Recipes: Screenshot Capture

How to automatically capture screenshots from running examples for documentation.

How it works

1. Start the example server with LOFIGUI_HOLD=1 (keeps server alive after model completes)
2. Trigger the model by hitting the server URL
3. Capture at timed intervals using url2svg (headless Chrome → SVG)
4. Kill the server

Taskfile commands

Command	Description
task docs:capture:01	Auto-capture polling + complete screenshots for example 01
task docs:capture	Capture all example screenshots
task docs:open:01	Start example 01 in HOLD mode for manual inspection

Per-example capture config

#	Port	Captures	Timing
01	1340	01_polling.svg (mid-run), 01_complete.svg (done)	2s delay for polling, 7s for complete

Adding captures for a new example

1. Add a docs:capture:NN task to Taskfile.yml:

   • Set dir to the example's go/ directory
   • Start server with LOFIGUI_HOLD=1 go run . &
   • Wait for port with curl loop
   • Trigger model, then capture at appropriate delays
   • Use trap to kill server on exit

2. Add the task to docs:capture's dependency list

3. Reference the SVGs from the example's docs page

Manual inspection

task docs:open:NN starts the server in HOLD mode without auto-capture. The server stays running until Ctrl-C, so you can:

• Open the page in a browser to check layout
• Run url2svg manually with different options
• Test the cancel button mid-flow

url2svg options

url2svg --url http://localhost:1340 -o output.svg           # default 1024x768
url2svg --url http://localhost:1340 -o output.svg -width 800  # custom width
url2svg --url http://localhost:1340 -o output.svg -full-page  # full scroll height