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

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#include <private/qquickshadereffect_p.h>
#include <private/qsgcontextplugin_p.h>
#include <private/qquickitem_p.h>
#include <private/qquickgenericshadereffect_p.h>
#if QT_CONFIG(opengl) /* || QT_CONFIG(vulkan) || defined(Q_OS_WIN) || defined(Q_OS_DARWIN) */
#include <private/qsgrhisupport_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
    \l{vertexShader}{vertex} and \l{fragmentShader}{fragment (pixel)} shader to a
    rectangle. It allows you to write effects such as drop shadow, blur,
    colorize and page curl directly in QML.

    \note Depending on the Qt Quick scenegraph backend in use, the ShaderEffect
    type may not be supported (for example, with the software backend), or may
    use a different shading language with rules and expectations different from
    OpenGL and GLSL.

    \section1 OpenGL and GLSL

    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

    \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::GraphicsInfo.

    Starting from Qt 5.8 ShaderEffect also supports reading the GLSL source
    code from files. Whenever the fragmentShader or vertexShader property value
    is a URL with the \c file or \c qrc schema, it is treated as a file
    reference and the source code is read from the specified file.

    \section1 Cross-platform, Cross-API ShaderEffect Items

    Some applications will want to be functional with multiple graphics
    APIs. This has consequences for ShaderEffect items because the supported
    shading languages may vary from backend to backend.

    There are two approaches to handle this: either write conditional property
    values based on GraphicsInfo.shaderType, or use file selectors. In practice
    the latter is strongly recommended as it leads to more concise and cleaner
    application code. The only case it is not suitable is when the source
    strings are constructed dynamically.

    \table 70%
    \row
    \li \qml
        import QtQuick 2.8 // for GraphicsInfo

        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
                    property variant color: Qt.vector3d(0.344, 0.5, 0.156)
                    fragmentShader: GraphicsInfo.shaderType === GraphicsInfo.GLSL ?
                        "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;"
                    : GraphicsInfo.shaderType === GraphicsInfo.RhiShader ?
                        "qrc:/shader.frag.qsb"
                    : ""
                }
            }
        }
        \endqml
    \row

    \li This is the first approach based on GraphicsInfo. Note that the value
    reported by GraphicsInfo is not up-to-date until the ShaderEffect item gets
    associated with a QQuickWindow. Before that, the reported value is
    GraphicsInfo.UnknownShadingLanguage. The alternative is to place the GLSL
    source code and the RHI-compatible shader pack into the files
    \c{shaders/effect.frag} and \c{shaders/+qsb/effect.frag}, include them in
    the Qt resource system, and let the ShaderEffect's internal QFileSelector do
    its job. The selector-less version is the GLSL source, while the \c qsb
    selector is used when running with the Qt graphics abstraction (RHI).
    Additionally, when using a version 3.2 or newer core profile context with
    OpenGL, GLSL sources with a core profile compatible syntax can be placed
    under \c{+glslcore}.
        \qml
        import QtQuick 2.8 // for GraphicsInfo

        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
                    property variant color: Qt.vector3d(0.344, 0.5, 0.156)
                    fragmentShader: "qrc:shaders/effect.frag" // selects the correct variant automatically
                }
            }
        }
        \endqml
    \endtable

    \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

    \section1 Other Notes

    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.

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

    \sa {Item Layers}
*/

class QQuickShaderEffectPrivate : public QQuickItemPrivate
{
    Q_DECLARE_PUBLIC(QQuickShaderEffect)

public:
    void updatePolish() override;
};

QSGContextFactoryInterface::Flags qsg_backend_flags();

QQuickShaderEffect::QQuickShaderEffect(QQuickItem *parent)
    : QQuickItem(*new QQuickShaderEffectPrivate, parent),
      m_impl(nullptr)
{
    setFlag(QQuickItem::ItemHasContents);

    m_impl = new QQuickGenericShaderEffect(this, this);
}

QQuickShaderEffect::~QQuickShaderEffect()
{
    // Delete the implementations now, while they still have have
    // valid references back to us.
    auto *impl = m_impl;
    m_impl = nullptr;
    delete impl;
}

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

    This property holds the fragment (pixel) shader's source code or a
    reference to the pre-compiled bytecode. Some APIs, like OpenGL, always
    support runtime compilation and therefore the traditional Qt Quick way of
    inlining shader source strings is functional. Qt Quick backends for other
    APIs may however limit support to pre-compiled bytecode like SPIR-V or D3D
    shader bytecode. There the string is simply a filename, which may be a file
    in the filesystem or bundled with the executable via Qt's resource system.

