Chrome DevTools Protocol

Methods

LayerTree.compositingReasons

Provides the reasons why the given layer was composited.

parameters
layerId
LayerId

The id of the layer for which we want to get the reasons it was composited.

Return Object
compositingReasons
array[ string ]

A list of strings specifying reasons for the given layer to become composited.

Deprecated
compositingReasonIds
array[ string ]

A list of strings specifying reason IDs for the given layer to become composited.

LayerTree.disable

Disables compositing tree inspection.

LayerTree.enable

Enables compositing tree inspection.

LayerTree.loadSnapshot

Returns the snapshot identifier.

parameters
tiles
array[ PictureTile ]

An array of tiles composing the snapshot.

Return Object
snapshotId
SnapshotId

The id of the snapshot.

LayerTree.makeSnapshot

Returns the layer snapshot identifier.

parameters
layerId
LayerId

The id of the layer.

Return Object
snapshotId
SnapshotId

The id of the layer snapshot.

LayerTree.profileSnapshot

parameters
snapshotId
SnapshotId

The id of the layer snapshot.

minRepeatCount
integer

The maximum number of times to replay the snapshot (1, if not specified).

minDuration
number

The minimum duration (in seconds) to replay the snapshot.

clipRect
DOM.Rect

The clip rectangle to apply when replaying the snapshot.

Return Object
timings
array[ PaintProfile ]

The array of paint profiles, one per run.

LayerTree.releaseSnapshot

Releases layer snapshot captured by the back-end.

parameters
snapshotId
SnapshotId

The id of the layer snapshot.

LayerTree.replaySnapshot

Replays the layer snapshot and returns the resulting bitmap.

parameters
snapshotId
SnapshotId

The id of the layer snapshot.

fromStep
integer

The first step to replay from (replay from the very start if not specified).

toStep
integer

The last step to replay to (replay till the end if not specified).

scale
number

The scale to apply while replaying (defaults to 1).

Return Object
dataURL
string

A data: URL for resulting image.

LayerTree.snapshotCommandLog

Replays the layer snapshot and returns canvas log.

parameters
snapshotId
SnapshotId

The id of the layer snapshot.

Return Object
commandLog
array[ object ]

The array of canvas function calls.

Events

LayerTree.layerPainted

parameters
layerId
LayerId

The id of the painted layer.

clip
DOM.Rect

Clip rectangle.

LayerTree.layerTreeDidChange

parameters
layers
array[ Layer ]

Layer tree, absent if not in the comspositing mode.

Types

LayerTree.Layer

Information about a compositing layer.

Type: object

properties
layerId
LayerId

The unique id for this layer.

parentLayerId
LayerId

The id of parent (not present for root).

backendNodeId
DOM.BackendNodeId

The backend id for the node associated with this layer.

offsetX
number

Offset from parent layer, X coordinate.

offsetY
number

Offset from parent layer, Y coordinate.

width
number

Layer width.

height
number

Layer height.

transform
array[ number ]

Transformation matrix for layer, default is identity matrix

anchorX
number

Transform anchor point X, absent if no transform specified

anchorY
number

Transform anchor point Y, absent if no transform specified

anchorZ
number

Transform anchor point Z, absent if no transform specified

paintCount
integer

Indicates how many time this layer has painted.

drawsContent
boolean

Indicates whether this layer hosts any content, rather than being used for transform/scrolling purposes only.

invisible
boolean

Set if layer is not visible.

scrollRects
array[ ScrollRect ]

Rectangles scrolling on main thread only.

stickyPositionConstraint
StickyPositionConstraint

Sticky position constraint information

LayerTree.LayerId

Unique Layer identifier.

Type: string

LayerTree.PaintProfile

Array of timings, one per paint step.

Type: array

LayerTree.PictureTile

Serialized fragment of layer picture along with its offset within the layer.

Type: object

properties
x
number

Offset from owning layer left boundary

y
number

Offset from owning layer top boundary

picture
string

Base64-encoded snapshot data.

LayerTree.ScrollRect

Rectangle where scrolling happens on the main thread.

Type: object

properties
rect
DOM.Rect

Rectangle itself.

type
string

Reason for rectangle to force scrolling on the main thread

Allowed Values: RepaintsOnScroll, TouchEventHandler, WheelEventHandler

LayerTree.SnapshotId

Unique snapshot identifier.

Type: string

LayerTree.StickyPositionConstraint

Sticky position constraints.

Type: object

properties
stickyBoxRect
DOM.Rect

Layout rectangle of the sticky element before being shifted

containingBlockRect
DOM.Rect

Layout rectangle of the containing block of the sticky element

nearestLayerShiftingStickyBox
LayerId

The nearest sticky layer that shifts the sticky box

nearestLayerShiftingContainingBlock
LayerId

The nearest sticky layer that shifts the containing block