Proposal for a visual debug mode

Description

This likely borders on something that could be achieved with a package, but integrating it into the compiler might also make sense, depending on the scope. So I'm proposing the idea here.

When setting layouts, it is often difficult to determine where a particular (possibly unwanted) spacing comes from or what the dimensions/indents etc. of a single element are. Of course, you can use fills and strokes to some degree, but this is often burdensome or doesn't show the whole picture in an easy-to-overview manner.

Similar to the inspector in HTML/CSS environments or tools like geometry/showframe or lua-visual-debug in the LaTeX universe, a debug mode would be very useful.

This mode could show, for example:

• Outlines of blocks and page parts without affecting the layout
• Dimensions and x/y position of blocks and boxes without affecting content or layout
• Spacings and paddings for each element
• Whitespace, line and page breaks
• Baselines and lines per element
• Broken characters

Use Case

This approach would make debugging more intuitive, significantly reducing support requests and enhancing ease of use.

Rudimentary examples (not showing many possible features mentioned above):


Image Source: https://tex.stackexchange.com/questions/2083/how-can-i-visualize-boxes

The proposal does not name any files, tests, or compiler entry points to inspect. Start by determining whether the functionality belongs in the compiler or an external package, then define a focused initial scope and acceptance criteria for the visual debug output before implementation.