path: root/src/quick/items/qquickshadereffect.cpp

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#include <private/qquickshadereffect_p.h>
#include <private/qsgcontextplugin_p.h>
#ifndef QT_NO_OPENGL
#include <private/qquickopenglshadereffect_p.h>
#endif

QT_BEGIN_NAMESPACE

/*!
    \qmltype ShaderEffect
    \instantiates QQuickShaderEffect
    \inqmlmodule QtQuick
    \inherits Item
    \ingroup qtquick-effects
    \brief Applies custom shaders to a rectangle

    The ShaderEffect type applies a custom OpenGL
    \l{vertexShader}{vertex} and \l{fragmentShader}{fragment} shader to a
    rectangle. It allows you to write effects such as drop shadow, blur,
    colorize and page curl directly in QML.

    There are two types of input to the \l vertexShader:
    uniform variables and attributes. Some are predefined:
    \list
    \li uniform mat4 qt_Matrix - combined transformation
       matrix, the product of the matrices from the root item to this
       ShaderEffect, and an orthogonal projection.
    \li uniform float qt_Opacity - combined opacity, the product of the
       opacities from the root item to this ShaderEffect.
    \li attribute vec4 qt_Vertex - vertex position, the top-left vertex has
       position (0, 0), the bottom-right (\l{Item::width}{width},
       \l{Item::height}{height}).
    \li attribute vec2 qt_MultiTexCoord0 - texture coordinate, the top-left
       coordinate is (0, 0), the bottom-right (1, 1). If \l supportsAtlasTextures
       is true, coordinates will be based on position in the atlas instead.
    \endlist

    In addition, any property that can be mapped to an OpenGL Shading Language
    (GLSL) type is available as a uniform variable. The following list shows
    how properties are mapped to GLSL uniform variables:
    \list
    \li bool, int, qreal -> bool, int, float - If the type in the shader is not
       the same as in QML, the value is converted automatically.
    \li QColor -> vec4 - When colors are passed to the shader, they are first
       premultiplied. Thus Qt.rgba(0.2, 0.6, 1.0, 0.5) becomes
       vec4(0.1, 0.3, 0.5, 0.5) in the shader, for example.
    \li QRect, QRectF -> vec4 - Qt.rect(x, y, w, h) becomes vec4(x, y, w, h) in
       the shader.
    \li QPoint, QPointF, QSize, QSizeF -> vec2
    \li QVector3D -> vec3
    \li QVector4D -> vec4
    \li QTransform -> mat3
    \li QMatrix4x4 -> mat4
    \li QQuaternion -> vec4, scalar value is \c w.
    \li \l Image -> sampler2D - Origin is in the top-left corner, and the
        color values are premultiplied. The texture is provided as is,
        excluding the Image item's fillMode. To include fillMode, use a
        ShaderEffectSource or Image::layer::enabled.
    \li \l ShaderEffectSource -> sampler2D - Origin is in the top-left
        corner, and the color values are premultiplied.
    \endlist

    The QML scene graph back-end may choose to allocate textures in texture
    atlases. If a texture allocated in an atlas is passed to a ShaderEffect,
    it is by default copied from the texture atlas into a stand-alone texture
    so that the texture coordinates span from 0 to 1, and you get the expected
    wrap modes. However, this will increase the memory usage. To avoid the
    texture copy, set \l supportsAtlasTextures for simple shaders using
    qt_MultiTexCoord0, or for each "uniform sampler2D <name>" declare a
    "uniform vec4 qt_SubRect_<name>" which will be assigned the texture's
    normalized source rectangle. For stand-alone textures, the source rectangle
    is [0, 1]x[0, 1]. For textures in an atlas, the source rectangle corresponds
    to the part of the texture atlas where the texture is stored.
    The correct way to calculate the texture coordinate for a texture called
    "source" within a texture atlas is
    "qt_SubRect_source.xy + qt_SubRect_source.zw * qt_MultiTexCoord0".

