Module layer_composition 

Rules for when a graphics layer is drawn into its own offscreen buffer and with which alpha.

Structs

LayerIsolation

What a layer needs to be composited from its own offscreen buffer.

Functions

effective_layer_isolation

Returns what layer needs to be composited from its own buffer, or None when it can be drawn directly.

folded_layer_alpha

The alpha layer’s content draws with when the layer is drawn in place: its own, or the 8-bit alpha of the isolated composite it needs.

layer_composite_params

The composite alpha and blend mode an isolated layer contributes at its parent, for callers that never read the isolation’s render effect and would otherwise deep-clone it once per layer per frame.

layer_for_content

Returns the layer to draw the content with inside the offscreen buffer: layer with its alpha reset to one when isolation moves the alpha to the composite step.

layer_requires_isolation

Whether layer must be drawn into an offscreen buffer first, given its compositing strategy, effect, blend mode and alpha.

local_content_layer_for

The alpha and colour filter of layer_for_content(layer, isolation) folded in place, without building it. The content layer differs from layer only in the alpha the isolation moves to the composite step, and only that alpha and the colour filter pass to the content, so the two clones the composed form performs — one GraphicsLayer, one RenderEffect — are pure waste.