From 2e9f404df3ad8d1db41ce66a5470962a921fa056 Mon Sep 17 00:00:00 2001
From: Enrico Turri <enricoturri@seznam.cz>
Date: Wed, 14 Nov 2018 13:29:57 +0100
Subject: [PATCH] Snap in gizmo move 3D when holding Shift pressed

---
 src/slic3r/GUI/GLGizmo.cpp | 5 +++++
 src/slic3r/GUI/GLGizmo.hpp | 6 ++++++
 2 files changed, 11 insertions(+)

diff --git a/src/slic3r/GUI/GLGizmo.cpp b/src/slic3r/GUI/GLGizmo.cpp
index 34627ca68a..6c96d821ae 100644
--- a/src/slic3r/GUI/GLGizmo.cpp
+++ b/src/slic3r/GUI/GLGizmo.cpp
@@ -1004,6 +1004,7 @@ const double GLGizmoMove3D::Offset = 10.0;
 GLGizmoMove3D::GLGizmoMove3D(GLCanvas3D& parent)
     : GLGizmoBase(parent)
     , m_displacement(Vec3d::Zero())
+    , m_snap_step(1.0)
     , m_starting_drag_position(Vec3d::Zero())
     , m_starting_box_center(Vec3d::Zero())
     , m_starting_box_bottom_center(Vec3d::Zero())
@@ -1160,6 +1161,10 @@ double GLGizmoMove3D::calc_projection(const UpdateData& data) const
         // finds projection of the vector along the staring direction
         projection = inters_vec.dot(starting_vec.normalized());
     }
+
+    if (data.shift_down)
+        projection = m_snap_step * (double)std::round(projection / m_snap_step);
+
     return projection;
 }
 
diff --git a/src/slic3r/GUI/GLGizmo.hpp b/src/slic3r/GUI/GLGizmo.hpp
index d64577f2c8..7156c0b02a 100644
--- a/src/slic3r/GUI/GLGizmo.hpp
+++ b/src/slic3r/GUI/GLGizmo.hpp
@@ -319,6 +319,9 @@ class GLGizmoMove3D : public GLGizmoBase
     static const double Offset;
 
     Vec3d m_displacement;
+
+    double m_snap_step;
+
     Vec3d m_starting_drag_position;
     Vec3d m_starting_box_center;
     Vec3d m_starting_box_bottom_center;
@@ -326,6 +329,9 @@ class GLGizmoMove3D : public GLGizmoBase
 public:
     explicit GLGizmoMove3D(GLCanvas3D& parent);
 
+    double get_snap_step(double step) const { return m_snap_step; }
+    void set_snap_step(double step) { m_snap_step = step; }
+
     const Vec3d& get_displacement() const { return m_displacement; }
 
 protected: