Code assumes iframe mode, exception in inline mode

[programmin]

In 4.9 RC the editor has this in wp-includes/js/mce-view.js:

			// Obtain the target width for the embed.
			if ( self.editor ) {
				maxwidth = self.editor.iframeElement.clientWidth - 20; // Minus the sum of horizontal margins and borders.
			}

This should probably be editor.bodyElement when an editor is in [inline ​https://www.tinymce.com/docs/demo/inline/] mode not the iframed mode.

self.editor.iframeElement causes an exception.

Possibly somewhat related to https://core.trac.wordpress.org/ticket/28929 but I hadn't noticed that problem recently.

@programmin can you provide an example for how inline mode could be forced the editor?

I understand TinyMCE has an inline mode, but can TinyMCE _for the WP editor_ get the inline mode? Sample code to do this would be appreciated.

The Wordpress post editor on wp-admin is not the only place you can include the wp editor. When you use inline mode that js file causes exception and this started on 4.9 testing.

@programmin Please provide some sample code for demonstrating this.

Per today's 4.9 bug scrub, we're punting this from 4.9 to 4.9.1 to allow for appropriate time for feedback/review/updates.

This can be demonstrated in the Gutenberg editor, which uses inline mode for rendering TinyMCE, including the Classic Text block. The related issue has been reported here:

​https://github.com/WordPress/gutenberg/issues/3568

The above patch changes the behavior to retrieve clientWidth from the body element, which supports both iframe and inline modes, and should recreate the expected behavior of assigning an embed maximum width corresponding to the available width of the editor body.

With 42416.diff​, embeds are appearing with the proper width in both the Text widget and the classic editor.

In 42390:

Editor: Fix determining TinyMCE editor width when in inline mode instead of iframe mode.

See #40854.
Amends [41985].
Props aduth.
Fixes #42416 for trunk.

In 42391:

Editor: Fix determining TinyMCE editor width when in inline mode instead of iframe mode.

See #40854.
Amends [41985].
Props aduth.
Fixes #42416 for 4.9.