[css-view-transitions-1] Replace 'snapshot viewport' with 'snapshot root' (w3c#8324)

* [CSS-VIEW-TRANSITIONS] Replace 'snapshot viewport' with 'snapshot root'

Author: bokand

css-view-transitions-1/Overview.bs

@@ -246,7 +246,7 @@ urlPrefix: https://html.spec.whatwg.org/multipage/rendering.html; type: dfn;
 		a [=pseudo-element root=].
 		Its [=originating element=] is the document's [=document element=].
 
-		Its [=containing block=] is the [=snapshot viewport=].
+		Its [=containing block=] is the [=snapshot root=].
 
 		The following is added to the [=HTML user agent style sheet=]:
 
@@ -259,8 +259,8 @@ urlPrefix: https://html.spec.whatwg.org/multipage/rendering.html; type: dfn;
 
 		<div class="note">
 			This pseudo-element provides a containing block for all ''::view-transition-group()'' pseudo-elements.
-			The aim of the style is to size the pseudo-element to cover the [=snapshot viewport=]
-			and position all ''::view-transition-group()'' pseudo-elements relative to the [=snapshot viewport origin=].
+			The aim of the style is to size the pseudo-element to cover the [=snapshot root=]
+			and position all ''::view-transition-group()'' pseudo-elements relative to the [=snapshot root origin=].
 		</div>
 
 	: <dfn>::view-transition-group( <<pt-name-selector>> )</dfn>
@@ -363,39 +363,39 @@ urlPrefix: https://html.spec.whatwg.org/multipage/rendering.html; type: dfn;
 
 	The initial phase is the first item in the sequence.
 
-## The snapshot viewport ## {#snapshot-viewport-concept}
+## The snapshot root ## {#snapshot-root-concept}
 
-	The <dfn>snapshot viewport</dfn> covers all areas of the window that could potentially display web content.
+	The <dfn>snapshot root</dfn> is a rectangle that covers all areas of the window that could potentially display web content.
 	This area is consistent regardless of root scrollbars or interactive widgets.
 
 	Issue: "Interactive widgets" refers to UI described within a property definition in [[css-viewport#interactive-widget-section]].
 	This should be extracted into an exported definition that can be used independently of the property.
 
 	<figure>
 		<img src="diagrams/phone-browser.svg" width="200" height="335" alt="A diagram of a phone screen, including a top status bar, a browser URL bar, web-content area with a floating scrollbar, a virtual keyboard, and a bottom bar with an OS back button">
-		<img src="diagrams/phone-browser-snapshot-viewport.svg" width="200" height="335" alt="The previous diagram, but highlights the area that's the 'snapshot' viewport, which includes everything except the top status bar and the bottom bar with the OS back button">
+		<img src="diagrams/phone-browser-snapshot-root.svg" width="200" height="335" alt="The previous diagram, but highlights the area that's the 'snapshot root', which includes everything except the top status bar and the bottom bar with the OS back button">
 		<figcaption>
-			An example of the [=snapshot viewport=] on a mobile OS.
+			An example of the [=snapshot root=] on a mobile OS.
 			The snapshot includes the URL bar, as this can be scrolled away.
 			The keyboard is included as this appears and disappears.
-			The top and bottom bars are part of the OS rather than the browser, so they're not included in the snapshot viewport.
+			The top and bottom bars are part of the OS rather than the browser, so they're not included in the snapshot root.
 		</figcaption>
 	</figure>
 
 	<figure>
 		<img src="diagrams/desktop-browser.svg" width="132" height="79" alt="A diagram of a desktop browser window, including a tab bar, a URL bar, and a web-content area featuring both horizontal and vertical scrollbars" style="height:auto; width: 600px">
-		<img src="diagrams/desktop-browser-snapshot-viewport.svg" width="132" height="79" alt="The previous diagram, but highlights the area that's the 'snapshot' viewport, which includes the web content area and the scrollbars" style="height:auto; width: 600px">
+		<img src="diagrams/desktop-browser-snapshot-root.svg" width="132" height="79" alt="The previous diagram, but highlights the area that's the 'snapshot root', which includes the web content area and the scrollbars" style="height:auto; width: 600px">
 		<figcaption>
-			An example of the [=snapshot viewport=] on a desktop OS.
+			An example of the [=snapshot root=] on a desktop OS.
 			This includes the scrollbars, but does not include the URL bar, as web content never appears in that area.
 		</figcaption>
 	</figure>
 
 	This means the snapshot canvas size is likely to be consistent for the [=document element=]'s [=captured element/old image=] and [=captured element/new element=].
 
-	The <dfn>snapshot viewport origin</dfn> refers to the start of the block and inline axes of the [=snapshot viewport=].
+	The <dfn>snapshot root origin</dfn> refers to the top-left corner of the [=snapshot root=].
 
-	The <dfn>snapshot viewport size</dfn> refers to the width and height of the [=snapshot viewport=] as a [=/tuple=] of two numbers.
+	The <dfn>snapshot root size</dfn> refers to the width and height of the [=snapshot root=] as a [=/tuple=] of two numbers.
 
 ## The [=view-transition layer=] stacking layer ## {#view-transition-stacking-layer}
 
@@ -493,7 +493,7 @@ urlPrefix: https://html.spec.whatwg.org/multipage/rendering.html; type: dfn;
 			When this is true, [=this=]'s [=active DOM transition=]'s [=ViewTransition/transition root pseudo-element=] renders as a child of [=this=]'s [=document element=],
 			and [=this=]'s [=document element=] is its [=originating element=].
 
