Where the cursor lands

The line is taken from the element under the pointer, not from its vertical position on the page, so it stays accurate in scaled slides.

Links are left alone: double-clicking one does not jump to the source.

Live reload

While the slideshow is open, saving the deck rebuilds it and the browser reloads at the slide you are editing (the one under the cursor when you save), so you can fix a slide and see it in the talk's layout without presenting again. Ink is kept. Edits are picked up only on save, and only for a slideshow started from this VS Code window.

The page checks for a new build once a second by loading a small <name>.html.version.js file written next to it, so it needs no server. Turn it off with scimax.marp.liveReload.

Present in an app window

To fill a window with the slides without taking over the whole screen (to share one window in a video call, or to present beside your notes), set

"scimax.marp.presentWindow": "app"

or, for one deck, add window: app to its front matter (window: tab turns it off for a deck when the setting is app):

---
marp: true
window: app
---

In an org file exported to Marp, #+MARP_WINDOW: app does the same.

The default is tab: the slideshow opens in a tab of your default browser. With app, Present opens it in a Chromium app window: no tabs, address bar or toolbar, just the slides, in a window you can size and move. Chrome, Edge, Chromium or Brave is found in the usual places; set scimax.marp.appBrowser to a path (or on macOS an application name such as Microsoft Edge) to choose one. If no browser is found, Present opens the slideshow in your default browser as before. Live reload, ink and the presenter tools work the same in an app window.

Presenting from an org file

A marp: link in an org file launches the slideshow when clicked (or with C-c C-o on it):

[[marp:talks/group-meeting.md][Group meeting slides]]
[[marp:talks/group-meeting.md::5][Start at slide 5]]

The path is relative to the org file (absolute paths and ~/ work too), and ::N starts at slide /N/. When the org file is exported, the link becomes an ordinary link to the .md file.

Hovering over the link shows a picture of the deck's first slide, the number of slides, and links to Edit the .md file, open its Preview beside the editor, or Present the slideshow (from slide N for a ::N link). The picture uses the deck's theme and inlines local images; remote images and web fonts are not loaded, so those may look different from the slideshow.

Zoom

The slider in the toolbar at the top sets the thumbnail width, from 80 to 640 pixels. The thumbnails flow into as many columns as fit. The default is 240 pixels, and the sorter remembers the zoom. The keys + and - step the zoom and 0 resets it; they are plain keys because Cmd+/=Cmd+- zoom the whole VS Code window. A trackpad pinch (or Ctrl + scroll wheel) zooms too.

The thumbnails re-render as you type (after a short pause). Slide boundaries come from Marp itself, so ---, *** and ___ separators and the headingDivider directive all split slides exactly as they do in the preview, and a --- inside a code block does not.

The view renders with its own copy of Marp Core and follows these settings (see Configuration):

Run Scimax: Refresh Marp Slide Thumbnails (cmd:scimax.marp.refreshSlides) after editing a theme file, since theme files are not watched.

Selecting slides

Click a thumbnail to select it, Cmd+click (Ctrl+click on Windows and Linux) to add or remove one, and Shift+click to select a range. Left and Right move the selection by one slide and Up and Down by one row of the grid (Shift extends it), Home and End jump to the first and last slide, and Cmd+A selects them all. Right-clicking a slide that is not selected selects just that slide, as in the Explorer.

Drag and drop

Drag a thumbnail to move its slide. A bar shows where it will land: between two thumbnails in the grid, or between two rows in a single column. Dragging a selected thumbnail moves the whole selection, in order, as one block, even when the selected slides were not next to each other. Dropping past the last thumbnail moves the slides to the end.

The slide menu

Right-click a thumbnail for these commands. They act on all selected slides when the clicked slide is part of the selection.

Reveal in Preview moves the editor cursor to the slide and opens the Slide Preview on it. Present from This Slide starts the Slideshow there. Export Deck lists every export (see Exporting Slides); it exports the whole deck.

