bella-presenter

A fast, native dual-screen PDF presenter for Typst & LaTeX slides.

Runs on macOS · Windows · Linux · Built with GPUI + PDFium

---

What it does

Open a PDF exported from Typst or LaTeX/Beamer and drive a talk with two windows:

• 🖥️ Presenter window - the current slide, a next-slide preview, your speaker notes, a talk timer, and a thumbnail strip of all slides.
• 📽️ Audience window - just the slide, on black, fullscreen on the projector.

It stays instant even on large decks (300+ pages) thanks to lazy rendering, a texture cache, and next-slide prefetch.

Screenshots

Start screen - launch with no file to pick from your recent decks, or just drag & drop a PDF onto the window.

Presenter window - current slide, next-slide preview, speaker notes, a centered slide counter / clock / timer, and the slide thumbnail strip.

Live annotation - hold the mouse over the current slide to draw freehand (mirrored on the audience screen); press P to switch between the laser pointer and drawing, and D to clear.

Audience webcam overlay - show the presenter in a configurable corner of the projected slide, here with the background removed and a freehand drawing on the slide.

The overlay can also be a circle, keeping the camera's background.

Camera settings - choose the camera, position, size and shape; set the background to normal, blurred or removed.

Install

Grab a prebuilt binary from the latest release — PDFium is bundled, so there is nothing else to install:

Platform	Asset	Notes
macOS (Apple Silicon)	bella-presenter-macos-arm64.zip	ad-hoc-signed .app; open via right-click → Open the first time
Linux (Debian/Ubuntu)	bella-presenter_<ver>_amd64.deb	sudo dpkg -i the file
Windows (x64)	bella-presenter-windows-x64.zip	portable (bella-presenter.exe + pdfium.dll)

Intel Macs and other Linux distros are not prebuilt — build from source.

One-line install

macOS & Linux — installs the .app into /Applications (clearing quarantine) or the .deb via dpkg:

curl -fsSL https://raw.githubusercontent.com/tschinz/bella-presenter/main/install.sh | bash

Windows (PowerShell) — extracts the portable build to %LOCALAPPDATA%\Programs\bella-presenter and adds a Start Menu shortcut:

irm https://raw.githubusercontent.com/tschinz/bella-presenter/main/install.ps1 | iex

Features

• Works with or without notes. Auto-detects Beamer/Typst "notes on second screen" decks (a double-width page whose right half is the notes) and splits them; plain decks just work.
• Two windows, second-screen aware. F5 opens the audience window — on a second screen it goes fullscreen there automatically; on a single screen it goes fullscreen over the presenter (all shortcuts still work). Esc quits it while the presenter keeps running.
• Thumbnail strip. A scrollable, resizable filmstrip of every slide; click to jump, and it follows the current slide. Toggle with T.
• Adaptive, resizable layout. Cycle 4 current/next/notes arrangements (or a H/V current+next split without notes) with L; drag any divider to resize. Sizes are remembered.
• Laser pointer & drawing, mirrored. Hold the mouse on the current slide for a pointer dot, or press P to draw freehand — shown live on the audience screen. Pick the colour from a swatch in the header.
• Zoom & pan. ⌥/⌘/Ctrl + scroll zooms at the cursor, the same keys + drag pan — on either window, mirrored to the room. Zooming grows the slide into the letterbox bars, so a portrait page fills the window width.
• Webcam overlay. Show your camera in a configurable corner of the audience window only (C). Choose a rectangle, rounded rectangle or circle, and set the size, source and mirroring from the ⚙ popover, which also shows a live preview and capture resolution. The camera runs only while presenting or while the settings popover is open.
• Background options. Keep the normal background, blur it, or remove it to show only the person. See the screenshots above. Removal uses a small built-in segmentation model (about 0.5 MB) and runs locally on the CPU; no images are uploaded.
• Talk timer + clock, light/dark theme. Large centered footer with slide number, wall clock, and a stopwatch that follows the presentation; pause, resume and reset it with K / R or the buttons next to it. Cycle system/dark/light theme from the header.
• Go to a slide. Type its number and press Enter; the footer shows what you typed.
• Clickable links. Links in the PDF work on either window: a click on a link to another slide jumps there, web and mail links open in the browser or mail app. The cursor turns into a hand over a link.
• Recent files + resume. Launch with no file to pick a recent deck; reopening resumes at the page you left off.
• Open with. Installed builds appear in the OS "Open with" menu for PDFs (macOS, Linux .deb, Windows via install.ps1); the file opens directly, also into a running instance.
• Updates. At start the app checks the latest GitHub release and offers to install it and restart (macOS replaces the .app, Linux installs the .deb via pkexec, Windows replaces the portable files). Never shown while presenting.
• Remembers everything. Window position, panel sizes, fonts, layout, theme, pointer colour, thumbnail strip, and recent files persist between sessions, in a single JSON file (~/.config/bella-presenter/state.json on macOS/Linux, %APPDATA%\bella-presenter\state.json on Windows).

