/****************************************************************************
**
** Copyright (C) 2012 Digia Plc and/or its subsidiary(-ies).
** Contact: http://www.qt-project.org/legal
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** This file is part of the Qt Mobility Components.
**
** $QT_BEGIN_LICENSE:LGPL$
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** GNU Lesser General Public License Usage
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** General Public License version 2.1 as published by the Free Software
** Foundation and appearing in the file LICENSE.LGPL included in the
** packaging of this file.  Please review the following information to
** ensure the GNU Lesser General Public License version 2.1 requirements
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** rights.  These rights are described in the Digia Qt LGPL Exception
** version 1.1, included in the file LGPL_EXCEPTION.txt in this package.
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** GNU General Public License Usage
** Alternatively, this file may be used under the terms of the GNU
** General Public License version 3.0 as published by the Free Software
** Foundation and appearing in the file LICENSE.GPL included in the
** packaging of this file.  Please review the following information to
** ensure the GNU General Public License version 3.0 requirements will be
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****************************************************************************/

import QtQuick 2.0

Effect {
    id: root
    divider: false
    parameters: ListModel {
        ListElement {
            name: "radius"
            value: 0.5
        }
        ListElement {
            name: "diffraction"
            value: 0.5
        }
    }

    property real posX: -1
    property real posY: -1

    QtObject {
        id: d
        property real oldTargetWidth: root.targetWidth
        property real oldTargetHeight: root.targetHeight
    }

    // Transform slider values, and bind result to shader uniforms
    property real radius: parameters.get(0).value * 100
    property real diffractionIndex: parameters.get(1).value

    onTargetWidthChanged: {
        if (posX == -1)
            posX = targetWidth / 2
        else if (d.oldTargetWidth != 0)
            posX *= (targetWidth / d.oldTargetWidth)
        d.oldTargetWidth = targetWidth
    }

    onTargetHeightChanged: {
        if (posY == -1)
            posY = targetHeight / 2
        else if (d.oldTargetHeight != 0)
            posY *= (targetHeight / d.oldTargetHeight)
        d.oldTargetHeight = targetHeight
    }

    fragmentShaderSrc: "uniform sampler2D source;
                        uniform lowp float qt_Opacity;
                        varying vec2 qt_TexCoord0;
                        uniform float radius;
                        uniform float diffractionIndex;
                        uniform float targetWidth;
                        uniform float targetHeight;
                        uniform float posX;
                        uniform float posY;

                        void main()
                        {
                            vec2 tc = qt_TexCoord0;
                            vec2 center = vec2(posX, posY);
                            vec2 xy = gl_FragCoord.xy - center.xy;
                            float r = sqrt(xy.x * xy.x + xy.y * xy.y);
                            if (r < radius) {
                                float h = diffractionIndex * 0.5 * radius;
                                vec2 new_xy = r < radius ? xy * (radius - h) / sqrt(radius * radius - r * r) : xy;
                                vec2 targetSize = vec2(targetWidth, targetHeight);
                                tc = (new_xy + center) / targetSize;
                                tc.y = 1.0 - tc.y;
                            }
                            gl_FragColor = qt_Opacity * texture2D(source, tc);
                        }"

    MouseArea {
        anchors.fill: parent
        onPositionChanged: { root.posX = mouse.x; root.posY = root.targetHeight - mouse.y }
    }
}