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Screenshots

rascal-0.34.0
rascal-tutor-0.18.4

Synopsis​

Take screenshots of (interactive) webcontent produced by Rascal code examples.

Description​

The rascal-shell feature offers the option to take screenshots of interative content.

Every time the shell detects content that is not strictly plaintext:

  • a headless browser is used to display the content.
  • a screenshot is taking every second until the visual content stabilizes.
  • the screenshot is saved as a PNG image with the markdown content.

This behavior simulates the effect that users have on the REPL when they produce visual content. For them normally a browser is started in their development environment to show the content and to interact with it.

Examples​

Any function that produces an http content server, like below, leads to a screenshot:

```rascal-shell
import vis::Charts;
barChart({<"bike",80>, <"car", 20>})
```

This produces:

rascal>import vis::Charts;
ok
rascal>barChart({<"bike",80>, <"car", 20>})

image


However, we can also hide the commands and only look at the image, using a prepare shell:

```rascal-prepare
import vis::Charts;
barChart({<"bike",20>, <"car", 80>})
```

This produces: image

Benefits​

  • Screenshots don't lie; you always see it in the documentation as the user will see it in their browser

Pitfalls​

  • The screenshot feature automatically turns off when the tutor startup code can not link a browser and a selenium driver to control that browser. A warning is printed with hints on how to configure mvn to fix this.