[css-paint-api] Remove the concept of overflow from paint.

Author: bfgeek

css-paint-api/Overview.bs

@@ -83,7 +83,6 @@ The {{RenderWorkletGlobalScope}} has a map of <b>name to paint instance map</b>.
         callback interface PaintClass {
             readonly attribute sequence&lt;DOMString&gt; inputProperties;
             void paint(PaintRenderingContext2D ctx, Geometry geom, StylePropertyMap inputProperties);
-            void overflow(StylePropertyMap inputProperties);
         };
     </pre>
 </div>
@@ -94,12 +93,11 @@ When the <dfn method for=RenderWorkletGlobalScope>registerPaint(<var>name</var>,
     3. If the result of <a>IsConstructor</a>(argument=|paintCtor|) is false, <a>throw</a> a <a>NotSupportedError</a> and abort all these steps.
     4. Let <var>prototype</var> be the result of <a>Get</a>(O=|paintCtor|, P="prototype").
     5. If the result of <a>IsCallable</a>(argument=<a>Get</a>(O=|prototype|, P="paint")) is false, <a>throw</a> a <a>NotSupportedError</a> and abort all these steps.
-    6. If the result of <a>HasProperty</a>(O=|prototype|, P="overflow") and <a>IsCallable</a>(argument=<a>Get</a>(O=|prototype|, P="overflow")) is false, <a>throw</a> a <a>NotSupportedError</a> and abort all these steps.
-    7. Let <var>inputProperties</var> be the result of <a>Get</a>(O=|paintCtor|, P="inputProperties").
-    8. If the result of <a>IsArray</a>(argument=|inputProperties|) is false, <a>throw</a> a <a>NotSupportedError</a> and abort all these steps.
-    9. Add the key-value pair (|name| - |inputProperties|) to the <b>paint name to input properties map</b> of the associated <a>document</a>.
-    10. Let <var>paintInstance</var> be the result of <a>Construct</a>(|paintCtor|).
-    11. Add the key-value pair (|name| - |paintInstance|) to the <b>name to paint instance map</b> of the {{RenderWorkletGlobalScope}}.
+    6. Let <var>inputProperties</var> be the result of <a>Get</a>(O=|paintCtor|, P="inputProperties").
+    7. If the result of <a>IsArray</a>(argument=|inputProperties|) is false, <a>throw</a> a <a>NotSupportedError</a> and abort all these steps.
+    8. Add the key-value pair (|name| - |inputProperties|) to the <b>paint name to input properties map</b> of the associated <a>document</a>.
+    9. Let <var>paintInstance</var> be the result of <a>Construct</a>(|paintCtor|).
+    10. Add the key-value pair (|name| - |paintInstance|) to the <b>name to paint instance map</b> of the {{RenderWorkletGlobalScope}}.
 
 Note: The list of CSS properties provided by the input properties getter can either be custom or native CSS properties.
 
@@ -155,14 +153,8 @@ Note: The {{PaintRenderingContext2D}} implements a subset of the {{CanvasRenderi
     {{CanvasUserInterface}} APIs.
 
 A {{PaintRenderingContext2D}} object has a <a>scratch bitmap</a>. This is initialised when the
-object is created. The size of the <a>scratch bitmap</a> is the size of the fragment it is rendering
-plus the size specified by the overflow method.
-
-The logical origin (0,0) is not necessarily placed at the origin of the <a>scratch bitmap</a>. If
-the fragment which is being painted has an associated overflow, the logical origin is placed at
-(overflow-left,overflow-top) of the <a>scratch bitmap</a>.
-
-Issue: Add image explaining origin vs. logical origin.
+object is created. The size of the <a>scratch bitmap</a> is the size of the fragment it is
+rendering.
 
 The size of the <a>scratch bitmap</a> does not necessarily represent the size of the actual bitmap
 that the user agent will use internally or during rendering. For example, if the visual viewport is
@@ -174,12 +166,11 @@ the <a>scratch bitmap</a> such that the user agent can subsequently draw onto a
 correct resolution. This also allows user agents to re-use the same output of the <a>scratch
 bitmap</a> repeatably while the visual viewport is being zoomed for example.
 
