[giow] (1) Define what should happen with canvas.toBlob() for zero-si…

…zed canvases.

Affected topics: Canvas, DOM APIs

git-svn-id: http://svn.whatwg.org/webapps@6880 340c8d12-0b0e-0410-8428-c7bf67bfef74

complete.html

 
   <header class=head id=head><p><a class=logo href=http://www.whatwg.org/><img alt=WHATWG height=101 src=/images/logo width=101></a></p>
    <hgroup><h1 class=allcaps>HTML</h1>
-    <h2 class="no-num no-toc">Living Standard &mdash; Last Updated 6 January 2012</h2>
+    <h2 class="no-num no-toc">Living Standard &mdash; Last Updated 7 January 2012</h2>
    </hgroup><dl><dt><strong>Web developer edition:</strong></dt>
     <dd><strong><a href=http://developers.whatwg.org/>http://developers.whatwg.org/</a></strong></dd>
     <dt>Multiple-page version:</dt>
    <li><p>Let <var title="">arguments</var> be the second and
    subsequent arguments to the method, if any.</li>
 
-   <li><p>Let <var title="">file</var> be <a href=#a-serialization-of-the-image-as-a-file>a serialization of the
-   image as a file</a>, using <var title="">arguments</var>.</li>
+   <li>
+
+    <p>If the canvas has no pixels (i.e. either its horizontal
+    dimension or its vertical dimension is zero) then let <var title="">result</var> be null.</p>
+
+    <p>Otherwise, let <var title="">result</var> be a
+    <code><a href=#blob>Blob</a></code> object representing <a href=#a-serialization-of-the-image-as-a-file>a serialization of the
+    image as a file</a>, using <var title="">arguments</var>.</p>
+
+   </li>
 
    <li><p>Return, but continue running these steps
    asynchronously.</li>
    steps.</li>
 
    <li><p><a href=#queue-a-task>Queue a task</a> to invoke the
-   <code>FileCallback</code> <var title="">callback</var> with a
-   <code><a href=#blob>Blob</a></code> object representing <var title="">file</var> as
-   its argument. The <a href=#task-source>task source</a> for this task is the
-   <dfn id=canvas-blob-serialization-task-source>canvas blob serialization task source</dfn>. <a href=#refsFILESYSTEMAPI>[FILESYSTEMAPI]</a> <a href=#refsFILEAPI>[FILEAPI]</a> </li>
+   <code>FileCallback</code> <var title="">callback</var> with <var title="">result</var> as its argument. The <a href=#task-source>task source</a>
+   for this task is the <dfn id=canvas-blob-serialization-task-source>canvas blob serialization task
+   source</dfn>. <a href=#refsFILESYSTEMAPI>[FILESYSTEMAPI]</a> <a href=#refsFILEAPI>[FILEAPI]</a> </li>
 
   </ol><p>When a user agent is to create <dfn id=a-serialization-of-the-image-as-a-file>a serialization of the image
   as a file</dfn>, optionally with some given <var title="">arguments</var>, it must create an image file in the format

index

 
   <header class=head id=head><p><a class=logo href=http://www.whatwg.org/><img alt=WHATWG height=101 src=/images/logo width=101></a></p>
    <hgroup><h1 class=allcaps>HTML</h1>
-    <h2 class="no-num no-toc">Living Standard &mdash; Last Updated 6 January 2012</h2>
+    <h2 class="no-num no-toc">Living Standard &mdash; Last Updated 7 January 2012</h2>
    </hgroup><dl><dt><strong>Web developer edition:</strong></dt>
     <dd><strong><a href=http://developers.whatwg.org/>http://developers.whatwg.org/</a></strong></dd>
     <dt>Multiple-page version:</dt>
    <li><p>Let <var title="">arguments</var> be the second and
    subsequent arguments to the method, if any.</li>
 
-   <li><p>Let <var title="">file</var> be <a href=#a-serialization-of-the-image-as-a-file>a serialization of the
-   image as a file</a>, using <var title="">arguments</var>.</li>
+   <li>
+
+    <p>If the canvas has no pixels (i.e. either its horizontal
+    dimension or its vertical dimension is zero) then let <var title="">result</var> be null.</p>
+
+    <p>Otherwise, let <var title="">result</var> be a
+    <code><a href=#blob>Blob</a></code> object representing <a href=#a-serialization-of-the-image-as-a-file>a serialization of the
+    image as a file</a>, using <var title="">arguments</var>.</p>
+
+   </li>
 
    <li><p>Return, but continue running these steps
    asynchronously.</li>
    steps.</li>
 
    <li><p><a href=#queue-a-task>Queue a task</a> to invoke the
-   <code>FileCallback</code> <var title="">callback</var> with a
-   <code><a href=#blob>Blob</a></code> object representing <var title="">file</var> as
-   its argument. The <a href=#task-source>task source</a> for this task is the
-   <dfn id=canvas-blob-serialization-task-source>canvas blob serialization task source</dfn>. <a href=#refsFILESYSTEMAPI>[FILESYSTEMAPI]</a> <a href=#refsFILEAPI>[FILEAPI]</a> </li>
+   <code>FileCallback</code> <var title="">callback</var> with <var title="">result</var> as its argument. The <a href=#task-source>task source</a>
+   for this task is the <dfn id=canvas-blob-serialization-task-source>canvas blob serialization task
+   source</dfn>. <a href=#refsFILESYSTEMAPI>[FILESYSTEMAPI]</a> <a href=#refsFILEAPI>[FILEAPI]</a> </li>
 
   </ol><p>When a user agent is to create <dfn id=a-serialization-of-the-image-as-a-file>a serialization of the image
   as a file</dfn>, optionally with some given <var title="">arguments</var>, it must create an image file in the format

source

    <li><p>Let <var title="">arguments</var> be the second and
    subsequent arguments to the method, if any.</p></li>
 
-   <li><p>Let <var title="">file</var> be <span>a serialization of the
-   image as a file</span>, using <var
-   title="">arguments</var>.</p></li>
+   <li>
+
+    <p>If the canvas has no pixels (i.e. either its horizontal
+    dimension or its vertical dimension is zero) then let <var
+    title="">result</var> be null.</p>
+
+    <p>Otherwise, let <var title="">result</var> be a
+    <code>Blob</code> object representing <span>a serialization of the
+    image as a file</span>, using <var title="">arguments</var>.</p>
+
+   </li>
 
    <li><p>Return, but continue running these steps
    asynchronously.</p></li>
    steps.</p></li>
 
    <li><p><span>Queue a task</span> to invoke the
-   <code>FileCallback</code> <var title="">callback</var> with a
-   <code>Blob</code> object representing <var title="">file</var> as
-   its argument. The <span>task source</span> for this task is the
-   <dfn>canvas blob serialization task source</dfn>. <a
-   href="#refsFILESYSTEMAPI">[FILESYSTEMAPI]</a> <a
+   <code>FileCallback</code> <var title="">callback</var> with <var
+   title="">result</var> as its argument. The <span>task source</span>
+   for this task is the <dfn>canvas blob serialization task
+   source</dfn>. <a href="#refsFILESYSTEMAPI">[FILESYSTEMAPI]</a> <a
    href="#refsFILEAPI">[FILEAPI]</a> </p></li>
 
   </ol>