113 lines
3.1 KiB
C++
113 lines
3.1 KiB
C++
/* -*- Mode: C++; tab-width: 4; indent-tabs-mode: nil; c-basic-offset: 4 -*- */
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/*
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* This file is part of the LibreOffice project.
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*
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* This Source Code Form is subject to the terms of the Mozilla Public
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* License, v. 2.0. If a copy of the MPL was not distributed with this
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* file, You can obtain one at http://mozilla.org/MPL/2.0/.
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*/
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#include <basegfx/utils/zoomtools.hxx>
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namespace basegfx::zoomtools
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{
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/** 2^(1/6) as the default step
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This ensures (unless the rounding is used) that 6 steps lead
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to double / half zoom level.
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*/
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const double ZOOM_FACTOR = 1.12246205;
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/**
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* Round a value against a specified multiple. Values below half
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* of the multiple are rounded down and all others are rounded up.
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*
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* @param nCurrent current value
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* @param nMultiple multiple against which the current value is rounded
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*/
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static sal_uInt16 roundMultiple(sal_uInt16 nCurrent, int nMultiple)
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{
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// round zoom to a multiple of nMultiple
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return (( nCurrent + nMultiple / 2 ) - ( nCurrent + nMultiple / 2 ) % nMultiple);
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}
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/**
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* Convert geometric progression results into more common values by
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* rounding them against certain multiples depending on the size.
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* Beginning with 50 the multiple is 5, with 100, 10, and so on.
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*
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* @param nCurrent current zoom factor
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*/
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static sal_uInt16 roundZoom(double nCurrent)
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{
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// convert nCurrent properly to int
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sal_uInt16 nNew = nCurrent + 0.5;
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// round to more common numbers above 50
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if (nNew > 1000) {
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nNew = roundMultiple(nNew, 100);
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} else if ( nNew > 500 ) {
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nNew = roundMultiple(nNew, 50);
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} else if ( nNew > 100 ) {
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nNew = roundMultiple(nNew, 10);
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} else if ( nNew > 50 ) {
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nNew = roundMultiple(nNew, 5);
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}
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return nNew;
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}
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/**
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* Make sure that a certain step isn't skipped during the zooming
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* progress.
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*
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* @param nCurrent current zoom factor
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* @param nPrevious previous zoom factor
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* @param nStep step which shouldn't be skipped
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*/
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static sal_uInt16 enforceStep(sal_uInt16 nCurrent, sal_uInt16 nPrevious, unsigned int nStep)
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{
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if ((( nCurrent > nStep ) && ( nPrevious < nStep ))
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|| (( nCurrent < nStep ) && ( nPrevious > nStep )))
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return nStep;
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else
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return nCurrent;
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}
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/**
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* Increasing the zoom level.
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*
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* @param nCurrent current zoom factor
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*/
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sal_uInt16 zoomIn(sal_uInt16 nCurrent)
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{
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sal_uInt16 nNew = roundZoom( nCurrent * ZOOM_FACTOR );
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// make sure some values are not skipped
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nNew = enforceStep(nNew, nCurrent, 200);
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nNew = enforceStep(nNew, nCurrent, 100);
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nNew = enforceStep(nNew, nCurrent, 75);
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nNew = enforceStep(nNew, nCurrent, 50);
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nNew = enforceStep(nNew, nCurrent, 25);
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return nNew;
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}
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/**
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* Decreasing the zoom level.
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*
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* @param nCurrent current zoom factor
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*/
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sal_uInt16 zoomOut(sal_uInt16 nCurrent)
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{
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sal_uInt16 nNew = roundZoom( nCurrent / ZOOM_FACTOR );
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// make sure some values are not skipped
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nNew = enforceStep(nNew, nCurrent, 200);
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nNew = enforceStep(nNew, nCurrent, 100);
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nNew = enforceStep(nNew, nCurrent, 75);
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nNew = enforceStep(nNew, nCurrent, 50);
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nNew = enforceStep(nNew, nCurrent, 25);
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return nNew;
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}
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} // namespace
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/* vim:set shiftwidth=4 softtabstop=4 expandtab: */
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