Scroll views

Widgets with scrolling contents (such as list views) are shown with green arrows:

Clipping

Clipping, for example when using the ClipRect widget, are shown
with a dashed pink line with a scissors icon:

Spacers

Spacer widgets are shown with a grey background,
such as this SizedBox without a child:

Show baselines

This option makes all baselines visible.
Baselines are horizontal lines used to position text.

This can be useful for checking whether text is precisely aligned vertically.
For example, the text baselines in the following screenshot are slightly misaligned:

The Baseline widget can be used to adjust baselines.

A line is drawn on any render box that has a baseline set;
alphabetic baselines are shown as green and ideographic as yellow.

You can also enable this in code:

Highlight repaints