ECS Systems

Classes
class	donner::svg::components::FilterSystem
	Handles parsing and instantiating SVG filter effects from the SVG DOM. More...
class	donner::svg::components::LayoutSystem
	Handles layout and bounds calculations for SVG elements. More...
class	donner::svg::components::PaintSystem
	Manages Paint Servers for gradients and patterns, handling style and structural inheritance and creating "computed" state and shadow trees for these elements. More...
class	donner::svg::components::ShadowTreeSystem
	Instantiates shadow trees for elements that are not part of the main render graph, such as "<use>" and "<pattern>" elements. More...
class	donner::svg::components::ShapeSystem
	Creates computed path for shapes such as "<circle>", "<line>", and "<path>". More...
class	donner::svg::components::StyleSystem
	Computes stylesheet information for elements, applying the CSS cascade and inheritance rules. More...

Detailed Description

Systems are the core of the ECS architecture. They contain the logic and are responsible for updating the components of entities.

• Systems contain logic and interact with components.
• Components are the data layer and contain the state, but no logic.

---

Class Documentation

donner::svg::components::FilterSystem

class donner::svg::components::FilterSystem

Handles parsing and instantiating SVG filter effects from the SVG DOM.

See also

https://drafts.fxtf.org/filter-effects/

Public Member Functions
void	createComputedFilter (EntityHandle handle, const FilterComponent &component, std::vector< parser::ParseError > *outWarnings)
	Create ComputedFilterComponent for the given entity, applying style information and style inheritance.
void	instantiateAllComputedComponents (Registry &registry, std::vector< parser::ParseError > *outWarnings)
	Create all ComputedFilterComponent in the tree.

Member Function Documentation

createComputedFilter()

void donner::svg::components::FilterSystem::createComputedFilter	(	EntityHandle	handle,
		const FilterComponent &	component,
		std::vector< parser::ParseError > *	outWarnings )

Create ComputedFilterComponent for the given entity, applying style information and style inheritance.

Parameters

handle	Entity handle to apply the filter to.
component	Filter effect for the current entity, so that this may only be called if one is present.
outWarnings	Warnings generated during parsing.

instantiateAllComputedComponents()

void donner::svg::components::FilterSystem::instantiateAllComputedComponents	(	Registry &	registry,
		std::vector< parser::ParseError > *	outWarnings )

Create all ComputedFilterComponent in the tree.

Parameters

registry	Registry to operate on.
outWarnings	Warnings generated during parsing.

donner::svg::components::LayoutSystem

class donner::svg::components::LayoutSystem

Handles layout and bounds calculations for SVG elements.

This system is responsible for calculating the the document size, viewboxes, and the bounds for elements.

