restore accidentally removed rectpack

use importc
#minor

source/stb/rectpack.d

@@ -0,0 +1,50 @@
+module stb.rectpack;
+import std, stb;
+
+struct TexturePacker
+{
+	this(stbrp_rect[] rects)
+	{
+		_rects = rects;
+		_nodes = new stbrp_node[TEX_MAX];
+	}
+
+	auto process()
+	{
+		auto w = binarySearch(0, TEX_MAX, a => canPack(a, a) ? -1 : 1);
+		auto h = binarySearch(0, w, a => canPack(w, a) ? -1 : 1);
+
+		// call once more because binarySearch can do some extra failing tries
+		canPack(w, h);
+
+		return tuple!(`w`, `h`)(w, h);
+
+	}
+
+private:
+	enum TEX_MAX = 16_384;
+
+	bool canPack(int w, int h)
+	{
+		stbrp_init_target(&_context, w, h, _nodes.ptr, cast(uint)_nodes.length);
+		return !!stbrp_pack_rects(&_context, _rects.ptr, cast(uint)_rects.length);
+	}
+
+	stbrp_rect[] _rects;
+	stbrp_node[] _nodes;
+	stbrp_context _context;
+}
+
+unittest
+{
+	stbrp_rect[3] arr;
+
+	arr[0] = stbrp_rect(0, 10, 20); // id, w, h
+	arr[1] = stbrp_rect(1, 20, 20);
+	arr[2] = stbrp_rect(2, 40, 20);
+
+	auto res = TexturePacker(arr).process;
+
+	assert(res.w == 40 && res.h == 40);
+	assert(arr[].all!(a => a.was_packed));
+}