    The output from the \l fragmentShader should be premultiplied. If
    \l blending is enabled, source-over blending is used. However, additive
    blending can be achieved by outputting zero in the alpha channel.

    \table 70%
    \row
    \li \image declarative-shadereffectitem.png
    \li \qml
        import QtQuick 2.0

        Rectangle {
            width: 200; height: 100
            Row {
                Image { id: img;
                        sourceSize { width: 100; height: 100 } source: "qt-logo.png" }
                ShaderEffect {
                    width: 100; height: 100
                    property variant src: img
                    vertexShader: "
                        uniform highp mat4 qt_Matrix;
                        attribute highp vec4 qt_Vertex;
                        attribute highp vec2 qt_MultiTexCoord0;
                        varying highp vec2 coord;
                        void main() {
                            coord = qt_MultiTexCoord0;
                            gl_Position = qt_Matrix * qt_Vertex;
                        }"
                    fragmentShader: "
                        varying highp vec2 coord;
                        uniform sampler2D src;
                        uniform lowp float qt_Opacity;
                        void main() {
                            lowp vec4 tex = texture2D(src, coord);
                            gl_FragColor = vec4(vec3(dot(tex.rgb,
                                                vec3(0.344, 0.5, 0.156))),
                                                     tex.a) * qt_Opacity;
                        }"
                }
            }
        }
        \endqml
    \endtable

    By default, the ShaderEffect consists of four vertices, one for each
    corner. For non-linear vertex transformations, like page curl, you can
    specify a fine grid of vertices by specifying a \l mesh resolution.

    \section1 ShaderEffect and Item Layers

    The ShaderEffect type can be combined with \l {Item Layers} {layered items}.

    \table
    \row
      \li \b {Layer with effect disabled} \inlineimage qml-shadereffect-nolayereffect.png
      \li \b {Layer with effect enabled} \inlineimage qml-shadereffect-layereffect.png
    \row
      \li \snippet qml/layerwitheffect.qml 1
    \endtable

    It is also possible to combine multiple layered items:

    \table
    \row
      \li \inlineimage qml-shadereffect-opacitymask.png
    \row
      \li \snippet qml/opacitymask.qml 1
    \endtable

    The \l {Qt Graphical Effects} module contains several ready-made effects
    for using with Qt Quick applications.

    \note Scene Graph textures have origin in the top-left corner rather than
    bottom-left which is common in OpenGL.

    For information about the GLSL version being used, see \l QtQuick::OpenGLInfo.

    \sa {Item Layers}
*/

QSGContextFactoryInterface::Flags qsg_backend_flags();

QQuickShaderEffect::QQuickShaderEffect(QQuickItem *parent)
    : QQuickItem(parent)
{
    setFlag(QQuickItem::ItemHasContents);

#ifndef QT_NO_OPENGL
    if (!qsg_backend_flags().testFlag(QSGContextFactoryInterface::SupportsShaderEffectV2))
        m_glImpl = new QQuickOpenGLShaderEffect(this, this);
    else
        m_glImpl = nullptr;
#endif
}

/*!
    \qmlproperty string QtQuick::ShaderEffect::fragmentShader

    This property holds the fragment shader's GLSL source code.
    The default shader expects the texture coordinate to be passed from the
    vertex shader as "varying highp vec2 qt_TexCoord0", and it samples from a
    sampler2D named "source".
*/

QByteArray QQuickShaderEffect::fragmentShader() const
{
#ifndef QT_NO_OPENGL
    if (m_glImpl)
        return m_glImpl->fragmentShader();
#endif
    return QByteArray();
}

void QQuickShaderEffect::setFragmentShader(const QByteArray &code)
{
#ifndef QT_NO_OPENGL
    if (m_glImpl)
        m_glImpl->setFragmentShader(code);
#endif
    Q_UNUSED(code);
}

