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Editorial review: Add documentation for Screen Capture extensions, element capture and region capture #36939

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Original file line number Diff line number Diff line change
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---
title: "BrowserCaptureMediaStreamTrack: clone() method"
short-title: clone()
slug: Web/API/BrowserCaptureMediaStreamTrack/clone
page-type: web-api-instance-method
status:
- experimental
browser-compat: api.BrowserCaptureMediaStreamTrack.clone
---

{{APIRef("Screen Capture API")}}{{SeeCompatTable}}{{securecontext_header}}

The **`clone()`** method of the {{domxref("BrowserCaptureMediaStreamTrack")}} interface returns a clone of the original `BrowserCaptureMediaStreamTrack`.

This method is functionally identical to {{domxref("MediaStreamTrack.clone()")}}, except that it handles cases where cropping or restriction have been applied to the track. The returned clone is identical to the original `BrowserCaptureMediaStreamTrack`, but with any cropping or restriction removed.
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The guide page says:

The element will not be cropped to if the track being cropped has clones or is not a track captured from the user's screen.

Is there anything we should capture in this API page about that?

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Note added


> [!NOTE]
> When attempting to crop a captured stream using {{domxref("BrowserCaptureMediaStreamTrack.cropTo", "cropTo()")}} or restrict it using {{domxref("BrowserCaptureMediaStreamTrack.restrictTo", "restrictTo()")}}, elements will not be cropped or restricted to if the track being captured has clones.
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Should we instead say something like: "If a track has clones, its cropTo() and restrictTo() will reject with an error." I think this is clearer than "elements will not be cropped or restricted to".

Also I couldn't see a source for this in the specification.

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See https://developer.chrome.com/docs/web-platform/element-capture#restricting and https://developer.chrome.com/docs/web-platform/region-capture#cropping. I don't think it is in the spec, rather it is a current technical limitation they are trying to work around. But I'm not sure if it is helpful to separate this information out as a result.

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Thanks for the info! It's usually our practice to distinguish between restrictions that are intentional per spec and browser bugs, and I think we ought to do that here, too.

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OK, done!


## Syntax

```js-nolint
clone()
```

### Parameters

None.

### Return value

A {{domxref("BrowserCaptureMediaStreamTrack")}} instance.

## Examples

```js
// Options for getDisplayMedia()
const displayMediaOptions = {
preferCurrentTab: true,
};

// Create crop target from DOM element
const demoElem = document.querySelector("#demo");
const cropTarget = await CropTarget.fromElement(demoElem);

// Capture video stream from user's webcam and isolate video track
const stream =
await navigator.mediaDevices.getDisplayMedia(displayMediaOptions);
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const [track] = stream.getVideoTracks();

// Crop video track
await track.cropTo(cropTarget);

// Create uncropped clone of the track
const clonedTrack = track.clone();
```

## Specifications

{{Specifications}}

## Browser compatibility

{{Compat}}

## See also

- [Screen Capture API](/en-US/docs/Web/API/Screen_Capture_API)
- [Using the Element Capture and Region Capture APIs](/en-US/docs/Web/API/Screen_Capture_API/Element_Region_Capture)
Original file line number Diff line number Diff line change
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---
title: "BrowserCaptureMediaStreamTrack: cropTo() method"
short-title: cropTo()
slug: Web/API/BrowserCaptureMediaStreamTrack/cropTo
page-type: web-api-instance-method
status:
- experimental
browser-compat: api.BrowserCaptureMediaStreamTrack.cropTo
---

{{APIRef("Screen Capture API")}}{{SeeCompatTable}}{{securecontext_header}}

The **`cropTo()`** method of the {{domxref("BrowserCaptureMediaStreamTrack")}} interface crops a self-capture stream to the area in which a specified DOM element is rendered.

## Syntax

```js-nolint
cropTo(cropTarget)
```

### Parameters

- `cropTarget`
- : A {{domxref("CropTarget")}} instance representing the element rendering area the stream should be cropped to, or `null`/`undefined`, in which case any previously-set cropping is removed from the track.
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### Return value

A {{jsxref("Promise")}} that resolves to {{jsxref("undefined")}}.