On Windows and Linux use Ctrl in place of Cmd. Cmd+Z and Cmd+Shift+Z (or Cmd+Y) in the sorter undo and redo in the editor. These keys work only while the Slide Sorter has focus. They are handled by the view itself, so they are not listed in Keyboard Shortcuts and cannot be rebound. Right-clicking empty space below the slides offers Paste Slide After and Insert New Slide After, which add to the end of the deck.

How the Markdown changes

Copy and Cut put the slides' Markdown on the system clipboard, joined with ---, so you can also paste them into another deck or any file. Paste reads Markdown from the clipboard: text copied from the view comes back as the same slides, and any other text becomes one new slide.

Pasting slides with images

Slides often show images by relative path, such as ![bg](figs/a.png), which would break in a deck in another folder. So Copy and Cut write every relative path in the slides as an absolute one, and Paste makes them relative to the deck you paste into. Pasting back into the same deck gives the original paths. This covers Markdown images and links, <img>, <video> and other HTML src attributes, and url(...) in directives such as <!-- _backgroundImage: url(bg.png) --> and in <style scoped> blocks. Code and URLs are left alone.

When you paste into a deck in another folder and some images are outside that deck's folder, Paste asks what to do:

• Copy the images into this deck's folder: an image under the source deck's folder keeps its path relative to the deck (figs/a.png goes to figs/a.png beside the new deck); any other image goes into figs/. A file already there with the same content is reused; a different file with the same name gets a numbered name (a-1.png).

• Link to the original images: the paths point back at the originals.

• Cancel paste.

Cut never moves or deletes images. Slides pasted with an ordinary Cmd+V in the editor keep the absolute paths, which work on your computer but not on someone else's.

Slide 1 never takes the front matter with it. Moving, pasting or deleting slides adds or drops --- separators as needed, so the first slide never starts with one and slides never merge. In a deck using headingDivider, a slide that starts with a divider-level heading gets no separator, since the heading already starts a slide. A slide's own directive comments (<!-- _class: lead -->) and speaker notes move with it.

Insert New Slide adds an empty slide (a --- line and a blank line) and moves the cursor into it, ready to type.

Hidden slides

Marp has no way to skip a slide, so Hide Slide wraps it in a comment that Scimax recognizes:

<!-- scimax-hidden
# Backup results
Details for questions.
scimax-hidden -->

Marp does not render the comment, so the slide is left out of the preview and of every export. Its thumbnail stays in the sorter, dimmed and marked hidden, and can be moved, copied or unhidden like any other slide. Any --> inside the hidden slide (such as its own directive comments) is written as -\-> so it cannot end the comment early, and Unhide restores it.

One side effect: Marp treats comments as presenter notes, so the hidden slide's text appears in the notes of the slide before it (for example in the presenter view of an HTML export).

Slides

New Slide from Layout

Each adds a slide after the current one, with tab stops to fill in.

Insert

Inserted at the cursor, as its own paragraph.

This Slide

Each sets a directive for just this slide, <!-- _name: value -->, at the top of the slide (or of every selected slide), replacing one already there. Choose (remove) or leave the text empty to remove it.

✅ Deck

Each sets a key in the front matter, or removes it.

Theme

The scimax theme

theme: scimax dresses a deck in the blues of the crystal Scimax unicorn, with the amber of its horn, laid out like orgmode.org: a pale background, serif text, sans-serif headings in deep blue (level 1 and 2) and amber (level 3), quotes as grey-blue cards with a blue edge, and code in blues with amber names. Title and section slides sit on faceted crystal like the logo. It ships with Scimax, so every deck can use it with no theme file or setting: the thumbnails, the preview, the slideshow, every export and scimax marp build all know it.

---
marp: true
theme: scimax
paginate: true
header: Group meeting
footer: Your name · Your university
---

• A header is a deep blue band across the top, and a footer is a pale strip across the bottom.

• <span class="todo">TODO</span> and <span class="done">DONE</span> colour a keyword: TODO in amber, DONE in grey.

• Fitted headings (# <!-- fit --> Title) work.

• A code block shows its language in a small tag in its top-right corner (Python, JavaScript, SQL, Plain text, ...), taken from the fence: ```sql is tagged SQL. Common languages are named; a fence with another language, or none, gets no tag. Live Python cells (```python run) have their own controls instead. All the bundled themes do this.

