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// Copyright (C) 2020 The Qt Company Ltd.
// Copyright (C) 2017 Jolla Ltd, author: <gunnar.sletta@jollamobile.com>
// SPDX-License-Identifier: LicenseRef-Qt-Commercial OR LGPL-3.0-only OR GPL-2.0-only OR GPL-3.0-only
// Qt-Security score:significant reason:default
import QtQuick
import Qt5Compat.GraphicalEffects.private
/*!
\qmltype DropShadow
\inqmlmodule Qt5Compat.GraphicalEffects
\since QtGraphicalEffects 1.0
\inherits QtQuick::Item
\ingroup qtgraphicaleffects-drop-shadow
\brief Generates a soft shadow behind the source item.
\note The MultiEffect component provides a drop shadow effect with some performance
advantages. For new code, it should be considered as an alternative to using Qt Graphical
Effects.
The DropShadow effect blurs the alpha channel of the input, colorizes the
result and places it behind the source object to create a soft shadow. The
shadow's color can be changed using the \l {DropShadow::color}{color}
property. The location of the shadow can be changed with the \l
horizontalOffset and \l verticalOffset properties.
\table
\header
\li Source
\li Effect applied
\row
\li \image Original_butterfly.png {Colorful butterfly graphic}
\li \image DropShadow_butterfly.png {Butterfly with drop shadow behind it}
\endtable
The soft shadow is created by blurring the image live using a gaussian
blur. Performing blur live is a costly operation. Fullscreen gaussian blur
with even a moderate number of samples will only run at 60 fps on highend
graphics hardware.
When the source is static, the \l cached property can be set to allocate
another buffer to avoid performing the blur every time it is drawn.
\note This effect is available when running with OpenGL.
\section1 Example
The following example shows how to apply the effect.
\snippet DropShadow-example.qml example
*/
Item {
id: root
DropShadowBase {
id: dbs
anchors.fill: parent
}
/*!
This property defines the source item that is going to be used as the
source for the generated shadow.
\note It is not supported to let the effect include itself, for
instance by setting source to the effect's parent.
*/
property alias source: dbs.source
/*!
\qmlproperty int DropShadow::radius
Radius defines the softness of the shadow. A larger radius causes the
edges of the shadow to appear more blurry.
The ideal blur is achieved by selecting \c samples and \c radius such
that \c {samples = 1 + radius * 2}, such as:
\table
\header \li Radius \li Samples
\row \li 0 \e{(no blur)} \li 1
\row \li 1 \li 3
\row \li 2 \li 5
\row \li 3 \li 7
\endtable
By default, the property is set to \c {floor(samples/2)}.
\table
\header
\li Output examples with different radius values
\li
\li
\row
\li \image DropShadow_radius1.png {Sharp shadow with radius 0}
\li \image DropShadow_radius2.png {Soft shadow with radius 6}
\li \image DropShadow_radius3.png {Very soft shadow with radius 12}
\row
\li \b { radius: 0 }
\li \b { radius: 6 }
\li \b { radius: 12 }
\row
\li \l samples: 25
\li \l samples: 25
\li \l samples: 25
\row
\li \l color: #000000
\li \l color: #000000
\li \l color: #000000
\row
\li \l horizontalOffset: 0
\li \l horizontalOffset: 0
\li \l horizontalOffset: 0
\row
\li \l verticalOffset: 20
\li \l verticalOffset: 20
\li \l verticalOffset: 20
\row
\li \l spread: 0
\li \l spread: 0
\li \l spread: 0
\endtable
\note The \c radius property is used to calculate the size of the effect's offscreen buffer.
Higher values will cause larger memory allocations.
*/
property alias radius: dbs.radius;
/*!
This property defines how many samples are taken per pixel when edge
softening blur calculation is done. Larger value produces better
quality, but is slower to render.
Ideally, this value should be twice as large as the highest required
radius value plus one, such as:
\table
\header \li Radius \li Samples
\row \li 0 \e{(no blur)} \li 1
\row \li 1 \li 3
\row \li 2 \li 5
\row \li 3 \li 7
\endtable
By default, the property is set to \c 9.
This property is not intended to be animated. Changing this property will
cause the underlying OpenGL shaders to be recompiled.
*/
property alias samples: dbs.samples
/*!
This property defines the RGBA color value which is used for the shadow.
By default, the property is set to \c "black".
\table
\header
\li Output examples with different color values
\li
\li
\row
\li \image DropShadow_color1.png {Butterfly with black shadow}
\li \image DropShadow_color2.png {Butterfly with blue shadow}
\li \image DropShadow_color3.png {Butterfly with semi-transparent shadow}
\row
\li \b { color: #000000 }
\li \b { color: #0000ff }
\li \b { color: #aa000000 }
\row
\li \l radius: 8
\li \l radius: 8
\li \l radius: 8
\row
\li \l samples: 17
\li \l samples: 17
\li \l samples: 17
\row
\li \l horizontalOffset: 0
\li \l horizontalOffset: 0
\li \l horizontalOffset: 0
\row
\li \l verticalOffset: 20
\li \l verticalOffset: 20
\li \l verticalOffset: 20
\row
\li \l spread: 0
\li \l spread: 0
\li \l spread: 0
\endtable
*/
property alias color: dbs.color
/*!