/*!
    \qmlproperty string QtQuick::ShaderEffect::vertexShader

    This property holds the vertex shader's GLSL source code.
    The default shader passes the texture coordinate along to the fragment
    shader as "varying highp vec2 qt_TexCoord0".
*/

QByteArray QQuickShaderEffect::vertexShader() const
{
#ifndef QT_NO_OPENGL
    if (m_glImpl)
        return m_glImpl->vertexShader();
#endif
    return QByteArray();
}

void QQuickShaderEffect::setVertexShader(const QByteArray &code)
{
#ifndef QT_NO_OPENGL
    if (m_glImpl)
        m_glImpl->setVertexShader(code);
#endif
    Q_UNUSED(code);
}

/*!
    \qmlproperty bool QtQuick::ShaderEffect::blending

    If this property is true, the output from the \l fragmentShader is blended
    with the background using source-over blend mode. If false, the background
    is disregarded. Blending decreases the performance, so you should set this
    property to false when blending is not needed. The default value is true.
*/

bool QQuickShaderEffect::blending() const
{
#ifndef QT_NO_OPENGL
    if (m_glImpl)
        return m_glImpl->blending();
#endif
    return true;
}

void QQuickShaderEffect::setBlending(bool enable)
{
#ifndef QT_NO_OPENGL
    if (m_glImpl)
        m_glImpl->setBlending(enable);
#endif
    Q_UNUSED(enable);
}

/*!
    \qmlproperty variant QtQuick::ShaderEffect::mesh

    This property defines the mesh used to draw the ShaderEffect. It can hold
    any \l GridMesh object.
    If a size value is assigned to this property, the ShaderEffect implicitly
    uses a \l GridMesh with the value as
    \l{GridMesh::resolution}{mesh resolution}. By default, this property is
    the size 1x1.

    \sa GridMesh
*/

QVariant QQuickShaderEffect::mesh() const
{
#ifndef QT_NO_OPENGL
    if (m_glImpl)
        return m_glImpl->mesh();
#endif
    return QVariant();
}

void QQuickShaderEffect::setMesh(const QVariant &mesh)
{
#ifndef QT_NO_OPENGL
    if (m_glImpl)
        m_glImpl->setMesh(mesh);
#endif
    Q_UNUSED(mesh);
}

/*!
    \qmlproperty enumeration QtQuick::ShaderEffect::cullMode

    This property defines which sides of the item should be visible.

    \list
    \li ShaderEffect.NoCulling - Both sides are visible
    \li ShaderEffect.BackFaceCulling - only front side is visible
    \li ShaderEffect.FrontFaceCulling - only back side is visible
    \endlist

    The default is NoCulling.
*/

QQuickShaderEffect::CullMode QQuickShaderEffect::cullMode() const
{
#ifndef QT_NO_OPENGL
    if (m_glImpl)
        return m_glImpl->cullMode();
#endif
    return NoCulling;
}

void QQuickShaderEffect::setCullMode(CullMode face)
{
#ifndef QT_NO_OPENGL
    if (m_glImpl)
        m_glImpl->setCullMode(face);
#endif
    Q_UNUSED(face);
}

/*!
    \qmlproperty bool QtQuick::ShaderEffect::supportsAtlasTextures

    Set this property true to confirm that your shader code doesn't rely on
    qt_MultiTexCoord0 ranging from (0,0) to (1,1) relative to the mesh.
    In this case the range of qt_MultiTexCoord0 will rather be based on the position
    of the texture within the atlas. This property currently has no effect if there
    is less, or more, than one sampler uniform used as input to your shader.

    This differs from providing qt_SubRect_<name> uniforms in that the latter allows
    drawing one or more textures from the atlas in a single ShaderEffect item, while
    supportsAtlasTextures allows multiple instances of a ShaderEffect component using
    a different source image from the atlas to be batched in a single draw.
    Both prevent a texture from being copied out of the atlas when referenced by a ShaderEffect.

    The default value is false.

