Line data    Source code

       1             : /* -*- Mode: C++; tab-width: 4; indent-tabs-mode: nil; c-basic-offset: 4 -*- */
       2             : /*
       3             :  * Version: MPL 1.1 / GPLv3+ / LGPLv3+
       4             :  *
       5             :  * The contents of this file are subject to the Mozilla Public License Version
       6             :  * 1.1 (the "License"); you may not use this file except in compliance with
       7             :  * the License or as specified alternatively below. You may obtain a copy of
       8             :  * the License at http://www.mozilla.org/MPL/
       9             :  *
      10             :  * Software distributed under the License is distributed on an "AS IS" basis,
      11             :  * WITHOUT WARRANTY OF ANY KIND, either express or implied. See the License
      12             :  * for the specific language governing rights and limitations under the
      13             :  * License.
      14             :  *
      15             :  * Major Contributor(s):
      16             :  * Copyright (C) 2012 Tim Hardeck <thardeck@suse.com>
      17             :  *
      18             :  * All Rights Reserved.
      19             :  *
      20             :  * For minor contributions see the git repository.
      21             :  *
      22             :  * Alternatively, the contents of this file may be used under the terms of
      23             :  * either the GNU General Public License Version 3 or later (the "GPLv3+"), or
      24             :  * the GNU Lesser General Public License Version 3 or later (the "LGPLv3+"),
      25             :  * in which case the provisions of the GPLv3+ or the LGPLv3+ are applicable
      26             :  * instead of those above.
      27             :  */
      28             : 
      29             : #include <basegfx/tools/zoomtools.hxx>
      30             : 
      31             : namespace basegfx
      32             : {
      33             : namespace zoomtools
      34             : {
      35             : 
      36             : /** 2^(1/6) as the default step
      37             : 
      38             :     This ensures (unless the rounding is used) that 6 steps lead
      39             :     to double / half zoom level.
      40             : */
      41             : const double ZOOM_FACTOR = 1.12246205;
      42             : 
      43             : /**
      44             : * Round a value against a specified multiple. Values below half
      45             : * of the multiple are rounded down and all others are rounded up.
      46             : *
      47             : * @param nCurrent current value
      48             : * @param nMultiple multiple against which the current value is rounded
      49             : */
      50           0 : static long roundMultiple(long nCurrent, int nMultiple)
      51             : {
      52             :     // round zoom to a multiple of nMultiple
      53           0 :     return (( nCurrent + nMultiple / 2 ) - ( nCurrent + nMultiple / 2 ) % nMultiple);
      54             : }
      55             : 
      56             : /**
      57             : * Convert geometric progression results into more common values by
      58             : * rounding them against certain multiples depending on the size.
      59             : * Beginning with 50 the multiple is 5, with 100, 10, and so on.
      60             : *
      61             : * @param nCurrent current zoom factor
      62             : */
      63           0 : static long roundZoom(double nCurrent)
      64             : {
      65             :     // convert nCurrent properly to int
      66           0 :     long nNew = nCurrent + 0.5;
      67             : 
      68             :     // round to more common numbers above 50
      69           0 :     if (nNew > 1000) {
      70           0 :         nNew = roundMultiple(nNew, 100);
      71           0 :     } else if ( nNew > 500 ) {
      72           0 :         nNew = roundMultiple(nNew, 50);
      73           0 :     } else if ( nNew > 100 ) {
      74           0 :         nNew = roundMultiple(nNew, 10);
      75           0 :     } else if ( nNew > 50 ) {
      76           0 :         nNew = roundMultiple(nNew, 5);
      77             :     }
      78             : 
      79           0 :     return nNew;
      80             : }
      81             : 
      82             : /**
      83             : * Make sure that a certain step isn't skipped during the zooming
      84             : * progress.
      85             : *
      86             : * @param nCurrent current zoom factor
      87             : * @param nPrevious previous zoom factor
      88             : * @param nStep step which shouldn't be skipped
      89             : */
      90           0 : static long enforceStep(long nCurrent, long nPrevious, int nStep)
      91             : {
      92           0 :     if ((( nCurrent > nStep ) && ( nPrevious < nStep ))
      93             :     || (( nCurrent < nStep ) && ( nPrevious > nStep )))
      94           0 :         return nStep;
      95             :     else
      96           0 :         return nCurrent;
      97             : }
      98             : 
      99             : /**
     100             : * Increasing the zoom level.
     101             : *
     102             : * @param nCurrent current zoom factor
     103             : */
     104           0 : long zoomIn(long nCurrent)
     105             : {
     106           0 :     long nNew = roundZoom( nCurrent * ZOOM_FACTOR );
     107             :     // make sure some values are not skipped
     108           0 :     nNew = enforceStep(nNew, nCurrent, 200);
     109           0 :     nNew = enforceStep(nNew, nCurrent, 100);
     110           0 :     nNew = enforceStep(nNew, nCurrent, 75);
     111           0 :     nNew = enforceStep(nNew, nCurrent, 50);
     112           0 :     nNew = enforceStep(nNew, nCurrent, 25);
     113           0 :     return nNew;
     114             : }
     115             : 
     116             : /**
     117             : * Decreasing the zoom level.
     118             : *
     119             : * @param nCurrent current zoom factor
     120             : */
     121           0 : long zoomOut(long nCurrent)
     122             : {
     123           0 :     long nNew = roundZoom( nCurrent / ZOOM_FACTOR );
     124             :     // make sure some values are not skipped
     125           0 :     nNew = enforceStep(nNew, nCurrent, 200);
     126           0 :     nNew = enforceStep(nNew, nCurrent, 100);
     127           0 :     nNew = enforceStep(nNew, nCurrent, 75);
     128           0 :     nNew = enforceStep(nNew, nCurrent, 50);
     129           0 :     nNew = enforceStep(nNew, nCurrent, 25);
     130           0 :     return nNew;
     131             : }
     132             : } // namespace zoomtools
     133             : } // namespace basegfx
     134             : 
     135             : /* vim:set shiftwidth=4 softtabstop=4 expandtab: */