Chrome DevTools Protocol

Methods

HeadlessExperimental.beginFrame

Sends a BeginFrame to the target and returns when the frame was completed. Optionally captures a screenshot from the resulting frame. Requires that the target was created with enabled BeginFrameControl. Designed for use with --run-all-compositor-stages-before-draw, see also https://goo.gl/3zHXhB for more background.

parameters
frameTimeTicks
number

Timestamp of this BeginFrame in Renderer TimeTicks (milliseconds of uptime). If not set, the current time will be used.

interval
number

The interval between BeginFrames that is reported to the compositor, in milliseconds. Defaults to a 60 frames/second interval, i.e. about 16.666 milliseconds.

noDisplayUpdates
boolean

Whether updates should not be committed and drawn onto the display. False by default. If true, only side effects of the BeginFrame will be run, such as layout and animations, but any visual updates may not be visible on the display or in screenshots.

screenshot
ScreenshotParams

If set, a screenshot of the frame will be captured and returned in the response. Otherwise, no screenshot will be captured. Note that capturing a screenshot can fail, for example, during renderer initialization. In such a case, no screenshot data will be returned.

Return Object
hasDamage
boolean

Whether the BeginFrame resulted in damage and, thus, a new frame was committed to the display. Reported for diagnostic uses, may be removed in the future.

screenshotData
string

Base64-encoded image data of the screenshot, if one was requested and successfully taken.

HeadlessExperimental.disable

Disables headless events for the target.

HeadlessExperimental.enable

Enables headless events for the target.

Events

HeadlessExperimental.needsBeginFramesChanged Deprecated

Issued when the target starts or stops needing BeginFrames. Deprecated. Issue beginFrame unconditionally instead and use result from beginFrame to detect whether the frames were suppressed.

parameters
needsBeginFrames
boolean

True if BeginFrames are needed, false otherwise.

Types

HeadlessExperimental.ScreenshotParams

Encoding options for a screenshot.

Type: object

properties
format
string

Image compression format (defaults to png).

Allowed Values: jpeg, png
quality
integer

Compression quality from range [0..100] (jpeg only).