pdfTeX and microtype: Protrusion influence on line-breaking breakpoints

Integration of Character Protrusion in Paragraph Building

The microtype package introduces character protrusion to improve the visual alignment of margins by extending specific glyphs beyond the edge of the text block. In pdfTeX, this feature is typically applied as a post-processing step after the paragraph builder has already determined the breakpoints.

Because the line-breaking algorithm relies on the original box dimensions, the perceived width changes only after the layout is finalized. This creates a discrepancy compared to engines like LuaTeX, where protrusion attributes can be integrated directly into the breaking process to optimize margin consistency.

When using pdfTeX (version 1.40+), it is unclear if there are configuration options to force the breaker to account for these protrusions during the initial calculation phase to prevent unexpected overfull boxes.

• Does the pdfTeX line-breaking algorithm remain entirely agnostic to protrusion settings during breakpoint selection?
• Can microtype settings be adjusted to influence the breaker's decision in pdfTeX, or is this behavior exclusive to LuaTeX?