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+/* -*- Mode: C++; tab-width: 4; indent-tabs-mode: nil; c-basic-offset: 4 -*- */
+/*
+ * This file is part of the LibreOffice project.
+ *
+ * This Source Code Form is subject to the terms of the Mozilla Public
+ * License, v. 2.0. If a copy of the MPL was not distributed with this
+ * file, You can obtain one at http://mozilla.org/MPL/2.0/.
+ *
+ * This file incorporates work covered by the following license notice:
+ *
+ * Licensed to the Apache Software Foundation (ASF) under one or more
+ * contributor license agreements. See the NOTICE file distributed
+ * with this work for additional information regarding copyright
+ * ownership. The ASF licenses this file to you under the Apache
+ * License, Version 2.0 (the "License"); you may not use this file
+ * except in compliance with the License. You may obtain a copy of
+ * the License at http://www.apache.org/licenses/LICENSE-2.0 .
+ */
+
+#include <basegfx/utils/tools.hxx>
+#include <basegfx/range/b2drange.hxx>
+
+#include <algorithm>
+
+namespace basegfx::utils
+{
+ namespace
+ {
+ double distance( const double& nX,
+ const double& nY,
+ const ::basegfx::B2DVector& rNormal,
+ const double& nC )
+ {
+ return nX*rNormal.getX() + nY*rNormal.getY() - nC;
+ }
+
+ void moveLineOutsideRect( ::basegfx::B2DPoint& io_rStart,
+ ::basegfx::B2DPoint& io_rEnd,
+ const ::basegfx::B2DVector& rMoveDirection,
+ const ::basegfx::B2DRange& rFitTarget )
+ {
+ // calc c for normal line form equation n x - c = 0
+ const double nC( rMoveDirection.scalar( io_rStart ) );
+
+ // calc maximum orthogonal distance for all four bound
+ // rect corners to the line
+ const double nMaxDistance( std::max(
+ 0.0,
+ std::max(
+ distance(rFitTarget.getMinX(),
+ rFitTarget.getMinY(),
+ rMoveDirection,
+ nC),
+ std::max(
+ distance(rFitTarget.getMinX(),
+ rFitTarget.getMaxY(),
+ rMoveDirection,
+ nC),
+ std::max(
+ distance(rFitTarget.getMaxX(),
+ rFitTarget.getMinY(),
+ rMoveDirection,
+ nC),
+ distance(rFitTarget.getMaxX(),
+ rFitTarget.getMaxY(),
+ rMoveDirection,
+ nC) ) ) ) ) );
+
+ // now move line points, such that the bound rect
+ // points are all either 'on' or on the negative side
+ // of the half-plane
+ io_rStart += nMaxDistance*rMoveDirection;
+ io_rEnd += nMaxDistance*rMoveDirection;
+ }
+ }
+
+ void infiniteLineFromParallelogram( ::basegfx::B2DPoint& io_rLeftTop,
+ ::basegfx::B2DPoint& io_rLeftBottom,
+ ::basegfx::B2DPoint& io_rRightTop,
+ ::basegfx::B2DPoint& io_rRightBottom,
+ const ::basegfx::B2DRange& rFitTarget )
+ {
+ // For the top and bottom border line of the
+ // parallelogram, we determine the distance to all four
+ // corner points of the bound rect (tl, tr, bl, br). When
+ // using the unit normal form for lines (n x - c = 0), and
+ // choosing n to point 'outwards' the parallelogram, then
+ // all bound rect corner points having positive distance
+ // to the line lie outside the extended gradient rect, and
+ // thus, the corresponding border line must be moved the
+ // maximum distance outwards.
+
+ // don't use the top and bottom border line direction, and
+ // calculate the normal from them. Instead, use the
+ // vertical lines (lt - lb or rt - rb), as they more
+ // faithfully represent the direction of the
+ // to-be-generated infinite line
+ ::basegfx::B2DVector aDirectionVertical( io_rLeftTop - io_rLeftBottom );
+ aDirectionVertical.normalize();
+
+ const ::basegfx::B2DVector aNormalTop( aDirectionVertical );
+ const ::basegfx::B2DVector aNormalBottom( -aDirectionVertical );
+
+ // now extend parallelogram, such that the bound rect
+ // point are included
+ moveLineOutsideRect( io_rLeftTop, io_rRightTop, aNormalTop, rFitTarget );
+ moveLineOutsideRect( io_rLeftBottom, io_rRightBottom, aNormalBottom, rFitTarget );
+ }
+}
+
+/* vim:set shiftwidth=4 softtabstop=4 expandtab: */