[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>