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/****************************************************************************
**
** Copyright (C) 2012 Digia Plc and/or its subsidiary(-ies).
** Contact: http://www.qt-project.org/legal
**
** This file is part of the Qt Graphical Effects module.
**
** $QT_BEGIN_LICENSE:BSD$
** 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 Digia Plc 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 "private"

Item {
    id: rootItem
    property real glowRadius: 0.0
    property real spread: 0.0
    property color color: "white"
    property real cornerRadius: glowRadius
    property bool cached: false

    ShaderEffectSource {
         id: cacheItem
         anchors.fill: shaderItem
         visible: rootItem.cached
         smooth: true
         sourceItem: shaderItem
         live: true
         hideSource: visible
     }

    ShaderEffect {
        id: shaderItem

        x: (parent.width - width) / 2.0
        y: (parent.height - height) / 2.0
        width: parent.width + rootItem.glowRadius * 2 + cornerRadius * 2
        height: parent.height + rootItem.glowRadius * 2 + cornerRadius * 2

        function clampedCornerRadius() {
            var maxCornerRadius = Math.min(rootItem.width, rootItem.height) / 2 + glowRadius;
            return Math.max(0, Math.min(rootItem.cornerRadius, maxCornerRadius))
        }

        property color color: rootItem.color
        property real inverseSpread: 1.0 - rootItem.spread
        property real relativeSizeX: ((inverseSpread * inverseSpread) * rootItem.glowRadius + cornerRadius * 2.0) / width
        property real relativeSizeY: relativeSizeX * (width / height)
        property real spread: rootItem.spread / 2.0
        property real cornerRadius: clampedCornerRadius()

        fragmentShader: "
            uniform highp float qt_Opacity;
            uniform mediump float relativeSizeX;
            uniform mediump float relativeSizeY;
            uniform mediump float spread;
            uniform lowp vec4 color;
            varying highp vec2 qt_TexCoord0;

            highp float linearstep(highp float e0, highp float e1, highp float x) {
                return clamp((x - e0) / (e1 - e0), 0.0, 1.0);
            }

            void main() {
                lowp float alpha =
                    smoothstep(0.0, relativeSizeX, 0.5 - abs(0.5 - qt_TexCoord0.x)) *
                    smoothstep(0.0, relativeSizeY, 0.5 - abs(0.5 - qt_TexCoord0.y));

                highp float spreadMultiplier = linearstep(spread, 1.0 - spread, alpha);
                gl_FragColor = color * qt_Opacity * spreadMultiplier * spreadMultiplier;
            }
        "
    }
}