From 792856a50501d13e41877512eeb8c39b762595f8 Mon Sep 17 00:00:00 2001
From: bubnikv <bubnikv@gmail.com>
Date: Tue, 29 Nov 2016 19:25:10 +0100
Subject: [PATCH] Bounding Box - new method align_to_grid

---
 xs/src/libslic3r/BoundingBox.cpp | 22 ++++++++++++++++++++++
 xs/src/libslic3r/BoundingBox.hpp |  3 +++
 2 files changed, 25 insertions(+)

diff --git a/xs/src/libslic3r/BoundingBox.cpp b/xs/src/libslic3r/BoundingBox.cpp
index bffe1dbfb..75ece90bf 100644
--- a/xs/src/libslic3r/BoundingBox.cpp
+++ b/xs/src/libslic3r/BoundingBox.cpp
@@ -277,4 +277,26 @@ BoundingBoxBase<PointClass>::overlap(const BoundingBoxBase<PointClass> &other) c
 template bool BoundingBoxBase<Point>::overlap(const BoundingBoxBase<Point> &point) const;
 template bool BoundingBoxBase<Pointf>::overlap(const BoundingBoxBase<Pointf> &point) const;
 
+
+// Align a coordinate to a grid. The coordinate may be negative,
+// the aligned value will never be bigger than the original one.
+static inline coord_t _align_to_grid(const coord_t coord, const coord_t spacing) {
+    // Current C++ standard defines the result of integer division to be rounded to zero,
+    // for both positive and negative numbers. Here we want to round down for negative
+    // numbers as well.
+    coord_t aligned = (coord < 0) ?
+            ((coord - spacing + 1) / spacing) * spacing :
+            (coord / spacing) * spacing;
+    assert(aligned <= coord);
+    return aligned;
+}
+
+void BoundingBox::align_to_grid(const coord_t cell_size)
+{
+    if (this->defined) {
+        min.x = _align_to_grid(min.x, cell_size);
+        min.y = _align_to_grid(min.y, cell_size);
+    }
+}
+
 }
diff --git a/xs/src/libslic3r/BoundingBox.hpp b/xs/src/libslic3r/BoundingBox.hpp
index 5f676151c..232dada80 100644
--- a/xs/src/libslic3r/BoundingBox.hpp
+++ b/xs/src/libslic3r/BoundingBox.hpp
@@ -65,6 +65,9 @@ class BoundingBox : public BoundingBoxBase<Point>
     BoundingBox rotated(double angle, const Point &center) const;
     void rotate(double angle) { (*this) = this->rotated(angle); }
     void rotate(double angle, const Point &center) { (*this) = this->rotated(angle, center); }
+    // Align the min corner to a grid of cell_size x cell_size cells,
+    // to encompass the original bounding box.
+    void align_to_grid(const coord_t cell_size);
     
     BoundingBox() : BoundingBoxBase<Point>() {};
     BoundingBox(const Point &pmin, const Point &pmax) : BoundingBoxBase<Point>(pmin, pmax) {};