pulp::canvas::ViewEffect Class Reference

Base class for GPU post-processing effects. More...

#include <view_effect.hpp>

Public Member Functions
virtual	~ViewEffect ()=default
virtual void	configure_layer (Canvas &canvas, float x, float y, float w, float h)=0
	Push the compositing layer(s) this effect needs, configured with its opacity, image filters, blend mode, etc.
virtual int	layer_count () const
	How many layers configure_layer() pushes.
virtual bool	needs_layer () const
	Whether this effect requires a compositing layer (most do).
virtual void	paint_overlay (Canvas &canvas, float x, float y, float w, float h)
	Paint an overlay on TOP of the already-painted subtree, but still INSIDE the effect's compositing layer(s) (called by View::paint_all just before the layers are popped).

Detailed Description

Base class for GPU post-processing effects.

Effects are applied to a View's compositing layer (via save_layer/restore). The Canvas abstraction handles the GPU-side compositing; concrete effects configure the layer paint properties.

Constructor & Destructor Documentation

~ViewEffect()

virtual pulp::canvas::ViewEffect::~ViewEffect ( )

virtualdefault

Member Function Documentation

configure_layer()

virtual void pulp::canvas::ViewEffect::configure_layer ( Canvas & canvas, float x, float y, float w, float h )

pure virtual

Push the compositing layer(s) this effect needs, configured with its opacity, image filters, blend mode, etc.

The subtree paints into the layer(s); the caller pops them once the subtree is done.

An implementation MUST push exactly layer_count() layers. The caller (View::paint_all) pops that many, so an effect that saves a different number than it reports unbalances the canvas save stack for the rest of the frame.

Implemented in pulp::canvas::ChromaticAberrationEffect, pulp::canvas::EffectChain, pulp::canvas::GpuBloomEffect, pulp::canvas::GpuBlurEffect, pulp::canvas::SkslPostEffect, and pulp::canvas::VignetteEffect.

layer_count()

virtual int pulp::canvas::ViewEffect::layer_count ( ) const

inlinevirtual

How many layers configure_layer() pushes.

One for a simple effect; EffectChain reports the sum across its children.

Reimplemented in pulp::canvas::EffectChain.

needs_layer()

virtual bool pulp::canvas::ViewEffect::needs_layer ( ) const

inlinevirtual

Whether this effect requires a compositing layer (most do).

Reimplemented in pulp::canvas::EffectChain.

paint_overlay()

virtual void pulp::canvas::ViewEffect::paint_overlay ( Canvas & canvas, float x, float y, float w, float h )

inlinevirtual

Paint an overlay on TOP of the already-painted subtree, but still INSIDE the effect's compositing layer(s) (called by View::paint_all just before the layers are popped).

This is how an effect that darkens or tints the finished content — a vignette drawing a radial gradient — is implemented, instead of the wrong "reduce the whole layer's opacity" approximation. Default: nothing.

Limitation: the overlay draws into the innermost still-open layer. That is correct for a single effect (the only non-chain path today), but in a multi-effect EffectChain (e.g. [vignette, blur]) an earlier effect's overlay lands in a later effect's layer and is filtered by it. See the View::paint_all call site — revisit if overlays-in-chains are needed.

Reimplemented in pulp::canvas::EffectChain, and pulp::canvas::VignetteEffect.

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The documentation for this class was generated from the following file:

• /home/runner/work/pulp/pulp/core/canvas/include/pulp/canvas/view_effect.hpp