Interface ICanvas3
interface ICanvas3
Extends ICanvas2
ICanvas3 interface extends ICanvas2 with support for backdrop filtering via SaveLayerConfig.
It defines a new ::saveLayerWithConfig method that accepts a SaveLayerConfig data object
to configure layer allocation with optional bounds, paint, and backdrop filter parameters.
See graphics-Canvas_UserGuide.md for details.
Methods
saveLayerWithConfig()
This method behaves the same asu32saveLayerWithConfig(SaveLayerConfig*config)
ICanvas::save, but in addition it allocates and redirects drawing to an
offscreen rendering target. When the balancing call to ICanvas::restore is made, the offscreen buffer is
drawn back to the current target of the ICanvas (which can potentially be a previous layer if these
calls are nested).
Unlike ICanvas2::saveLayer, this method accepts a SaveLayerConfig struct that groups all optional
parameters and adds support for backdrop filtering. When SaveLayerConfig::backdropFilter is set, existing
content behind the layer is filtered (e.g., blurred) before new content is drawn on top. Content drawn between
this call and ICanvas::restore appears unfiltered on top of the filtered backdrop.
To constrain the backdrop filter region, apply ICanvas::clipRect or ICanvas::clipRRect before
calling this method, as SaveLayerConfig::bounds is ignored when a backdrop filter is present.
Parameters
config
SaveLayerConfig* — Required
The SaveLayerConfig specifying optional bounds, paint, and backdrop filter.
Individual fields within the config may be null.
Returns
u32
A save count identifier for restoring this layer state by passing it to ICanvas::restoreToCount.