• The fonts are ones orgmode.org uses when they are installed (Droid Serif, Noto Serif) and otherwise Cambria or Georgia, so nothing is downloaded and the deck looks the same offline.

To change it, choose New Custom Theme... and start from scimax: the new theme does @import 'scimax'; and changes only what you set. The CSS is in media/marp/themes/scimax.css in the extension. Marp for VS Code's own preview does not know the theme; Scimax's previews and exports do.

The steampunk, cyberpunk, steel and steelpunk themes

Four more themes ship with Scimax and work the same way as scimax: no theme file or setting needed, and the thumbnails, preview, slideshow, exports and scimax marp build all know them. All have the same lead and invert classes and the same todo / done spans as scimax, and fitted headings work.

---
marp: true
theme: steampunk   # or cyberpunk, steel, steelpunk
paginate: true
---

The fonts are ones that come with macOS or are common elsewhere, with plain serif or sans-serif fallbacks, so nothing is downloaded and decks look the same offline. The CSS is in media/marp/themes/steampunk.css, media/marp/themes/cyberpunk.css, media/marp/themes/steel.css and media/marp/themes/steelpunk.css in the extension; to change one, choose New Custom Theme... and start from it.

Custom themes

New Custom Theme... asks for a name and a theme to start from (Marp's, scimax, steampunk, cyberpunk, steel or steelpunk), then:

1. writes themes/<name>.css in the workspace folder (next to the deck outside a workspace), with /* @theme <name> */, @import '<base>'; and commented-out rules for the usual things to change;

2. adds it to scimax.marp.themes (in the workspace settings);

3. sets theme: <name> in the deck;

4. opens the CSS beside the deck.

Uncomment and change the rules, and save: the thumbnails and preview update on every save of a theme file. The Marpit theme CSS reference lists what a theme can style.

Actions

The last part of the menu has Present, Present from Current Slide, Slide Preview, Slide Sorter, Edit with Claude Code and Export Deck, then Marp Help.

Keys in the slideshow

h shows how a slide is written: its Markdown, as in the deck (the first slide with the front matter), in a panel at the top right. The panel follows you from slide to slide, so you can walk through a deck and its source together; Copy puts the slide's Markdown on the clipboard. It needs the source in the HTML, which every deck built by Scimax has.

Marp's own keys (f full screen, p presenter view, arrows) still work, also after you click into a widget: the arrows, PageUp, PageDown, Home and End go on to the slideshow unless the widget uses them itself, or you are typing in one of its fields. Moving the mouse over a widget that fills the slide brings back Marp's buttons at the bottom. Its overview button (the four squares) works too, and each slide's ink and notes show on its thumbnail. A note's bar drags it; its ● picks a colour, – shrinks it to an icon and × deletes it, and right-clicking a note offers the same three. The right-click menu also has Fullscreen (f).

Talk timer

Give the length of the talk with a timer key and a small countdown sits in the top-right corner of every slide:

---
marp: true
presenter: true
timer: 20
---

A bare number is minutes; 20m, 45:00, 1h30m and 90s also work. Deck → Talk Timer... in the Marp menu (cmd:scimax.marp.deck.timer) sets it, and turns on the presenter tools if the deck does not have them (the timer is one of them).

A deck with presenter tools but no timer can get one during the show: right-click a slide and choose Add a talk timer..., or press Alt+T (Option+T on a Mac), then type the length and press Enter. It behaves like a timer from the deck, starting when you move to the next slide. It is kept for that slideshow in the browser until you right-click the timer and choose Remove the timer; the deck file is not changed, so add timer: to keep it for good.

• It starts by itself the first time you move off the slide the show opened on. t (or a click on the timer) starts and pauses it; T resets it to the full time.

• To change the time during the show, right-click the timer for a menu (Start/Pause, Reset, Add a minute, Take off a minute, Set time..., and Back to the deck's time), press + or - to add or take off a minute, or press Alt+T (Option+T on a Mac) and type a time (20, 12:30, 90s, 1h30m), then Enter. A time set this way keeps the timer running if it was, and T resets to it; the deck file is not changed.

