Usage hints for emacs-reveal presentations

Presentations are generated with emacs-reveal and make use of the HTML presentation framework reveal.js.

Icons, keys, navigation
- Newer presentations (starting end of 2023) contain icons (“custom controls”) at lower left with direct access of selected presentation features
- In general, “n” and “p” move to next and previous slide; mouse wheel works as well
- Type slide’s number followed by Enter to jump to that slide
- Browser history (may need two attempts to work)
- Zoom with Ctrl-Mouse or Alt-Mouse
- Search with Ctrl-Shift-F (press “enter” for subsequent search hits)
- Since August 2021, presentations use the linear navigation mode of reveal.js. Use URL parameter default-navigation to revert to the default navigation mode of reveal.js (e.g., https://oer.gitlab.io/emacs-reveal-howto/howto.html?default-navigation).
PDF export
- Use URL parameter print-pdf (e.g., https://oer.gitlab.io/OS/Operating-Systems-JiTT.html?print-pdf), then print to PDF file (usually, Ctrl-p)
  - Reveal.js documents this to work with Chromium/Chrome, suggested settings
  - Newer build pipelines may generate this type of PDF as well; your instructor might inform you about this
- Alternatively, depending on the specific project, PDFs might also have been generated via LaTeX from org source files. If available, those PDF versions are accessible by replacing .html in a presentation’s URL with .pdf
- Alternatively, instead of PDF export you may want to download and annotate/enrich source files
  - Org mode, which is plain text
Offline use
- Presentations can be downloaded from build pipelines of source projects as self-contained zip archives
  - Extract contents and open local HTML file(s) in browser
  - Depending on the presentation and its features, you may see cross-origin request security settings errors. Then, start a local web browser for the directory of your presentation, e.g.: python -m SimpleHTTPServer or php -S localhost:8000
- Alternatively, clone source repository and build presentations locally
Audio with audio slideshow plugin
- Depending on the presentation, playback may or may not start automatically
  - To toggle audio, type “a” (or “+” for older presentations)
- Audio controls are shown at bottom left (use right-click for more functionality such as speed control)
- Newer presentations (starting 2024) add URL parameters
  - audio-autoplay either to turn autoplay on or audio-autoplay=false to turn it off
  - audio-speed, e.g., audio-speed=2.0 for double speed
  - audio-advance to control whether to go to next slide when audio ends; use audio-advance=-1 to turn this off, audio-advance=1000 to advance after 1000 ms
  - E.g., this URL does not advance and plays at higher speed: https://oer.gitlab.io/oer-courses/it-systems/03-Boolean-Logic-I.html?audio-advance=-1&audio-speed=1.5
Notes
- Slides contain additional notes if you see the folder icon
  - Several options to make notes visible
    - Press comment icon of custom controls (if present)
    - Press “v” to open the “courseware view”
    - Click on folder icon or press “s” to see the “speaker notes view”
      - For the speaker notes view you need to allow pop-ups
      - If the pop-up window does not work, you may need to press “s” twice or close the pop-up window once
- If the slide contains audio, the notes are a transcript of the audio’s text
Links
- In presentations, internal and external links (the former are also called relative, while the latter embed a domain in the URL) are styled differently
  - Different colors for internal (blue) and external (green) links
    - Internal links that stay within the presentation come with additional indicators whether they point to a previous (◂) or an upcoming (▸) slide
  - Special link icons for “non-local” links
    - A generic indicator as in this external link to a page explaining external links, which are typically served by independent organizations with their own agendas, with or without their own privacy policies
    - But also for links between different presentations (in particular, this allows to recognize forward references, which may be safely ignored upon first contact)
    - Besides, special icons may indicate whether the non-local link leads to
      - basic contents, e.g., enlightenment (if you cannot explain the linked term, you may want to follow the link before proceeding; this does not imply that you need to read all of the linked page…),
      - contents beyond learning objectives, e.g., post-quantum cryptography (which you can ignore for grading purposes)
      - contents that are introduced briefly and revisited with more details later on (icon ↔)
  - In summary, presentations (not this page) use several link styles:
    - External (green with icon)
      - Possibly with different icons hinting at “importance”
    - Relative into different presentation (blue with icon)
    - Relative within presentation (blue), either with backward (◂) or forward (▸) indicator
- Some students ask for the removal of links. This can be configured with URL parameter hidelinks, which hides most links. In addition, with a numeric value such as hidelinks=24, different types of links are hidden based on the following bit values:
  - 1: Hide backward links
  - 2: Hide forward links
  - 4: Hide links between presentations
  - 8: Hide links to other resources under oer.gitlab.io
  - 16: Hide external links
  - 32: Hide links going beyond current scope
  E.g., with hidelinks=28 (28 = 16 + 8 + 4) neither external links (16) nor links to other resources under oer.gitlab.io (8) nor links to other presentations (4) would be displayed

Reveal.js is restricted on mobile browsers without keyboard shortcuts. Newer presentations (since April 2022) allow, depending on OS and browser, to open in fullscreen mode (without superfluous address bar) if the presentation is added as app icon the home screen and started from there.

The document CONTRIBUTING.org contains hints on how to provide feedback or contribute improvements for OER within the group oer at GitLab.