ZoomControl.qml Example File

 /****************************************************************************
 **
 ** Copyright (C) 2012 Nokia Corporation and/or its subsidiary(-ies).
 ** Contact: http://www.qt-project.org/
 **
 ** This file is part of the examples of the Qt Toolkit.
 **
 ** $QT_BEGIN_LICENSE:BSD$
 ** You may use this file under the terms of the BSD license as follows:
 **
 ** "Redistribution and use in source and binary forms, with or without
 ** modification, are permitted provided that the following conditions are
 ** met:
 **   * Redistributions of source code must retain the above copyright
 **     notice, this list of conditions and the following disclaimer.
 **   * Redistributions in binary form must reproduce the above copyright
 **     notice, this list of conditions and the following disclaimer in
 **     the documentation and/or other materials provided with the
 **     distribution.
 **   * Neither the name of Nokia Corporation and its Subsidiary(-ies) nor
 **     the names of its contributors may be used to endorse or promote
 **     products derived from this software without specific prior written
 **     permission.
 **
 ** THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS
 ** "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT
 ** LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR
 ** A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT
 ** OWNER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL,
 ** SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT
 ** LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE,
 ** DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY
 ** THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
 ** (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE
 ** OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE."
 **
 ** $QT_END_LICENSE$
 **
 ****************************************************************************/

 import QtQuick 2.0
 import QtMultimedia 5.0

 Item {
     id : zoomControl
     property real currentZoom : 1
     property real maximumZoom : 1
     signal zoomTo(real value)

     MouseArea {
         id : mouseArea
         anchors.fill: parent

         property real initialZoom : 0
         property real initialPos : 0

         onPressed: {
             initialPos = mouseY
             initialZoom = zoomControl.currentZoom
         }

         onMousePositionChanged: {
             if (pressed) {
                 var target = initialZoom * Math.pow(2, (initialPos-mouseY)/zoomControl.height);
                 target = Math.max(1, Math.min(target, zoomControl.maximumZoom))
                 zoomControl.zoomTo(target)
             }
         }
     }

     Item {
         id : bar
         x : 16
         y : parent.height/4
         width : 24
         height : parent.height/2
         opacity : 0

         Rectangle {
             anchors.fill: parent

             smooth: true
             radius: 8
             border.color: "black"
             border.width: 2
             color: "white"
             opacity: 0.3
         }

         Rectangle {
             x : 0
             y : parent.height * (1.0 - (zoomControl.currentZoom-1.0) / (zoomControl.maximumZoom-1.0))
             width: parent.width
             height: parent.height - y
             smooth: true
             radius: 8
             color: "black"
             opacity: 0.5
         }

         states: State {
             name: "ShowBar"
             when: mouseArea.pressed || zoomControl.currentZoom > 1.0
             PropertyChanges { target: bar; opacity: 1 }
         }

         transitions: [
             Transition {
                 to : "ShowBar"
                 NumberAnimation { properties: "opacity"; duration: 100 }
             },
             Transition {
                 from : "ShowBar"
                 NumberAnimation { properties: "opacity"; duration: 500 }
             }
         ]
     }
 }