dsh-pptx-sidebar

Read .pptx / .pptm decks in the DSH sidebar — the slides in presentation order, with their text, bullet levels, speaker notes and inline pictures.

This is a reading view, not a slide reproduction. No absolute positioning, no theme fonts, no placeholder inheritance, no animation. The viewer says so in its header, because a layout difference that looks like a rendering bug is worse than a plainly-labelled limitation.

It is a dsh-better-sidebar consumer: it registers a file previewer and renders inside the Side card's preview area. Without that plugin it loads, warns once, and does nothing.

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Install

dsh plugin --profile <profile> add github:drscrewdriver/dsh-pptx-sidebar#<sha>
dsh plugin --profile <profile> add dsh-pptx-sidebar@0.1.0     # once published

Then restart the DSH host — a browser refresh is not enough for a new loader row. Verify without starting anything:

dsh --profile <profile> --dump-config | Select-String dsh-pptx-sidebar

Manual installation is three steps, not one — see cordis.patch.yml. Doing only steps 1 and 3 produces a profile where the package is present, the patch row is present, and nothing loads, silently.

What it does / does not do

Done	Not done
Slide list in p:sldIdLst order	Visual layout, absolute positioning
Text paragraphs, per-paragraph bullet levels	Theme/master font resolution
Title detection from placeholder type	Placeholder inheritance (see below)
Speaker notes from notesSlide parts	Charts re-rendered as charts
Inline pictures as blob URLs	Animation, transitions, timings
Real tables (a:tbl)	Comments, revision marks
Bold / italic runs	Editing, writing back
Seven circuit-breaker ceilings	Legacy .ppt (BIFF/OLE2), WPS formats

The placeholder inheritance line (deliberate)

A slide often shows text it does not contain: numbers, footers, and title text that live in slideLayout / slideMaster, referenced through a p:ph placeholder. Resolving that means re-implementing PowerPoint's inheritance chain — including lstStyle level overrides and which layout the slide actually uses.

v1 does not do it. Only the slide's own part is read. The consequence is stated rather than hidden: a slide whose text is entirely inherited renders with no text. That is a visible omission, not a corruption — the opposite trade (inheriting wrongly) would show text that is not on the slide.

Width adaptation

The sidebar pane is resizable, so the reading view adapts to it — within bounds, because "adaptive" is not a licence to keep growing or shrinking:

Knob	Value	Why
Base width	360 px	The factor is exactly 1 here, so the usual pane width renders the layout 0.1.0 shipped
Floor	0.9×	A narrow pane still gets readable type
Ceiling	1.15×	A wide pane gets comfortable type, not enormous type
Quantisation	2 decimals	A drag re-lays-out on 0.01 steps, not on every pixel

The factor is derived from the pane width and written to the --reader-scale custom property; the root font-size becomes 13px × scale and the slide content is expressed in em, so text reflows at the new size instead of being transform-scaled (which would blur glyphs).

Only the document scales. Titles, bullets, paragraphs, notes, tables and image captions follow the factor; the header strip, the slide strip, the breaker banner and the loading/empty states keep their fixed size. Chrome that changes size while you drag a divider reads as a glitch rather than as responsiveness.

Two related decisions:

• An unmeasurable width falls back to 1, not to a bound. Before the first measurement the width is 0, and rendering that as "as narrow as possible" would flash tiny type every time a deck is opened.
• Pictures do not scale. They render at the size the shape transform states and are only capped by the pane; magnifying a bitmap past its natural size to track the text would make it softer, not more faithful.

The pipeline

archive bytes (host /sidebar/file, custom loader)
  → archive-size gate                      refuse before any unpacking
  → central directory (declared-size gate) refuse a lying part before inflating
  → streaming inflate + total budget       the zip-bomb gate
  → ppt/presentation.xml                   p:sldIdLst — slide ORDER
  → ppt/_rels/presentation.xml.rels        rId → slides/slideN.xml
  → ppt/slides/slideN.xml                  p:spTree → p:sp / p:pic / p:graphicFrame
  │     p:txBody → a:p → a:pPr@lvl (level), a:r → a:rPr(b/i) + a:t
  │     p:pic    → a:blip@r:embed → slide rels → ppt/media/*
  │     p:grpSp  → recursed, never flattened away
  ├→ ppt/slides/_rels/slideN.xml.rels      .../notesSlide → notesSlides/notesSlideN.xml
  └→ rules: a slide too long loses only its own tail; notes absent is silence

Pictures are pulled out of the zip and turned into object URLs. An embedded image lives inside the archive, so there is no host route to point at — this is not "reading files ourselves", it is using the bytes the host already handed over.

Seven circuit-breaker ceilings

Dimension	Default	Over it
Archive size	8 MB	BLOCKED — refused before any unpacking
Total inflate	64 MB	BLOCKED — the zip-bomb gate
One part	32 MB	BLOCKED — a single oversized XML part
Slides	300	TRUNCATED — the reader stops walking the deck
Slide text	20 000 chars	that slide's remaining text elided
Images	200	further pictures skipped
One image	8 MB	that picture skipped (not even inflated)

At most one warning per dimension, structurally — warnings live in a Map<reason, warning>, so a dimension that trips on every slide produces one line, not sixty.

The per-slide text ceiling elides only the offending slide. A per-block ceiling would shave every slide equally and lose information the deck had budget for; the failure mode we accept instead is "slide 12 is cut short".

Tests

npm install
npm run verify          # build (bundle load gate) + tests
npm test                # 19 checks

The fixture is a real pptx-shaped zip built in the test file, with a genuine tiny PNG. It is hostile where the format is:

• p:sldIdLst lists slide2 before slide1, so sorting parts by filename would pass every other assertion and still be wrong;
• one slide relationship uses an absolute target, another is External;
• ppt/slideLayouts/slideLayout1.xml carries MASTER TEXT MUST NOT APPEAR, which must never surface — that is what "no placeholder inheritance" means here.

Layout

File	Role
pptx.ts	The reader: parts, relationships, shape tree, notes, pictures
circuit-breaker.ts	The seven ceilings and the single-warning-per-dimension rule
zip.ts / xml.ts	Container reading; targeted XML scanning with depth counting
PptxViewer.tsx	Slide strip, current-slide rendering, object-URL lifetime
locales.ts	zh / en dictionaries, including every warning template
seams.ts	Structural mirrors of the client services we consume

The zip and XML code is copied from the sibling document plugin rather than shared. Two users of this code is not yet the threshold for extracting a package — that would add a third thing to publish and version-lock.

License

MIT