Keyboard & mouse shortcuts

Input	Action
→ / Space / PageDown / scroll down	Next slide
← / PageUp / scroll up	Previous slide
Home / End	First / last slide
F5 / Esc	Start / quit presentation
B	Blank the audience screen (black)
W	Close the file, back to the start screen
R	Reset the talk timer
K	Pause / resume the talk timer (also a button in the footer)
Number + Enter	Go to that slide (Esc cancels)
L	Flip layout
T	Toggle the thumbnail strip
S	Swap presenter / presentation screens
+ / −	Footer font larger / smaller
O	Open a PDF
C	Toggle the webcam overlay (settings in the ⚙ popover)
P / D	Toggle laser pointer / drawing · delete all drawings
Hold mouse on current slide (either window)	Laser pointer / draw (shown on the audience screen)
Click a link (pointer mode)	Follow it: jump to the slide, or open a web or mail link
Ctrl, Alt/⌥ or ⌘ + scroll / drag (either window)	Zoom at the cursor / pan the zoomed slide
Double-click (audience)	Toggle fullscreen
Drag & drop a PDF	Open it

All mouse features work on either window and drive the same shared state, so the pointer, drawings, and zoom always mirror between the presenter and audience screens. The Shortcuts button in the header shows this list in-app.

Webcam

Enable it with C or from the ⚙ popover in the header. The overlay appears on the audience window only (hidden while the screen is blanked with B).

• Source: all cameras the OS reports are listed; use ⟳ to rescan. The app picks the best mode of at least 720p at about 30 fps, and the popover shows the resolution actually received. Capture details lists the modes the camera offers, useful when a camera delivers less than expected.
• Layout: corner, size, shape and mirror are saved with your other settings.
• Shape: rectangle, rounded rectangle or circle.
• Background: Keep (normal image), Blur (person stays sharp) or Remove (transparent background, showing only the person). Removal ignores the shape setting. Quality improves with a sharper camera image.
• Permissions: on macOS the first start asks for camera access. When running with just run from a terminal, that terminal app needs camera access in System Settings > Privacy & Security > Camera. The bundled .app carries its own usage description.

Build from source

Rendering needs Google's PDFium (loaded at runtime). Fetch the prebuilt library for your platform once, then run:

just setup-pdfium        # downloads PDFium into third_party/pdfium/ (git-ignored)
just run                 # open the example deck (no notes)
just run-notes           # open the example deck (with speaker notes)
just run file=deck.pdf   # open your own PDF

Without just: cargo run --release -- examples/04-aprog-ptr-en.pdf (PDFium must be reachable — next to the binary, in third_party/pdfium/lib/, or via $PDFIUM_LIB_DIR).

Packaging

Releases are built by CI on a v* tag: a macOS .app (zipped, ad-hoc signed), a Linux .deb, and a Windows portable zip. To build a self-contained bundle yourself (icon + PDFium included) with cargo-bundle:

just bundle        # bundle for the current OS

Per-format recipes (run each on its target OS — cargo-bundle does not cross-build): just bundle-mac (.app), just bundle-deb (.deb), just bundle-appimage (.AppImage, Linux-only, not shipped in releases), just bundle-msi (.msi, Windows, needs WiX). just bundle-mac ad-hoc signs the .app so it isn't reported as "damaged" locally.

Development

just            # list all recipes
just test       # run tests (headless; need PDFium present)
just clippy     # lint
just build      # release build into bin/

The About window lists every third-party library with its license, generated from the dependency tree with cargo-about and embedded into the app; regenerate with just thirdparty after changing dependencies.

License

Licensed under the MIT license. PDF rendering uses Google's PDFium (BSD-3-Clause), bundled with the application. Background removal uses the MediaPipe selfie segmentation model (Apache-2.0, ONNX conversion by onnx-community) with ONNX Runtime; full license texts are in the app's About window and in assets/thirdparty.md.

The logo is built from one of the Ferris illustrations in the free-ferris-pack by Maria Letta (CC0-1.0).