• It turns amber in the last 5 minutes (the last fifth of a short talk), red in the last minute, and after time is up counts the overtime as -1:05.

• The audience window and Marp's presenter view (p), where the countdown sits next to Marp's clock, show the same time: pausing in one pauses both. The time is kept in the browser's local storage, so a reload, or a live reload when you save the deck, does not reset it.

• After a rehearsal, press T before the talk. A timer untouched for 12 hours, or a deck rebuilt with a different timer, starts afresh.

• It is not printed and is not in PDF, PowerPoint or image exports.

Exercise countdowns

A countdown fence puts a countdown box on a slide, for an exercise or a discussion. The first line is the time, the rest is the label (Markdown):

```countdown 3:00
Discuss with your neighbour: *which step is rate limiting?*
```

The time is written as for the talk timer: a bare number is minutes, and 3:00, 90s and 2m30s also work (the default is 5 minutes). Insert → Exercise Countdown... in the Marp menu (cmd:scimax.marp.insert.countdown) adds one and turns on the presenter tools.

• e (or a click on the box) starts and pauses the countdown on the current slide; E resets it.

• At zero it flashes red and reads "Time's up".

• It runs in step in the audience window and the presenter view, and is kept across a reload.

• The Markdown preview and the slide thumbnails show the box; PDF and PowerPoint exports show it with its full time.

Blank, zoom and go to a slide

• Blank screen. b turns the audience screen black and w white, so the room looks at you instead of the slide. Press the key again, Esc, or click to bring the slide back. Pressed in Marp's presenter view, it blanks the audience window and the presenter view shows a reminder instead of going blank itself.

• Zoom. x then drag a box over a dense figure or table to magnify that part to fill the screen (a click magnifies 2.5 times around that point). The audience window zooms too. x or Esc zooms out, as does moving to another slide. The pen still works while zoomed and the ink stays on the slide.

• Go to a slide. g opens a list of slides by number and title. Type a number or words from a slide's title or text, use the arrows, and press Enter. Without the list, type a slide number and press Enter: 1 2 Enter goes to slide 12.

Live captions

v shows what you say as captions at the bottom of the slides, two lines at a time. Words still being recognised are grey. The captions fade out after a pause. Press v again to turn them off. "Captions at the top" in the right-click menu moves them out of the way of a slide's footer.

The captions use the browser's speech recognition. Chrome and Edge send the audio to their speech service, so they need a network connection. Firefox has no speech recognition. The first time, Chrome asks to use the microphone. The language comes from the deck's lang: directive (for example lang: de-DE), or from the browser's language if the deck has none.

Press v in the window you are working in. If you present from Marp's presenter view (p), press it there: the presenter view listens, and the captions show on the audience screen and, smaller, in the presenter view. Live reload keeps them on, but Chrome may ask for the microphone again.

Until the first words are heard, the caption bar says "Listening…". If something goes wrong, the bar says what it is instead: the microphone is blocked, there is no microphone, or the speech service can't be reached. The browser console (Cmd+Option+J) logs each problem with a [marp-captions] prefix. If the bar says "Listening…" but nothing appears while you speak, check which microphone Chrome uses: click the icon at the right of the address bar, or open chrome://settings/content/microphone.

Everything that is recognised is kept, with the time and the slide, so "Save transcript…" in the right-click menu writes it as Markdown, with one section per slide:

## Slide 3: Reaction mechanism

[00:04:12] The rate-limiting step here is the C–H activation.

The transcript grows over every talk given from the deck until "Clear transcript" empties it.

Recording the talk

The slideshow can record itself, the mouse and your voice as a video. V (Shift+V) does not start recording at once: it opens the Microphone window (see below), where you can check the microphone and its level, record a 5 second test, and get situated. Press ● Record there when you are ready. Chrome asks which tab to share: pick the slideshow. ■ Stop in the window, or V while recording, stops. Chrome then opens a save dialog, with <deck>-<date>-<time>.mp4 as the suggested name, so you choose the name and folder (Firefox downloads the video instead). If you cancel, "Save the recording…" in the right-click menu asks again, until the next recording. If the browser blocks pop-ups for the deck, V opens the panel at the top right of the slideshow instead, and ● Record there records this tab (the panel closes first so it is not in the video).

