Shared Whiteboard

Two independent drawing desks share one board over a virtual serial cable. Each peer keeps its own ink, cursor and status while remote strokes appear in the same canvas.

Run it

Build the examples with devenv shell -- lcom-ng-build, then run:

lcom-ng run-pair build/examples/serial_whiteboard left \
  --right build/examples/serial_whiteboard right

Try a complete workflow

Open the paired runtime, draw on either desk, and compare the views. Change ink, toggle the grid, or draw with Shift and the arrow keys. Use resync to restore agreement after a sequence gap.

Controls

• Mouse drag: draw. Number keys: ink. Shift+arrows: draw with the keyboard.
• G: grid. S: resync. R: reconnect. F1: help.

Command shortcuts work on macOS; Ctrl shortcuts work on other hosts. Esc closes help first. Cmd/Ctrl+W closes the app.

In the app

These are actual runtime captures. Open a screenshot for a larger view; use Left and Right to browse, and Escape to close.

Two desks, one boardBoth peers connect over the virtual serial cable.

Draw togetherEach board shows both local and remote strokes.

The other side of the conversationThe right desk keeps its own ink and cursor while sharing the same board.

A clear canvasG hides the guide grid without changing any strokes.

Resynchronize the drawingS replays the local stroke snapshot to the other desk.

Draw from the keyboardShift + arrow keys draws precise segments, arrows alone move the cursor.

A shared surface, familiar controlsF1 explains drawing, colors, clearing and resynchronization.

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Two desks, one board · Both peers connect over the virtual serial cable.

What it demonstrates

UART framing, sequence numbers, reconnect and resync, PS/2 input, local ownership and shared rendering.

Both windows must remain open for collaboration. A disconnected peer is reported in the interface; local drawing still belongs to its own desk.

Source: examples/serial_whiteboard.c.

Refresh these screenshots

devenv shell -- python3 scripts/capture_gallery.py --app serial-whiteboard

See the screenshot workflow to add states or check freshness.