The promise will reject if:

- The track [`kind`](/en-US/docs/Web/API/MediaStreamTrack/kind) is not `"video"`, or its [`readyState`](/en-US/docs/Web/API/MediaStreamTrack/readyState) is not `"live"`.
- The crop target element no longer exists.
- The track being cropped has clones or is not a track captured from the user's screen.
- `CropTarget` is not a {{domxref("CropTarget")}} instance, `null`, or `undefined`.
- `CropTarget` was created in a tab other than the one being captured.
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Same question as in the guide page, how is this possible?

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same as other page; deleted!


## Examples

### Basic cropping example

```js
// Options for getDisplayMedia()
const displayMediaOptions = {
preferCurrentTab: true,
};

// Create crop target from DOM element
const demoElem = document.querySelector("#demo");
const cropTarget = await CropTarget.fromElement(demoElem);

// Capture video stream from user's webcam and isolate video track
const stream =
await navigator.mediaDevices.getDisplayMedia(displayMediaOptions);
const [track] = stream.getVideoTracks();

// Crop video track
await track.cropTo(cropTarget);

// Broadcast cropped stream in <video> element
videoElem.srcObject = stream;
```

See [Using the Element Capture and Region Capture APIs](/en-US/docs/Web/API/Screen_Capture_API/Element_Region_Capture) for in-context example code.

### Stopping the cropping

You can stop the cropping by making a call to `cropTo()` on a previously-cropped track, passing an argument of `null` to it:

```js
// Stop cropping
await track.cropTo(null);
```

## Specifications

{{Specifications}}

## Browser compatibility

{{Compat}}

## See also

- [Screen Capture API](/en-US/docs/Web/API/Screen_Capture_API)
- [Using the Element Capture and Region Capture APIs](/en-US/docs/Web/API/Screen_Capture_API/Element_Region_Capture)
40 changes: 40 additions & 0 deletions files/en-us/web/api/browsercapturemediastreamtrack/index.md
Original file line number Diff line number Diff line change
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---
title: BrowserCaptureMediaStreamTrack
slug: Web/API/BrowserCaptureMediaStreamTrack
page-type: web-api-interface
status:
- experimental
browser-compat: api.BrowserCaptureMediaStreamTrack
---

{{APIRef("Screen Capture API")}}{{SeeCompatTable}}

The **`BrowserCaptureMediaStreamTrack`** interface of the {{domxref("Screen Capture API", "Screen Capture API", "", "nocode")}} represents a single video track. It extends the {{domxref("MediaStreamTrack")}} class with methods to limit the part of a self-capture stream (for example, a user's screen or window) that is captured.

{{InheritanceDiagram}}

## Instance methods

- {{domxref("BrowserCaptureMediaStreamTrack.clone", "clone()")}} {{Experimental_Inline}}
- : Returns an uncropped, unrestricted clone of the original `BrowserCaptureMediaStreamTrack`.
- {{domxref("BrowserCaptureMediaStreamTrack.cropTo", "cropTo()")}} {{Experimental_Inline}}
- : Crops a self-capture stream to the area in which a specified DOM element is rendered.
- {{domxref("BrowserCaptureMediaStreamTrack.restrictTo", "restrictTo()")}} {{Experimental_Inline}}
- : Restricts a self-capture stream to a specific DOM element.

## Examples

See [Using the Element Capture and Region Capture APIs](/en-US/docs/Web/API/Screen_Capture_API/Element_Region_Capture) for in-context example code.

## Specifications

{{Specifications}}

## Browser compatibility

{{Compat}}

## See also

- [Screen Capture API](/en-US/docs/Web/API/Screen_Capture_API)
- [Using the Element Capture and Region Capture APIs](/en-US/docs/Web/API/Screen_Capture_API/Element_Region_Capture)
Original file line number Diff line number Diff line change
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---
title: "BrowserCaptureMediaStreamTrack: restrictTo() method"
short-title: restrictTo()
slug: Web/API/BrowserCaptureMediaStreamTrack/restrictTo
page-type: web-api-instance-method
browser-compat: api.BrowserCaptureMediaStreamTrack.restrictTo
---

{{APIRef("Screen Capture API")}}{{SeeCompatTable}}{{securecontext_header}}

The **`restrictTo()`** method of the {{domxref("BrowserCaptureMediaStreamTrack")}} interface restricts a self-capture stream to a specific DOM element (and its descendants).

## Syntax

```js-nolint
restrictTo(restrictionTarget)
```

### Parameters

- `restrictionTarget`
- : A {{domxref("RestrictionTarget")}} instance representing the element the stream should be restricted to, or `null`/`undefined`, in which case any previously-set restriction is removed from the track.
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### Return value

A {{jsxref("Promise")}} that resolves to {{jsxref("undefined")}}.