See also

https://www.w3.org/TR/SVG2/coords.html

Public Types
enum class	InvalidSizeBehavior {   ZeroSize ,   ReturnDefault }
	Controls the behavior of LayoutSystem::calculateCanvasScaledDocumentSize for invalid sizes. More...
Public Member Functions
Regular properties
std::optional< float >	intrinsicAspectRatio (EntityHandle entity) const
	Calculate the intrinsic aspect ratio per https://svgwg.org/svg2-draft/coords.html#SizingSVGInCSS, which defines how content is scaled to fit the viewport.
Vector2i	calculateDocumentSize (Registry &registry) const
	Calculate the document size of the current entity.
Boxd	getViewport (EntityHandle entity)
	Get the viewport affecting the current entity.
bool	overridesViewport (EntityHandle entity) const
	Returns true if the given entity overrides the viewport.
Vector2i	calculateCanvasScaledDocumentSize (Registry &registry, InvalidSizeBehavior behavior) const
	Get the document size scaled to fit the canvas.
Transformd	getEntityFromParentTranform (EntityHandle entity)
	Get the entity-from-parent transform for the current entity.
Transformd	getEntityContentFromEntityTransform (EntityHandle entity)
	Get the transform for entityContent-from-entity, which is an additional transform for specific elements that define their own coordinate system, such as nested "<svg>" and "<use>" elements.
void	setEntityFromParentTransform (EntityHandle entity, const Transformd &entityFromParent)
	Set the entity-from-parent transform for the current entity.
Transformd	getEntityFromWorldTransform (EntityHandle entity)
	Get the entity-from-world transform for the current entity, representing the entity position relative to the world after applying all parent transformations.
void	invalidate (EntityHandle entity)
	Invalidate cached state for the current entity, such as the computed viewport and entity-from-world transform.
Computed properties
void	instantiateAllComputedComponents (Registry &registry, std::vector< parser::ParseError > *outWarnings)
	Create all computed components, such as ComputedViewboxComponent and ComputedSizedElementComponent.
Boxd	computeSizeProperties (EntityHandle entity, const SizedElementProperties &sizeProperties, const std::map< RcString, parser::UnparsedProperty > &unparsedProperties, const Boxd &viewbox, FontMetrics fontMetrics, std::vector< parser::ParseError > *outWarnings)
	Evaluates SizedElementProperties and returns the resulting bounds, using precomputed style information.
const ComputedSizedElementComponent &	createComputedSizedElementComponentWithStyle (EntityHandle handle, const ComputedStyleComponent &style, FontMetrics fontMetrics, std::vector< parser::ParseError > *outWarnings)
	Creates a ComputedSizedElementComponent for the linked entity, using precomputed style information.
const ComputedLocalTransformComponent &	createComputedLocalTransformComponentWithStyle (EntityHandle handle, const ComputedStyleComponent &style, const FontMetrics &fontMetrics, std::vector< parser::ParseError > *outWarnings)
	Creates a ComputedLocalTransformComponent for the linked entity, using precomputed style information.
std::optional< Boxd >	clipRect (EntityHandle handle) const
	If this element establishes a clipping context, returns the clip rect in the parent's coordinate system.
Transformd	computeSizedElementTransform (EntityHandle handle, const ComputedSizedElementComponent &computedSizedElement) const
	Computes the transformation from the parent's coordinate system into the coordinate system established by this sized element.

Member Enumeration Documentation

InvalidSizeBehavior

enum class donner::svg::components::LayoutSystem::InvalidSizeBehavior

strong

Controls the behavior of LayoutSystem::calculateCanvasScaledDocumentSize for invalid sizes.

Enumerator
ZeroSize	Return a size of 0x0.
ReturnDefault	Return the default document size (512x512).

Member Function Documentation

calculateCanvasScaledDocumentSize()

Vector2i donner::svg::components::LayoutSystem::calculateCanvasScaledDocumentSize	(	Registry &	registry,
		InvalidSizeBehavior	behavior ) const

Get the document size scaled to fit the canvas.

Parameters

registry	ECS registry
behavior	Controls the behavior when the document size is invalid, either returning a default size or empty box.

calculateDocumentSize()

Vector2i donner::svg::components::LayoutSystem::calculateDocumentSize

(

Registry &

registry

)

const

Calculate the document size of the current entity.

This is the size of the document viewport (the area that the SVG content is rendered into).

Parameters

registry

ECS registry

clipRect()

std::optional< Boxd > donner::svg::components::LayoutSystem::clipRect

(

EntityHandle

handle

)

const

If this element establishes a clipping context, returns the clip rect in the parent's coordinate system.

Parameters

handle

Entity handle.

Returns

std::optional<Boxd> Clip rect, or std::nullopt if this element does not establish a clipping context.

computeSizedElementTransform()

Transformd donner::svg::components::LayoutSystem::computeSizedElementTransform	(	EntityHandle	handle,
		const ComputedSizedElementComponent &	computedSizedElement ) const

Computes the transformation from the parent's coordinate system into the coordinate system established by this sized element.

Parameters

handle	Entity handle.
computedSizedElement	Precomputed sized element information.