• Format. Chrome and Edge write MP4 (H.264 video, AAC audio) that QuickTime and other players can play. Firefox writes WebM. The video is the size of the tab when recording starts, at most 1080p. If the window changes size later (for example going full screen), the picture is scaled to fit, with black bars. A tab only sends a new frame when something changes, so a talk made of slides gives a small file.

• Sound. Your microphone is mixed with any sound the deck plays (videos, audio). Captions and the recording share one microphone, so Chrome asks for it once per page. The microphone, and how its sound is processed, are set in the Microphone panel (M, see below). Recording starts with a notice that names the microphone in use. If it records nothing for 15 seconds, a notice says so. Chrome does not remember the microphone permission for slideshows opened from a file, so it asks again after a reload.

• The mouse. A recording of a tab does not show the mouse pointer, so while recording the slideshow draws a yellow ring around it, which shrinks when you click. It is hidden while the laser pointer (l) is on. Turn it off with "Highlight the mouse while recording" in the right-click menu.

• Captions. Captions on the screen (v) are in the video. "Save captions of the recording (.vtt)…" also saves what was said during the recording as WebVTT subtitles, which video players and ffmpeg can use: #+begin_src sh ffmpeg -i talk.mp4 -i talk.vtt -c copy -c:s mov_text talk-captioned.mp4 #+end_src

• Presenter view. V in Marp's presenter view opens the same Microphone window. While recording, the presenter view shows ● REC, the time and a small level meter for the microphone, and is not recorded itself.

Open the Microphone window and start recording before you go full screen: opening a window and the sharing dialog can take the browser out of full screen. The video stays in the browser until you stop. Closing the tab while recording asks first, and live reload waits until the recording is saved. If you stop with Chrome's own "Stop sharing" button, a "Save the recording…" button appears on the slideshow: Chrome only opens the save dialog after a click or key press, so click it to choose where the video goes.

The microphone

M (Shift+M), V, or "Microphone…" in the right-click menu, opens a panel to set up the microphone for recordings and captions, like the audio controls of a streaming app. The panel opens in a small window of its own, so it never covers the slides: put it beside them, or on the laptop screen while the slides are on the projector. M in the slideshow closes it again, as do Esc and × in the window. If the browser blocks pop-ups for the deck, the panel opens at the top right of the slideshow instead.

The window's top row has a ● Record / ■ Stop button for recording the talk. As from the presenter view, Chrome asks which tab to share: pick the slideshow. The window is not recorded, so it can stay open for the whole talk, showing the recording time and the level meter, and ■ Stop saves the video. While it is recording, closing the window asks you to stop first. In the window, V also starts and stops recording. When a recording was started in another window, the button is greyed out and says so. Settings changed in the window apply at once to captions and a recording in the slideshow.

The settings are kept in the browser and apply to every deck. Changing them during a recording or while captions are on carries on with the new settings. If the chosen microphone is unplugged, the system default is used.

Echo, or a voice that sounds "in a box". This is almost always the microphone being far from your mouth, so it records the room's reflections as much as your voice. Webcam, monitor and laptop microphones are like this; the panel warns when the microphone in use looks like one. No setting removes room echo after it is recorded. Choose a USB or headset microphone and put it a hand's width or two from your mouth. With a microphone that close, turning off echo cancellation, noise suppression and automatic gain often sounds more natural, and the voice filter can help a bit in a bare room.

Editing slides in the slideshow

For last-minute polish just before a talk, d lets you fix the slides in the slideshow itself: correct a typo, move a heading, make a figure bigger, or hide a line. A bar at the top says what is selected and what you can do. The edits stay in the HTML; they do not change the Markdown.

• Edits are kept in the browser's local storage, so a reload keeps them, and Marp's presenter view shows them as you make them. You edit in the audience window, not the presenter view.

