QgsShadowEffect class

Base class for paint effects which offset, blurred shadows.

Reference

Base classes

class QgsPaintEffect: Base class for visual effects which can be applied to QPicture drawings.

Derived classes

class QgsDropShadowEffect: A paint effect which draws an offset and optionally blurred drop shadow.
class QgsInnerShadowEffect: A paint effect which draws an offset and optionally blurred drop shadow within a picture.

Public functions

auto blendMode() const -> QPainter::CompositionMode: Returns the blend mode for the effect.
auto blurLevel() const -> int: Returns the blur level (strength) for the shadow.
auto color() const -> QColor: Returns the color used for the shadow.
auto offsetAngle() const -> int: Returns the angle used for offsetting the shadow.
auto offsetDistance() const -> double: Returns the distance used for offsetting the shadow.
auto offsetMapUnitScale() const -> const QgsMapUnitScale&: Returns the map unit scale used for the shadow offset distance.
auto offsetUnit() const -> QgsUnitTypes::RenderUnit: Returns the units used for the shadow offset distance.
auto opacity() const -> double: Returns the opacity for the effect.
auto properties() const -> QgsStringMap override: Returns the properties describing the paint effect encoded in a string format.
void readProperties(const QgsStringMap& props) override: Reads a string map of an effect's properties and restores the effect to the state described by the properties map.
void setBlendMode(const QPainter::CompositionMode mode): Sets the blend mode for the effect.
void setBlurLevel(const int level): Sets blur level (strength) for the shadow.
void setColor(const QColor& color): Sets the color for the shadow.
void setOffsetAngle(const int angle): Sets the angle for offsetting the shadow.
void setOffsetDistance(const double distance): Sets the distance for offsetting the shadow.
void setOffsetMapUnitScale(const QgsMapUnitScale& scale): Sets the map unit scale used for the shadow offset distance.
void setOffsetUnit(const QgsUnitTypes::RenderUnit unit): Sets the units used for the shadow offset distance.
void setOpacity(const double opacity): Sets the opacity for the effect.

Protected functions

auto boundingRect(const QRectF& rect, const QgsRenderContext& context) const -> QRectF override: Returns the bounding rect required for drawing the effect.
void draw(QgsRenderContext& context) override: Handles drawing of the effect's result on to the specified render context.
auto exteriorShadow() const -> bool pure virtual: Specifies whether the shadow is drawn outside the picture or within the picture.

Function documentation

QPainter::CompositionMode QgsShadowEffect::blendMode() const

Returns the blend mode for the effect.

Returns	blend mode used for drawing the effect on to a destination paint device

int QgsShadowEffect::blurLevel() const

Returns the blur level (strength) for the shadow.

Returns	blur level. Value will be between 0 and 16, with larger values indicating greater blur strength.

QColor QgsShadowEffect::color() const

Returns the color used for the shadow.

Returns	shadow color

int QgsShadowEffect::offsetAngle() const

Returns the angle used for offsetting the shadow.

Returns	offset angle in degrees clockwise from North

double QgsShadowEffect::offsetDistance() const

Returns the distance used for offsetting the shadow.

Returns	offset distance. Distance units are retrieved via offsetUnit()

const QgsMapUnitScale& QgsShadowEffect::offsetMapUnitScale() const

Returns the map unit scale used for the shadow offset distance.

Returns	map unit scale for offset distance

QgsUnitTypes::RenderUnit QgsShadowEffect::offsetUnit() const

Returns the units used for the shadow offset distance.

Returns	units for offset distance

double QgsShadowEffect::opacity() const

Returns the opacity for the effect.

Returns	opacity value between 0 and 1 inclusive, where 0 is fully transparent and 1 is fully opaque

QgsStringMap QgsShadowEffect::properties() const override

Returns the properties describing the paint effect encoded in a string format.

Returns	string map of properties, in the form property key, value

void QgsShadowEffect::readProperties(const QgsStringMap& props) override

Reads a string map of an effect's properties and restores the effect to the state described by the properties map.

Parameters
props	effect properties encoded in a string map

void QgsShadowEffect::setBlendMode(const QPainter::CompositionMode mode)

Sets the blend mode for the effect.

Parameters
mode	blend mode used for drawing the effect on to a destination paint device

void QgsShadowEffect::setBlurLevel(const int level)

Sets blur level (strength) for the shadow.

Parameters
level	blur level. Values between 0 and 16 are valid, with larger values indicating greater blur strength.

void QgsShadowEffect::setColor(const QColor& color)

Sets the color for the shadow.

Parameters
color	shadow color

void QgsShadowEffect::setOffsetAngle(const int angle)

Sets the angle for offsetting the shadow.

Parameters
angle	offset angle in degrees clockwise from North

void QgsShadowEffect::setOffsetDistance(const double distance)

Sets the distance for offsetting the shadow.

Parameters
distance	offset distance. Units are specified via setOffsetUnit()

void QgsShadowEffect::setOffsetMapUnitScale(const QgsMapUnitScale& scale)

Sets the map unit scale used for the shadow offset distance.

Parameters
scale	map unit scale for offset distance

void QgsShadowEffect::setOffsetUnit(const QgsUnitTypes::RenderUnit unit)

Sets the units used for the shadow offset distance.

Parameters
unit	units for offset distance

void QgsShadowEffect::setOpacity(const double opacity)

Sets the opacity for the effect.

Parameters
opacity	double between 0 and 1 inclusive, where 0 is fully transparent and 1 is fully opaque

QRectF QgsShadowEffect::boundingRect(const QRectF& rect, const QgsRenderContext& context) const override protected

Returns the bounding rect required for drawing the effect.

Parameters
rect	original source bounding rect
context	destination render context
Returns	modified bounding rect

This method can be used to expand the bounding rect of a source picture to account for offset or blurring effects.

void QgsShadowEffect::draw(QgsRenderContext& context) override protected

Handles drawing of the effect's result on to the specified render context.

Parameters
context	destination render context

Derived classes must reimplement this method to apply any transformations to the source QPicture and draw the result using the context's painter.

bool QgsShadowEffect::exteriorShadow() const pure virtual protected

Specifies whether the shadow is drawn outside the picture or within the picture.

Returns	true if shadow is to be drawn outside the picture, or false to draw shadow within the picture