Returns

Transformd Transformation from the parent's coordinate system into the sized element's coordinate system.

computeSizeProperties()

Boxd donner::svg::components::LayoutSystem::computeSizeProperties	(	EntityHandle	entity,
		const SizedElementProperties &	sizeProperties,
		const std::map< RcString, parser::UnparsedProperty > &	unparsedProperties,
		const Boxd &	viewbox,
		FontMetrics	fontMetrics,
		std::vector< parser::ParseError > *	outWarnings )

Evaluates SizedElementProperties and returns the resulting bounds, using precomputed style information.

Parameters

entity	Entity handle.
sizeProperties	Size properties to evaluate.
unparsedProperties	Unparsed properties to evaluate.
viewbox	Viewbox to use when converting size percentages.
fontMetrics	Font metrics, used to scale lengths.
outWarnings	Output vector of parse errors, if any.

Returns

Computed bounds.

createComputedLocalTransformComponentWithStyle()

const ComputedLocalTransformComponent & donner::svg::components::LayoutSystem::createComputedLocalTransformComponentWithStyle	(	EntityHandle	handle,
		const ComputedStyleComponent &	style,
		const FontMetrics &	fontMetrics,
		std::vector< parser::ParseError > *	outWarnings )

Creates a ComputedLocalTransformComponent for the linked entity, using precomputed style information.

Parameters

handle	Entity handle.
style	Precomputed style information for this element
fontMetrics	Font metrics, used to scale lengths
outWarnings	Output vector of parse errors, if any.

createComputedSizedElementComponentWithStyle()

const ComputedSizedElementComponent & donner::svg::components::LayoutSystem::createComputedSizedElementComponentWithStyle	(	EntityHandle	handle,
		const ComputedStyleComponent &	style,
		FontMetrics	fontMetrics,
		std::vector< parser::ParseError > *	outWarnings )

Creates a ComputedSizedElementComponent for the linked entity, using precomputed style information.

Parameters

handle	Entity handle.
style	Precomputed style information for this element
fontMetrics	Font metrics, used to scale lengths
outWarnings	Output vector of parse errors, if any.

Returns

reference to the computed component

getEntityContentFromEntityTransform()

Transformd donner::svg::components::LayoutSystem::getEntityContentFromEntityTransform

(

EntityHandle

entity

)

Get the transform for entityContent-from-entity, which is an additional transform for specific elements that define their own coordinate system, such as nested "<svg>" and "<use>" elements.

This transform is used to convert coordinates from the entity's coordinate system to the coordinate system of its content.

For example, a nested SVG element, where for the inner SVG element the content transform is scale(2) translate(50 50):

<svg xmlns="http://www.w3.org/2000/svg" viewBox="0 0 200 200">
  <svg x="50" y="50" width="100" height="100" viewBox="0 0 50 50">
    <rect x="0" y="0" width="50" height="50" fill="red"/>
  </svg>
</svg>

Parameters

entity

Current entity.

getEntityFromParentTranform()

Transformd donner::svg::components::LayoutSystem::getEntityFromParentTranform

(

EntityHandle

entity

)

Get the entity-from-parent transform for the current entity.

Parameters

entity

Current entity.

getEntityFromWorldTransform()

Transformd donner::svg::components::LayoutSystem::getEntityFromWorldTransform

(

EntityHandle

entity

)

Get the entity-from-world transform for the current entity, representing the entity position relative to the world after applying all parent transformations.

Parameters

entity

Current entity.

getViewport()

Boxd donner::svg::components::LayoutSystem::getViewport

(

EntityHandle

entity

)

Get the viewport affecting the current entity.

This may be the viewport of a viewport-defining parent element or the document viewport.

Parameters

entity

Current entity.

instantiateAllComputedComponents()

void donner::svg::components::LayoutSystem::instantiateAllComputedComponents	(	Registry &	registry,
		std::vector< parser::ParseError > *	outWarnings )

Create all computed components, such as ComputedViewboxComponent and ComputedSizedElementComponent.

Parameters

registry	ECS registry.
outWarnings	Output vector of parse errors, if any.

intrinsicAspectRatio()

std::optional< float > donner::svg::components::LayoutSystem::intrinsicAspectRatio

(

EntityHandle

entity

)

const

Calculate the intrinsic aspect ratio per https://svgwg.org/svg2-draft/coords.html#SizingSVGInCSS, which defines how content is scaled to fit the viewport.

