 
@@ -276,8 +272,9 @@ namespace MLEM.Misc {
         /// <param name="position">The drawing location on screen.</param>
         /// <param name="sourceRectangle">An optional region on the texture which will be rendered. If null - draws full texture.</param>
         /// <param name="color">A color mask.</param>
-        public void Add(Texture2D texture, Vector2 position, Rectangle? sourceRectangle, Color color) {
-            this.Add(texture, position, sourceRectangle, color, 0, Vector2.Zero, 1, SpriteEffects.None, 0);
+        /// <returns>The <see cref="Item"/> that was created from the added data</returns>
+        public Item Add(Texture2D texture, Vector2 position, Rectangle? sourceRectangle, Color color) {
+            return this.Add(texture, position, sourceRectangle, color, 0, Vector2.Zero, 1, SpriteEffects.None, 0);
         }
 
         /// <summary>
@@ -288,8 +285,9 @@ namespace MLEM.Misc {
         /// <param name="destinationRectangle">The drawing bounds on screen.</param>
         /// <param name="sourceRectangle">An optional region on the texture which will be rendered. If null - draws full texture.</param>
         /// <param name="color">A color mask.</param>
-        public void Add(Texture2D texture, Rectangle destinationRectangle, Rectangle? sourceRectangle, Color color) {
-            this.Add(texture, destinationRectangle, sourceRectangle, color, 0, Vector2.Zero, SpriteEffects.None, 0);
+        /// <returns>The <see cref="Item"/> that was created from the added data</returns>
+        public Item Add(Texture2D texture, Rectangle destinationRectangle, Rectangle? sourceRectangle, Color color) {
+            return this.Add(texture, destinationRectangle, sourceRectangle, color, 0, Vector2.Zero, SpriteEffects.None, 0);
         }
 
         /// <summary>
@@ -299,8 +297,9 @@ namespace MLEM.Misc {
         /// <param name="texture">A texture.</param>
         /// <param name="position">The drawing location on screen.</param>
         /// <param name="color">A color mask.</param>
-        public void Add(Texture2D texture, Vector2 position, Color color) {
-            this.Add(texture, position, null, color);
+        /// <returns>The <see cref="Item"/> that was created from the added data</returns>
+        public Item Add(Texture2D texture, Vector2 position, Color color) {
+            return this.Add(texture, position, null, color);
         }
 
         /// <summary>
@@ -310,8 +309,39 @@ namespace MLEM.Misc {
         /// <param name="texture">A texture.</param>
         /// <param name="destinationRectangle">The drawing bounds on screen.</param>
         /// <param name="color">A color mask.</param>
-        public void Add(Texture2D texture, Rectangle destinationRectangle, Color color) {
-            this.Add(texture, destinationRectangle, null, color);
+        /// <returns>The <see cref="Item"/> that was created from the added data</returns>
+        public Item Add(Texture2D texture, Rectangle destinationRectangle, Color color) {
+            return this.Add(texture, destinationRectangle, null, color);
+        }
+
+        /// <summary>
+        /// Removes the given item from this batch.
+        /// Note that this batch needs to currently be batching, meaning <see cref="BeginBatch"/> has to have been called previously.
+        /// </summary>
+        /// <param name="item">The item to remove</param>
+        /// <returns>Whether the item was successfully removed</returns>
+        /// <exception cref="InvalidOperationException">Thrown if this method is called before <see cref="BeginBatch"/> was called</exception>
+        public bool Remove(Item item) {
+            if (!this.batching)
+                throw new InvalidOperationException("Not batching");
+            if (this.items.Remove(item)) {
+                this.batchChanged = true;
+                return true;
+            }
+            return false;
+        }
+
+        /// <summary>
+        /// Clears the batch, removing all currently batched vertices.
+        /// After this operation, <see cref="Vertices"/> will return 0.
+        /// </summary>
+        /// <exception cref="InvalidOperationException">Thrown if this method is called before <see cref="BeginBatch"/> was called</exception>
+        public void ClearBatch() {
+            if (!this.batching)
+                throw new InvalidOperationException("Not batching");
+            this.items.Clear();
+            this.texture = null;
+            this.batchChanged = true;
         }
 
