A picture of one slide answers a narrower question than the one a theme
picker is asked. What a person wants to know is what a deck will look
like in this theme — all of it, at the size it will be shown, with the
fonts substituted the way they will be. One rendered slide showed one
layout, in content someone then read instead of looking at.
So: a sample deck per theme. Every layout the renderer can draw — title,
bullets with a sub-point, both two-column forms, table, callout, figure,
full-slide figure, section divider, a custom slide with shapes, an arrow
and a chart, and a references slide — with filler text throughout.
Download it, open it, see the theme.
The text is deliberately meaningless. Clinical content in a specimen
invites you to read it, and then you are judging the teaching rather
than the type; that is what the old croup slide got wrong.
No engine. The previous preview needed a Gotenberg round trip and a
pdftoppm to produce a PNG, cached on disk because of what it cost, and
could fail in ways a missing picture cannot explain. python-pptx builds
the file in ~330ms and PowerPoint draws it. The link is a plain anchor,
so it is there whether or not anything on the server is well.
The figure placeholder rides the same path a generated figure does —
attachFigures downgrades a figure slide with no picture to bullets and
an image slide to a section, so without it the sample would silently
stop showing those two layouts.
Verified: all five themes build, 11 slides, the chart is a real chart
and the placeholder embeds as real media.
Co-Authored-By: Claude Opus 5 <noreply@anthropic.com>
Claude-Session: https://claude.ai/code/session_01Dv6sqaY6Vq3ChZHMem3cnU
A deck had exactly one look. The slide vocabulary is structural — bullets,
compare, table, callout, figure — and none of it carries a colour, so "make it
yellow" had nowhere to land but the image prompts, and produced yellow figures
on a blue deck.
A theme is a palette and a typeface in assets/deck-themes.json. render_pptx.py
rebinds INK, MUTED, ACCENT, RULE and PAPER from it in one place, so every slide
builder follows without a line changing in any of them — five themes restyle ten
slide types for free. An unusable theme leaves the default standing, because a
deck in the wrong colours beats a deck that will not render.
The theme rides on the deck, which is already the renderer's spec, so nothing
has to thread it through. It is validated against the same catalogue the
renderer reads: an id the renderer would ignore is never stored, so a deck
cannot claim a look it does not have.
PUT /my-resources/:id/theme re-skins a stored deck — a column write, no model
call, nothing that can reword a slide — and the next download is in the new
colours. Offered in the library only on rows that have a deck; flat markdown has
no palette.
Previews are rendered by the renderer, one representative compare slide per
theme, cached because each costs a pptx render, a Gotenberg round trip and a
rasterise. Drawn rather than mocked up: a hand-made swatch drifts the moment a
palette or a layout changes, and a preview that is not true is worse than none.
Co-Authored-By: Claude Opus 5 <noreply@anthropic.com>
Claude-Session: https://claude.ai/code/session_01Dv6sqaY6Vq3ChZHMem3cnU
