1 files changed, 136 insertions, 0 deletions
diff --git a/src/2geom/parallelogram.cpp b/src/2geom/parallelogram.cpp
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+++ b/src/2geom/parallelogram.cpp
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+/*
+ * Authors:
+ *   Thomas Holder
+ *   Sergei Izmailov
+ *
+ * Copyright 2020 Authors
+ *
+ * SPDX-License-Identifier: LGPL-2.1 or MPL-1.1
+ */
+
+#include <2geom/basic-intersection.h>
+#include <2geom/parallelogram.h>
+
+#include <cassert>
+
+namespace Geom {
+
+namespace {
+/// Return true if `p` is inside a unit rectangle
+inline bool unit_rect_contains(Point const &p)
+{
+    return 0 <= p.x() && p.x() <= 1 && //
+           0 <= p.y() && p.y() <= 1;
+}
+
+/// N'th corner of a unit rectangle
+inline Point unit_rect_corner(unsigned i)
+{
+    assert(i < 4);
+    unsigned const y = i >> 1;
+    unsigned const x = (i & 1) ^ y;
+    return Point(x, y);
+}
+} // namespace
+
+Point Parallelogram::corner(unsigned i) const
+{
+    assert(i < 4);
+    return unit_rect_corner(i) * m_affine;
+}
+
+Rect Parallelogram::bounds() const
+{
+    Rect rect(corner(0), corner(2));
+    rect.expandTo(corner(1));
+    rect.expandTo(corner(3));
+    return rect;
+}
+
+bool Parallelogram::intersects(Parallelogram const &other) const
+{
+    if (m_affine.isSingular() || other.m_affine.isSingular()) {
+        return false;
+    }
+
+    auto const affine1 = other.m_affine * m_affine.inverse();
+    auto const affine2 = affine1.inverse();
+
+    // case 1: any corner inside the other rectangle
+    for (unsigned i = 0; i != 4; ++i) {
+        auto const p = unit_rect_corner(i);
+        if (unit_rect_contains(p * affine1) || //
+            unit_rect_contains(p * affine2)) {
+            return true;
+        }
+    }
+
+    // case 2: any sides intersect (check diagonals)
+    for (unsigned i = 0; i != 2; ++i) {
+        auto const A = corner(i);
+        auto const B = corner((i + 2) % 4);
+        for (unsigned j = 0; j != 2; ++j) {
+            auto const C = other.corner(j);
+            auto const D = other.corner((j + 2) % 4);
+            if (non_collinear_segments_intersect(A, B, C, D)) {
+                return true;
+            }
+        }
+    }
+
+    return false;
+}
+
+bool Parallelogram::contains(Point const &p) const
+{
+    return !m_affine.isSingular() && //
+           unit_rect_contains(p * m_affine.inverse());
+}
+
+bool Parallelogram::contains(Parallelogram const &other) const
+{
+    if (m_affine.isSingular()) {
+        return false;
+    }
+
+    auto const inv = m_affine.inverse();
+
+    for (unsigned i = 0; i != 4; ++i) {
+        if (!unit_rect_contains(other.corner(i) * inv)) {
+            return false;
+        }
+    }
+
+    return true;
+}
+
+Coord Parallelogram::minExtent() const
+{
+    return std::min(m_affine.expansionX(), //
+                    m_affine.expansionY());
+}
+
+Coord Parallelogram::maxExtent() const
+{
+    return std::max(m_affine.expansionX(), //
+                    m_affine.expansionY());
+}
+
+bool Parallelogram::isSheared(Coord eps) const
+{
+    return !are_near(dot(m_affine.xAxis(), m_affine.yAxis()), //
+                     0.0, eps);
+}
+
+} // namespace Geom
+
+/*
+  Local Variables:
+  mode:c++
+  c-file-style:"stroustrup"
+  c-file-offsets:((innamespace . 0)(inline-open . 0)(case-label . +))
+  indent-tabs-mode:nil
+  fill-column:99
+  End:
+*/
+// vim: filetype=cpp:expandtab:shiftwidth=4:tabstop=8:softtabstop=4:fileencoding=utf-8:textwidth=99 :