    With GLSL the default shader expects the texture coordinate to be passed
    from the vertex shader as \c{varying highp vec2 qt_TexCoord0}, and it
    samples from a sampler2D named \c source.

    \sa vertexShader, GraphicsInfo
*/

QByteArray QQuickShaderEffect::fragmentShader() const
{
    return m_impl->fragmentShader();
}

void QQuickShaderEffect::setFragmentShader(const QByteArray &code)
{
    m_impl->setFragmentShader(code);
}

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

    This property holds the vertex shader's source code or a reference to the
    pre-compiled bytecode. Some APIs, like OpenGL, always support runtime
    compilation and therefore the traditional Qt Quick way of inlining shader
    source strings is functional. Qt Quick backends for other APIs may however
    limit support to pre-compiled bytecode like SPIR-V or D3D shader bytecode.
    There the string is simply a filename, which may be a file in the
    filesystem or bundled with the executable via Qt's resource system.

    With GLSL the default shader passes the texture coordinate along to the
    fragment shader as \c{varying highp vec2 qt_TexCoord0}.

    \sa fragmentShader, GraphicsInfo
*/

QByteArray QQuickShaderEffect::vertexShader() const
{
    return m_impl->vertexShader();
}

void QQuickShaderEffect::setVertexShader(const QByteArray &code)
{
    m_impl->setVertexShader(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
{
    return m_impl->blending();
}

void QQuickShaderEffect::setBlending(bool enable)
{
    m_impl->setBlending(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
{
    return m_impl->mesh();
}

void QQuickShaderEffect::setMesh(const QVariant &mesh)
{
    m_impl->setMesh(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
{
    return m_impl->cullMode();
}

void QQuickShaderEffect::setCullMode(CullMode face)
{
    return m_impl->setCullMode(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
{
    return m_impl->supportsAtlasTextures();
}

void QQuickShaderEffect::setSupportsAtlasTextures(bool supports)
{
    m_impl->setSupportsAtlasTextures(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.

    When runtime compilation is not in use and the shader properties refer to
    files with bytecode, the status is always Compiled. The contents of the
    shader is not examined (apart from basic reflection to discover vertex
    input elements and constant buffer data) until later in the rendering
    pipeline so potential errors (like layout or root signature mismatches)
    will only be detected at a later point.

    \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
{
    return m_impl->log();
}

QQuickShaderEffect::Status QQuickShaderEffect::status() const
{
    return m_impl->status();
}

bool QQuickShaderEffect::event(QEvent *e)
{
    if (m_impl)
        m_impl->handleEvent(e);
    return QQuickItem::event(e);
}

void QQuickShaderEffect::geometryChange(const QRectF &newGeometry, const QRectF &oldGeometry)
{
    m_impl->handleGeometryChanged(newGeometry, oldGeometry);
    QQuickItem::geometryChange(newGeometry, oldGeometry);
}

QSGNode *QQuickShaderEffect::updatePaintNode(QSGNode *oldNode, UpdatePaintNodeData *updatePaintNodeData)
{
    return m_impl->handleUpdatePaintNode(oldNode, updatePaintNodeData);
}

void QQuickShaderEffect::componentComplete()
{
    m_impl->maybeUpdateShaders();
    QQuickItem::componentComplete();
}

void QQuickShaderEffect::itemChange(ItemChange change, const ItemChangeData &value)
{
    m_impl->handleItemChange(change, value);
    QQuickItem::itemChange(change, value);
}

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

QString QQuickShaderEffect::parseLog() // for OpenGL-based autotests
{
    return m_impl->parseLog();
}

void QQuickShaderEffectPrivate::updatePolish()
{
    Q_Q(QQuickShaderEffect);
    if (!qmlEngine(q))
        return;
    q->m_impl->maybeUpdateShaders();
}

QT_END_NAMESPACE

#include "moc_qquickshadereffect_p.cpp"