Add "emulation.setScreenAreaOverride" command.

Author: lutien

index.bs

@@ -285,6 +285,7 @@ spec: CSSOM-VIEW; urlPrefix: https://drafts.csswg.org/cssom-view/
     text: visual viewport page left; url: #dom-visualviewport-pageleft
     text: visual viewport page top; url: #dom-visualviewport-pagetop
     text: visual viewport; url: #visual-viewport
+    text: web-exposed available screen area; url: #web-exposed-available-screen-area
     text: web-exposed screen area; url: #web-exposed-screen-area
 spec: DOM; urlPrefix: https://dom.spec.whatwg.org/
   type: dfn
@@ -3210,6 +3211,15 @@ A [=remote end=] has a <dfn>viewport overrides map</dfn> which is a weak map bet
 A [=remote end=] has a <dfn>locale overrides map</dfn> which is a weak map between
 [=navigables=] or [=user contexts=] and string.
 
+A <dfn>screen area</dfn> is a [=struct=] with an [=struct/item=] named
+<dfn attribute for="screen area">height</dfn> which is an integer,
+a [=struct/item=] named <dfn attribute for="screen area">width</dfn> which is an integer,
+a [=struct/item=] named <dfn attribute for="screen area">x</dfn> which is an integer,
+a [=struct/item=] named <dfn attribute for="screen area">y</dfn> which is an integer.
+
+A [=remote end=] has a <dfn>screen area overrides map</dfn> which is a weak map between
+[=navigables=] or [=user contexts=] and [=screen area=].
+
 A [=remote end=] has a <dfn>timezone overrides map</dfn> which is a weak map between
 [=navigables=] or [=user contexts=] and string.
 
@@ -6445,6 +6455,116 @@ The [=remote end steps=] with |command parameters| and |session| are:
 
 </div>
 
+#### The emulation.setScreenAreaOverride Command ####  {#command-emulation-setScreenAreaOverride}
+
+The <dfn export for=commands>emulation.setScreenAreaOverride</dfn> command
+emulates [=web-exposed screen area=] and [=web-exposed available screen area=] of the given top-level traversables or user contexts.
+
+<dl>
+   <dt>Command Type</dt>
+   <dd>
+    <pre class="cddl" data-cddl-module="remote-cddl">
+      emulation.SetScreenAreaOverride = (
+        method: "emulation.setScreenAreaOverride",
+        params: emulation.SetScreenAreaOverrideParameters
+      )
+
+      emulation.ScreenArea = {
+        width: js-uint,
+        height: js-uint
+      }
+
+      emulation.SetScreenAreaOverrideParameters = {
+        screenArea: emulation.ScreenArea / null,
+        ? contexts: [+browsingContext.BrowsingContext],
+        ? userContexts: [+browser.UserContext],
+      }
+    </pre>
+   </dd>
+   <dt>Return Type</dt>
+   <dd>
+      <pre class="cddl" data-cddl-module="local-cddl">
+      emulation.SetScreenAreaOverrideResult = EmptyResult
+      </pre>
+   </dd>
+</dl>
+
+<div algorithm>
+
+The <dfn export>WebDriver BiDi emulated screen area</dfn> steps given a given [=/navigable=] |navigable|:
+
+1. Let |top-level traversable| be |navigable|’s [=navigable/top-level traversable=].
+
+1. Let |user context| be |top-level traversable|'s [=associated user context=].
+
+1. If [=screen area overrides map=] [=map/contains=] |top-level traversable|, return
+   [=screen area overrides map=][|top-level traversable|].
+
+1. If [=screen area overrides map=] [=map/contains=] |user context|, return
+   [=screen area overrides map=][|user context|].
+
+1. Return null
+
+</div>
+
+<div algorithm="remote end steps for emulation.setScreenAreaOverride">
+
+The [=remote end steps=] with |command parameters| are:
+
+1. If |command parameters| [=map/contains=] "<code>userContexts</code>"
+   and |command parameters| [=map/contains=] "<code>contexts</code>",
+   return [=error=] with [=error code=] [=invalid argument=].
+
+1. If |command parameters| doesn't [=map/contain=] "<code>userContexts</code>"
+   and |command parameters| doesn't [=map/contain=] "<code>contexts</code>",
+   return [=error=] with [=error code=] [=invalid argument=].
+
+1. Let |emulated screen area| be |command parameters|["<code>screenArea</code>"].
+
+1. If |emulated screen area| is not null:
+
+   1. [=map/Set=] |emulated screen area|["<code>x</code>"] to 0.
+
+   1. [=map/Set=] |emulated screen area|["<code>y</code>"] to 0.
+
+1. Let |navigables| be a [=/set=].
+
+1. If the <code>contexts</code> field of |command parameters| is present:
+
+   1. Let |navigables| be the result of [=trying=] to
+      [=get valid top-level traversables by ids=] with
+      |command parameters|["<code>contexts</code>"].
+
+1. Otherwise:
+
+   1. Assert the <code>userContexts</code> field of |command parameters| is present.
+
+   1. Let |user contexts| be the result of [=trying=] to [=get valid user contexts=]
+      with |command parameters|["<code>userContexts</code>"].
+
+   1. For each |user context| of |user contexts|:
+
+      1. If |emulated screen area| is null, [=map/remove=] |user context| from
+         [=screen area overrides map=].
+
+      1. Otherwise, [=map/set=] [=screen area overrides map=][|user context|] to |emulated screen area|.
+
+      1. [=list/For each=] |top-level traversable| of the list of all
+         [=/top-level traversables=] whose [=associated user context=] is
+         |user context|:
+
+         1. [=list/Append=] |top-level traversable| to |navigables|.
+
+1. For each |navigable| of |navigables|:
+
+   1. If |emulated screen area| is null, [=map/remove=] |navigable| from [=screen area overrides map=].
+
+   1. Otherwise, [=map/set=] [=screen area overrides map=][|navigable|] to |emulated screen area|.
+
+1. Return [=success=] with data null.
+
+</div>
+
 #### The emulation.setScreenOrientationOverride Command ####  {#command-emulation-setScreenOrientationOverride}
 
 The <dfn export for=commands>emulation.setScreenOrientationOverride</dfn> command