From 34a6856a6784c0f0959c64c173e0edf55fb15d7f Mon Sep 17 00:00:00 2001
From: Ivan Mahonin <bh@icystar.com>
Date: Feb 23 2020 13:14:56 +0000
Subject: improve synfig::Matrix


---

diff --git a/synfig-core/src/synfig/matrix.cpp b/synfig-core/src/synfig/matrix.cpp
index 5f6c5d0..a26751c 100644
--- a/synfig-core/src/synfig/matrix.cpp
+++ b/synfig-core/src/synfig/matrix.cpp
@@ -111,29 +111,28 @@ Matrix2::operator+=(const Matrix2 &rhs)
 	return *this;
 }
 
+Matrix2::value_type
+Matrix2::det() const
+	{ return m00*m11 - m01*m10; }
+
 bool
-Matrix2::is_invertible()const
-	{ return approximate_not_equal(m00*m11, m01*m10); }
+Matrix2::is_invertible() const
+	{ return approximate_not_zero(det()); }
 
 Matrix2&
 Matrix2::invert()
 {
-	value_type det(m00*m11 - m01*m10);
-	if (approximate_not_equal(det, 0.0))
-	{
-		value_type k = 1.0/det;
+	value_type d = det();
+	if (approximate_not_zero(d)) {
+		value_type k = 1/d;
 		std::swap(m00, m11);
 		std::swap(m01, m10);
 		m00 *= k; m01 *= -k;
 		m11 *= k; m10 *= -k;
-	}
-	else
-	if (m00*m00 + m01*m01 > m10*m10 + m11*m11)
-	{
+	} else
+	if (m00*m00 + m01*m01 > m10*m10 + m11*m11) {
 		m10 = m01; m01 = 0; m11 = 0;
-	}
-	else
-	{
+	} else {
 		m01 = m10; m00 = 0; m10 = 0;
 	}
 	return *this;
@@ -321,6 +320,21 @@ Matrix3::get_inverted()const
 		p*(m00*m11 - m01*m10) );
 }
 
+Matrix3&
+Matrix3::normalize_by_z()
+{
+	Real k = m02*m02 + m12*m12 + m22*m22;
+	if (k > real_precision<Real>()*real_precision<Real>()) {
+		k = 1/sqrt(k);
+		if (m22 < 0) k = -k;
+		for(int i = 0; i < 3; ++i)
+			for(int j = 0; j < 3; ++j)
+				m[i][j] *= k;
+	}
+	return *this;
+}
+
+
 String
 Matrix3::get_string(int spaces, String before, String after)const
 {
diff --git a/synfig-core/src/synfig/matrix.h b/synfig-core/src/synfig/matrix.h
index 66d5f77..e051cbf 100644
--- a/synfig-core/src/synfig/matrix.h
+++ b/synfig-core/src/synfig/matrix.h
@@ -98,6 +98,9 @@ public:
 	bool is_identity() const
 		{ return *this == Matrix2(); }
 
+	Matrix2& set_zero()
+		{ return *this = Matrix2(Vector(), Vector()); }
+
 	//!set_scale member function. Sets a scale matrix
 	//! @param sx Scale by X axis
 	//! @param sy Scale by Y axis
@@ -171,6 +174,8 @@ public:
 	Matrix2 operator+(const Matrix2 &rhs)const
 		{ return Matrix2(*this) += rhs; }
 
+	value_type det() const;
+
 	bool is_invertible()const;
 
 	Matrix2& invert();
@@ -274,6 +279,9 @@ public:
 	bool is_identity() const
 		{ return *this == Matrix3(); }
 
+	Matrix3& set_zero()
+		{ return *this = Matrix3(Vector3(), Vector3(), Vector3()); }
+		
 	//!set_scale member function. Sets a scale matrix
 	//! @param sx Scale by X axis
 	//! @param sy Scale by Y axis
@@ -373,7 +381,15 @@ public:
 
 	Matrix3& invert()
 		{ return *this = get_inverted(); }
-
+	
+	Matrix3 get_normalized_by_z() const
+		{ return Matrix3(*this).normalize_by_z(); }
+	
+	Matrix3& normalize_by_z();
+	
+	Matrix2 to_2d() const
+		{ return Matrix2(m00, m01, m10, m11); }
+	
 	//!Get the string of the Matrix
 	//!@return String type. A string representation of the matrix
 	//!components.
diff --git a/synfig-core/src/synfig/rect.h b/synfig-core/src/synfig/rect.h
index 1f6d372..eb30294 100644
--- a/synfig-core/src/synfig/rect.h
+++ b/synfig-core/src/synfig/rect.h
@@ -265,7 +265,7 @@ public:
 	value_type get_width()const { return maxx - minx; }
 	value_type get_height()const { return maxy - miny; }
 
-	bool is_inside(const Point& x)
+	bool is_inside(const Point& x) const
 	{
 		return approximate_less_or_equal(minx, x[0])
 			&& approximate_less_or_equal(x[0], maxx)
diff --git a/synfig-core/src/synfig/vector.h b/synfig-core/src/synfig/vector.h
index 70e2046..37acdaa 100644
--- a/synfig-core/src/synfig/vector.h
+++ b/synfig-core/src/synfig/vector.h
@@ -451,8 +451,10 @@ public:
 		{ return Vector3(_x/rhs._x, _y/rhs._y, _z/rhs._z); }
 	Vector3 one_divide_coords() const
 		{ return Vector3(1.0/_x, 1.0/_y, 1.0/_z); }
-	Vector3 divide_z() const
-		{ value_type tmp = 1.0/_z; return Vector3(_x*tmp, _y*tmp, 1.0); }
+	Vector3 divide_z() const {
+		if (approximate_zero(_z)) return Vector3();
+		value_type tmp = 1.0/_z; return Vector3(_x*tmp, _y*tmp, 1.0);
+	}
 	Vector to_2d() const
 		{ return Vector(_x, _y); }
 };