made texture atlases have an underlying texture region as well

MLEM/Textures/TextureRegion.cs

@@ -72,7 +72,8 @@ namespace MLEM.Textures {
         /// Creates a new texture region that spans the entire texture
         /// </summary>
         /// <param name="texture">The texture to use</param>
-        public TextureRegion(Texture2D texture) : this(texture, new Rectangle(0, 0, texture.Width, texture.Height)) {
+        public TextureRegion(Texture2D texture) :
+            this(texture, new Rectangle(0, 0, texture.Width, texture.Height)) {
         }
 
         /// <summary>
@@ -83,7 +84,8 @@ namespace MLEM.Textures {
         /// <param name="v">The y coordinate of the top left corner of this area</param>
         /// <param name="width">The width of this area</param>
         /// <param name="height">The height of this area</param>
-        public TextureRegion(Texture2D texture, int u, int v, int width, int height) : this(texture, new Rectangle(u, v, width, height)) {
+        public TextureRegion(Texture2D texture, int u, int v, int width, int height) :
+            this(texture, new Rectangle(u, v, width, height)) {
         }
 
         /// <summary>
@@ -92,7 +94,39 @@ namespace MLEM.Textures {
         /// <param name="texture">The texture to use</param>
         /// <param name="uv">The top left corner of this area</param>
         /// <param name="size">The size of this area</param>
-        public TextureRegion(Texture2D texture, Point uv, Point size) : this(texture, new Rectangle(uv, size)) {
+        public TextureRegion(Texture2D texture, Point uv, Point size) :
+            this(texture, new Rectangle(uv, size)) {
+        }
+
+        /// <summary>
+        /// Creates a new texture region which is a sub-region of the given texture region
+        /// </summary>
+        /// <param name="region">The texture region to create a sub-region of</param>
+        /// <param name="area">The new texture region area</param>
+        public TextureRegion(TextureRegion region, Rectangle area) :
+            this(region, area.Location, area.Size) {
+        }
+
+        /// <summary>
+        /// Creates a new texture region which is a sub-region of the given texture region
+        /// </summary>
+        /// <param name="region">The texture region to create a sub-region of</param>
+        /// <param name="u">The x coordinate of the top left corner of this area</param>
+        /// <param name="v">The y coordinate of the top left corner of this area</param>
+        /// <param name="width">The width of this area</param>
+        /// <param name="height">The height of this area</param>
+        public TextureRegion(TextureRegion region, int u, int v, int width, int height) :
+            this(region, new Point(u, v), new Point(width, height)) {
+        }
+
+        /// <summary>
+        /// Creates a new texture region which is a sub-region of the given texture region
+        /// </summary>
+        /// <param name="region">The texture region to create a sub-region of</param>
+        /// <param name="uv">The top left corner of this area</param>
+        /// <param name="size">The size of this area</param>
+        public TextureRegion(TextureRegion region, Point uv, Point size) :
+            this(region.Texture, region.Position + uv, size) {
         }
 
     }

MLEM/Textures/UniformTextureAtlas.cs

@@ -12,9 +12,10 @@ namespace MLEM.Textures {
     public class UniformTextureAtlas : GenericDataHolder {
 
         /// <summary>
-        /// The texture to use for this atlas
+        /// The <see cref="TextureRegion"/> that this uniform texture atlas uses as its basis.
+        /// In most cases, <see cref="Region"/> has the full area of the underlying <see cref="Texture"/>.
         /// </summary>
-        public readonly Texture2D Texture;
+        public readonly TextureRegion Region;
         /// <summary>
         /// The amount of sub-regions this atlas has in the x direction
         /// </summary>
@@ -32,6 +33,11 @@ namespace MLEM.Textures {
         /// </summary>
         public readonly int RegionHeight;
         /// <summary>
+        /// The texture to use for this atlas.
+        /// Note that <see cref="Region"/> stores the actual area that we depend on.
+        /// </summary>
+        public Texture2D Texture => this.Region.Texture;
+        /// <summary>
         /// Returns the <see cref="TextureRegion"/> at this texture atlas's given index.
         /// The index is zero-based, where rows come first and columns come second.
         /// </summary>
@@ -55,24 +61,35 @@ namespace MLEM.Textures {
 
         private readonly Dictionary<Rectangle, TextureRegion> regions = new Dictionary<Rectangle, TextureRegion>();
 
+        /// <summary>
+        /// Creates a new uniform texture atlas with the given texture region and region amount.
+        /// This atlas will only ever pull information from the given <see cref="TextureRegion"/> and never exit the region's bounds.
+        /// </summary>
+        /// <param name="region">The texture region to use for this atlas</param>
+        /// <param name="regionAmountX">The amount of texture regions in the x direction</param>
+        /// <param name="regionAmountY">The amount of texture regions in the y direction</param>
+        public UniformTextureAtlas(TextureRegion region, int regionAmountX, int regionAmountY) {
+            this.Region = region;
+            this.RegionAmountX = regionAmountX;
+            this.RegionAmountY = regionAmountY;
+            this.RegionWidth = region.Width / regionAmountX;
+            this.RegionHeight = region.Height / regionAmountY;
+        }
+
         /// <summary>
         /// Creates a new uniform texture atlas with the given texture and region amount.
         /// </summary>
         /// <param name="texture">The texture to use for this atlas</param>
         /// <param name="regionAmountX">The amount of texture regions in the x direction</param>
         /// <param name="regionAmountY">The amount of texture regions in the y direction</param>
-        public UniformTextureAtlas(Texture2D texture, int regionAmountX, int regionAmountY) {
+        public UniformTextureAtlas(Texture2D texture, int regionAmountX, int regionAmountY) :
-            this.Texture = texture;
+            this(new TextureRegion(texture), regionAmountX, regionAmountY) {
-            this.RegionAmountX = regionAmountX;
-            this.RegionAmountY = regionAmountY;
-            this.RegionWidth = texture.Width / regionAmountX;
-            this.RegionHeight = texture.Height / regionAmountY;
         }
 
         private TextureRegion GetOrAddRegion(Rectangle rect) {
             if (this.regions.TryGetValue(rect, out var region))
                 return region;
-            region = new TextureRegion(this.Texture,
+            region = new TextureRegion(this.Region,
                 rect.X * this.RegionWidth, rect.Y * this.RegionHeight,
                 rect.Width * this.RegionWidth, rect.Height * this.RegionHeight);
             this.regions.Add(rect, region);