This may return std::nullopt if the aspect ratio is not defined.

Parameters

entity

Current entity.

invalidate()

void donner::svg::components::LayoutSystem::invalidate

(

EntityHandle

entity

)

Invalidate cached state for the current entity, such as the computed viewport and entity-from-world transform.

Parameters

entity

Current entity.

overridesViewport()

bool donner::svg::components::LayoutSystem::overridesViewport

(

EntityHandle

entity

)

const

Returns true if the given entity overrides the viewport.

Parameters

entity

Current entity.

setEntityFromParentTransform()

void donner::svg::components::LayoutSystem::setEntityFromParentTransform	(	EntityHandle	entity,
		const Transformd &	entityFromParent )

Set the entity-from-parent transform for the current entity.

Parameters

entity	Current entity.
entityFromParent	New transform.

donner::svg::components::PaintSystem

class donner::svg::components::PaintSystem

Manages Paint Servers for gradients and patterns, handling style and structural inheritance and creating "computed" state and shadow trees for these elements.

See also

https://www.w3.org/TR/SVG2/pservers.html

Public Member Functions
const ComputedStopComponent &	createComputedStop (EntityHandle handle, const StopComponent &stop, std::vector< parser::ParseError > *outWarnings)
	Create a ComputedStopComponent for the given entity handle and its attached StopComponent, which applies CSS styling information and presentation attributes.
void	instantiateAllComputedComponents (Registry &registry, std::vector< parser::ParseError > *outWarnings)
	Create ComputedGradientComponent for all entities in the registry that have a GradientComponent.
void	createShadowTrees (Registry &registry, std::vector< parser::ParseError > *outWarnings)
	Create shadow trees for all gradient and pattern elements in the registry that have a valid href="" attribute.

Member Function Documentation

createComputedStop()

const ComputedStopComponent & donner::svg::components::PaintSystem::createComputedStop	(	EntityHandle	handle,
		const StopComponent &	stop,
		std::vector< parser::ParseError > *	outWarnings )

Create a ComputedStopComponent for the given entity handle and its attached StopComponent, which applies CSS styling information and presentation attributes.

Parameters

handle	Entity handle to create the computed gradient for
stop	Stop component attached to handle
outWarnings	Containing any warnings found

createShadowTrees()

void donner::svg::components::PaintSystem::createShadowTrees	(	Registry &	registry,
		std::vector< parser::ParseError > *	outWarnings )

Create shadow trees for all gradient and pattern elements in the registry that have a valid href="" attribute.

This must be called before instantiateAllComputedComponents.

Parameters

registry	Registry used to find all GradientComponent and PatternComponent components to compute shadow trees
outWarnings	Containing any warnings found

instantiateAllComputedComponents()

void donner::svg::components::PaintSystem::instantiateAllComputedComponents	(	Registry &	registry,
		std::vector< parser::ParseError > *	outWarnings )

Create ComputedGradientComponent for all entities in the registry that have a GradientComponent.

This assumes that createShadowTrees has already been called.

Note that this function does not produce any warnings, its signature is used to create a common API pattern.

Parameters

registry	Registry used to find all GradientComponent
outWarnings	Containing any warnings found

donner::svg::components::ShadowTreeSystem

class donner::svg::components::ShadowTreeSystem

Instantiates shadow trees for elements that are not part of the main render graph, such as "<use>" and "<pattern>" elements.

See also

https://www.w3.org/TR/SVG2/struct.html#UseShadowTree

https://www.w3.org/TR/SVG2/pservers.html#PaintServerTemplates

Public Member Functions
void	teardown (Registry &registry, ComputedShadowTreeComponent &shadow)
	Destroy the instantiated shadow tree.
std::optional< size_t >	populateInstance (EntityHandle entity, ComputedShadowTreeComponent &shadow, ShadowBranchType branchType, Entity lightTarget, const RcString &href, std::vector< parser::ParseError > *outWarnings)
	Create a new computed shadow tree instance, such as the shadow tree for a "<use>" element or a "<pattern>" element.

