Clarify "8.1. The copy action" in regards to copying selected data

[danburzo]

I've initially logged it on w3c/editing#168 but was directed to the Selection API / Clipboard API repos — not sure what the interdependencies are, so I'm logging it here.

I think the Copy action needs some clarification on:

3.1. Copy the selected contents, if any, to the clipboard. Implementations should create alternate text/html and text/plain clipboard formats when content in a web page is selected.

In regards to how the selection translates to HTML content. Case in point, browsers treat a Selection whose Range is set to either a Node (via range.selectNode) or a Node's contents (via range.selectNodeContents) the same way:

• Firefox will copy the Node's inner HTML to the clipboard
• Chrome and Safari will copy the Node's outer HTML to the clipboard

I believe there needs to be a way for authors to specify if the Node as a whole should be included in the clipboard, or just its content.

[mbrodesser]

To achieve compatibility across browsers, it should additionally be specified how the selected contents are copied.

For instance, when selecting rows in a table, current browser behavior (Chrome, Firefox) when pasting them to the clipboard is to create a tab between the content of two adjacent cells.

Example: open the following in a browser, select all and copy-paste to a text editor:
data:text/html,<table><tr><td>x</td><td>y</td><tr/> <tr><td>a</td> <td>b</td></tr> </table>

However, if the selected elements have the display property block, Chrome and Firefox create line breaks between two adjacent cells.

Example: open the following in a browser, select all and copy-paste to a text editor:
data:text/html,<table><tr><td><p>x</td><td><p>y</td><tr/> <tr> <td><p>a</td> <td><p>b</td> </tr> </table>

Having such and potentially other related details specified would help achieving a reasonable and consistent behavior across browsers.