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Download the DotPad SDK for use offline

Source: R/dotpad_config.R
maidr_download_dotpad_sdk.Rd

maidr.js drives a DotPad tactile display through the vendor's SDK, which it does not bundle: the braille engine inside it is a 14 MB liblouis build, and every document would carry it for the few readers who own the device. By default maidr.js imports the vendor's published copy from jsDelivr, pinned to a commit, the first time a DotPad is connected – the one path an offline document (use_cdn = FALSE) still takes to the network.

Usage

maidr_download_dotpad_sdk(
  dir = maidr_dotpad_sdk_dir(),
  force = FALSE,
  quiet = FALSE
)

Arguments

dir

Where to write. Defaults to the option maidr.dotpad_sdk_dir, the environment variable MAIDR_DOTPAD_SDK_DIR, or a per-user cache directory.

force

Refetch files that are already present and correct.

quiet

Say nothing about what was fetched.

Value

The directory, invisibly.

Details

This fetches that pinned copy once – the module, the liblouis build, and the LGPL licence text and wrapper sources the vendor asks redistributors to keep beside it – verifying every file against its recorded size and digests (MD5, and SHA-256 on R 4.5 or later), and writes a manifest.json beside them naming the commit they came from. From then on show() and save_html() copy it into lib/dotpad-sdk-<version>/ next to every use_cdn = FALSE document and tell maidr.js where it is, so a reader connects a DotPad without the network. A file already present and correct is left alone, so a second call costs nothing.

A page served from somewhere else – an intranet host, or a knitr document, whose charts live in srcdoc frames with no base URL for a relative path to resolve against – names its copy by URL instead, through the options maidr.dotpad_sdk_url and maidr.dotpad_asset_base_url; see maidr-options. A configured URL wins over a downloaded copy.

See also

maidr-options for naming a copy by URL

Examples

if (FALSE) { # \dontrun{
maidr_download_dotpad_sdk() # about 14 MB, once
save_html(p, "chart.html", use_cdn = FALSE) # carries the SDK in lib/
} # }