• s saves the deck with its edits, ink and notes in one file, and opening that file brings the edits back. The JSON save (S) and load (i) include them too. m cannot put them in Markdown, and says so.

• Edits belong to the content of their slide. If you change a slide in the Markdown and the slideshow reloads, that slide's edits are set aside rather than put in the wrong place, and a message says so. Slides you did not change keep theirs, even if they moved.

• Text you paste while typing is plain text; maths in a paragraph stays as it is. Code cells, countdowns and widgets can be moved and resized but not typed in.

• Printing (Cmd+P) shows the slides as edited.

• N (Shift+N) adds a blank slide after the current one, whether or not you are editing, and opens it for editing: t adds a text box, Cmd+V pastes. It has the slide's look (theme, class, colours) but none of its content. Cmd+N is not used because browsers keep it for a new window and a page cannot take it over.

• Adding, hiding, deleting or showing a slide reloads the page (Marp fixes its list of slides as the show opens) and comes back to that slide, still editing. The right-click menu has the same actions, also when you are not editing: Add a slide after this one, Hide this slide (Delete this slide for one added here), and Show hidden slide.

• In Marp's overview (the four squares), drag a thumbnail to move that slide: a blue bar shows where it will go. Right-clicking a thumbnail offers Go to this slide, Add a slide after this one, Hide this slide (or Delete), Move to the start, Move to the end, and Show hidden slide. Slides hidden in the slideshow stay in the overview, greyed out with a dashed border where they were; click one (or right-click, Show this slide again) to bring it back. Each change reloads the slideshow and opens the overview again, except Add, which goes to the new slide, ready to edit. Slides hidden in the Markdown are not in the slideshow at all, so the overview does not show them.

• Like the other edits, added, hidden and moved slides are kept in the HTML, not the Markdown: s saves them in the copy of the deck, and Marp's presenter view shows them too. Ink and notes stay with their slide; speaker notes and page numbers follow the new order. Ink on an added slide cannot go in annotated Markdown (m). To keep a slide for good, add it to the Markdown (or use Hide Slide there, see Hidden slides).

• Sticky notes still work while editing: drag one by its bar, click it to type in it. The pen, eraser and spotlight are off while editing, and ink strokes cannot be selected or moved.

To keep a change for good, make it in the Markdown too.

Keeping the ink

Ink and notes belong to the slide they were drawn on and are kept in the browser's local storage, so a reload does not lose them. Scimax presents a deck with presenter tools from the same private folder every time, so the ink is still there when you present it again. To keep the ink for good, move it to another machine or share it, press s: the browser downloads one HTML file with the theme, images, iframes, fonts, tools and ink inside. Open it anywhere, keep annotating, and press s again.

Live Python cells

Mark a Python code block with run to make it a cell you can edit and run during the talk:

```python run
import numpy as np
np.linspace(0, 1, 5)
```

Insert one with Insert → Python Cell... (cmd:scimax.marp.insert.pythonCell), which also adds presenter: true if the deck does not have it.

In the slideshow, click a cell to edit it. Shift+Enter (or ▶) runs it and leaves the editor, so the arrow keys change slides again without reaching for the mouse. Ctrl+Enter (Cmd+Enter on macOS) runs it and keeps editing, for when you want to change the code and run it again. Esc leaves the editor without running. PageUp and PageDown, which presentation clickers send, always change slides, even while you are editing a cell. ↺ restores the original code and ⟲ restarts Python. All cells share one Python session, like a notebook. Output shows printed text, errors, the value of the last expression and matplotlib figures.

Code that fails is useful for teaching, so errors stay in view. The cell shows the traceback with the failing lines of code (as Jupyter does), and the error message itself (e.g. NameError: name 'y' is not defined) also appears in red in the cell's bar. The output keeps up to 45% of the cell's height, even when the slide's CSS makes the editor taller (e.g. .pyc .cm-editor { max-height: 600px !important; }); the editor scrolls instead.

```python run
val: str = input("Enter your value: ")
print(type(val))
print("doubled:", 2 * float(val))
```

Running cells in VS Code

Press C-c C-c in a run cell to run it while you write the deck, without presenting. The output shows in a Python panel beside the editor, from the same Pyodide the slideshow uses, so code that works there works in the talk.

