PowerPoint export: the diagram is a single item, not editable shapes

[adamjohnwright]

Reported by curators: "Download a diagram as PPTX, open it in real PowerPoint, then right-click the diagram → Graphics Format → Convert to Shape." Their answer: "NO — The whole pathway diagram is treated as a single item."

Status: open, not started.

Why we asked rather than tested it: there is no PowerPoint on the build machine. The file is validated structurally by e2e/downloads.spec.ts — it checks a PPTX contains PPTX and is the right figure — but "opens in PowerPoint and converts to editable shapes" is a different claim and we have no automated coverage of it. The curators' answer is the test result here.

Next step: compare against what production's exporter produces for the same diagram, since the old Java exporter is what curators are used to. If production yields editable shapes and ours yields one, the difference is in how our renderer emits the PPTX.

[adamjohnwright]

Fixed in b1af460. A downloaded PPTX is now built out of shapes rather than
holding a picture of the diagram.

What you get. For the Intrinsic Pathway for Apoptosis (R-HSA-109606),
635 shapes: one per compartment, one per connector, one per entity, and one
per sub-pathway tint. Each is selectable and movable the moment the file
opens — no Convert to Shape step. The file is 32 KB, against roughly
1.5 MB when it carried the diagram as a vector image.

The slide is the size of the diagram, which is what the old Java
exporter does too: 56 by 32 inches for this pathway, with labels at 5 to
53pt. Fitting the diagram onto an ordinary 13.3in slide instead — which is
what a slide holding a picture wants — put every label at 1.65pt.

Where the shapes come from. The site's own page reports every position,
colour, opacity, dash and font from the live style, and the exporter writes
those out as OOXML. It is a spelling of the diagram rather than a second
opinion about it, which is what made the old exports drift from the site.

What it does not carry yet, both worth telling us about if they matter:

• The small decorations the style draws with background images — so a
  complex loses the band that marks it as one.
• The rounded corners on connectors that use round-segments routing. The
  points are right; the corners are square.

What we could not test. There is no PowerPoint on the build machine, so
"it opens cleanly in PowerPoint" is still your check rather than ours. What
was checked here: the package's relationships all resolve, every part has a
declared content type, every part parses, the element ordering matches
production's own PPTX for the same pathway, no shape reaches past the slide
edge, and no path point leaves its own coordinate space. Those are the
things that make PowerPoint offer to repair a file.

Please try it on beta and say whether the shapes are the ones you wanted.