\qmlproperty real QtGraphicalEffects::DropShadow::horizontalOffset
\qmlproperty real QtGraphicalEffects::DropShadow::verticalOffset
HorizontalOffset and verticalOffset properties define the offset for the
rendered shadow compared to the DropShadow item position. Often, the
DropShadow item is anchored so that it fills the source element. In this
case, if the HorizontalOffset and verticalOffset properties are set to
0, the shadow is rendered exactly under the source item. By changing the
offset properties, the shadow can be positioned relatively to the source
item.
The values range from -inf to inf. By default, the properties are set to
\c 0.
\table
\header
\li Output examples with different horizontalOffset values
\li
\li
\row
\li \image DropShadow_horizontalOffset1.png {Shadow offset to the left}
\li \image DropShadow_horizontalOffset2.png {Shadow centered below}
\li \image DropShadow_horizontalOffset3.png {Shadow offset to the right}
\row
\li \b { horizontalOffset: -20 }
\li \b { horizontalOffset: 0 }
\li \b { horizontalOffset: 20 }
\row
\li \l radius: 4
\li \l radius: 4
\li \l radius: 4
\row
\li \l samples: 9
\li \l samples: 9
\li \l samples: 9
\row
\li \l color: #000000
\li \l color: #000000
\li \l color: #000000
\row
\li \l verticalOffset: 0
\li \l verticalOffset: 0
\li \l verticalOffset: 0
\row
\li \l spread: 0
\li \l spread: 0
\li \l spread: 0
\endtable
\table
\header
\li Output examples with different verticalOffset values
\li
\li
\row
\li \image DropShadow_horizontalOffset2.png {Shadow centered below}
\li \image DropShadow_spread1.png {Shadow with vertical offset}
\row
\li \b { horizontalOffset: 0 }
\li \b { horizontalOffset: 0 }
\row
\li \l radius: 4
\li \l radius: 8
\row
\li \l samples: 9
\li \l samples: 17
\row
\li \l color: #000000
\li \l color: #000000
\row
\li \l verticalOffset: 0
\li \l verticalOffset: 20
\row
\li \l spread: 0
\li \l spread: 0
\endtable
*/
property alias horizontalOffset: dbs.horizontalOffset
property alias verticalOffset: dbs.verticalOffset
/*!
This property defines how large part of the shadow color is strengthened
near the source edges.
The value ranges from 0.0 to 1.0. By default, the property is set to \c
0.0.
\table
\header
\li Output examples with different spread values
\li
\li
\row
\li \image DropShadow_spread1.png {Shadow with no spread}
\li \image DropShadow_spread2.png {Shadow with medium spread}
\li \image DropShadow_spread3.png {Shadow with full spread}
\row
\li \b { spread: 0.0 }
\li \b { spread: 0.5 }
\li \b { spread: 1.0 }
\row
\li \l radius: 8
\li \l radius: 8
\li \l radius: 8
\row
\li \l samples: 17
\li \l samples: 17
\li \l samples: 17
\row
\li \l color: #000000
\li \l color: #000000
\li \l color: #000000
\row
\li \l horizontalOffset: 0
\li \l horizontalOffset: 0
\li \l horizontalOffset: 0
\row
\li \l verticalOffset: 20
\li \l verticalOffset: 20
\li \l verticalOffset: 20
\endtable
*/
property alias spread: dbs.spread
/*!
\internal
Starting Qt 5.6, this property has no effect. It is left here
for source compatibility only.
### Qt 6: remove
*/
property bool fast: false
/*!
This property allows the effect output pixels to be cached in order to
improve the rendering performance. Every time the source or effect
properties are changed, the pixels in the cache must be updated. Memory
consumption is increased, because an extra buffer of memory is required
for storing the effect output.
It is recommended to disable the cache when the source or the effect
properties are animated.
By default, the property is set to \c false.
*/
property alias cached: dbs.cached
/*!
This property determines whether or not the effect has a transparent
border.
When set to \c true, the exterior of the item is padded with a 1 pixel
wide transparent edge, making sampling outside the source texture use
transparency instead of the edge pixels. Without this property, an
image which has opaque edges will not get a blurred shadow.
In the image below, the Rectangle on the left has transparent borders
and has blurred edges, whereas the Rectangle on the right does not:
By default, this property is set to \c true.
\snippet DropShadow-transparentBorder-example.qml example
\image DropShadow-transparentBorder.png
{Rectangles showing difference between transparent border settings}
*/
property alias transparentBorder: dbs.transparentBorder
}