• All cells of the deck share one Python, as in the slideshow. The run hidden cells run first, once, before the first cell you run.

• Each output is labelled with its slide and cell number; click the label to go to the cell. Clear removes the output and Restart restarts Python.

• input() shows a text box in the panel, as in the slideshow (Enter answers, Esc cancels).

• The panel is for one deck at a time: running a cell of another deck restarts Python for that deck.

• A presenter: offline deck runs from the Python files it carries, so this works without a connection too; otherwise Pyodide is downloaded when the first cell runs.

• Cells run only in a trusted workspace. The cells are also in Insert → Python Cell... and the commands are in the Marp menu's Insert section.

• C-c C-c in a plain ```python block (no run, no header arguments) also runs it in this panel, labelled with its slide and line, so you can try a code example without writing its output onto the slide. The block stays ordinary highlighted code in the talk. A block with header arguments (```python :results output) runs with Babel and writes its results into the deck (Code Block Execution).

• C-c C-c elsewhere in a Markdown file keeps its usual meaning (run a Babel code block, toggle a checkbox).

Offline Python

Set presenter: offline instead of presenter: true (or choose "On, with offline Python" in Deck → Presenter Tools...) to put Python inside the deck, so its cells run with no internet connection:

---
marp: true
presenter: offline
---

• When you present or export HTML (h), Scimax adds Pyodide and the packages the deck's run cells import (with their dependencies) to the HTML file. Pyodide is downloaded once per version and cached in the extension's storage, so later builds need no connection either.

• Packages are found from the top-level import / from ... import lines of the run cells. To include a package that is only imported later, during the talk, import it in a run hidden cell.

• The file grows by about 12 MB for Python alone, and to 35-45 MB with numpy, matplotlib and pandas. It loads in a few seconds from disk.

• %pip install, and packages that are not part of Pyodide (for example pycse or seaborn), still need a connection; the deck tries to download them, and the cell shows an error when it cannot. The Output panel (Scimax Marp Export) lists the packages that were included and those that were not.

• s keeps the embedded Python, so the annotated copy also runs offline.

• In the slideshow of a presenter: true deck, right-click → Save a copy that works offline... saves <deck>-offline.html. That copy contains Python, the packages chosen as above (including any edits you made to the cells), and your ink, notes and edits. The browser downloads Python for it, so you need a connection while saving, but not afterwards. When you save that copy again with s, it keeps the -offline name.

Checking a deck for offline use

Scimax Marp: Check for Offline Use (cmd:scimax.marp.checkOffline, also Deck → Check for Offline Use in the Marp menu) builds the deck in a temporary folder and lists in the Problems panel what would not work without an internet connection, each on the line it comes from:

• Python cells in a deck with presenter: true (Python is downloaded when the deck opens; use presenter: offline)

• %pip lines, and imports of packages that are not part of Pyodide, in an offline deck

• images and other files that are not found

• images, videos and scripts loaded from the web, and fonts or styles a theme loads from the web (shown on the theme: line)

Presenting or exporting HTML (h) an offline deck runs the same check and says when it found something. The problems are cleared when the deck is closed or checked again.

Notes

• The tools are added only in a trusted workspace, since the deck's HTML and Python run in the browser. In an untrusted workspace Scimax warns and shows the plain slideshow.

• A deck with presenter: true is built with Marp CLI's --html option, so raw HTML in its slides is rendered. The slide thumbnails and previews allow all HTML for these decks too (in a trusted workspace), so an <iframe> widget shows there as well, whatever scimax.marp.enableHtml says.

• Scimax passes its own markdown-it engine to Marp CLI (--engine), which replaces an engine set in a Marp CLI configuration file for these decks.

• The fonts for KaTeX math are downloaded once and cached, so deck.html also typesets math offline. Fonts that a theme loads from the web (an @import of a font service) fall back to local fonts without a connection.

• The browser files live in media/marpPresent/ of the extension; the Output panel (Scimax Marp Export) lists what was inlined and any missing files.