         /// <inheritdoc />
@@ -323,33 +353,52 @@ namespace MLEM.Misc {
             GC.SuppressFinalize(this);
         }
 
-        private void Add(Texture2D texture, Vector2 pos, Vector2 offset, Vector2 size, float sin, float cos, Color color, Vector2 texTl, Vector2 texBr, float depth) {
-            this.Add(texture,
+        private Item Add(Texture2D texture, Vector2 pos, Vector2 offset, Vector2 size, float sin, float cos, Color color, Vector2 texTl, Vector2 texBr, float depth) {
+            return this.Add(texture,
                 new VertexPositionColorTexture(new Vector3(pos.X + offset.X * cos - offset.Y * sin, pos.Y + offset.X * sin + offset.Y * cos, depth), color, texTl),
                 new VertexPositionColorTexture(new Vector3(pos.X + (offset.X + size.X) * cos - offset.Y * sin, pos.Y + (offset.X + size.X) + offset.Y * cos, depth), color, new Vector2(texBr.X, texTl.Y)),
                 new VertexPositionColorTexture(new Vector3(pos.X + offset.X * cos - (offset.Y + size.Y) * sin, pos.Y + offset.X * sin + (offset.Y + size.Y) * cos, depth), color, new Vector2(texTl.X, texBr.Y)),
                 new VertexPositionColorTexture(new Vector3(pos.X + (offset.X + size.X) * cos - (offset.Y + size.Y) * sin, pos.Y + (offset.X + size.X) * sin + (offset.Y + size.Y) * cos, depth), color, texBr));
         }
 
-        private void Add(Texture2D texture, Vector2 pos, Vector2 size, Color color, Vector2 texTl, Vector2 texBr, float depth) {
-            this.Add(texture,
+        private Item Add(Texture2D texture, Vector2 pos, Vector2 size, Color color, Vector2 texTl, Vector2 texBr, float depth) {
+            return this.Add(texture,
                 new VertexPositionColorTexture(new Vector3(pos, depth), color, texTl),
                 new VertexPositionColorTexture(new Vector3(pos.X + size.X, pos.Y, depth), color, new Vector2(texBr.X, texTl.Y)),
                 new VertexPositionColorTexture(new Vector3(pos.X, pos.Y + size.Y, depth), color, new Vector2(texTl.X, texBr.Y)),
                 new VertexPositionColorTexture(new Vector3(pos.X + size.X, pos.Y + size.Y, depth), color, texBr));
         }
 
-        private void Add(Texture2D texture, VertexPositionColorTexture tl, VertexPositionColorTexture tr, VertexPositionColorTexture bl, VertexPositionColorTexture br) {
+        private Item Add(Texture2D texture, VertexPositionColorTexture tl, VertexPositionColorTexture tr, VertexPositionColorTexture bl, VertexPositionColorTexture br) {
             if (!this.batching)
                 throw new InvalidOperationException("Not batching");
             if (this.texture != null && this.texture != texture)
                 throw new ArgumentException("Cannot use multiple textures in one batch");
+            var item = new Item(tl, tr, bl, br);
+            this.items.Add(item);
             this.texture = texture;
-            this.vertices.Add(tl);
-            this.vertices.Add(tr);
-            this.vertices.Add(bl);
-            this.vertices.Add(br);
             this.batchChanged = true;
+            return item;
+        }
+
+        /// <summary>
+        /// A struct that represents an item added to a <see cref="StaticSpriteBatch"/> using <c>Add</c> or any of its overloads.
+        /// An item returned after adding can be removed using <see cref="Remove"/>.
+        /// </summary>
+        public class Item {
+
+            internal readonly VertexPositionColorTexture TopLeft;
+            internal readonly VertexPositionColorTexture TopRight;
+            internal readonly VertexPositionColorTexture BottomLeft;
+            internal readonly VertexPositionColorTexture BottomRight;
+
+            internal Item(VertexPositionColorTexture topLeft, VertexPositionColorTexture topRight, VertexPositionColorTexture bottomLeft, VertexPositionColorTexture bottomRight) {
+                this.TopLeft = topLeft;
+                this.TopRight = topRight;
+                this.BottomLeft = bottomLeft;
+                this.BottomRight = bottomRight;
+            }
+
         }
 
     }