-			Note: The position of the [=ViewTransition/transition root pseudo-element=] within the [=document element=] does not matter, as the [=ViewTransition/transition root pseudo-element=]'s [=containing block=] is the [=snapshot viewport=].
+			Note: The position of the [=ViewTransition/transition root pseudo-element=] within the [=document element=] does not matter, as the [=ViewTransition/transition root pseudo-element=]'s [=containing block=] is the [=snapshot root=].
 	</dl>
 
 # API # {#api}
@@ -642,11 +642,11 @@ urlPrefix: https://html.spec.whatwg.org/multipage/rendering.html; type: dfn;
 		:: a ''::view-transition''.
 			Initially a new ''::view-transition''.
 
-		: <dfn>initial snapshot viewport size</dfn>
+		: <dfn>initial snapshot root size</dfn>
 		:: a [=tuple=] of two numbers (width and height), or null.
 			Initially null.
 
-			Note: This is used to detect changes in the [=snapshot viewport size=],
+			Note: This is used to detect changes in the [=snapshot root size=],
 			which causes the transition to [=skip the view transition|skip=].
 			[Discussion of this behavior](https://github.com/w3c/csswg-drafts/issues/8045).
 	</dl>
@@ -725,7 +725,7 @@ urlPrefix: https://html.spec.whatwg.org/multipage/rendering.html; type: dfn;
 
 		1. Let |document| be |transition|'s [=relevant global object's=] [=associated document=].
 
-		1. Set |transition|'s [=ViewTransition/initial snapshot viewport size=] to the [=snapshot viewport size=].
+		1. Set |transition|'s [=ViewTransition/initial snapshot root size=] to the [=snapshot root size=].
 
 		1. [=list/For each=] |element| of every {{Element}} and [=pseudo-element=] connected to |document|,
 			in [paint order](https://drafts.csswg.org/css2/#painting-order):
@@ -762,13 +762,13 @@ urlPrefix: https://html.spec.whatwg.org/multipage/rendering.html; type: dfn;
 			1. Set |capture|'s [=captured element/old styles=] to the following:
 
 				: 'transform'
-				:: A CSS transform that would place |element|
-					from the [=snapshot viewport origin=] to its current quad.
+				:: A transform that would map |element|'s [=border box=] from
+					the [=snapshot root origin=] to its current visual position.
 				:: This value is identity for the [=document element=].
 
 				: 'width'
 				: 'height'
-				:: The size of the [=snapshot viewport=] if |element| is the [=document element=],
+				:: The size of the [=snapshot root=] if |element| is the [=document element=],
 					otherwise, the width and height of |element|'s border box.
 
 				: 'object-view-box'
@@ -820,7 +820,7 @@ urlPrefix: https://html.spec.whatwg.org/multipage/rendering.html; type: dfn;
 
 						Note: This happens if |transition| was [=skip the view transition|skipped=] before this point.
 
-					1. If |transition|'s [=ViewTransition/initial snapshot viewport size=] is not equal to the [=snapshot viewport size=],
+					1. If |transition|'s [=ViewTransition/initial snapshot root size=] is not equal to the [=snapshot root size=],
 						then [=skip the view transition=] for |transition|, and return.
 
 					1. Set [=document/transition suppressing rendering=] to false.
@@ -923,8 +923,8 @@ urlPrefix: https://html.spec.whatwg.org/multipage/rendering.html; type: dfn;
 
 		1. If |element| is the [=document element=], then:
 
-			1. Render the region of the |element| and the [=top layer=] that intersects the [=snapshot viewport=],
-				on a transparent canvas the size of the [=snapshot viewport=],
+			1. Render the region of the |element| and the [=top layer=] that intersects the [=snapshot root=],
+				on a transparent canvas the size of the [=snapshot root=],
 				following the [=capture rendering characteristics=], and these additional characteristics:
 
 				- Areas outside |element|'s [=scrolling box=] should be rendered as if they were scrolled to, without moving or resizing the [=layout viewport=].
@@ -954,7 +954,7 @@ urlPrefix: https://html.spec.whatwg.org/multipage/rendering.html; type: dfn;
 					</figure>
 
 			1. Return the canvas as an image.
-				The natural size of the image is equal to the [=snapshot viewport=].
+				The natural size of the image is equal to the [=snapshot root=].
 
 		1. Otherwise:
 
@@ -1029,7 +1029,7 @@ urlPrefix: https://html.spec.whatwg.org/multipage/rendering.html; type: dfn;
 
 			1. Return.
 
-		1. If |transition|'s [=ViewTransition/initial snapshot viewport size=] is not equal to the [=snapshot viewport size=],
+		1. If |transition|'s [=ViewTransition/initial snapshot root size=] is not equal to the [=snapshot root size=],
 			then [=skip the view transition=] for |transition|, and return.
 
 		1. [=Update pseudo-element styles=] for |transition|.
@@ -1210,7 +1210,7 @@ urlPrefix: https://html.spec.whatwg.org/multipage/rendering.html; type: dfn;
 
 				1. Set |height| to the current height of |capturedElement|'s [=new element=]'s [=border box=].
 
-				1. Set |transform| to a transform that maps the |capturedElement|'s [=new element=]'s [=border box=] from document origin to its quad from the [=snapshot viewport origin=].
+				1. Set |transform| to a transform that would map |capturedElement|'s [=new element=]'s [=border box=] from the [=snapshot root origin=] to its current visual position.
 
 				1. Set |writingMode| to the [=computed value=] of 'writing-mode' on |capturedElement|'s [=new element=].