Keep the empty content of the figure and footnote macros reachable by one click in the WYSIWYG editor

In the WYSIWYG editor, the empty content of the figure and footnote macros is still there, but its click target is too small, or has no size at all, so the user cannot put the cursor back in it with the mouse.

The macros to change:

• figure: when the image and the caption of a figure are deleted, the content collapses to a 0 px high area that a click cannot reach. A figure whose text content is emptied keeps a 20 px line, which one click enters.
• footnote: the empty macro keeps its footnote number, the only click target of the macro, about 6 by 20 pixels, below the 24 by 24 pixels of WCAG 2.5.8 Target Size (Minimum).

The fix is done in the stylesheet of the edited content, ContentSheet.xml: give these click targets a minimum size of 24 by 24 pixels, so that one click puts the cursor in the empty content of a figure, and selects an empty footnote. XRENDERING-830 covers editing the content of a footnote in place.

KOs covered

Impact found on macro fluidity

These 2 KOs come from the WYSIWYG usability audit of the macros, under the criterion E5 empty of its usability criteria, which asks that an empty content still renders in the editor and stays editable, with no zero-width area that cannot receive the cursor. The page of each macro, linked in the table, has the full notes and the steps to reproduce.