doc-present: Showing slides with Emacs

This package is meant to display presentation slides with a two monitor setup. On one screen it shows the actual slides, and on the other a so called “presenter screen”, showing not only the current slide but also the next one, a timer and also optional notes which can be drawn from an Org file. It also features an overview mode to quickly select certain slides.

Requirements

• Emacs 24.x (I test only with x=3; older version may or may not work).
• Emacs must be built with Imagemagick support (so no Win32/OSX at the moment)

Quick Tour

• First, you should increase the variable doc-view-resolution for better rendering quality (300 should be enough).
• Load the file doc-present.el and eval-buffer it.
• Load the PDF file containing your slides; doc-view mode should kick in and display the first slide, converting the rest in the background. Wait until all slides are converted (progress is shown in the modeline).
• Connect your laptop to the presentation monitor/projector and do whatever you have to do to set it up so that you have a usual two-monitor setup, i.e., one screen is (virtually) next to the other and you can drag windows to and fro.
• M-x doc-present
• A new frame should pop up, showing the first slide and a little text saying that you should drag this frame to the presentation screen. Do exactly that and then press f to toggle fullscreen.
• In the other frame, on your laptop screen, you should see the presenter window; it shows the current slide, next slide, timer, etc.
• Use s to start the stop-watch timer at the beginning of your talk. Use cursor keys to navigate between slides, the . key to blank out the presentation screen, and o to enter overview mode. Press h for a quick summary of available keys.
• When finished, press q.

The long story

Being fed up with the existing PDF viewers, especially their rendering quality and lacking capabilities for doing presentations, I decided that Emacs must save the day yet once again.

doc-view

Emacs ships with doc-view, which can render PDFs by using ghostscript to convert the pages to png files. By increasing the variable doc-view-resolution, you should get excellent quality, and from my experience ghostscript’s PDF support is better than libpoppler’s.

The first thing you need to do though is to increase the value for doc-view-resolution. The needed value depends on the resolution of your presentation monitor, of course, but don’t be fooled by your 24”-monitor 1920x1200 pixel IPS-panel; from my experience, most presentation projectors still have 1024x768, which means that a value of 300 should be more than enough. You can choose higher values just to be on the safe side, but converting and scaling those images to the correct size will be noticeably slower, so I’d rather not do that.

The main slide frame

When you start doc-present, a new frame will be generated which is the main slide frame. It is a special frame with no minibuffer, mode-line, fringes, etc., so that almost all space can be used for displaying your slides. I’m saying ‘almost’ because there are two caveats:

• The size of an Emacs frame can only be multiples of the frame’s default font size. That means, if you have a 8x16 font, it’s width and height will be automatically reduced to be divisible by 8 and 16, resp.
• Since the frame has no fringes, its rightmost column is reserved for displaying the truncation/continuation characters for overlong lines.

There’s a dirty trick though: We simply choose a very tiny default font for the frame. Since Emacs can nowadays use freely scalable XFT fonts, we can choose such a font for the main slide frame and scale it down so that it is just 1 pixel wide and 2 pixels high. That means, the rightmost column will just be one pixel, and it will always exactly fit in the screen’s resolution.

All this happens automatically, but you have to make sure that the used font family does actually exist on your system. Simply do

M-x customize-face RET doc-present-tiny-xft-font RET

The default is Bitstream Charter, which I guess should exist on most modern GNU/Linux systems.

You should set doc-present-slide-frame-background-color to the background color of your slides (default: white); this is important if your slides don’t exactly fit the presentation screen (because of different aspect ratios). Also, the rightmost 1-pixel column will have this color.

The presenter frame

By default, the presenter frame shows a stop-watch timer, the current and maximum slide number, the local time, the current and next slide and optionally notes for the current slide.

This can be changed in practically every way; see the variable doc-present-presenter-layout to change what and where stuff is displayed. Also, doc-present-current-slide-width and doc-present-next-slide-width change the width of the current/next slide.

Available keys

• Right, Down, PgDown, Space, Return: Next Slide
• Left, Up, PgUp: Previous Slide
• f: Toggle fullscreen of main slide frame
• s: Start/Stop the stop-watch timer
• .: Black out the main slide frame
• o: Start overview mode
• m: Create a new main slide frame
• h: Quick help
• q: Quit

Overview mode

The overview mode shows all slides of your presentation in a miniature view; it can be triggered by pressing o. You can then move between the different slides with the cursor keys, and pressing Return will show a slide in the main slide frame while staying in overview mode in the presenter frame. Pressing the Space key will show the slide and switch to the presentation mode.

If you press o once again in overview mode, the main slide frame will switch to overview mode as well. This can be very helpful for the Q&A after the talk since it makes it easier for people in the audience to refer to certain slides.

Notes

You can display additional notes on the presenter frame for each slide. This is done by creating an Org file which has the same name like your PDF, but with the suffix ‘-notes’ added to it; that means, if your PDF file is called presentation.pdf, your Org file must be named presentation-notes.org. It must be of the following form:

 * 1
   - These are the notes for slide 1
   - Do your motivational thing
 * 2-5
   - These are other notes
   - They will be displayed on slides 2 to 5

Granted, this is not very flexible, especially when you insert slides, since then you’ll have to adapt all the numbers, so you should really do your notes when the slides are finished. Also note that if you’re successively revealing parts of your slides, those will be separate pages in your PDF. If you have better ideas on how to uniquely link notes to certain slides, I’m all ears.

Frame focus

Usually, it shouldn’t make a difference which of the frames currently has focus. Keys should work in both of them, but still you should make sure that the presenter frame always has focus; it’s simply better tested and also “more natural”. While it is possible in Emacs to select a certain frame, your window manager likely changes that depending on your mouse position. Therefore, this is something only you can manually ensure. If doc-present notices that the presenter frame does not have focus, it will show you a warning, but it will work nonetheless.

Another reason why you should give focus to the presenter frame is to avoid redraws of the slide, which usually leads to flickering. This is especially noticeable when the mouse is over the slide picture. Still, a small flicker from time to time seems to be unavoidable, but I don’t think it’s a big issue (just blame it on the projector).

Speed

Scaling images with Emacs isn’t particularly fast, so there usually is a noticeable delay before the next slide is displayed. You will notice however that once a slide was displayed, moving back and forth again will be fast because the image is now in Emacs’ image cache. Unfortunately, the only way to cache images is to actually display them on the correct frame in the scaled size, which usually isn’t feasible before a presentation.

So really, you will have to live with this delay. If you want to quickly select frames, you should use overview mode. You might also want to try setting imagemagick-render-type to ‘1’, which can speed things up as well.

Screenshots