textium: Specify atlas packer traits

textium/src/lib.rs

@@ -8,6 +8,7 @@ mod error;
 mod texture;
 mod geometry;
 mod rasterizer;
+mod packer;
 
 use std::iter::Iterator;
 use std::collections::HashMap;

textium/src/packer/mod.rs

@@ -0,0 +1,50 @@
+use ::texture::{Buffer2d, ResizeableBuffer2d};
+use ::geometry::Rect;
+
+pub trait Packer {
+    type Buffer: Buffer2d;
+
+    fn new(b: Self::Buffer) -> Self;
+    fn pack<O>(&mut self, buf: &O) -> Option<Rect<usize>>
+        where O: Buffer2d<Pixel=<Self::Buffer as Buffer2d>::Pixel>; // buffer with same pixel type as this atlas
+
+    fn set_margin(&mut self, margin: usize);
+    fn buf(&self) -> &Self::Buffer;
+    fn buf_mut(&mut self) -> &mut Self::Buffer;
+    fn into_buf(self) -> Self::Buffer; // TODO: consider actually implementing Into?
+
+    fn dimensions(&self) -> (usize, usize);
+    fn set_dimensions(&mut self, w: usize, h: usize);
+}
+
+pub trait GrowingPacker: Packer {
+    fn pack_resize<F, O>(&mut self, buf: &O, resize_fn: F) -> Rect<usize>
+        where O: Buffer2d<Pixel=<<Self as Packer>::Buffer as Buffer2d>::Pixel>,
+              F: Fn((usize, usize)) -> (usize, usize);
+}
+
+impl <A, P> GrowingPacker for P
+    where A: ResizeableBuffer2d, P: Packer<Buffer = A>
+{
+    fn pack_resize<F, O>(&mut self, buf: &O, resize_fn: F) -> Rect<usize>
+        where O: Buffer2d<Pixel=<<Self as Packer>::Buffer as Buffer2d>::Pixel>,
+              F: Fn((usize, usize)) -> (usize, usize)
+        {
+            match self.pack(buf) {
+                Some(p) => p,
+                None => {
+                    let (w, h) = self.dimensions();
+                    let (w_, h_) = resize_fn((w, h));
+                    if w_ <= w || h_ <= h {
+                        panic!("Resize functions must make the buffer larger!");
+                    }
+
+                    self.buf_mut().resize(w_, h_);
+                    self.set_dimensions(w_, h_);
+
+                    // recurse, trying this new size
+                    self.pack_resize(buf, resize_fn)
+                }
+            }
+        }
+}