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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/.
*/
#include <basegfx/utils/zoomtools.hxx>
namespace basegfx::zoomtools
{
/** 2^(1/6) as the default step
This ensures (unless the rounding is used) that 6 steps lead
to double / half zoom level.
*/
const double ZOOM_FACTOR = 1.12246205;
/**
* Round a value against a specified multiple. Values below half
* of the multiple are rounded down and all others are rounded up.
*
* @param nCurrent current value
* @param nMultiple multiple against which the current value is rounded
*/
static long roundMultiple(long nCurrent, int nMultiple)
{
// round zoom to a multiple of nMultiple
return (( nCurrent + nMultiple / 2 ) - ( nCurrent + nMultiple / 2 ) % nMultiple);
}
/**
* Convert geometric progression results into more common values by
* rounding them against certain multiples depending on the size.
* Beginning with 50 the multiple is 5, with 100, 10, and so on.
*
* @param nCurrent current zoom factor
*/
static long roundZoom(double nCurrent)
{
// convert nCurrent properly to int
long nNew = nCurrent + 0.5;
// round to more common numbers above 50
if (nNew > 1000) {
nNew = roundMultiple(nNew, 100);
} else if ( nNew > 500 ) {
nNew = roundMultiple(nNew, 50);
} else if ( nNew > 100 ) {
nNew = roundMultiple(nNew, 10);
} else if ( nNew > 50 ) {
nNew = roundMultiple(nNew, 5);
}
return nNew;
}
/**
* Make sure that a certain step isn't skipped during the zooming
* progress.
*
* @param nCurrent current zoom factor
* @param nPrevious previous zoom factor
* @param nStep step which shouldn't be skipped
*/
static long enforceStep(long nCurrent, long nPrevious, int nStep)
{
if ((( nCurrent > nStep ) && ( nPrevious < nStep ))
|| (( nCurrent < nStep ) && ( nPrevious > nStep )))
return nStep;
else
return nCurrent;
}
/**
* Increasing the zoom level.
*
* @param nCurrent current zoom factor
*/
long zoomIn(long nCurrent)
{
long nNew = roundZoom( nCurrent * ZOOM_FACTOR );
// make sure some values are not skipped
nNew = enforceStep(nNew, nCurrent, 200);
nNew = enforceStep(nNew, nCurrent, 100);
nNew = enforceStep(nNew, nCurrent, 75);
nNew = enforceStep(nNew, nCurrent, 50);
nNew = enforceStep(nNew, nCurrent, 25);
return nNew;
}
/**
* Decreasing the zoom level.
*
* @param nCurrent current zoom factor
*/
long zoomOut(long nCurrent)
{
long nNew = roundZoom( nCurrent / ZOOM_FACTOR );
// make sure some values are not skipped
nNew = enforceStep(nNew, nCurrent, 200);
nNew = enforceStep(nNew, nCurrent, 100);
nNew = enforceStep(nNew, nCurrent, 75);
nNew = enforceStep(nNew, nCurrent, 50);
nNew = enforceStep(nNew, nCurrent, 25);
return nNew;
}
} // namespace
/* vim:set shiftwidth=4 softtabstop=4 expandtab: */
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