Member Function Documentation

populateInstance()

std::optional< size_t > donner::svg::components::ShadowTreeSystem::populateInstance	(	EntityHandle	entity,
		ComputedShadowTreeComponent &	shadow,
		ShadowBranchType	branchType,
		Entity	lightTarget,
		const RcString &	href,
		std::vector< parser::ParseError > *	outWarnings )

Create a new computed shadow tree instance, such as the shadow tree for a "<use>" element or a "<pattern>" element.

For "<pattern>" paint servers, there may be multiple shadow trees originating from the same entity, for both a 'fill' and a 'stroke', so this component can hold multiple shadow trees simultaneously.

Parameters

entity	The entity to create the shadow tree for.
shadow	The computed shadow tree component to populate.
branchType	Determines which branch of the tree to attach to. There may be multiple instances with a shadow tree, but only ShadowBranchType::Main will be traversed in the render tree.
lightTarget	Target entity to reflect in the shadow tree.
href	The value of the href attribute for the shadow tree, for diagnostics.
outWarnings	If provided, warnings will be added to this vector.

Returns

The index of the offscreen shadow tree, if branchType is not the ShadowBranchType::Main branch. Returns std::nullopt if it is.

teardown()

void donner::svg::components::ShadowTreeSystem::teardown	(	Registry &	registry,
		ComputedShadowTreeComponent &	shadow )

Destroy the instantiated shadow tree.

Parameters

registry	The registry.
shadow	The computed shadow tree component to tear down.

donner::svg::components::ShapeSystem

class donner::svg::components::ShapeSystem

Creates computed path for shapes such as "<circle>", "<line>", and "<path>".

See also

https://www.w3.org/TR/SVG2/shapes.html

Public Member Functions
template<typename T >
ComputedPathComponent *	createComputedPath (EntityHandle handle, const T &component, const FontMetrics &fontMetrics, std::vector< parser::ParseError > *outWarnings)
	Convert the given shape to a path, evaluating CSS styling information and presentation attributes.
ComputedPathComponent *	createComputedPathIfShape (EntityHandle handle, const FontMetrics &fontMetrics, std::vector< parser::ParseError > *outWarnings)
	Convert the given shape to a path, if the provided entity contains a shape.
void	instantiateAllComputedPaths (Registry &registry, std::vector< parser::ParseError > *outWarnings)
	Create ComputedPathComponent for all entities in the registry that have a shape component.
std::optional< Boxd >	getShapeBounds (EntityHandle handle)
	Get the bounds for the given entity in the entity's local space, if it has a shape component.
std::optional< Boxd >	getShapeWorldBounds (EntityHandle handle)
	Get the bounds for the given entity in world space, if it has a shape component.
bool	pathFillIntersects (EntityHandle handle, const Vector2d &point, FillRule fillRule)
	Returns true if the shape's path fill intersects the given point.
bool	pathStrokeIntersects (EntityHandle handle, const Vector2d &point, double strokeWidth)
	Returns true if the shape's path stroke intersects the given point, using an approximate computation from the stroke-width.

Member Function Documentation

createComputedPath()

template<typename T >

ComputedPathComponent * donner::svg::components::ShapeSystem::createComputedPath ( EntityHandle handle, const T & component, const FontMetrics & fontMetrics, std::vector< parser::ParseError > * outWarnings )

inline

Convert the given shape to a path, evaluating CSS styling information and presentation attributes.

Returns the ComputedPathComponent if the path was successfully created, or nullptr if the path could not be created.

Paths may not be created if the shape is invalid, such as a circle with a negative radius.

Suported components:

• CircleComponent
• EllipseComponent
• LineComponent
• PathComponent
• PolyComponent
• RectComponent

Parameters

handle	Entity handle to create the computed path for
component	Shape component attached to handle
fontMetrics	Font metrics, used to scale lengths
outWarnings	Containing any warnings found

createComputedPathIfShape()

ComputedPathComponent * donner::svg::components::ShapeSystem::createComputedPathIfShape	(	EntityHandle	handle,
		const FontMetrics &	fontMetrics,
		std::vector< parser::ParseError > *	outWarnings )

Convert the given shape to a path, if the provided entity contains a shape.

