Draw on a diagram

Circle a region, sketch an arrow, scribble a remark — by hand, on top of the boxes.

1. Open a JSON-backed diagram and press Edit.
2. Pick Pen in the toolbar (or press p). Choose a color (∅ is the theme's ink) and a width.
3. Drag on the canvas. Scrolling still pans and Ctrl + wheel still zooms while the pen is active — with a mouse or trackpad. On a touch screen a second finger is ignored while you are drawing, so a resting palm cannot hijack the stroke; switch back to Select to pan and zoom by touch.
4. Eraser (e) removes a stroke per click. Esc returns to Select. Every stroke is one undo step.
5. Autosave writes .diagrams/src/<name>.drawings.json next to the model. Commit it with the rest.

Hiding and showing. The ✎ control in the corner, and the Drawings row in the legend (when the diagram has one), switch every stroke off and on. That is a viewer preference — the published page opens with drawings shown, and the PNG always includes them.

Pointing, not drawing. To point at something during a screenshare, use the laser pointer instead: L (or ◉ in the corner controls) in either mode, drag to draw a red trail that fades out after a second. It is never saved, it works inside containers too, and Esc switches it off.

What moves and what does not. Strokes sit at absolute canvas coordinates. On a plane with automatic layout, adding a node can slide the boxes out from under your ink; freeze the plane (Auto-layout off) or save positions first if the drawing must line up. Drawings are shown at the top level only — enter a container and they disappear until you come back.

See also

• Publish and share — drawings ship with the page and the PNG
• Drawings reference — every field the file may carry
• The model — why the strokes live outside it