    \since 5.4
    \since QtQuick 2.4
*/

bool QQuickShaderEffect::supportsAtlasTextures() const
{
#ifndef QT_NO_OPENGL
    if (m_glImpl)
        return m_glImpl->supportsAtlasTextures();
#endif
    return false;
}

void QQuickShaderEffect::setSupportsAtlasTextures(bool supports)
{
#ifndef QT_NO_OPENGL
    if (m_glImpl)
        m_glImpl->setSupportsAtlasTextures(supports);
#endif
    Q_UNUSED(supports);
}

/*!
    \qmlproperty enumeration QtQuick::ShaderEffect::status

    This property tells the current status of the OpenGL shader program.

    \list
    \li ShaderEffect.Compiled - the shader program was successfully compiled and linked.
    \li ShaderEffect.Uncompiled - the shader program has not yet been compiled.
    \li ShaderEffect.Error - the shader program failed to compile or link.
    \endlist

    When setting the fragment or vertex shader source code, the status will become Uncompiled.
    The first time the ShaderEffect is rendered with new shader source code, the shaders are
    compiled and linked, and the status is updated to Compiled or Error.

    \sa log
*/

/*!
    \qmlproperty string QtQuick::ShaderEffect::log

    This property holds a log of warnings and errors from the latest attempt at compiling and
    linking the OpenGL shader program. It is updated at the same time \l status is set to Compiled
    or Error.

    \sa status
*/

QString QQuickShaderEffect::log() const
{
#ifndef QT_NO_OPENGL
    if (m_glImpl)
        return m_glImpl->log();
#endif
    return QString();
}

QQuickShaderEffect::Status QQuickShaderEffect::status() const
{
#ifndef QT_NO_OPENGL
    if (m_glImpl)
        return m_glImpl->status();
#endif
    return Uncompiled;
}

bool QQuickShaderEffect::event(QEvent *e)
{
#ifndef QT_NO_OPENGL
    if (m_glImpl)
        m_glImpl->handleEvent(e);
#endif
    return QQuickItem::event(e);
}

void QQuickShaderEffect::geometryChanged(const QRectF &newGeometry, const QRectF &oldGeometry)
{
#ifndef QT_NO_OPENGL
    if (m_glImpl)
        m_glImpl->handleGeometryChanged(newGeometry, oldGeometry);
#endif
    QQuickItem::geometryChanged(newGeometry, oldGeometry);
}

QSGNode *QQuickShaderEffect::updatePaintNode(QSGNode *oldNode, UpdatePaintNodeData *updatePaintNodeData)
{
#ifndef QT_NO_OPENGL
    if (m_glImpl)
        return m_glImpl->handleUpdatePaintNode(oldNode, updatePaintNodeData);
#endif
    return nullptr;
}

void QQuickShaderEffect::componentComplete()
{
#ifndef QT_NO_OPENGL
    if (m_glImpl)
        m_glImpl->handleComponentComplete();
#endif
    QQuickItem::componentComplete();
}

void QQuickShaderEffect::itemChange(ItemChange change, const ItemChangeData &value)
{
#ifndef QT_NO_OPENGL
    if (m_glImpl)
        m_glImpl->handleItemChange(change, value);
#endif
    QQuickItem::itemChange(change, value);
}

bool QQuickShaderEffect::isComponentComplete() const
{
    return QQuickItem::isComponentComplete();
}

void QQuickShaderEffect::sourceDestroyed(QObject *object)
{
#ifndef QT_NO_OPENGL
    if (m_glImpl)
        m_glImpl->handleSourceDestroyed(object);
#endif
    Q_UNUSED(object);
}

void QQuickShaderEffect::propertyChanged(int mappedId)
{
#ifndef QT_NO_OPENGL
    if (m_glImpl)
        m_glImpl->handlePropertyChanged(mappedId);
#endif
    Q_UNUSED(mappedId);
}

QT_END_NAMESPACE