Returns the ComputedPathComponent if the path was successfully created, or nullptr if the path could not be created.

Paths may not be created if the shape is invalid, such as a circle with a negative radius.

Parameters

handle	Entity handle to create the computed path for
fontMetrics	Font metrics, used to scale lengths
outWarnings	Containing any warnings found

getShapeBounds()

std::optional< Boxd > donner::svg::components::ShapeSystem::getShapeBounds

(

EntityHandle

handle

)

Get the bounds for the given entity in the entity's local space, if it has a shape component.

Parameters

handle

Entity handle to get the bounds for

getShapeWorldBounds()

std::optional< Boxd > donner::svg::components::ShapeSystem::getShapeWorldBounds

(

EntityHandle

handle

)

Get the bounds for the given entity in world space, if it has a shape component.

Parameters

handle

Entity handle to get the bounds for

instantiateAllComputedPaths()

void donner::svg::components::ShapeSystem::instantiateAllComputedPaths	(	Registry &	registry,
		std::vector< parser::ParseError > *	outWarnings )

Create ComputedPathComponent for all entities in the registry that have a shape component.

This assumes that StyleSystem::computeAllStyles has already been called.

Parameters

registry	Registry used to find all shape components
outWarnings	Containing any warnings found

pathFillIntersects()

bool donner::svg::components::ShapeSystem::pathFillIntersects	(	EntityHandle	handle,
		const Vector2d &	point,
		FillRule	fillRule )

Returns true if the shape's path fill intersects the given point.

Parameters

handle	Entity handle containing the shape
point	Point to intersect
fillRule	Fill rule to use for the intersection test

pathStrokeIntersects()

bool donner::svg::components::ShapeSystem::pathStrokeIntersects	(	EntityHandle	handle,
		const Vector2d &	point,
		double	strokeWidth )

Returns true if the shape's path stroke intersects the given point, using an approximate computation from the stroke-width.

Parameters

handle	Entity handle containing the shape
point	Point to intersect
strokeWidth	Stroke width to use for the intersection test

donner::svg::components::StyleSystem

class donner::svg::components::StyleSystem

Computes stylesheet information for elements, applying the CSS cascade and inheritance rules.

See also

https://www.w3.org/TR/SVG2/shapes.html

Public Member Functions
const ComputedStyleComponent &	computeStyle (EntityHandle handle, std::vector< parser::ParseError > *outWarnings)
	Compute the style for the given entity handle, applying the CSS cascade and inheritance rules.
void	computeAllStyles (Registry &registry, std::vector< parser::ParseError > *outWarnings)
	Computes the style for all entities in the registry.
void	computeStylesFor (Registry &registry, std::span< const Entity > entities, std::vector< parser::ParseError > *outWarnings)
	Computes the style for the given entities in the registry.

Member Function Documentation

computeAllStyles()

void donner::svg::components::StyleSystem::computeAllStyles	(	Registry &	registry,
		std::vector< parser::ParseError > *	outWarnings )

Computes the style for all entities in the registry.

Parameters

registry	Registry to compute the styles, used to query for all entities in the tree.
outWarnings	Containing any warnings found

computeStyle()

const ComputedStyleComponent & donner::svg::components::StyleSystem::computeStyle	(	EntityHandle	handle,
		std::vector< parser::ParseError > *	outWarnings )

Compute the style for the given entity handle, applying the CSS cascade and inheritance rules.

Parameters

handle	Entity handle to compute the style for
outWarnings	Containing any warnings found

Returns

Computed style component for the entity

computeStylesFor()

void donner::svg::components::StyleSystem::computeStylesFor	(	Registry &	registry,
		std::span< const Entity >	entities,
		std::vector< parser::ParseError > *	outWarnings )

Computes the style for the given entities in the registry.

Parameters

registry	Registry containing the entities
entities	Entities to compute
outWarnings	Containing any warnings found