The promise will reject if:

- The track [`kind`](/en-US/docs/Web/API/MediaStreamTrack/kind) is not `"video"`, or its [`readyState`](/en-US/docs/Web/API/MediaStreamTrack/readyState) is not `"live"`.
- The restriction target element no longer exists.
- The track being restricted has clones or is not a track captured from the user's screen.
- `RestrictionTarget` is not a {{domxref("RestrictionTarget")}} instance, `null`, or `undefined`.
- `RestrictionTarget` was created in a tab other than the one being captured.

## Examples

### Basic restriction example

```js
// Options for getDisplayMedia()
const displayMediaOptions = {
preferCurrentTab: true,
};

// Create restriction target from DOM element
const demoElem = document.querySelector("#demo");
const restrictionTarget = await RestrictionTarget.fromElement(demoElem);

// Capture video stream from user's webcam and isolate video track
const stream =
await navigator.mediaDevices.getDisplayMedia(displayMediaOptions);
const [track] = stream.getVideoTracks();

// Restrict video track
await track.restrictTo(restrictionTarget);

// Broadcast restricted stream in <video> element
videoElem.srcObject = stream;
```

See [Using the Element Capture and Region Capture APIs](/en-US/docs/Web/API/Screen_Capture_API/Element_Region_Capture) for in-context example code.

### Stopping the restriction

You can stop the restriction by making a call to `restrictTo()` on the same track, passing an argument of `null` to it:

```js
// Stop restricting
await track.restrictTo(null);
```

## Specifications

{{Specifications}}

## Browser compatibility

{{Compat}}

## See also

- [Screen Capture API](/en-US/docs/Web/API/Screen_Capture_API)
- [Using the Element Capture and Region Capture APIs](/en-US/docs/Web/API/Screen_Capture_API/Element_Region_Capture)
67 changes: 67 additions & 0 deletions files/en-us/web/api/croptarget/fromelement_static/index.md
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---
title: "CropTarget: fromElement() static method"
short-title: fromElement()
slug: Web/API/CropTarget/fromElement_static
page-type: web-api-static-method
browser-compat: api.CropTarget.fromElement_static
---

{{APIRef("Screen Capture API")}}{{SeeCompatTable}}{{securecontext_header}}

The **`fromElement()`** static method of the {{domxref("CropTarget")}} interface returns a `CropTarget` instance that can be used to crop a captured video track to the area in which a specified element is rendered.

## Syntax

```js-nolint
CropTarget.fromElement(element)
```

### Parameters

- `element`
- : A reference to an {{domxref("Element")}} that you want to use as a crop target.

### Return value

A {{jsxref("Promise")}} that resolves to a {{domxref("CropTarget")}} object instance, which can then be passed to {{domxref("BrowserCaptureMediaStreamTrack.CropTo()")}} to crop the video captured in the track to just the area the specified DOM element is rendered in.

`CropTarget` objects are serializable. They can be passed to another document using {{domxref("Window.postMessage()")}}, for example.
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Oh I suppose that's how it would be possible to get one from another tab!

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Dammmnit. I've added those details back in on the reference pages.

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Yes, sorry about this! But please see also #36939 (comment).


## Examples

```js
// Options for getDisplayMedia()
const displayMediaOptions = {
preferCurrentTab: true,
};

// Create crop target from DOM element
const demoElem = document.querySelector("#demo");
const cropTarget = await CropTarget.fromElement(demoElem);

// Capture video stream from user's webcam and isolate video track
const stream =
await navigator.mediaDevices.getDisplayMedia(displayMediaOptions);
const [track] = stream.getVideoTracks();

// Crop video track
await track.cropTo(cropTarget);

// Broadcast cropped stream in <video> element
videoElem.srcObject = stream;
```

See [Using the Element Capture and Region Capture APIs](/en-US/docs/Web/API/Screen_Capture_API/Element_Region_Capture) for in-context example code.

## Specifications

{{Specifications}}

## Browser compatibility

{{Compat}}

## See also

- [Screen Capture API](/en-US/docs/Web/API/Screen_Capture_API)
- [Using the Element Capture and Region Capture APIs](/en-US/docs/Web/API/Screen_Capture_API/Element_Region_Capture)
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