A library for the Chrome Devtools Protocol.
A library for the Chrome Devtools Protocol (CDP). It provides access to Chrome, enabling tasks such as printing a page or opening a tab.
Chrome Devtools Protocol: https://chromedevtools.github.io/devtools-protocol/
cdp-hs
A Haskell library for the Chrome Devtools Protocol (CDP), generated from the protocol's definition files.
Example usage
Ensure Chrome is running with the remote debugging port enabled:
$ chromium --headless --remote-debugging-port=9222 https://wikipedia.com
The following program can be used to print a page to PDF, with Base64 encoded data being read in chunks:
{-# LANGUAGE OverloadedStrings #-}
module Main where
import Data.Maybe
import Data.Default
import qualified Data.ByteString.Base64.Lazy as Base64
import qualified Data.ByteString.Lazy as BL
import qualified Data.Text as T
import qualified Data.Text.Lazy as TL
import qualified Data.Text.Lazy.Encoding as TL
import qualified CDP as CDP
main :: IO ()
main = CDP.runClient def printPDF
printPDF :: CDP.Handle -> IO ()
printPDF handle = do
-- send the Page.printToPDF command
r <- CDP.sendCommandWait handle $ CDP.pPagePrintToPDF
{ CDP.pPagePrintToPDFTransferMode = Just CDP.PPagePrintToPDFTransferModeReturnAsStream
}
-- obtain stream handle from which to read pdf data
let streamHandle = fromJust . CDP.pagePrintToPDFStream $ r
-- read pdf data 24000 bytes at a time
let params = CDP.PIORead streamHandle Nothing $ Just 24000
reads <- whileTrue (not . CDP.iOReadEof) $ CDP.sendCommandWait handle params
let dat = map decode reads
BL.writeFile "mypdf.pdf" $ BL.concat dat
decode :: CDP.IORead -> BL.ByteString
decode ior = if (CDP.iOReadBase64Encoded ior == Just True)
then Base64.decodeLenient lbs
else lbs
where
lbs = TL.encodeUtf8 . TL.fromStrict . CDP.iOReadData $ ior
whileTrue :: Monad m => (a -> Bool) -> m a -> m [a]
whileTrue f act = do
a <- act
if f a
then pure . (a :) =<< whileTrue f act
else pure [a]
More examples can be found in examples.
Generating the CDP library
cabal run cdp-gen
Current state
Commands and events for all non-deprecated domains are supported.
Sessions can also be created with a target (such as a tab), which can be used to restrict the scope of commands and events for the target. See examples/sessions.hs for example usage.
Contributing
PRs are welcome! If you would like to discuss changes or have any feedback, feel free to open an issue.
Acknowledgements
This began as a Summer of Haskell / GSoC project. Albert Krewinkel (@tarleb), Jasper Van der Jeugt (@jaspervdj) and Romain Lesur (@RLesur) provided valuable feedback and support which along with raising the library's quality, has made this all the more enjoyable to work on.
References
- https://jaspervdj.be/posts/2013-09-01-controlling-chromium-in-haskell.html
- https://www.jsonrpc.org/specification.