Text parked beside the slide

How the text is hidden

A shape states its position and size as <a:off> and <a:ext> inside its transform, in EMUs against the slide's own width and height. Dragging the box past the canvas edge in the PowerPoint editor changes only those numbers. The shape and its text remain in the slide part; the rendered slide shows blank space.

Why a model still reads it

Position is a rendering property. An extractor reads <a:t> runs in document order and has no notion of a canvas, so text sitting a metre to the left of the slide arrives in the same stream as the title.

What we do about it

The shape's rectangle is first resolved into slide space — enclosing p:grpSp groups apply their chOff/chExt to off/ext mapping, and a placeholder with no transform of its own inherits the layout's matching rectangle. isRectOffSlide then judges by AREA: after a one-point slack on the corner test, a shape counts as off-slide when the share of its area overlapping the canvas falls below limits.offSlideMaxVisibleShare. A shape with no extent keeps the corner test and reports. Tables are judged the same way from the p:graphicFrame's own p:xfrm. The reason is off-canvas, graded high and flagged; visibilityOf maps it to never.

How often it fires

4.5% of 199 real Zenodo conference decks (corpus-zenodopptx, re-measured after the group-transform fix), measured 2026-08-27.

This is an alert-volume number and nothing else. It says how often the alarm sounds on documents as found — not how often it is right, and not whether what it found was harmless. Documents as found may themselves carry concealment. Read it against the population named above rather than as a property of documents in general.