Deck Editing Rules

How to make STRUCTURAL edits (delete / reorder / cross-deck import) to an existing .pptx and how to apply illustration backgrounds — distinct from generating slide structure (see rules/slide-generation-rules.md).

Don't Edit Decks With python-pptx

• python-pptx and clipboard Slides.Paste drop each slide's <p:bg> picture fill, flattening illustrated decks whose full-bleed art is a background fill.
• python-pptx editing OOXML from outside the app breaks strict OOXML that Keynote refuses to open.
• All structural edits go through RunDeckOps — there is no python-pptx slide-delete / slide-reorder path.

Use Real PowerPoint via RunDeckOps (macOS)

• Drive the actual PowerPoint app so PowerPoint serializes the file — fonts, full-bleed backgrounds, masters, and relationships are preserved and the output stays Keynote-openable. The original is never modified (the macro writes a COPY).
• skills/presentation-creator/scripts/RunDeckOps.bas builds the target deck with Slides.InsertFromFile (the programmatic "Reuse Slides", keep-source- formatting — NOT clipboard paste). Invoke it through skills/presentation-creator/scripts/run-deck-ops.sh:

  run-deck-ops.sh <basePath> <outPath> <importSpec> <orderStr> <replaceStr>
  # orderStr: "BASE:1 BASE:2 voxxed:13 BASE:49"  (alias:1-based-slide-#)

• One-time setup is a manual, GUI-bound sequence (enable VBA macros, create the DeckOps.pptm macro container, import the .bas, grant Automation consent). Walk the user through it interactively the first time — see skills/presentation-creator/references/deck-editing-setup.md.

Add a Generated Illustration as a Slide Background

• A generated illustration must become the slide's BACKGROUND FILL, not a top-pasted picture: the layout's halftone-dot overlay sits above the slide background but below shapes, so a pasted picture lands above the dots.
• Don't hand-build the slide in python-pptx: a fresh deck can't borrow the source deck's layout (and its overlay).
• RunDeckOps.bas's MakeBgImageSlide clones a comic template slide, sets Slide.Background.Fill.UserPicture, retitles, and saves a 1-slide deck. Pick a template whose title sits in the image's clear safe zone. Invoke via skills/presentation-creator/scripts/make-bg-slide.sh, then import with run-deck-ops.sh (order token <alias>:1).
• Generate the illustration first with the illustrations skill, then make it a background slide here.

Set Illustration Backgrounds in Bulk at Creation Time

• When building a NEW deck, FULL-slide illustrations must also be slide BACKGROUND FILLS, not picture shapes — same overlay reason as above. python-pptx must not insert them as shapes, and must not be the last writer (it re-drops <p:bg> fills on save).
• apply-illustrations-to-deck.py records each FULL slide in a backgrounds manifest (--backgrounds-out) and applies only scrim + title; it does NOT insert FULL-slide pictures. IMG+TXT slides keep a left-column picture shape.
• RunDeckOps.bas's ApplyBackgrounds then sets all FULL backgrounds via Slide.Background.Fill.UserPicture in one pass. Invoke via skills/presentation-creator/scripts/apply-backgrounds.sh <baseCopy> <out> <manifest.json>.
• Run this as the FINAL write of the build — after the structural walk, scrim/ title, and speaker-note injection — so no later python-pptx save drops the fills.

macOS-Only — VBA Layer Untestable in CI

• The PowerPoint-driving layer (VBA + AppleScript) needs the Microsoft PowerPoint app and macOS Automation, so it CANNOT run in Linux CI. Validate it manually: re-open output in PowerPoint AND Keynote; confirm size recovers and a <p:bg>-blipFill check finds the expected slides.
• The deterministic Python/shell helpers (illustration apply, manifest→spec) ARE unit-tested in tests/ — only the PowerPoint-driving layer is exempt.

Mac PowerPoint VBA Landmines (all handled in RunDeckOps)

• Filename collision: PowerPoint keys open decks by filename and silently returns an already-open same-named deck from Presentations.Open. Always operate on UNIQUELY-NAMED copies; the macro also guards and errors loudly.
• Slide.MoveTo / Slides.FindBySlideID raise E_INVALIDARG on current Mac builds — avoided by appending in target order via InsertFromFile.
• SaveCopyAs rejects FileFormat / EmbedTrueTypeFonts enum args — use a bare SaveCopyAs FileName:=... (base is already .pptx).
• Sandboxed PowerPoint can't create a file in a Google Drive File-Provider folder (E_FAIL): save to a local staging path, then move into Drive with the shell. run-deck-ops.sh does this automatically.