-When the user agent is to <dfn>create a PaintRenderingContext2D object</dfn> for a given
-|width|, |height| and |overflowOffset| it <em>must</em> run the following steps:
+When the user agent is to <dfn>create a PaintRenderingContext2D object</dfn> for a given |width|,
+|height| it <em>must</em> run the following steps:
     1. Create a new {{PaintRenderingContext2D}}.
     2. <a>Set bitmap dimensions</a> for the context's <a>scratch bitmap</a> to |width| and |height|.
-    3. Set the logical origin of the <a>scratch bitmap</a> to |overflowOffset|.
-    4. Return the new {{PaintRenderingContext2D}}.
+    3. Return the new {{PaintRenderingContext2D}}.
 
 Drawing an image {#drawing-an-image}
 ====================================
@@ -211,32 +202,18 @@ When the user agent wants to <dfn>draw an image</dfn> of a <<paint()>> for a <va
 
     5. Let <var>styleMap</var> be a new {{StylePropertyMap}} populated with <em>only</em> the <a>computed value</a>'s for properties listed in |inputProperties|.
 
-    6. Let <var>overflow</var> be the result <a>invoke a method on a class inside a Worklet</a> given "overflow" as the <em>methodPropertyKey</em> and [|styleMap|] as the <em>arguments</em> with the following options:
-        - To <a>create a worklet global scope</a> the user agent will:
-
-            Return a new {{RenderWorkletGlobalScope}}.
-        - To <a>lookup a class instance on a worklet global scope</a> given a |workletGlobalScope|, the user agent will:
-
-            Return the result of looking up |name| on the |workletGlobalScope|'s <b>name to paint instance map</b>.
-
-        Note: User agents may have to compute overflow before entering their paint phase in order to determine which fragments to paint (overflow changes what could be seen on the output device).
-            User agents may opt into running the steps up to this point, to determine overflow, then continuing later to determine the drawn image for the fragments which need painting.
-
-    7. Let <var>renderingContext</var> be the result of <a>create a PaintRenderingContext2D object</a> given:
-        - "overflowOffset" - The logical offset for the <a>scratch bitmap</a> specified by |overflow|.
-        - "width" - The width of the |fragment| plus the additional width specified by |overflow|.
-        - "height" - The height of the |fragment| plus the additional height specified by |overflow|.
+    6. Let <var>renderingContext</var> be the result of <a>create a PaintRenderingContext2D object</a> given:
+        - "width" - The width of the |fragment|.
+        - "height" - The height of the |fragment|.
 
         Note: The |renderingContext| must not be re-used between invocations of paint. Implicitly this means that there is no stored data, or state on the |renderingContext| between invocations.
             For example you can't setup a clip on the context, and expect the same clip to be applied next time the paint method is called.
 
-        Issue: TODO add note we should specify the output of overflow.
-
-    8. Let <var>geometry</var> be a new {{Geometry}} initialized to the width and height of the |fragment|.
+    7. Let <var>geometry</var> be a new {{Geometry}} initialized to the width and height of the |fragment|.
 
         Issue(w3c/css-houdini-drafts#23): Decide geometry information should be in level 1.
 
-    9. To produce the image output, <a>invoke a method on a class inside a Worklet</a> given "paint" as the <em>methodPropertyKey</em> and [|renderingContext|, |geometry|, |styleMap|] as the <em>arguments</em> with the following options:
+    8. To produce the image output, <a>invoke a method on a class inside a Worklet</a> given "paint" as the <em>methodPropertyKey</em> and [|renderingContext|, |geometry|, |styleMap|] as the <em>arguments</em> with the following options:
         - To <a>create a worklet global scope</a> the user agent will:
 
             Return a new {{RenderWorkletGlobalScope}}.
@@ -250,7 +227,7 @@ When the user agent wants to <dfn>draw an image</dfn> of a <<paint()>> for a <va
 
         Note: User agents should provide tooling within their debugging tools to show authors a partial output of the image, if an exception is thrown.
 
-    10. Set the <b>paint valid flag</b> for the <<paint()>> function on the |fragment| to <a>paint-valid</a>.
+    9. Set the <b>paint valid flag</b> for the <<paint()>> function on the |fragment| to <a>paint-valid</a>.
 
 Note: The user agent should consider long running paint functions similar to long running script in the main execution context.
     For example, they should show a "unresponsive script" dialog or similar.